Drill Bench Hydraulics User Guide

Drillbench Hydraulics User Guide Page i

TABLE OF CONTENTS

Page

1. INTRODUCTION 1

2. INPUT 3 2.1 Input parameters 3 2.2 The input file 3

2.2.1 Library 3 2.2.2 Range checking 4

2.3 Input navigators and menu bars 5 2.3.1 Description 5 2.3.2 Formation 6 2.3.3 Survey 7 2.3.4 Pore pressure and Fracture pressure 10 2.3.5 Wellbore geometry 10 2.3.6 String 14 2.3.7 Mud 16 2.3.8 Temperature 24

2.4 Expert Input Parameters 25 2.4.1 Model parameters 26 2.4.2 Eccentricity 27 2.4.3 Surface pipeline 28 2.4.4 RCH and choke 29

3. CALCULATION AND OUTPUT 30 3.1.1 Hydraulics 30 3.1.2 Surge & swab 31 3.1.3 Sensitivity analysis 33 3.1.4 Bit optimization 34 3.1.5 Volumetric displacement 35

4. MENUS AND TOOLBARS 37 4.1 File 37

4.1.1 New 37 4.1.2 Import 37 4.1.3 Export 38

4.2 View 38 4.2.1 Well schematic 39 4.2.2 39 4.2.3 Log view 40 4.2.4 Navigation bar 41 4.2.5 Input 41 4.2.6 Expert input 41 4.2.7 Simulation 41

4.3 Tools 41 4.3.1 Take snapshot 41 4.3.2 Report 41 4.3.3 Validate parameters 46 4.3.4 Edit unit settings 46 4.3.5 Options 47

Drillbench Hydraulics User Guide Page ii

4.3.6 Export of charts 50 4.3.7 Help 51 4.3.8 About 52

5. Appendix A: Technical documentation 53 5.1 Hydraulics 53

5.1.1 Adjustment of density 53 5.1.2 Adjustment of rheology 53 5.1.3 Input and output 55

5.2 Hole cleaning 55 5.2.1 Moore correlation 55 5.2.2 Zhou model: Horizontal and inclined wellbore 58 5.2.3 Input and output 59

5.3 Surge and swab 60 5.3.1 Input and output 60

5.4 Sensitivity 60 5.4.1 Input and output 60 5.4.2 Bit optimization 60 5.4.3 Maximum bit nozzle velocity 61 5.4.4 Maximum bit hydraulic power 61 5.4.5 Maximum jet impact force 62 5.4.6 Optimization with Hydraulics 63 5.4.7 Input and output 63

6. KEYBOARD SHORTCUTS 64

7. ACKNOWLEDGEMENT 65

8. REFERENCES 66

Drillbench Hydraulics User Guide Page 1

1. INTRODUCTION

Hydraulics is a tool for performing steady state computations of hydraulic

parameters in an oil well during drilling operations. Computations of pressure,

equivalent viscosity, velocity & ECD during drilling are performed in the Hydraulics

mode. In Surge & swab, computations of pressure, ECD, return rate & max string

movement are performed. There are also options for performing Bit optimization,

and computations of Volumetric displacement for a sequence of fluid flows. The

application also includes an easy to use Sensitivity analysis feature.

The Hydraulics user interface consists of 4 main areas; the menu line and the

toolbar at the top of the window, and in the main Hydraulics window there is a

navigation bar to the left and a data entry window to the right, as shown in Figure

1-1.

There are three navigation groups: Input and Expert input for input navigators and

Calculation for calculation & output navigators. The data entry window displays

either input parameters or computed output parameters depending on selected

navigator.

To enter input, choose the input navigators, to compute, choose calculation

navigators.

Figure 1-1: Navigation menu bar and data entry window.

The menu line

A standard menu line with File, Edit, View, Tools and Help entries. File operations,

selecting views and simulation control may be done from here.


The toolbar

Standard commands like File New, File Open, Save, Copy, Cut, Paste and

Undo, are placed in a toolbar for easy access. These commands can also be

accessed by standard Windows keyboard shortcuts (ref. Chapter 6).

Navigation bar

The navigation bar contains:

- Input for specification of the most frequently used input parameters

- Expert input for specification of optional or expert features

- Simulation for calculation and output of results

Data entry window

Displays either input parameters or calculated output parameters depending on the

current selection in the navigation bar.


2. INPUT

2.1 Input parameters

Before computations can be performed, essential input must be entered in the data

entry views, or loaded from an input file. To enter the data, select one of the input

navigators. Input is given in seven data entry views entered by clicking the

corresponding navigators.

2.2 The input file

The input file contains all the data describing the case. However, operational

parameters such as pump rate and ROP must be given directly in the simulation

windows.

A new case can either be created by building a new file or by editing an old file. The

data needed for a simulation may be selected from the library or specified in the

input parameter sheets. Details about the input parameter sheets and the library are

presented in more details in section 2.3.

If you have used older versions of Drillbench, you can open your input files as

normal and you will be notified that your input has been upgraded. Note that this

upgrade is irreversible – files saved from this version cannot be loaded in

older versions of Drillbench.

When using Hydraulics to create an input file, default values are assumed for the

formation parameters and the physical models. The default values are chosen to fit

the "typical case". Select New from the File menu to generate a new input file.

Input files created with other Drillbench applications can also be used in Hydraulics,

since all Drillbench application share the same data model.

2.2.1 Library

Data is entered in the parameter input section. Some of the input data can be

selected from a library.

The library is a tool for reuse of data and it contains information about fluids, pipes,

casings and tools that is likely to be used in many operations. The case specific data

are entered in the parameter input section. This is typically survey data, operational

conditions and temperature data. The entries from the library are selected in the

parameter input sections for “Wellbore geometry”, “String” and “Mud”.

The items/components that can be found and stored in the library are:

Riser

Casing/Liner

String components

Bit


Mud (Drilling fluid)

The find a specific item or component in the library it is set up with an option to filter

out some specific items or components. You can set up several different filters to

make your library search more detailed if preferred. If you choose not to use the

filter option, all items or components in the library will be listed for the specific

category.

If you do not find a suitable item or component in the library, you can specify all the

properties of the item or component manually and then add the item or component

to the library by right-clicking on the name.

Figure 2-1: Library browser for casings.

2.2.2 Range checking

Most input parameters have a defined minimum and maximum value range. If an

entered value is outside its range, Hydraulics highlights the value by setting the

background color of the input field to light red. The valid range is shown in the

status bar at the bottom of the window when pointing the mouse at the invalid field.


2.3 Input navigators and menu bars

The navigation bar to the left of Figure 1-1 is described in the following sections. The

input navigators are summarized below.

Summary A brief summary of the most important input data

Description Information about the present study/case

Formation Defines the formations and geothermal properties

Pore pressure & Fracture pressure

:Defines pore- and fracture pressure with depth

Survey Describes the well trajectory

Wellbore geometry Defines the casing program for the well

String Configuring and defining the drill string and bit

Mud Defines the drilling fluid

Temperature Defines temperatures and temperature model

To add or remove rows in tables, use the following commands:

Ctrl+Ins : add a new row for defining additional casings, while

Ctrl+Del : delete a row

Hints are shown in the status bar at the bottom of the window when pointing the

mouse at tables.

2.3.1 Description

Use the Description window to specify the current case. The input is self-

explanatory and consists of the essential information needed to identify the case.

Use the comment line to distinguish several computations performed for the same

case.


Figure 2-2: Description window.

2.3.2 Formation

The formation input contains all information about the environment where the well is

going to be drilled. Different horizontal layers are defined together with the

properties for each layer.

For offshore wells at least two lithologies are required: seawater and formation. If

more detailed knowledge about the geology and thermophysical properties of the

different geological layers are available, several formation layers with different

properties can be defined.

Seawater specification can also be differentiated. Especially for deep-water wells

this can be of importance. It is possible to select different temperature (geothermal)

gradients at different water depths.

Default values are given for seawater and formation. However, it can be necessary

to change the defaults, since the geothermal gradient is defined as a material

property. It is important to note that even if other properties are the same - if the

geothermal gradient changes a new lithology should be defined.

The window consists of five columns. The first three specifies the name and the top

and bottom depths. Column 4 contains geothermal gradient. Column 5 contains an

option to edit the properties for the different layers. The properties are set with

default values and should only be changed if other values are to be used.


Figure 2-3: Formation input window.

2.3.3 Survey

The input data for the survey are measured depth, inclination and azimuth. The

simulator calculates the true vertical depth (TVD) by using the minimum curvature

algorithm. The angle is given as deviation from the vertical, which means that an

angle of 90 indicates the horizontal. The angle between two points is the average

angle between the points. The simulator handles horizontal wells, but angles higher

than 100 are not recommended. This window is optional and the well is assumed

vertical if no data is entered.

Figure 2-4: Specification of survey data.


The survey data can be entered manually, copied from a spread-sheet or imported

from an existing survey file. Figure 2-4 show the survey data table and a 2D sketch

of the well trajectory.

Inclination data can also be imported from file (Ref.Figure 2-5) by choosing File

Import Survey data or RMSwellplan data.

Figure 2-5: Menu option for survey data import.

The RMSwellplan option opens a File open dialogue window and a *.dwf file can be

selected. The survey data import is different as this option opens a file import

application as shown in Figure 2-6.

The import application is very general and can handle different units, different

column order or delimiter. It can also handle a various number of header or footer

lines.


Figure 2-6: Survey Import window.

The survey profile can be previewed in 3D, by selecting View Survey plot.

Figure 2-7: 3D survey plot.


2.3.4 Pore pressure and Fracture pressure

This optional window defines the pore pressure and the corresponding fracture

pressure for various depths.

Give measured depth and the corresponding pore pressure gradient in the upper

table, and measured depth and corresponding fracture pressure gradient in the

lower table. The corresponding TVD values are displayed for information purposes.

The pore- and fracture pressure gradients are plotted to give a means of graphical

verification of the input.

Figure 2-8: Specification of pore pressure & fracture pressure.

2.3.5 Wellbore geometry

This window defines the casings used throughout the study (see Figure 2-9

Casing types are selected from the Library. Select from the drop down list in the first

column. Once a casing type is selected, the hanger and the setting depth must be

given. A sketch of the casing design is plotted on the right side of the window.


Figure 2-9: Specification of Riser, casing and liner data.

Riser

Figure 2-10: Riser.

The riser is specified by the length (water depth) and the riser type. The list for riser

type refers to entries in the library.


Figure 2-11: Library browser for Casings and Risers.

Casing/Liner

Due to the fact that the temperature model is two-dimensional, it is normal to include

all the casings and the materials surrounding them in the specification of the well. If

the dynamic temperature model is not going to be used, it is enough to specify the

innermost layer of casings and liners, and data in the columns “Hole diameter”, “Top

of cement”, and “Material above cement” will not be used.

Figure 2-12: Casing/Liner.


Each row in the casing and liner window is used for specifying the information

necessary for one casing string.

The first column contains the casing/liner name. This is a drop down button with

reference to the casing and liner library. All the information about dimensions and

properties are taken from the library.

The second column is the hanger depth. It specifies the starting point of the casing.

The hanger depth will often be equal to the water depth. If there are deeper liners,

the hanger depths for these should be specified as well.

The third column is used to specify the setting depth for the casing.

In the fourth and fifth column the inner and outer diameter of the casing is specified

(these values will be taken from the library, but can be manually updated as well).

In the sixth column the hole diameter outside the casing is specified.

In the seventh column the top of cement is specified. The eighth column is

specifying the material above the cement. Note that even if it is cemented to the

seabed, there will be a seawater column on top of the cement.

The last column has an option to manually update some properties of the casing,

including thermophysical properties.

Figure 2-13: Properties of casing.

Open hole

The open hole length and diameter are defined implicitly by the string length and the

bit diameter.


2.3.6 String

You may choose to use tool joints in the calculations. You must then specify an

average stand length in order to let the program calculate the numbers of tool joints.

Figure 2-14: Average stand length and tool joints.

Select components from the library browser to configure the drill string. The

selection is performed from a drop down list in the first column of the table. All

components, including the bottom hole assembly (BHA) are defined from the bit and

upward in this table.

Figure 2-15: String configuration.

It is possible to create items with custom dimensions by modifying diameters of an

already defined item. Note that this is only intended for testing items that are not

defined in the library. To add new items to the library, right click on the component.

It is also possible to edit/view the properties of the different components by clicking

in the last column of the chosen component.


Figure 2-16: Properties for components.

The bit is defined separately. Select the bit from the library browser by picking from

the drop down list. It is possible to edit the bit dimensions and properties. The flow

area through the nozzles is defined either by entering the total flow area (TFA) or by

entering the diameter of each nozzle. To add a newly created bit to the library, click

on the Add to library button.

Figure 2-17: Bit configuration.


2.3.7 Mud

The appropriate drilling fluid is selected from the library from the drop down menu in

the mud window. If the desired drilling fluid is not available in the library, the drilling

fluid has to be properly defined using the input fields for component densities, PVT,

Thermophysical properties and rheology. The newly created drilling fluid can be

added to the library by using the Add to library button in the upper right corner.

Figure 2-18: Mud window.

Component densities

Below the drilling fluid entry, the fluid component densities are displayed.

Unless the fluid density is calculated based on data from a field mud, see Measured

PVT model below, a component density model is used. In this case, the p, T

dependency of each phase will be treated separately, and a resulting density will be

calculated based on the weight fractions of each phase and the density of the mud

at standard conditions.

Base oil density and water density are specified at standard conditions (1 bar,15°C /

14.7 psia and 60 °F).

Solid density is the density of the weight material. A solid density of 4.2 sg is

suggested by default, which corresponds to the density of barite. In these


calculations, the compressibility of solids is assumed to be negligible, an assumption

that in most cases is fairly correct.

Density refers to the density of the whole mud phase and must be specified at the

corresponding reference temperature and atmospheric pressure.

The last parameter to be specified is the mud Oil/water ratio. The ratio is specified

as 'oil volume%/water volume%' (e.g. '80/20').

Figure 2-19: Component densities.

PVT model

Two different PVT models are available, Measured PVT model or a Density

correlations PVT model. The model is selected from the PVT model dropdown list.

Figure 2-20: PVT model.

Measured

The measured PVT model is based on measured fluid and oil density data for

different pressure and temperatures. The measured values can be specified by

clicking on the PVT properties button in the PVT section.


Clicking the properties button opens a sub-window with two tab sheets; one for

density of the whole fluid and one for density of the base oil.

Figure 2-21: Specification of PVT data for measured PVT option.

Both tab sheets contain spreadsheet tables that support copy and paste between

other programs and Drillbench.

Mud density

The table for mud density consists of a spreadsheet component with temperature

data in the first row and pressure in the first column. The densities are filled in for

each pair of pressure and temperature. This table is not needed unless Measured

PVT is chosen as PVT model.


Figure 2-22: PVT-window.

Base oil density

The table for base oil density consists of a spreadsheet component with temperature

data in the first row and pressure in the first column. The densities are filled in for

each pair of pressure and temperature. This table is not needed unless Measured

PVT is chosen as PVT model.


Density correlations

Figure 2-23: Density correlations PVT model.

Oil density submodel

Three models (Sorelle(oil), Glassø, Standing) are available, these are based on

experimental work on different oil samples. There is also a possibility to enter

measurements on the actual fluid.

Standing : The Standing model was originally presented in 1947. The correlations

were formulated based on experimental work on Californian oils, and were

since reformulated in 1974.

Glassø (recommended): The Glassø model is similar to the Standing model, but

it is formulated for North Sea oils. Both the Standing and Glassø models are

valid only for the low to moderate pressure range. Above this, in the high

pressure and temperature range, the Vazques and Beggs model (Reference III)

is used.

Sorelle (oil): The Sorelle model is based on laboratory measurements of diesel

oil. The model is formulated for HPHT conditions.

Table: The table approach uses the PVT properties spreadsheet component, as

described in the section above under Measured PVT model, for entering

experimental data for base oil densities.

Water density submodel

There are three options available: Dodson & Standing, Kemp & Thomas and

Sorelle.

Dodson & Standing (recommended): Dodson and Standing have published a

correlation for compressibility and thermal expansion of pure water.


Kemp & Thomas: The Kemp and Thomas model is formulated for brines. The model

compensates the change of compressibility and thermal expansion of brine due to variations

in the ionic interaction with elevated pressures and temperatures. The brine content in the

mud must be known if this model is selected. A sub-window appears when clicking the Brine

button and the weight fractions of each salt can be specified. The weight fractions are

relative to the whole fluid.

Figure 2-24: Brine data.

Brine data is only relevant if the Kemp & Thomas model is selected as water density

model.

Sorelle (water): Sorelle et. al. also formulated a correlation for the water phase. The

correlation is based on literature data.

Thermophysical properties

The thermophysical properties of the drilling fluid can be edited/viewed by clicking

the Thermophysical properties button.

The data in this sheet is used in the dynamic temperature model.

All the parameters, Specific heat capacity, Thermal conductivity, Density and Static

viscosity, can be given either as a constant value or as a temperature dependent

value. Default values are displayed to the left. These values are automatically

calculated based on entered component densities. Values can be customized by

enabling the checkbox next to a field.


Figure 2-25: Thermophysical properties of drilling fluid.

Rheology

The Rheology model dropdown list is used to specify which correlation should be

used for calculation of rheology data at elevated pressure and temperature. Three

models are available; Power law, Bingham and Robertson-Stiff model. Robertson-

Stiff is the recommended model for most situations.

It is possible to enter pressure and temperature dependent rheology data or the

rheology curve can be given for only one pressure and temperature value.

The data are entered in the shear rate vs. shear stress (Fann reading) table for

selected combinations of pressure and temperature. The rheology table is a

spreadsheet table and it is possible to use copy and paste between other programs

and Drillbench.

If Robertson-Stiff is chosen as rheology model, where applicable, the table should

contain at least three Fann readings.

For Newtonian fluids, the check box must be enabled before the viscosity can be

entered. The pressure loss computations for Newtonian fluids are equal for the

Power law, Bingham and Robertson Stiff models. However, the ordinary variant

uses built in models for pressure and temperature dependency, the extension HPHT

gives the same viscosity at all pressures and temperatures.

Note: The Newtonian viscosity will overwrite the Fann readings in the tables. So if

the user wants to switch between a Newtonian and a non-Newtonian model, two

different fluids should be defined.


Figure 2-26: Rheology input.

Figure 2-27: Fann tables.


2.3.8 Temperature

Figure 2-28: Temperature input window.

Platform

The first item to be selected in the temperature window is the model for the injection

temperature. Platform temperature data is used only when the Dynamic temperature

model is selected. The data specifies how to calculate the surface temperature of

the drilling fluid just before being pumped into the drill string.

If Constant mud injection temperature is selected, the temperature of the mud

pumped into the well will be the same throughout the simulation.

If Constant temperature difference is selected, the mud injection temperature will

always be the given number of degrees below the mud outlet temperature, which is

continuously being calculated, and will thus vary with time.

The third option is Surface temperature model. The user has to specify initial pit

tank temperature and the total volume of the pit tanks that the mud passes through

from the outlet back to the pumps.

Dynamic temperature model/Measured data

The next item to be selected in the temperature window is whether the dynamic

temperature model should be used or not.


The simplest case will be to use Measured data. In this case a temperature profile is

specified for the mud inside drill pipe and annulus. Pairs of measured depth and

temperatures are entered both in the drill string and in the annulus. The number of

pairs may be different for annulus and drill string. The program will interpolate

between the entered points to get the information needed for the calculations. The

first data points in the tables are the mud temperature at surface.

If Dynamic temperature model is selected, the heat transfer and temperature will be

computed dynamically with grid cells generated both in the radial direction and along

the flow line. The dynamic temperature model needs to know if the mud inlet

temperature should be constant, at a constant difference from the mud outlet or if a

surface temperature model should be used to calculate the inlet temperature. The

third options an initial pit temperature is expected and a heat loss constant to define

how fast the mud cools down. This is specified in the upper part of this window.

2.4 Expert Input Parameters

The expert input parameters have been divided into four main groups.

Model parameters

Number of grid points

Eccentricity Eccentricity of the drill string

Surface pipeline Pressure loss in surface equipment

RCH and choke Specifications for RCH and choke


2.4.1 Model parameters

Figure 2-29: Model parameters window.

Number of Grid cells

In this tab sheet the user specifies the number of grid cells used to create the

underlying mathematical model. Increasing the number of grid cells will increase the

accuracy of the simulation, but at the cost of the computation time. The computation

time will at best increase linearly with respect to the grid cells. To avoid the

simulation from becoming too time-consuming it is recommended to set this

parameter around 50. Maximum number of cells is 2000.


2.4.2 Eccentricity

Figure 2-30: Eccentricity window.

If “maximum eccentricity in deviated sections” is selected from the drop-down menu,

the program will use maximum eccentricity above a given deviation, concentric drill

string in vertical section, and smooth transition in between. Tool joints are taken into

account if used (see the “String” window).

Eccentricity of the drill string versus depth can be entered in this sheet. The default

value is 0, i.e. drill string is taken to be concentric if the table is empty. Each line

gives eccentricity from the specified depth and downwards. Eccentricity is zero

above the first depth.

The sum of standoff and eccentricity is by definition always 100 %.


2.4.3 Surface pipeline

If there is a considerable loss of pressure in the surface piping between the pump

and the wellhead, the surface pressure loss should be entered in this window. A

linear interpolation will be used between the reading points, and a graphical

verification of the surface pressure loss is plotted. The simulator assumes a linear

interpolation from no pressure loss at zero flow rate up to the lowest flow rate entry,

and a constant pressure loss at all rates above the maximum flow rate entry.

Figure 2-31: Surface pipeline window.

Note: The flow rate table must be given in increasing order.


2.4.4 RCH and choke

Figure 2-32: RCH and choke window.

Choke

If you are using a rotating control head (RCH), enable it in this window and specify

information for the choke. The inner diameter of the choke must be given. The

simulator automatically adds a surface pipe length to the system.

The user may control the well pressure in a dynamic simulation by modifying the

well head pressure. In the choke input window the user specifies how to operate the

choke by selecting either Pressure, Opening or Automatic from the Choke control

drop down list. If Automatic choke control is selected, you also have to specify a

constant bottomhole ECD.

Separator

A separator working pressure has to be set if “Use RCH” is enabled.


3. CALCULATION AND OUTPUT

A variety of calculations can be performed with Hydraulics. Like the input window,

the calculation window is divided into two: a navigation menu bar to the left and data

entry with graphical display of the calculated results to the right, see Figure 3-2:.

The user chooses a type of calculation by selecting one of the Calculation

navigators on the left side of Figure 3-2:. The calculation navigators are summarized

below:

Hydraulics Determine hydraulic behavior during drilling

Surge & swab Calculate the tripping limitations

Sensitivity analysis Vary one parameter sequentially to study its sensitivity

Bit optimization Optimize bit nozzle size (TFA)

Volumetric displacement

Calculate fluid front position and total volume pumped

All calculations are displayed in plots. All plots can be edited by pressing the right

mouse button in the plot and selecting Plot properties. To print the plot or change

its appearance, use the plot properties dialog, shown in the Figure below.

Figure 3-1: The plot properties dialog.

3.1.1 Hydraulics

The Hydraulics calculation window is shown in Figure 3-2:. Before performing

calculations, some operational parameters must be entered.

The cuttings transport model has two options: No slip and Slip. If No slip is chosen,

the cuttings are transported at the same velocity as the drilling mud (i.e. perfect hole

cleaning). If Slip is chosen, the cuttings diameter and either minimum relative

cuttings velocity or maximum cuttings concentration must be provided, and

Hydraulics will compute the minimum velocity needed to transport the cuttings out of


the well. For section with inclinations of 30 deg or more the Zhou model [4] is used

to predict the critical flow rate for hole cleaning. The Zhou model is show as

separate curve along with the Moore correlation model.

Figure 3-2: Simulation - Hydraulics.

The results from the calculations are shown in plots of the following parameters, all

plotted versus depth:

ECD (Equivalent circulation density)

Pressure

Temperature

Equivalent viscosity

Velocity

Cuttings (velocity/transport ratio)

Critical flow rate (hole cleaning, Moore and Zhou model)

The casing shoe position is indicated on all plots by a dashed line.

3.1.2 Surge & swab

The surge & swab calculations are used to calculate the tripping limitations. It

includes three calculation modes: fixed pipe velocity, maximum surge velocity, and

maximum swab velocity. The results from the computations are shown in plots of the

following parameters, all plotted versus bit depth:

Maximum string velocity

Return flow rate

Pressure



The fixed pipe velocity mode is used to compute the well pressures at a known

tripping rate. The maximum surge/swab velocity modes are used to find the

maximum tripping speed that can be used without exceeding the pore- and fracture

pressure limitations.

Not all of the control parameters are needed in the various modes. The currently

superfluous parameters are disabled accordingly. Pump rate is used only if pump

connected is chosen in the top status entry. Drill string velocity is used only if fixed

pipe velocity is chosen as calculation mode. Safety margin is used only if max

surge/swab velocity is chosen as calculation mode.

Figure 3-3: Calculation - Surge & swab, calculate tripping limitations.

The safety margin defines how close to the pore pressure the well pressure is

allowed to decrease during swab, or how close to the fracture pressure the well

pressure is allowed to rise during surge. The factor refers to no surge swab pressure

- for swabbing, the pressure at TD is used as reference and for surge, the pressure

at the shoe is used as reference.

Example: We wish to compute the pressure while swabbing from 2000m MD to 1000m MD with safety margin 0.25. The pore pressure at TD is 350 bar, while the static well pressure at TD is 390 bar, giving a pressure difference of 40 bar. In this case, Hydraulics will compute the tripping velocity that gives 350+(40x0.25) =360 bar well pressure at TD.


If the lowermost drill string end is closed, choose Float in the float status entry. If it

is open, choose No float.

In the case of swabbing, calculations start with the bit at lower bit depth. The bit is

moved upwards in steps according to the entry in number of steps, ending at the

upper bit depth. One steady state computation is performed at each bit depth. Upper

and lower bit depths are both included in the number of steps. For surge the

computations are similar, with the upper bit depth as the starting point. Maximum

string velocity and return flow rate is plotted vs. bit depth. Pressure in annulus and

ECD is plotted vs. well depth. The bit is assumed to be positioned at the lowermost

depth.

Note: The pipe velocity is defined as positive into the well and negative out of the

well, hence:

Surge positive velocity

Swab negative velocity

3.1.3 Sensitivity analysis

In Sensitivity analysis, several hydraulic computations are performed with one input

parameter automatically altered between each computation. The Sensitivity analysis

window is shown in

The results are available in the following plots:


Pressure,

Equivalent viscosity,


Velocity

ECD at casing shoe and bottom hole, and

Pressure at casing shoe and bottom hole

Before the computations are performed, you must choose the varying parameter.

The selection is performed from the drop-down menu in the X-axis parameter entry.

In addition to the parameter interval between each computation, an upper and lower

boundary must be entered.

Figure 3-4: Calculation – Sensitivity analysis.

The following input parameters are available as varying parameter (X):

Pump rate

Rotation velocity

Density

Plastic viscosity

Yield point

3.1.4 Bit optimization

The Bit optimization module is used to find optimal bit nozzle size (TFA) and pump

rate as function of bit depth. The Bit optimization window is shown in Figure. The

results are available in the following plots:

Optimal bit area, and


Optimal pump rate

Figure 3-5: Calculation – Bit optimization.

It is assumed that the drilling is most efficient at the optimal flow area and flow rate.

Optimal bit nozzle size and flow rate are plotted versus bit depth. There are two

ways of optimizing these parameters. You can either optimize by calculating the

maximum bit hydraulic horsepower, or by calculating the maximum jet impact force.

The jet impact force will be within 90% of its maximum when bit power is at its

maximum, and vice versa. Thus the difference between these two models is

marginal.

To find the optimal bit nozzle area and pump rate, the maximum pump pressure and

pump power outlet must be provided.

One steady state computation is performed at each bit depth according to

upper/lower bit depth and number of depths (including the boundaries). Remember

that the higher the numbers of depths, the longer the computations take.

3.1.5 Volumetric displacement

The volumetric displacement module is used to determine the fluid front positions in

the well and the total pumped volume during a sequence of fluid flow, see Figure

3-6. The fluids that are to be pumped are chosen from the drop down menus in the

first column in the table. If the fluids are not available the database must be updated

using Drillbench (see Appendix B).


Figure 3-6: Calculation – Volumetric displacement.

Enter the pump rate and the volume of each fluid. The time period in the fourth

column is computed automatically. The density in the fifth column is loaded from the

database and may be altered by the user.

Start the sequence of fluid flow by pressing the Start button. The simulation can be

paused at any time.

Fluid front positions and pumped volume are plotted vs. time. The fluid in the first

line of the table is assumed to fill the well at simulation start-up. Thus this fluid will

not appear in the fluid front plot.


4. MENUS AND TOOLBARS

Menus and toolbar icons have standard Windows functionality. We assume that

Hydraulics users are familiar with Windows operations, and will only describe the

menu and toolbar functions specially designed for Hydraulics.

4.1 File

4.1.1 New

Use New in the File menu to create an input file from scratch. This dialog offers

choices of starting with a blank file or with predefined templates. The template path

is configured in the option dialog.

Figure 4-1: New file dialog.

4.1.2 Import

Use Import to import either a survey file on ASCII format or survey data from the

RMSwellplan application. When selecting the appropriate survey data file the survey

data import dialog appears. Select the appropriate column delimiter, the units used

in the survey file and the number of header/footer lines to be skipped.


Figure 4-2: Survey data input from a text file.

The survey file must be in ASCII format with columns for measured depth,

inclination and azimuth. By default, the program assumes measured depth in the

first column, inclination in the second column and azimuth in the third column. If this

is not the case, the column headers can be rearranged by drag and drop: Press the

left mouse button on the column header, drag to the correct position and release the

mouse button.

4.1.3 Export

Use Export to save the survey data in the RMSwellplan (*.dwf) file format.

4.2 View

Used to switch between Input and Calculation on the Navigation bar, see Figure 4-3.

The navigation bar and log view can be displayed and hidden by checking their tag

in the menu.


Figure 4-3: Switching between Input and Calculation navigators by the menu bar.

4.2.1 Well schematic

A schematic plot that includes the riser, seabed, casing/liner program, open hole

and the drill string is shown by selecting View Well schematic or by toggling the

well schematic button in tool bar. A visual inspection of the well can reveal errors in

the input data. The well schematic has a view properties window to toggle items and

labels to be drawn, which can be opened from the popup menu item Properties… .

Figure 4-4: Well schematic view.

4.2.2

To view a three-dimensional representation of the survey, select View Survey

plot. The default view is in front of the XY-plane. To rotate the view around the well,

move the mouse in the direction of desired rotation while pressing the left mouse

button. To zoom in, move the mouse up while pressing the right mouse button. To

zoom out, move the mouse down while pressing the right mouse button. To move

the figure, move the mouse while pressing the left mouse button and the shift key.

There is a menu line in the survey plot with a File and a View menu. To reset the

view, select View Reset camera from the plot’s menu line. The plot can be saved

in a variety of formats by selecting File Save As… from the plot’s menu line.


Figure 4-5: 3D-survey plot view.

4.2.3 Log view

By default, the log view is located in the lower part of the main window. It displays

errors, warnings and information messages concerning input data and

calculations. Use the check box on the View Log View menu to display or hide

the log. Double-clicking an error or warning leads the user to the input page that

caused the problem. Clicking the right mouse button over the log displays a menu

offering the following commands:

Clear messages

This command empties the log.

Save messages

This command lets you save the log contents to a text file for later review.

Show timestamp


This check box toggles the use of timestamps for the lines in the log. This feature

can be used to distinguish messages from various runs and can be helpful when the

content of the log is saved to a file.

4.2.4 Navigation bar

Toggle the navigation bar on/off. Hiding the navigation bar can be useful to make

more room for the main input or simulation window. The state of this selection is

saved between sessions.

4.2.5 Input

Switch to an Input window.

4.2.6 Expert input

Switch to an Expert input window.

4.2.7 Simulation

Switch to a Simulation window.

4.3 Tools

In the Tools menu, the user can access an input and output reports. The Tools

menu is also where the user provides various paths to databases and defines

measurement unit preferences.

4.3.1 Take snapshot

The snapshot feature places a snapshot of the active plot window on the Clipboard,

which can then be pasted into reports or presentations. Combined with customized

plot layouts this is a very useful tool for presentation of simulation results.

4.3.2 Report

4.3.2.1 Input report

The input report contains all input information within an easy-to-read and useful

report. It is listed on the Tools menu on the main bar in Hydraulics; see Figure 4-6.


Figure 4-6: The Tools menu – Input report.

The report is in HTML format and uses standard HTML style sheets (CSS) to define

the visual layout. This makes it easy to customize the format (fonts, colors etc.).

Hydraulics provides a default style sheet (ircss.css) which can be edited or replaced

to match the user preferred report style. Figure 4-7 shows the layout used in

Hydraulics.

Figure 4-7: Layout of the Input report.

The format of the report makes it easy to export data to other applications as

Microsoft Excel etc. The file can be opened by Excel directly, or the tables can be

copied from the input report to an Excel-sheet by standard copy and paste.

However, if you are using Internet Explorer to view the input report, a far simpler

way is included in this version. The data can be exported directly to an Excel sheet

by a right-click on the table and then select Export to Microsoft Excel, see Figure

4-8. Then an Excel-sheet is opened containing the data in the selected table from

the input report.


Figure 4-8: Export of Survey data from the input report to Excel.

4.3.2.2 Input report

The most important input parameters in the currently selected input file are

displayed and can be printed from the input summary report. The contents of the

input report are fixed, and are shown in the figure below.

Well trajectory, pore pressure and fracture pressure gradients as well as casing

program are presented in plots. Drill fluid properties, drill string elements and bit

dimensions are given in tables. The case description is found in the header section.

Use the toolbar on the top of the Input report window for accessing functionality for

page setup, printing, saving and loading of input reports.


Figure 4-9: Input data to Hydraulics.

4.3.2.3 Current results

The current results report includes a summary of the key information for the case

and a copy of all the available plots.


Figure 4-10: Current results report.


4.3.2.4 Hydraulics system report

Hydraulics also has a system report as shown in Figure 4-11. The system report list

the operational data and then hydraulic parameters as velocity, Reynolds number,

Flow regime, ECD and pressure loss in each section. It also includes summary

pressure losses over typical parts of the well, pump pressure and ECD at important

positions.

Figure 4-11: Hydraulics system report.

4.3.3 Validate parameters

This command validates the input data and reports errors and warnings in the log

view. If the message relates to an input parameter, double click the message to

access the page in question. It can be started either by pressing:

on the toolbar or by selecting Tools Validate parameters from the menu

bar.

4.3.4 Edit unit settings

To edit the unit setting, you can select Tools Edit unit setting from the menu bar,

or click on the unit name in the status bar to pop up the unit menu.


Figure 4-12: Unit menu.

The unit menu is allows quick change of unit sets and access to the unit edit page.

4.3.5 Options

To open the options tab window, you can select it from the menu bar or by clicking

on on the toolbar.

This is a dialog that controls the Drillbench program settings. This window is divided

in 3 sheets: General, Appearance and Unit definitions, which are described below.

4.3.5.1 General

Figure 4-13: Location of the databases used in Hydraulics.

Library path

Fluids, casings and string components are selected from a library. The location of

the library file is entered in this field. The library selected here is shared among all


Drillbench applications. Use the arrow in the right corner of the field to select from a

list of previous paths.

Template path

Path to Drillbench default template files.

At program startup

Reload last used file resumes the session you were working on when exiting

Presmod the last time.

Remember last selected page

Start at the page you were on when exiting Hydraulic the last time.

View

Option to control if log window should open automatically when new messages are

produced by Drillbench. Default is to automatically open log.

Input file

Show input read diagnostics

This is an option to enable diagnostic messages when loading an input file. This

should normally not be used. It is only to be used when having trouble loading an

input file. You may be asked by Drillbench support to turn this option on.

4.3.5.2 Appearance

Allow the user to modify color theme, icon style and tab layout in Presmod according

to personal preference.


Figure 4-14: Hydraulics mud window with different color settings.

4.3.5.3 Unit definitions

The unit settings can be changed by selecting the Unit definitions tab found under

Tools Options in the menu bar, see Figure 4-15. Each unit is defined separately

and saved in a specified unit file. However, predefined sets of units can be selected

from the drop down menu. By default, SI units, metric (European) units and field

units are available. You can create your own set of units by selecting the preferred

units and save to file with a new name.


Figure 4-15: Definition of units.

4.3.6 Export of charts

Charts can be exported as Vector Markup Language (VML) files. VML is an

application of Extensible Markup Language (XML) 1.0 which defines a format for the

encoding of vector information together with additional markup to describe how that

information may be displayed and edited.

Right click on the chart of interest, and select Export as shown in Figure 4-17


Figure 4-16: Export-command by right-click on the chart.

When selecting Export, the window Figure 4-17 in Here you can select in which

format the figure should be saved. Save the chart with an appropriate name.

Figure 4-17: Export-command by right-click on the chart.

4.3.7 Help

To open the Help window in Hydraulics you can select it from Help Help topics or

you can open it by pressing F1.

The Help window will give you a short description and explanation of all the different

windows in Hydraulics.

When pressing F1 from an input window, the help page for the current window will

be displayed.


4.3.8 About

The Help About option gives you information about Hydraulics version number

and the expiry date of the current license.

Figure 4-18: The About window in Hydraulics.


5. Appendix A: Technical documentation

Hydraulics is an advanced steady state hydraulics calculator, which uses very

complex models to obtain accurate and reliable results. It is a standalone application

from the software Presmod under the Drillbench® software suite [1].

Hydraulics has a number of features in addition to those found in the steady state

part of Presmod. These are summarized below, and this section further describes

the new features utilized in Hydraulics, that is not present in Presmod.

Automatic bit optimization, i.e. find maximum bit hydraulic power or jet impact force when pump pressure is fixed and pump power is restricted to be below a maximum value.

Calculate cutting slip and its effect on bottom whole pressure.

Sensitivity analysis versus a number of different parameters.

Automatic adjustment of rheology when both laboratory and field data are available.

Repeat automatically bit optimization and surge/swab calculations for a number of different bit depths within a specified range.

Include contribution to surge and swab pressures from acceleration of drilling fluid.

5.1 Hydraulics

A complex and accurate fluid description can be given in the Drillbench database.

Drillbench must be used to enter or modify the database (See Appendix B), but data

can be imported into Hydraulics directly from the database.

Database descriptions of fluids must be modified to match Hydraulics input. With the

procedure given below, information from the database on pressure and temperature

dependence of density and rheology are fully exploited, also when Hydraulics input

data does not match database data.

ROP will be taken into account through modified density and annular flow rates.

5.1.1 Adjustment of density

Use the algorithm that is used for altering inlet density during a dynamic simulation,

and fill the well with the modified fluid.

5.1.2 Adjustment of rheology

Plastic viscosity p and yield point y are calculated using FANN readings at the

two highest shear rates, which are normally at FANN rotation rates 300 and 600

RPM. A standard FANN viscometer is tuned such that


300600 p B1

PY 300 B2

with plastic viscosity is in Cp and yield in lbm/100ft2. Note that elsewhere in this

document, SI units are used throughout.

In Hydraulics, fluid rheology can be defined in several ways:

1. Rheology data at many different pressures and temperatures can be entered in the Drillbench database. Drillbench is required to enter or modify data, but fluid data can be imported into Hydraulics directly from the database without starting Drillbench.

2. p ,

y , and 3 RPM reading at standard conditions can be specified under

“Input - Drilling fluid” in Hydraulics.

3. FANN data at standard conditions can be entered under “Input - Drilling fluid” in Hydraulics.

4. p and y in each of the calculation windows.

The following rules are used to combine the different kinds of input data:

1. p and y specified in the current calculation windows, overrides p and

y

data under “Input - Drilling fluid”.

2. If specified p and y does not match database rheology data at lowest

pressure and temperature, database rheology data at lowest pressure and temperature are modified to match specified p and

y , and database

rheology data at other pressures and temperatures are modified accordingly.

3. If p , y and 3 RPM reading are specified under “Input - Drilling fluid”,

database rheology data at the lowest pressure and temperature are replaced by data at 600, 300 RPM that corresponds to the specified p and

y , in

addition to the specified 3 RPM reading. Modifications under point 2 are always carried out before point 3.

4. If rheology data at standard conditions are specified under “Input - Drilling fluid”, database rheology data are first modified to match p and y (see point

2), then database data at the lowest pressure and temperature are replaced by the rheology data given under “Input - Drilling fluid”.

An advantage of scaling rheology data rather than making calculations with the Bingham model when p and y are specified is that deviations from the Bingham

model in the rheology data are maintained. Data is just scaled such that best fit

values of Bingham parameters get the desired values. Another advantage is that results with unmodified rheology are maintained if the changed p and y are the

same as the best fit values at standard conditions.


5.1.3 Input and output

For input flow rates, RPM, ROP, density, p ,

y , 3RPM, etc., plot a number of

interesting parameters versus depth, down to bit depth, which is fixed.

5.2 Hole cleaning

The following theory is based on Section 4.16 “Particle slip velocity” in Ref. [2]

Define particle Reynolds number by

a

sslf dvN

Re B3

and friction factor by

KAE

Ff B4

here F is viscous drag force, A is characteristic area, and KE is kinetic energy per

unit volume, given by

2

21

slfK vE B5

For calculation of terminal velocity, set

sfsbo gVFWF B6

where W is particle weight, boF is buoyant force, and sV is particle volume. If A for a

perfect sphere is used,

f

fsssl

f

dgv

3

4 B7

For Reynolds numbers below 0.1, the Stokes law give acceptable accuracy. Stokes

law is obtained by using

Re

24

Nf B8

Expressions for apparent viscosity and friction factor are given by correlations. Ref.

[2] gives three commonly used correlations, and find that the Moore correlation is

the one that matches published data best.

5.2.1 Moore correlation

Formula 4.107 in Ref. [2] (see also Ref. [3]) reads

n

n

n

av

ddK

0208.0

2

144

11

12 B9


where v is average fluid velocity. In consistent units the formula is:

nn

an

n

dd

vK

3

12121

12

B10

An alternative expression is given by Reed and Pilehvari, and is equivalent to the

above formula with the power of the rightmost factor reduced from n to n-1:

1

8

n

eff

aD

vK B11

with

12

332

n

nDDD ioeff B12

According to Moors correlation, friction factor is essentially constant at

approximately 1.5 for Reynolds numbers above 300.

2Re,Re

2Re,Re1Re,

Re

1Re,Re

Re

,5.1

,22

,40

NN

NNNN

NNN

f B13

Ref. [2] uses 300 and 3 2Re,1Re, NN , which can be modified to avoid

discontinuities without altering the friction factor very much. Accordingly we will use

3058.320

402

1Re,

N B14

and

11.2155.1

222

2Re,

N B15

Reynolds vs. friction factor with the new transition Reynolds numbers is plotted in

Figure 5-1.


Figure 5-1: Particle friction factor vs. Reynolds number according to the Moore

correlation.

From this basis the particle Reynolds number, slip velocity, and friction factor can be

calculated. Friction factor and particle Reynolds number can be eliminated to obtain

an explicit formula for slv within each of the three flow regimes. The expressions are

2Re,Re

2Re,Re1Re,

3

122

3

2

1Re,Re

2

9

8

,33

2

,30

1

NNgd

NNNdg

NNgd

v

f

fs

s

s

fa

fs

a

fss

sl

B16

The following calculation procedure is used:

a) Calculate slv and ReN assuming transitional regime ( 2Re,Re1Re, NNN ), and

determine flow regime.

b) If 1Re,Re NN or 2Re,Re NN , redo calculation of slv and ReN using the

corresponding expression in Eq. 3.13.

It can be shown mathematically that the Reynolds number calculated under b) is

consistent with the flow regime determined under a).

10-1

100

101

102

103

100

101

102

103

Particle Reynolds number

Friction facto

r

Friction factor, Moore correlation

f N

Re,1

NRe,2


5.2.2 Zhou model: Horizontal and inclined wellbore

For section with inclinations of 30 deg or more the Zhou model [4] is used to predict

the critical flow rate for hole cleaning. The model prediction versus available

experimental reports has been compared and showed good agreement.

The volume of cuttings accumulated in the annulus is very sensitive to the

liquid flow rate;

Injection of gas has positive effect on high viscosity fluid and the effect is

less when the fluid has lower viscosity.

High gas-liquid ratio has positive effects on cuttings transport for a given

liquid flow rate;

Increase of hole angle (from vertical) results in great increase of required

mud velocity; 60 to 0 deg from vertical is the most difficult angle to clean;

Small size cutting are easier to be transported with high viscosity fluid

compare to lager cuttings; and it becomes much more difficult when the size

down to 0.5mm;

Increase mud weight will help hole cleaning;

The effect of pressure on cuttings concentration is related to gas in-situ

volume, high pressure will cause a decrease of cuttings transport.


Figure 5-2: Hydraulics – Critical flow rate.


A new input parameter is particle size, sd . Cuttings density can be taken from input

to the temperature model.

Possible output parameters are slip velocity, cuttings transport ratio, volume fraction

of cuttings. These may be plotted versus depth with bit depth fixed. Alternatively,

worst values along the annulus may be plotted versus bit depth. Results may also

be applied for other hydraulic calculations.

Cuttings transport ratio is defined by

v

v

v

vF slT

T 1 B17

which is unity if cuttings move with same average velocity as mud, and zero if

cuttings do not move relative to the well. Volume fraction of cuttings is

mTs

ss

qFq

qf

B18


where sq and mq are volume flow rate of cuttings and mud. Assuming cuttings size

is larger than size of individual grains, cuttings rate is

dt

dDAb

B19

where bA is area cut by the bit.

Suggested definition of acceptable cuttings transport: 1.0TF

5.3 Surge and swab

New features relative to Presmod surge and swab are:

A loop over bit depths in a given range. New grid is generated for each bit depth.

Acceleration pressure. Acceleration pressure will be calculated assuming incompressible fluids (an advanced dynamic simulation would be required to take compression properly into account), and added to frictional effects.


Two options:

1. Maximum string velocity (surge or swab) as a function of bit depth (within a given range), with pressure staying inside the pore-fracture pressure window. Expected to be relatively time consuming.

2. Pressure at bit as a function of bit depth using specified drill string velocity.

Mud column below bit only contributes to dynamic effects, which are not taken into

account.

5.4 Sensitivity

Parameters like density, plastic viscosity ( p ), yield stress ( y ), flow rate and

rotational rate, can be used for sensitivity studies.


The sensitivity analysis will produce plots of pressure and ECD at bottom, casing shoe, and observation points versus flow rate, RPM, density, p , and y . Bit depth

is fixed.

5.4.2 Bit optimization

The following theory is based on Section 4.13 “Jet Bit Nozzle Size Selection” in Ref.

[2].

Most commonly used hydraulic design parameters are


t nozzle velocity

bit hydraulic horsepower

jet impact force

Pump pressure, which must be kept at or below its maximum value, can be written

as

dbp ppp B20

where the first right hand side term is bit pressure loss and the second is the sum of

all other pressure effects including frictional pressure loss, pressure loss across

area changes, acceleration effects, and u-tube effects. The contribution from

turbulent frictional pressure loss inside the drill string is normally dominant. The

following simplified model is used below to demonstrate important effects:

m

d cqp B21

where c and m are constants with m typically close to 1.75. With realistic drilling

fluids, c and m are not constants, but depend on pressure, temperature, and shear

rate. Shear rate depends on both flow rate and diameters.

Using the simplified model, Ref. [2] states that when hydraulic horsepower is at its

maximum, bit hydraulic horsepower will be within 90% of it maximum and vice

versa.

5.4.3 Maximum bit nozzle velocity

Pressure loss across bit is

2

2

d

nb

C

vp

B22

which can be inverted to get bit velocity as

b

dn

pCv

B23

If mud density is fixed, bit pressure loss must be increased as much as possible to

obtain maximum velocity. This is obtained by reducing mud flow rate to the minimum

rate that ensures good hole cleaning, and then reduce nozzle diameters as far as

possible without exceeding pump pressure.

Hence, maximum nozzle velocity without exceeding maximum pump pressure is

obtained when flow rate is at a minimum.

5.4.4 Maximum bit hydraulic power

Bit hydraulic power is given by

qpP bHb B24


Also here, bit pressure loss bp can be increased by reducing flow rate and

decreasing nozzle diameters as far as possible without exceeding maximum pump

pressure. More detailed hydraulic calculations are required to determine whether the

product of bit pressure loss and flow rate increases or decreases as flow rate

increases. Bit hydraulic power will always have a maximum at some flow rate since

it tends to zero when flow rate approaches zero (bit pressure loss cannot exceed

maximum pump pressure plus u-tube effects), and it tends to zero as flow rate is

increased towards the rate where pd pp .

The maximum bit hydraulic power is obtained by maximizing the right hand side of

qppqpP dpbHb B25

with pp fixed at its maximum pump pressure.

By simplification,

1

m

pp

p

d B26

is obtained by setting the derivative of HbP with respect to q equal to zero. With

m=1.75, the simplified model predicts that maximum bit hydraulic power is obtained

when bit pressure loss is 63.6 % of pump pressure.

For a more general result, hydraulic power is represented by the function

)(qqfPHb B27

which gives

0)()( qfqqfdq

dPHb B28

5.4.5 Maximum jet impact force

Jet impact force is given by

bdnj pqCvqv

t

m

t

mvF

B29

It can be shown that the bit Reynolds number

a

nn

bit

dvRe

B30

where the index n refers to nozzles, is maximized when jet impact force is

maximized. Some experiments find that penetration rate is proportional to bit

Reynolds number raised to a constant power.

The simplified model for dp predicts maximum jet impact force when


2

2

m

pp

p

d B31

With m=1.75, the simplified model predicts that maximum jet impact force is

obtained when bit pressure loss is 46.7 % of pump pressure.

5.4.6 Optimization with Hydraulics

Use built in pressure models to optimize bit hydraulic power or jet impact force with

the following constraints:

(1) Pump pressure below maximum

(2) Stay at flow rates low enough to allow pumping at maximum pump pressure without exceeding maximum pump power outlet.

(3) Flow rate high enough to ensure satisfactorily cuttings transport.

This procedure has advantages over the formalism used in Ref. [2]:

Frictional pressure loss and pressure losses across area changes are calculated using pressure and temperature dependent rheology and density, with a three-parameter rheology model. The parameter m, which is constant in Ref. [2], becomes a function of pressure, temperature, and shear rate.

Differences in hydrostatic pressure inside and outside drill string are taken into account.


New input parameters are:

maximum pump pressure,

pump power outlet,

parameter selection (maximum bit hydraulic horsepower or maximum jet impact force).

Minimum flow rate for good cuttings transport can either be calculated, be an

additional input parameter, or set to zero.

Possible output parameters are nozzle area, flow rate, and bit pressure loss, and

pressure loss in the rest of the system with optimal nozzle area and flow rate. These

may be reported at the bit depth specified in the input file, or plotted versus bit depth

throughout the current open hole section. In the latter case, beginning and end of

open hole section must be specified somehow (may also be used for e.g. surge

swab calculations).


6. KEYBOARD SHORTCUTS

Alt+F open File menu Alt+E open Edit menu Alt+V open View menu Alt+S open Simulation menu Alt+T open Tools menu Alt+H open Help menu Ctrl+N New file Ctrl+O Open Ctrl+S Save Ctrl+C Copy Ctrl+X Cut Ctrl+V Paste Alt+BkSp Undo Ctrl+Ins Insert rows in a table Ctrl+Del Delete rows in a table F9 Start F8 Step Ctrl+F2 Reset Ctrl+F12 Take snapshot Ctrl+U Edit unit settings


7. ACKNOWLEDGEMENT

Drillbench uses the following third-party tools:

JEDI Visual Component Library (JVCL) JVCL portions are licensed from Project JEDI, and the source code can be obtained from http://jvcl.sourceforge.net/

JEDI CODE LIBRARY (JCL) JCL portions are licensed from Project JEDI, and the source code can be obtained from http://homepages.borland.com/jedi/jcl/

The Visualization ToolKit (VTK) VTK is copyright © 1993-2004 Ken Martin, Will Schroeder, Bill Lorensen All rights reserved. VTK is available from http://www.vtk.org/

Nullsoft Scriptable Install System (NSIS) NSIS is copyright (C) 1999-2006 Nullsoft, Inc. and is available from http://nsis.sourceforge.net/

TeeChart TeeChart is copyright © David Berneda 1995-2006. All Rights Reserved. http://www.steema.com/

LiquidXML LiquidXML is copyright ©2006 Liquid Technologies Limited. All rights reserved. http://www.liquid-technologies.com/

FLEXlm FLEXlm is copyright ©2002-2006 Macrovision Corporation. All rights reserved. http://www.macrovision.com/

TMS Component Pack TMS Component Pack is copyright © 2001-2009 by tmssoftware.com. All rights reserved

http://jvcl.sourceforge.net/

http://homepages.borland.com/jedi/jcl/

http://www.vtk.org/

http://nsis.sourceforge.net/

http://www.steema.com/

http://www.liquid-technologies.com/

http://www.macrovision.com/


8. REFERENCES

[1] Drillbench Presmod documentation.

[2] A. T. Bourgoyne Jr., K. K. Millheim, M. E. Chenevert, F. S. Young Jr.; "Applied Drilling

Hydraulics", First printing, Society of Petroleum Engineers, 1986.

[3] P. L. Moore: "Drilling Practices Manual", The Petroleum Publishing Co., Tulsa, 1974.

[4] L. Zhou: “Hole Cleaning During UBD in Horizontal and Inclined Wellbore”, IADC/SPE

Drilling Conference, Miami, 2006.

Documents

Drill Bench Hydraulics User Guide