Coring & Coring Analysis 2

SORAN UNIVERSTYSCHOOL OF ENGINEERING

FACULTY OF PETROLEUM ENGINEERING

CORING AND CORING ANALYSIS

DRILLING ENGINEERING I (PENG 313)

Prepared by: Reband Azad Raza

Supervised by: Mr. Jagar Ali

Date: 11/15/2015

DRILLING ENGINEERING I (PENG 313)CORING AND CORING ANALYSIS

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Table of ContentsCORING AND CORE ANALYSIS......................................................................................................................3

CORING:.......................................................................................................................................................3

Introduction:...............................................................................................................................................4

TYPES OF CORING:.......................................................................................................................................5

CONVENTIONAL CORING:............................................................................................................................5

SIDEWALL CORING: (SWCs).........................................................................................................................7

Percussion coring:.......................................................................................................................................8

Rotary coring:..............................................................................................................................................9

CORING PROCEDURES:..............................................................................................................................10

CORING ANALYSIS......................................................................................................................................12

Porosity:....................................................................................................................................................12

Absolute porosity:.....................................................................................................................................13

Permeability:.............................................................................................................................................15

The wettability:..........................................................................................................................................17

Abstract: This report will present a brief description about coring and coring Analysis and the

techniques and the types of coring and their procedures.


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CORING AND CORE ANALYSIS

CORING:

Definition: core is sample of cylindrical section of underground formation; most core samples

are obtained by drilling with special drills into the substance, for example sediment or rock, with

a hollow steel tube called a core drill. The hole made for the core sample is called the "core

hole". Many of different coring techniques for many type of Medias under different conditions.

In the process of coring, tube of coring is pushed into the formation by more or less based on

hard of formation. The tube removed in the laboratory, it is checked and analyzed by different

ways of technique and equipment depending on the data requested.

Figure 1.1: coring samples

(Abhishek and Larissa, September 2014)


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Introduction:

Main reason for coring is to achieve geological information, in the oil company the geology

section department they will achieve data based on the test’s they want practice on the core

sample. As a result, coring will processed for a many of reasons. Because of large size of the

sample, many type of data will obtain, the followings are some data achieved by core sample:

• Porosity – the capable of pores to holding fluids.

• Permeability –it’s a linked connection between pores in porous media.

• Saturation – the occupied space in the pores by formation fluids.

Of a secondary importance is the additional information relating to formation boundaries, large

scale sedimentary structures, undisturbed paleontological data, and the opportunity for

uncontaminated geochemical sampling.

Most of the basics behind coring operations is presented in the Advanced Logging Procedures

Workbook, however, it is best to review the two main reasons why coring takes place at the Well

site

1. Strati graphically - the oil company will core a formation (generally accomplished on

development wells)

2. Hydrocarbon Shows - the oil company will core any formation based upon unexpected

hydrocarbon shows (generally done on wildcat wells).


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TYPES OF CORING:

Two types of coring operations are used:

1. Conventional (at the time of drilling)

2. Sidewall (while wireline logging)

CONVENTIONAL CORING:

conventional drilling is common used type of coring which is using special hollow bits which is

allow geologists and engineers to define the properties of any formation ,while drilling the

hollow bit set to the head of drill collar instead of common drilling bits and then it will be drilled

to reached formation while conventional coring process, the driller first drills well down to a

zone of interested formation by using a conventional drill bit and drill string, A field geologist

will monitors drilling operation to decide when to start coring operations, when the geologists

decided to start coring, driller start to pull out the drill bit in the bore hole, the crew of drilling

they will change the normal bit to hollow coring bit .

The hollow coring bit: the special designed bit with hollow space inside the bit which is help

the coring to done in cylindrically and the obtained core it will carry out in the core barrel which

cylindrically tube ,core barrel consists of two cylindrically tube which is inner barrel and outer

barrel and a core catcher ,the barrels are linked to swivel that allows the inner barrel to remain

fixed while outer rotates with the bit of coring, When the core barrel is being full, the driller will

pull out the drill string into surface and the core barrel will obtained .


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Figure 1.2: hollow bot

(Matt and Tony, 2015)

The following are recommendations which apply to conventional coring:

1. Precaution must be taken to completely insure that the well is free of junks; like small pieces

(bit teeth, tong dies … because it will destroy the core bit, either its diamond or conventional.

2. The cores head must be run down into well at a normal safe speed to avoid damage from

beating a dog-leg which is curved.


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SIDEWALL CORING: (SWCs)

plugs of taken rock from the hole bore wall, a SWCs are commonly obtained by wireline tools,

and wireline tool can reach multiple zones , After the driller man reached a casing point and

drills to total depth (TD) , the drill pipe it will pulled out of the well and the entire well will

prepare to logging before casing is being set, Sidewall sample cores practically are being

obtained after logging tools have been runs before, running the logging tolls before side wall

coring will gives geologists suitable time to pick depth of cores after logging tools will identify

the zones in the borehole , spontaneous potential log and Gamma Ray log will be used to

correlate between depth of the core and open hole depth , Sidewall coring (SWCs) equipment’s

are being controlled at the surface unit, and sidewall coring and can obtain samples from the

wall of a wellbore more than 90 selected depths.

Figure 1.3: Rotary Sidewall Coring



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Most common two types of sidewall coring are: percussion and rotary

Percussion coring tool or also called core gun, has core barrels bullets, by using small explosive

Charges will let core barrels into the side of the well to capture cores samples of selected zones,

And the rotary will use horizontal core bit drilling to obtain cores from sidewalls of formations.

Percussion coring:

the part of bullet series puts down into well bore by wireline tool into interested coring point,

then the bullets shots into formation core gun will obtain [1.125 to 1.75 in] in length and will

obtain [0.688 to 1 in.] in diameter.

Figure 1.4: bullet series Figure 1.5: bullets

(Abhishek and Larissa, September 2014) (Abhishek and Larissa, September 2014)


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Rotary coring:

Rotary coring tool is horizontal drilling to obtain core samples using small type of bits which is

cut core sample at side wall of wellbore, sidewall rotary coring tool will use diamond drill bit,

core gun (percussion) is most common using tool ,but rotary coring it will use in hard rock

formations and deep water reservoirs ,core gun will obtain [1.125 to 1.75 in] in length and will

obtain [0.688 to 1 in.] in diameter, and rotary coring tool will obtain [2.5 in.] long and [1.5 in.] in

diameter the rotary coring has three times volume than percussion.

Figure 1.6: Rotary Sidewall coring



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Coring selection point:

Coring point it will select and be deiced with field supervisors and geologists, for selection any

point must be following being considered:

• The well must be logged and correlated

• The Variety formation separated and defined

• The decision must be taken for selection the type of bit using

• The type of fluid must be considered while coring

• The length and stress for drilling string

• The geologists must nearly monitors the deep of penetration while drilling

• Slow ROP rate of penetration while reaching near interested coring point

• The core bullet and their ability of perforate should be decided

CORING PROCEDURES:

Before to start coring process, there should be meeting with all those have roles in the coring

operations they must ensure that followings:

• All drilling items in the process are ready and suitable

Including all the equipment’s of the rig , monitors , gauges ,etc

The correct drilling fluid properties must selected and obtained

The wellbore is cleaned properly

The core barrel set in correct position


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The type of core bit being used

Convectional coring procedure:

When the drill bit reached near interested zone of coring the entire drill string and bit will put out

and coring barrel’s will be plugged with drilling string and selected fluid will be circulate while

coring and the hollow bit will run out into wellbore then the hollow bit starts to cut interested

formation then the cutted coring starts to go into inside core barrel and outside barrel rotates with

drilling string , and then after core obtained the drilling string will put out and then core barrel

being separated then the role of analysis of the core will being start .

Sidewall coring (bullets) procedure:

After the wellbore being drilled and before the casing program being start, the part of bullet

series puts down into well bore by wireline tool into interested coring point, then the bullets

shots into formation core gun will obtain [1.125 to 1.75 in] in length and will obtain [0.688 to 1

in.] in diameter, this procedure takes time and cost up on the drilling operation, and comparing

with convectional drilling this method will obtain less core sample in size and diameter.

Sidewall coring (rotary or horizontal drilling) procedure:

After the wellbore being drilled and before the casing program being start, the small size of

diamond bit use horizontal drilling to cut interested formation to obtain the core, while the

horizontal bit coring puts down into the well bore by wireline tool, and rotary coring tool will

obtain [2.5 in.] long and [1.5 in.] in diameter the rotary coring has three times volume than

percussion, but less obtains in core sample than conventional coring.


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CORING ANALYSIS

Most common tests of core analysis are followings:

• Porosity

• Permeability

• Saturation

• Wettability

Special tests on core sample are followings:

• Overburden pressure

• Capillary pressure

• Surface tension

Porosity:

According to tarek (2001) the porosity of a rock is a measure of the storage capacity (pore

volume) that is capable of holding fluids.

In the past geological time sediments were deposited and then it’s packed during all this times

and spaces between grains had been formed, some voids become isolated by cementation.


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Figure 1.7: Porosity

(Dejebbar and Erle, 2012)

There are two type of porosity:

• Absolute porosity

• Effective porosity

Absolute porosity:

According to tarek (2001) the absolute porosity is defined as the ratio of the total pore space in

the rock to that of the bulk volume.

ϕa=bulk voulme−grain voulmebulk voulme

Effective porosity:

According to tarek (2001) the effective porosity is the percentage of interconnected pore space with respect to the bulk volume.

ϕ= interconnect ed pore voulmebulk voulme


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Figure 1.7: table of Range of porosity


Methods of measuring porosity:

1: helium expansion method:

Dry core sample it will put in a chamber and then the pressure in chamber will measured without

core and it will measure again with core inside chamber, by putting gas volume in constant and

pressure changing the pore volume will measured

2: injection of the mercury with applied pressure:

The core sample will put under high pressure of mercury, then the mercury with this high

pressure will go inside the core, the volume of mercury will measures the total volume of pore.


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Permeability:

According to tarek (2001) the ability of a rock to transport reservoir fluids (different for oil,

water and gas). Depends on porosity, grain size, sorting and fluid characteristics.

Figure 1.8: permeability in difference grains


Absolute permeability: The permeability of the rock which is occupied by single fluid.

Effective porosity: The permeability of the rock that one fluid with presence of another fluid.


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Methods of measuring permeability:

There are two type of measuring:

•The steady-sate

This method set as accurate method of measuring will use an oil and water both to inject in input

until output rates equal input rate.

Oil+water Oil+water

Un steady-sate

This method is less accurate but it’s faster than the steady-state method, this method will

measures the amount of water in input rates and its compared with water + oil volume in out

rates.

Water oil +water


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The wettability:

According to (Dejebbar and Erle, 2012) it’s the tendency of one fluid to spread on or adhere to a

solid surface in the presence of other immiscible fluids.

The tendency oil and water and any other fluids are deference in solid surface , and they have

different angle of contact, the water angle is 0 angle to 75 which is less than oil or mercury,while

mercury has more 105 to 180 degree.

Figure 1.9 the wettability of different materials



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References:

1-Tarek, A. (2001) Reservoir Engineering Handbook, Houston Texas, Gulf Publishing

Company.

2-Abhishek, A.laressa, w. (2015) oil field Review, Schlumberger Publishing, Denmark

3- Matt, V.Tony, S.(2014) oil field Review, Schlumberger Publishing, Denmark

4-Dejbbar,T.Erle,D.(2012) Petrophysics, Second Edition, British Library, oxford UK

5-Carl, G. (1960) Drilling and Well Completion, Prentice Hall-Inc, Texas, Usa.

6-James, A. (1960) Petroleum Reservoir Engineering,McGraw Hill-Inc,New york Usa.

Documents

Coring & Coring Analysis 2