Mud Logging – A Combination of Direct and Indirect Measurements

Petrophysical Data Acquisition Basics

Learning Objectives

By the end of this lesson, you will be able to:

Understand the process of mudlogging including hydrocarbon shows and lithology determination.

Identify the components of the drilling mud system and describe where cuttings samples and gas samples are collected.

Identify lithology and hydrocarbon type (oil or gas) from Mudlog in a hydrocarbon bearing zone.

Mud Logging

Diluted gas drawn from Gas Trap agitator in mud returns Chromatograph and hot wire analyze stream for hydrocarbons

• Total combustible gas using hot wire• Chromatograph with FID for specific hydrocarbons (C1 -C6)

Drill cuttings collected from shale shaker• Washed, described by mud logging engineer• Lithology, oil shows, fluorescence, compared to gas data

Sample and gas lag times must be measured or calculated Interpreted log combines ROP, lithology, HC gas readings, and

detailed cuttings descriptions, all plotted vs. depth

Lithology determination Formation fluid typing Well positioning within stratigraphy

• Selection of casing and/or coring points

Detection of geo-pressures Drilling Optimization

• Bit selection; hydraulics

Mud Logging Applications

Notes: • Cuttings lithology when intervals drilled with PCD

bits

• Fluid typing, ROP, pressure, bit runs still useful

The Drilling Mud System

Where are drilling mud

samples collected?

Drill Cuttings Samples Collected at the Shale Shaker

Mud Log – Processing Flow

Sampledat theshaker

Agitator/ Gas Trap in Possum Belly

Hot Wire (Total Combustible)

Gas Detector

Chromatograph(Gas Components

by FID + GC)

InterpretiveMudlog Output (ASCII/LAS) or

graphic formats

Drill Cuttings Interpretation

Drilling Engineering Data

Log

Mud Logging Wellsite Units

Combination Digital, Analog Unit Digital Unit

Logging Unit

Geology Side

Mud Logging: Evaluation

ROP log used for well-well correlation Cuttings lithology Gas Analysis Oil staining on cuttings (e.g., chlorothene solvent cut):

• water zone: no staining• oil zone: more heavy components• gas zone: only light components

• Color of fluorescence when sample wetted with solvent, viewed in UV light is excellent clue

Mud Logging Components

Sample, gas for analysis• Samples each

5-30 feet as requested• Continual total gas• Components each 12-15

minutes

Data output is graphic, digital

• Spreadsheet• ASCII• LAS

Analysis of Total Gas − ComponentsHydrogen generator

PC withIChrom

Igniter Glow Plug 24 volt

Oiler

FID Detector BlockHeated to 250C

Jet

Metal Tube tocatch Ions – 240 volts(Collector)

Balston Filter

Possum belly or ditch• Gas trap• Agitator motor• Gas lines• Condensate bottle

Pneumatics panel• Vacuum pump• Moisture Filters• Flow regulators

HP6890 Gas Chromatograph• Total gas• Gas chromatography

Courtesy of BakerInteq

Lithology Determination Takes Practice!

Large cuttings are cavings Fine cuttings of Woodford shale with no cavings

Measuring Time – Depth Sample Lag

Drilling Rate/Porosity Relationship

Hydrocarbon Tests on Cuttings

Staining, bleeding, odor, gas, iridescence (color) (Pos., Neg., Quest.)

Natural fluorescence (UV): Distribution, intensity, color 5 = strong... 0 = nil

Solvent cut test (Chlorothene): Minerals will not produce cut fluorescence

Acetone test (light oil): Hydrocarbons cause milky white solution

Acid test: Bouncing motion of cutting if HC present

Pyrolysis test (“burn it”)

Hot water test: Oil film at surface

Graphical Mud Log Exercise

Hydrocarbon Fluorescence

API°

(45°) blue-white to violet

(35-45°) white

(25-35°) yellow to cream

(15-25°) orange

(below 15°) brown

Sample fluorescence (approximate)

Now… Is this a Good Show?

Learning Objectives

Understand the process of mudlogging including hydrocarbon shows and lithology determination.

Identify the components of the drilling mud system and describe where cuttings samples and gas samples are collected.

Identify lithology and hydrocarbon type (oil or gas) from Mudlog in a hydrocarbon bearing zone.