Baker Hughes INTEQ
Introduction to Coring
Through coring, Engineers, Geologistsand Petrophysicists gain access to
reservoir information that can be
gathered in no other way. Data on the
formation’s lithology, flow
characteristics, storage capacity and
production potential are just a few of the
valuable types of information that can be
obtained by a successful coring program.
This chapter discusses what coring is and
the benefits associated with the process.
It also describes how to plan a successful
coring project and the BHI coring
services that are available.
Coring Definition
Coring is the removal of sample formation material from a
wellbore. To the extent possible, core samples are taken in
an undamaged, physically unaltered state. The formation
material may be solid rock, friable rock, conglomerates,
unconsolidated sands, coal, shales, gumbos, or clays.
Coring can be conducted by various methods with a variety
of tools. But in the oilfield, coring is generally
accomplished by two methods:
• Full Hole Coring: Core material ranging in
diameter from 1¾" to 5¼" is recovered inside of a
core barrel in vertical, deviated, horizontal, or
sidetracked wells. Depending upon the coring
system employed, the core can be recovered in
preserved or unpreserved states, and can be used for
a wide range of analytical applications. Baker
Hughes INTEQ offers a complete range of full-hole
coring services.
• Sidewall Coring: Cylindrical plug-shaped samples,
generally 1" in diameter, are recovered from the
walls of the wellbore by percussion or rotary coring
techniques. This sampling takes place in the first
few inches of the wellbore wall in regions that
generally are invaded by drilling fluid filtrates. The
resulting samples are unpreserved and frequently
are damaged by the recovery procedure. Sidewall
core plugs are of limited use from an analytical
standpoint. Baker Hughes INTEQ does not offer
sidewall coring services.
Table of Contents
Table of Contents
List of Figures
List of Tables
Chapter 1
Introduction to Coring
Coring Definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-2
The Purpose of Coring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-3
Geological Evaluations . . . . . . . . . . . . . . . . . . . . . . . . . . 1-3
Completion Evaluations . . . . . . . . . . . . . . . . . . . . . . . . . 1-4
Engineering Evaluations . . . . . . . . . . . . . . . . . . . . . . . . . 1-4
Planning the Successful Coring Program . . . . . . . . . . . . . . . . 1-6
Coring Services . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-6
Conversion Factors and Physical Constants . . . . . . . . . . . . . . 1-6
Chapter 2
Coring Systems
High Torque HT Series Core Barrels . . . . . . . . . . . . . . . . . . . 2-1
HT Series™ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-1
HT Series Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-2
Coremaster™ Series Core Barrels . . . . . . . . . . . . . . . . . . . . . 2-5
Coremaster Features & Benefits . . . . . . . . . . . . . . . . . . . 2-7
Conventional 250P Core Barrels . . . . . . . . . . . . . . . . . . . . . . 2-9
250P Series Core Barrels . . . . . . . . . . . . . . . . . . . . . . . . . 2-9
250P Core Barrel Features . . . . . . . . . . . . . . . . . . . . . . . 2-11
350P Slimhole Core Barrel . . . . . . . . . . . . . . . . . . . . . . . . . 2-13
350P Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-13
350P Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-13
Hydro-Lift™ Full Closure Catcher . . . . . . . . . . . . . . . . . . . 2-15
Tool Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-16
Hydro-Lift Features & Benefits . . . . . . . . . . . . . . . . . . . 2-17
Core Barrel HT-Series . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-18
Core Barrel 250P / 350P Mechanical Properties . . . . . . . . . .2-19
CoreDrill™ Coring-While-Drilling . . . . . . . . . . . . . . . . . . .2-24
CoreDrill Model 1a . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-26
CoreDrill Features/Benefits . . . . . . . . . . . . . . . . . . . . . .2-26
CoreDrill Navi-Gamma Tool (Model 2) . . . . . . . . . . . . .2-27
Motor Coring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-28
Drop Ball Sub and Downhole Activated Flow Diverter . .2-29
Integral Coring Motor System . . . . . . . . . . . . . . . . . . . . . . .2-30
Modular Coring Systems . . . . . . . . . . . . . . . . . . . . . . . . . . .2-32
Horizontal Coring Systems . . . . . . . . . . . . . . . . . . . . . . . . .2-35
Long Radius Coring System . . . . . . . . . . . . . . . . . . . . .2-35
Medium Radius Coring System . . . . . . . . . . . . . . . . . . .2-35
Oriented Coring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-36
Application . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-37
Survey Tools . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-38
Electronic Magnetic Survey Tool . . . . . . . . . . . . . . . . . .2-38
Positive Latch . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-40
Modular Magnetic Tool . . . . . . . . . . . . . . . . . . . . . . . . .2-41
MMT Features . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-42
CoreGard™ Low Invasion Coring System . . . . . . . . . . . . . .2-44
Filtrate Invasion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-44
Bit Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-45
Inner Tube Pilot Shoe . . . . . . . . . . . . . . . . . . . . . . . . . .2-46
CoreGard Features . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-46
Drilling Fluids Additives . . . . . . . . . . . . . . . . . . . . . . . . . . .2-47
Drilling Fluids Bridging Solids . . . . . . . . . . . . . . . . . . .2-47
Tracers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-48
ISOTAG . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-48
DFE-1503 Water-Base Mud . . . . . . . . . . . . . . . . . .2-49
DFE-432 Oil-Based Mud . . . . . . . . . . . . . . . . . . . . .2-51
Tracers for Water-Base Fluids . . . . . . . . . . . . . . . . . . . .2-53
Chemical Salts . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-54
Stable Isotopes . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-54
Radioactive Isotopes . . . . . . . . . . . . . . . . . . . . . . . .2-54
Tracers for Oil-Base Fluids . . . . . . . . . . . . . . . . . . . . . .2-55
Gel CoringSM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-57
Gel Coring Benefits . . . . . . . . . . . . . . . . . . . . . . . . . . .2-59
In Situ Data Gathering Pressure Coring . . . . . . . . . . . . . . . . 2-62
IDGS Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-63
IDGS Equipment Description . . . . . . . . . . . . . . . . . 2-64
Service Unit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-65
HTHP (High Temperature High Pressure) Coring . . . . . . . . . 2-67
So Coring – Reservoir Characterization Coring . . . . . . . . . . 2-69
So Coring Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-69
So Coring Benefits . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-69
Underbalanced Coring . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-70
Coiled Tubing Coring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-71
Chapter 3
Inner Barrel Components
Bottomhole Assembly . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-1
Inner Coring Barrels and Liners . . . . . . . . . . . . . . . . . . . . . . . 3-3
Steel Inner Barrels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-3
Aluminum Inner Tubes . . . . . . . . . . . . . . . . . . . . . . . . . . 3-4
Fiberglass Inner Tubes . . . . . . . . . . . . . . . . . . . . . . . . . . 3-5
Plastic Liners . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-6
Disposable Liners . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-6
Inner Tube-to-Rock Friction . . . . . . . . . . . . . . . . . . . 3-7
JamBuster™ Anti-Jamming Coring System . . . . . . . . . . . . . . 3-9
JamBuster Benefits . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-12
Long Distance Adjustment . . . . . . . . . . . . . . . . . . . . . . . . . 3-12
Core Jam Indicator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-12
Principle of Operation . . . . . . . . . . . . . . . . . . . . . . . . . . 3-12
Drop Ball Subs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-14
Side Entry Drop Ball Sub . . . . . . . . . . . . . . . . . . . . . . . 3-14
Downhole Activated Flow Diverter . . . . . . . . . . . . . . . . 3-14
Application . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-15
Pressure Venting Check Valves . . . . . . . . . . . . . . . . . . . 3-16
Standard Pressure Check Valve . . . . . . . . . . . . . . . . 3-16
Spring-Loaded Pressure Check Valve . . . . . . . . . . . 3-17
Inner Tube Stabilization . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-17
Chapter 4
Coring Bits
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4-1
PDC (Polycrystalline Diamond Compact) Bits . . . . . . . . .4-2
Anti-Whirl™ PDC Bits . . . . . . . . . . . . . . . . . . . . . . . . . .4-4
PDC Cutter Options . . . . . . . . . . . . . . . . . . . . . . . . . . . .4-6
Gold Series Cutters . . . . . . . . . . . . . . . . . . . . . . . . . .4-6
Black Diamond™ Cutters . . . . . . . . . . . . . . . . . . . . .4-8
Engineering Cutter Layout . . . . . . . . . . . . . . . . . . . . . . . .4-8
Natural Diamond Bits . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4-11
Impregnated (Synthetic Diamond) Bits . . . . . . . . . . . . . . . . .4-11
Core Bit Selection Guide . . . . . . . . . . . . . . . . . . . . . . . . . . .4-12
PDC Coring Bits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4-13
Ballaset® Core Bits . . . . . . . . . . . . . . . . . . . . . . . . . . .4-14
Natural Diamond Core Bits . . . . . . . . . . . . . . . . . . . . . .4-14
Chapter 5
Coring Procedures
Nomenclature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5-1
Major Core Barrel Components . . . . . . . . . . . . . . . . . . . .5-1
Other Components . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5-3
Coring System Preparations . . . . . . . . . . . . . . . . . . . . . . . . . .5-4
Outer Barrel Makeup . . . . . . . . . . . . . . . . . . . . . . . . . . .5-4
Core Barrels Shorter than Derrick Height . . . . . . . . .5-4
Core Barrels Longer than Derrick Height . . . . . . . . .5-7
Considerations . . . . . . . . . . . . . . . . . . . . . . . . . .5-8
Standard Barrel Application . . . . . . . . . . . . . . . .5-8
Loading Inner Barrels/Tubes . . . . . . . . . . . . . . . . . . . . . . . .5-12
Procedures for Fiberglass & Aluminum Barrels . . . . . . .5-12
Inner Tube Adjustment . . . . . . . . . . . . . . . . . . . . . . . . .5-13
Shims . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5-14
Long Distance Adjustment . . . . . . . . . . . . . . . . . . . .5-16
Procedures for Plastic Liners or Inner Tubes . . . . . . . . . .5-17
Plastic Liners . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5-17
Running Plastic Liners w/ 250P Series Core Barrel . 5-17
Loading 30-ft Core Barrel . . . . . . . . . . . . . . . . . 5-18
Unloading 30-ft Core Barrel . . . . . . . . . . . . . . . 5-19
Loading 60-ft Core Barrel . . . . . . . . . . . . . . . . . 5-20
Unloading 60-ft Core Barrel . . . . . . . . . . . . . . . 5-22
Coring with Plastic Liners . . . . . . . . . . . . . . . . . . . . 5-24
General Coring Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . 5-26
Check Points Before Coring . . . . . . . . . . . . . . . . . . . . . 5-26
Running in Hole . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-26
Conditioning Hole . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-26
Dropping Ball to Start Coring . . . . . . . . . . . . . . . . . . . . 5-27
Rotary Rig Connection Procedure . . . . . . . . . . . . . . . . . 5-28
Top Drive Connection Procedure . . . . . . . . . . . . . . . . . . 5-30
Operating Parameters . . . . . . . . . . . . . . . . . . . . . . . . . . 5-31
Circulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-31
Annular Velocities . . . . . . . . . . . . . . . . . . . . . . . . . 5-31
Circulation Volumes . . . . . . . . . . . . . . . . . . . . . . . . 5-32
Coring with Lost Circulation Material . . . . . . . . . . . . . . 5-32
Rotary Speed . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-33
Weight on Bit (WOB) . . . . . . . . . . . . . . . . . . . . . . . . . . 5-34
Feeding Weight . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-34
Standpipe Pressure Fluctuations . . . . . . . . . . . . . . . . . . 5-35
Breaking Core . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-35
Jamming . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-36
Pulling-Out-Of-Hole . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-36
Conventional . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-36
Vented Inner Barrels . . . . . . . . . . . . . . . . . . . . . . . . 5-37
Breaking Out of Outer and Inner Barrels . . . . . . . . . . . . 5-37
Retrieving Drop Ball . . . . . . . . . . . . . . . . . . . . . . . . 5-37
Normal Operations . . . . . . . . . . . . . . . . . . . . . . . . . 5-37
Lay Down/Cutting of Inner Barrel . . . . . . . . . . . . . . 5-39
Outer Barrel Breakdown Procedure . . . . . . . . . . . . . . . . 5-42
Back-off of Safety Joint . . . . . . . . . . . . . . . . . . . . . . . . 5-43
Procedure Summary . . . . . . . . . . . . . . . . . . . . . . . . 5-45
Retrieval of Inner Barrel when Core Barrel Safety Joint has
Backed Off and Outer Barrel is Left in Hole . . . . 5-46
Check/Change-Out Core Bit on Multi-Section Barrels . . 5-47
Makeup of Barrel After Bit Check/Replacement . . . . 5-48
Motor Coring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-49
JamBuster Coring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5-50
Shear Pins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5-50
Set-Up Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5-50
Jam Indicator Operations . . . . . . . . . . . . . . . . . . . . . . . .5-53
Fishing Tools . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5-53
Hydro-Lift Procedures . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5-54
Hydro-Lift Make Up . . . . . . . . . . . . . . . . . . . . . . . . . . .5-54
Hydro-Lift Coring Operations . . . . . . . . . . . . . . . . . . . .5-57
High Pressure Coring . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5-61
Pressure Relief Check Valves . . . . . . . . . . . . . . . . . . . .5-61
Pulling Out Of Hole . . . . . . . . . . . . . . . . . . . . . . . . . . .5-61
Procedure 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5-62
Procedure 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5-62
Core Barrel Maintenance (On-Site) . . . . . . . . . . . . . . . . . . .5-63
Safety – H2S Wells . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5-64
Wellsite Core Handling . . . . . . . . . . . . . . . . . . . . . . . . . . . .5-65
GammaTrak Surface Logging . . . . . . . . . . . . . . . . . . . .5-65
Wellsite Core Evaluation Unit . . . . . . . . . . . . . . . . . . . .5-66
Core Stabilization/Preservation . . . . . . . . . . . . . . . . . . . . . .5-69
Conventional Core Recovery . . . . . . . . . . . . . . . . . . . . .5-69
Stabilized Core Recovery . . . . . . . . . . . . . . . . . . . . . . .5-69
Basic Preservation . . . . . . . . . . . . . . . . . . . . . . . . .5-72
Freezing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5-73
Stabilization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5-74
Chapter 6
Coring Fishing Diagrams
250P Series . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6-2
HT Series . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6-7
CoreDrill Series . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6-10
Appendix A
Conversion Factors & Physical Constants
Physical Constants . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A-44
Gas Constants (R) . . . . . . . . . . . . . . . . . . . . . . . . . A-44
Acceleration of Gravity (Standard) . . . . . . . . . . . . A-44
Velocity of Sound in Dry Air @ 0°C and 1 ATM . . . A-44
Heat of Fusion of Water . . . . . . . . . . . . . . . . . . . . A-44
Heat of Vaporization of Water 1.0 ATM . . . . . . . . . A-44
Specific Heat of Air . . . . . . . . . . . . . . . . . . . . . . . . A-44
Density of Dry Air @ 0°C and 760 mm . . . . . . . . . A-44
Appendix B
Tables and Charts
Table B-1 HT Series Outer Barrel Mechanical Properties . . . B-1
Table B-2 Coremaster Series Outer Barrel Mech. Properties B-1
Table B-3 250P Series Outer Barrel Mechanical Properties . B-2
Table B-4 250P/350P/HT Series Inner Tube Mech. Properties B-3
Table B-5 Aluminum Inner Tube (IT) Specifications . . . . . . B-5
Table B-6 Aluminum Inner Tube Properties (6061-T6) . . . . B-5
Table B-7 Spacing of Aluminum Inner Tubes Based on
Thermal Expansion Coefficients . . . . . . . . . . . . . . . . . . . . . B-6
Table B-8 Spacing of Fiberglass Inner Tubes Based on
Thermal Expansion Coefficients . . . . . . . . . . . . . . . . . . . . . B-7
Table B-9 Inner Tube Relative Thermal Expansion . . . . . . . B-8
Table B-10 Fiberglass Inner Tube Dimensions . . . . . . . . . . . B-9
Table B-11 Fiberglass Inner Tube Specifications . . . . . . . . . B-9
Table B-12 Fiberglass Inner Tube Critical Buckling Pressure B-10
Table B-13 Fiberglass Inner Tube Axial Tensile Strength . . B-10
Table B-14 L.D. Adjustment System Calculation . . . . . . . . B-11
Table B-15 Possible Causes for Standpipe Pressure Changes B-12
Table B-16 Drillstring Connection Conversion . . . . . . . . . . B-13
Table B-17 API Reg. Pin Connections by Bit Size . . . . . . . B-14
Table B-18 Drill Collar Weights (lbs/ft) . . . . . . . . . . . . . . . B-14
Table B-19 Duplex Pump Capacities* (gallons/stroke) . . . . B-15
Table B-20 Triplex Pump Capacities* (gallons/stroke) . . . . B-16
Table B-21 Drill Collar Weights . . . . . . . . . . . . . . . . . . . . . B-17
Table B-22 Casing Drift Sizes . . . . . . . . . . . . . . . . . . . . . . . B-18
Table B-23 Tubing Drift Sizes . . . . . . . . . . . . . . . . . . . . . . . B-21
Table B-24 Fluid Density and Pressure Gradients . . . . . . . . B-22
Table B-25 Inch to Metric Conversion . . . . . . . . . . . . . . . . . B-23
Table B-26 Fraction Conversion Chart . . . . . . . . . . . . . . . . B-24
Table B-27 Core Barrel Pressure Drop Calculations . . . . . . B-25