Upload
others
View
31
Download
6
Embed Size (px)
Citation preview
Coring Operations Basics
MUDLOGGING, CORING, AND CASED HOLE LOGGING BASICS
LEARNING OBJECTIVES
By the end of this lesson, you will be able to:
Understand why cores are justified and who needs core data
Identify which type of core is most suitable based on data requirements and budget
Identify three types of cores and explain the advantages and disadvantages of each type
Understand the basic components of a whole coring equipment string
═════════════════════════════════════════════════════════════════════════
© PetroSkills, LLC., 2016. All rights reserved._____________________________________________________________________________________________
1
COPYRIGHT
OBJECTIVE: REVIEW CORING OPERATIONS
Coring process and types/equipment
Core handling at wellsite
Value of Core Information
OBJECTIVE: REVIEW CORING OPERATIONS
═════════════════════════════════════════════════════════════════════════
2_____________________________________________________________________________________________
© PetroSkills, LLC., 2016. All rights reserved.
COPYRIGHT
CORE ANALYSIS
Why Core? Usually the responsibility of
the subsurface team to justify the expense and risk of taking cores
Need cores to determine the basic petrophysicalparameters including reservoir porosity and permeability
Information needed is subtle and complex
Obtaining high quality cores requires careful planning
Usually services of a consultant coring expert are required
Special attention must be paid to mud properties to minimize alteration of the cores
INTRODUCTION: WHY CUT A CORE?
Calibrating core‐derived properties with log response is critical
Calibrating core-derived properties with log response is critical!
═════════════════════════════════════════════════════════════════════════
© PetroSkills, LLC., 2016. All rights reserved._____________________________________________________________________________________________
3
COPYRIGHT
THE ROCKS HAVE A STORY TO TELL…YOU NEED TO KNOW THE RIGHT QUESTIONS!
Reservoir Potential Depositional Environment Diagenetic history Quality (production potential)
of the rocks Correlate lithologic
characteristics to log properties
Fluid sensitivities to completion chemicals
How to maximize production and minimize formation damage using proper exploitation procedures
RESERVOIR ROCK SPECIMENS (CORES)
Reasons core data are important:
Fundamental information for reservoir exploration, description and exploitation.
Positive evidence of hydrocarbon presence, storage capacity (porosity), flow capacity (permeability).
Interpretation of the probable production of oil, gas or water.
Understand reservoir performance, well treatment responses, calibration of well logs, a basis for reservoir estimation, modeling and exploitation.
═════════════════════════════════════════════════════════════════════════
4_____________________________________________________________________________________________
© PetroSkills, LLC., 2016. All rights reserved.
COPYRIGHT
WHY CORE AND FLUID SAMPLES?UNCERTAINTY = RISK
WHY CORE AND FLUID SAMPLES?UNCERTAINTY = RISK
═════════════════════════════════════════════════════════════════════════
© PetroSkills, LLC., 2016. All rights reserved._____________________________________________________________________________________________
5
COPYRIGHT
WHY CORE AND FLUID SAMPLES?UNCERTAINTY = RISK
Reservoir Characterization and Modeling require a quantified and realistic description of formation properties
Reservoir geometry, internal structures and heterogeneities, impact on fluid flow
Size of reservoir, reservoir producing mechanisms, field development strategy and COSTS
Maximize field returns
Rule of Thumb: Obtain at least one good quality whole core from each significant reservoir that is developed
WHO NEEDS CORE DATA?
Geology Core description Facies analysis Stratification Lithology Diagenesis Geologic age Pore geometry
Petrophysics Porosity, perm, Sw Capillary pressure pore
geometry, saturation Electrical properties CEC Acoustic properties
Reservoir Engineering Relative permeability Capillary pressure curves Critical gas saturation Pore volume
compressibility Waterflood parameters
Production Technology Well injectivity Rock mechanical data Mineralogy/lithology for
cementing, stimulation8 inches
Carbonate breccia contains low gravity oil
═════════════════════════════════════════════════════════════════════════
6_____________________________________________________________________________________________
© PetroSkills, LLC., 2016. All rights reserved.
COPYRIGHT
THE CORING EQUIPMENT AND PROCEDURES
FULL DIAMETER CORE BIT VS. SIDEWALL CORING
Percussion Sidewall Cores
Whole Cores
═════════════════════════════════════════════════════════════════════════
© PetroSkills, LLC., 2016. All rights reserved._____________________________________________________________________________________________
7
COPYRIGHT
SIDEWALL CORING TYPES
Percussion Lowest cost alternative Explosive charges for
each hollow bullet Significantly disturbs the
rock sample Best recovery in
unconsolidated lithologies
Rotary Drilled with small
diamond bit Recovers virtually
undisturbed sample Rotating head cuts
horizontal plug Multiple samples per run
SIDEWALL SAMPLE GUN
Sample
Formation
BulletIgniter
Power charge
Wire cables
═════════════════════════════════════════════════════════════════════════
8_____________________________________________________________________________________________
© PetroSkills, LLC., 2016. All rights reserved.
COPYRIGHT
SIDEWALL CORE RETRIEVAL
Chronological Sample Taker (CST)
Procedure at the surface Samples are pressed from
bullets at surface Placed into plastic bottles
with screw-on tops, tight gas seal
Labeled for depth
PERCUSSION SIDEWALL CORING (SWC)
Advantages: Disadvantages
Highest quality sidewall samples recovered from unconsolidated sand formations Typically Miocene and younger geologic age sediments
Usable rock samples may also be recovered from hard rocks Including carbonates and consolidated sandstones
Samples from the harder formations may be shattered and disturbed, but are still useful for petrographic studies and making thin sections for geologic examination
═════════════════════════════════════════════════════════════════════════
© PetroSkills, LLC., 2016. All rights reserved._____________________________________________________________________________________________
9
COPYRIGHT
PERCUSSION SIDEWALL CORING (SWC)
Advantages: Large number of samples
in single trip (e.g., 90) Coring points are
individually selected using wireline logs
Available for temp up to 500oF
Faster and more cost effective
Good in soft rocks
Disadvantages Sample quality degraded Tumbling Partial penetration Sample damage due to
impact
Large “washed out” holes cause poor recovery
Sample size is small
ROTARY SIDEWALL CUTTER AND PLUGS
Plugs up to 2 inches long, 0.875 to 1 inch diameter
═════════════════════════════════════════════════════════════════════════
10_____________________________________________________________________________________________
© PetroSkills, LLC., 2016. All rights reserved.
COPYRIGHT
FULL DIAMETER OR WHOLE CORING
Coring or Cuttings?
Core Bit and BarrelFormation SamplesBit
CORING BIT
═════════════════════════════════════════════════════════════════════════
© PetroSkills, LLC., 2016. All rights reserved._____________________________________________________________________________________________
11
COPYRIGHT
FULL DIAMETER CORE
FULL DIAMETER (WHOLE) CORE
Advantages: Disadvantages:
Whole cores provide the best quality and least disturbed samples for most petrophysical and geomechanical analysis.
═════════════════════════════════════════════════════════════════════════
12_____________________________________________________________________________________________
© PetroSkills, LLC., 2016. All rights reserved.
COPYRIGHT
FULL DIAMETER (WHOLE) CORE
Advantages: Long, continuous sample of
formation Selection of plug, whole core
depths of core optimized Can maintain saturations
better Wider spectrum of
observations and tests Depositional facies and sequence
determination Vertical plugs possible
Disadvantages: Typically taken in multiplies of
30 ft. sections Coring done while drilling not
afterwards Requires one to several special
trips in hole Typically slower drilling to enhance
recovery Mudlog gas not reliable through cored
intervals More expensive than sidewall
options Higher potential for “getting
stuck” while coring Higher potential for “swabbing-
in” while POOH with core
CORING TYPES: WHAT ARE TRADE-OFFS?
Percussion Sidewall Coring (SWC) Relatively inexpensive Depths more precise based
on previous logging runs (open hole or LWD)
Typically more shattered or compacted by the impact
Full Diameter Whole Cores Cut more or less “blind”;
open hole logs missing Larger rock volume for
analysis Requires special well site
handling, transportation beyond that required by SWC processes
Rotary SWC (RSWC) Sample quality better, more
expensive than percussion Good in consolidated
lithologies
No matter what the type of core, remember to make description and subsample core before leaving location!
═════════════════════════════════════════════════════════════════════════
© PetroSkills, LLC., 2016. All rights reserved._____________________________________________________________________________________________
13
COPYRIGHT
LEARNING OBJECTIVES
Understand why cores are justified and who needs core data
Identify which type of core is most suitable based on data requirements and budget
Identify three types of cores and explain the advantages and disadvantages of each type
Understand the basic components of a whole coring equipment string
═════════════════════════════════════════════════════════════════════════
14_____________________________________________________________________________________________
© PetroSkills, LLC., 2016. All rights reserved.
COPYRIGHT