Coring Operations Basics
Petrophysical Data Acquisition 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
Objective: Review Coring Operations
Coring process and types/equipment
Core handling at wellsite
Value of Core Information
Core Analysis
OUTLINE Why Core? Wellsite Requirements for High Quality Core Early Core Data Opportunities
Introduction: Why Cut a Core?
Calibrating core‐derived properties with log response is critical
That’s why !!!!
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)
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.
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
• Reduce exploration, sanction, and development risks • maximize field returns
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
The Coring Process and Types of Cores
Full Diameter Core Bit vs. Sidewall Coring
Sidewall Coring Types
Percussion• Explosive charges for
each hollow bullet• Best recovery in
unconsolidated lithologies
Rotary• Rotating head cuts
horizontal plug• Multiple samples per run
Sidewall Sample Gun
Sidewall Core Retrieval
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:• 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
Limitations:• Sample quality
– Tumbling– Partial penetration– Sample damage due to impact
• Large holes• Sample size• any others?
Rotary Sidewall Cutter and Plugs
Plugs up to 2 inches long, 0.875 to 1 inch diameter
Full Diameter or Whole Coring
Coring or Cuttings?
Core Bit and BarrelFormation Samples
Coring Bit
Full Diameter Core
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
Limitations:• Typically taken in 20 – 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?
Sidewall coring (SWC) • Depths more precise based on previous logging runs (open hole or
LWD)• Relatively inexpensive• Typically more fractured or compressed
Rotary SWC (RSWC)• Sample quality better, more expensive than percussion• Good in consolidated lithologies
Full diameter (FD)• 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 No matter what the type of core, remember to make description
and subsample core before leaving location!
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