Petrophysical Data Acquisition Basics. Coring Operations Basics

Transcription

1 Petrophysical Data Acquisition Basics Coring Operations Basics

2 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

3 Objective: Review Coring Operations Coring process and types/equipment Core handling at wellsite Value of Core Information

4 Core Analysis OUTLINE Why Core? Wellsite Requirements for High Quality Core Early Core Data Opportunities

5 Introduction: Why Cut a Core? Calibrating core derived properties with log response is critical That s why!!!!

6 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

7 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.

8 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

9 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 8 inches Carbonate breccia contains low gravity oil Production Technology Well injectivity Rock mechanical data Mineralogy/lithology for cementing, stimulation

10 The Coring Process and Types of Cores

11 Full Diameter Core Bit vs. Sidewall Coring

12 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

13 Sidewall Sample Gun

14 Sidewall Core Retrieval Samples are pressed from bullets at surface Placed into plastic bottles with screw-on tops, tight gas seal Labeled for depth

15 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 500 o F 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?

16 Rotary Sidewall Cutter and Plugs Plugs up to 2 inches long, to 1 inch diameter

17 Full Diameter or Whole Coring Formation Samples Core Bit and Barrel Coring or Cuttings?

18 Coring Bit

19 Full Diameter Core

20 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 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

21 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!

22 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