In-situ Formation Strength Testing via Sidewall Coring
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Solution Overview
Problem
Current methods for estimating in-situ formation properties in oil and gas wells face challenges due to irreversible changes in core and fluid samples during transport and the inability to accurately recreate in-situ conditions, as well as a lack of information on formation direction and rock properties.
Innovation Solution
A well logging apparatus equipped with a formation strength test device and a rotary sidewall coring tool that applies force to a core sample using extendable pistons, while sensors measure deformation to estimate radial and axial properties, allowing for in-situ testing without removing the sample from the formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If core samples are retrieved from the borehole for laboratory testing, then formation properties can be determined, but the samples undergo irreversible changes during transport and in-situ conditions cannot be accurately recreated
Solution Approach 1:
The formation itself serves as the test specimen through in-situ testing. The testing device applies compressive force directly to the formation at the borehole location, allowing the formation to test itself without requiring sample extraction. This eliminates transport-related sample degradation and preserves authentic in-situ conditions throughout the testing process.
Solution Approach 2:
A testing device acts as an intermediary between the measurement system and the formation. The device includes a piston that applies controlled compressive force, a bearing that contacts the formation, and sensors that measure deformation. This intermediary system enables direct in-situ measurement without sample retrieval while maintaining measurement accuracy.
2Loss of information
If downhole fluid tests are performed, then fluid samples can be analyzed, but information relating to formation direction and rock properties is not obtained
Solution Approach 1:
The testing device performs multiple functions: it applies controlled compressive force to the formation, measures axial and radial deformation, determines formation strength properties, and characterizes directional rock mechanics behavior. This multi-functional capability replaces the need for separate fluid sampling and rock property testing operations.
Solution Approach 2:
The device combines force application, deformation measurement, and property determination into a single integrated in-situ testing system. By merging these functions at the borehole location, the system simultaneously obtains formation strength, directional properties, and rock mechanics characteristics that were previously requiring separate testing operations.
3Measurement precision
If laboratory test fixtures are used to recreate in-situ conditions, then formation properties can be measured, but the recreated conditions may not accurately reflect actual in-situ conditions
Solution Approach 1:
The invention extracts the essential testing function (compressive force application and deformation measurement) from the complex laboratory test fixture environment. By bringing the simplified testing capability directly to the formation in-situ, the system eliminates the need for complex recreated conditions while maintaining measurement relevance.
Solution Approach 2:
Instead of attempting to copy the entire laboratory testing environment downhole, the invention creates a simplified functional copy that performs the critical measurement function. The downhole testing device replicates the essential compressive loading and deformation measurement capabilities needed to determine formation strength properties without requiring full laboratory condition recreation.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This method provides reliable and accurate estimation of formation properties, including stress, Young's modulus, Poisson's ratio, and unconfined compressive strength, under actual in-situ conditions, enhancing the assessment of subterranean formations for hydrocarbon production.
Implementation Method 1
A force is applied against the top surface of the core sample using a piston driven by a drive device. The compression of the core sample is measured by a displacement gage as the core sample is loaded.
Implementation Method 2
The formation strength test device includes a piston and a plurality of extendable members. The extendable members are extendable in a radial direction from the piston in an annular pattern about the piston.
Data Source
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AI summary
A method and apparatus for estimating one or more formation properties using in-situ measurements conducted at or near a coring location include a coring tool adapted to cut a core sample in a formation, a member having a distal end that engages a borehole wall substantially adjacent the core sample, and a drive device that engages the member to the borehole wall with a force sufficient to estimate formation strength.