Fluid Sensitivity Index for Shale Rock Stability
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Solution Overview
Problem
Current geo-mechanical modeling for drilling operations relies on virgin rock mechanical properties without considering rock-fluid interactions, leading to misleading information due to the degradation of rock mechanical properties by sensitive drilling muds, necessitating an assessment of fluid sensitivity for accurate input data.
Innovation Solution
A method to determine a Fluid Sensitivity Index (FSI) using uniaxial compressive strength (UCS) tests on shale rock samples before and after interaction with water-based muds, evaluating the fractional loss of UCS to quantify mud system reactivity and guide drilling operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If water-based muds are used for drilling operations, then environmental impact is reduced, but rock mechanical properties degrade due to fluid reactivity
Solution Approach 1:
The patent changes the chemical composition parameters of water-based muds by adding specific inhibitors and chemicals to reduce rock reactivity. The mud formulation is adjusted to maintain environmental benefits while preventing degradation of rock mechanical properties through chemical modification of the fluid composition.
Solution Approach 2:
The patent introduces chemical inhibitors as intermediary substances between the water-based mud and the rock formation. These inhibitors act as mediators that prevent direct harmful reactions between the mud and rock, reducing fluid sensitivity while maintaining the environmental advantages of water-based systems.
2Device complexity
If virgin rock mechanical properties are used for geo-mechanical modelling, then modelling simplicity is maintained, but accuracy is reduced due to rock-fluid interaction effects
Solution Approach 1:
The patent performs preliminary UCS testing on rock samples that have been exposed to drilling muds before geo-mechanical modelling. This preliminary action of pre-conditioning the rock samples with actual mud exposure ensures that the mechanical properties used in modelling reflect real wellbore conditions, improving accuracy without significantly increasing complexity.
Solution Approach 2:
The patent implements a feedback mechanism where UCS test results from mud-exposed rock samples are used to update and refine geo-mechanical models. This feedback loop ensures that modelling accuracy is continuously improved by incorporating actual rock-fluid interaction data, while the systematic approach keeps complexity manageable.
3Object-affected harmful factors
If non-inhibitive or low-inhibitive water-based muds are used, then environmental benefits are maintained, but rock stability is compromised due to high fluid sensitivity
Solution Approach 1:
The patent modifies the chemical parameters of water-based muds by incorporating specific inhibitors and additives. This changes the mud's interaction characteristics with rock, reducing fluid sensitivity and improving rock stability while maintaining the environmental benefits of water-based formulations through careful parameter optimization.
Solution Approach 2:
The patent introduces chemical inhibitors as intermediary substances that mediate between the water-based mud and rock formation. These intermediaries prevent direct harmful reactions, stabilizing rock composition and reducing fluid sensitivity while allowing water-based muds to retain their environmental advantages.
Data Source
AI summary
A method of evaluating fluid sensitivity of a water-based muds on a shale rock. The method includes providing a sample of the shale rock from a portion of a formation, where the portion of the formation is positioned outside of a reservoir region. The sample of the shale rock is separated into a first portion and a second portion. The first portion is subjected to a UCS test for detecting a first uniaxial compressive strength (UCS) value (UCSo). The second portion is converted into a prepared sample utilizing a test preparation procedure. The prepared sample is subjected to the UCS test for detecting a second UCS value (UCS1). A fluid sensitivity index (FSI) is determined utilizing the detected UCS0 and USC1 values.