Behind-Casing Hydraulic Conductivity Measurement
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Solution Overview
Problem
Pressure transient tests in hydrocarbon reservoirs often fail to account for behind-casing flow between reservoir layers, leading to inaccurate reservoir parameter estimation and potential hydrocarbon loss due to fluid diversion between layers.
Innovation Solution
A method to measure behind-casing hydraulic conductivity using an analytical model that quantifies the fluid conductivity of cement in the well annulus, allowing for the determination of fluid flow rates between layers and correcting pressure transient test results by accounting for zonal isolation effectiveness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If pressure transient tests are conducted without accounting for behind-casing flow, then the test procedure is simple and quick, but the reservoir parameter estimation becomes inaccurate
Solution Approach 1:
The patent introduces an intermediary analytical model that acts as a mediator between the pressure transient test data and the reservoir parameter estimation. This model incorporates behind-casing flow as an intermediate factor that connects the observed pressure behavior with the actual reservoir properties, allowing accurate parameter estimation without complicating the field test procedure itself
Solution Approach 2:
The patent replaces the need for complex physical measurement devices or additional field equipment with an analytical modeling approach. By using mathematical models to account for behind-casing flow effects, the system substitutes mechanical/physical complexity with computational analysis, maintaining procedural simplicity while improving measurement accuracy
2Reliability
If zonal isolation is assumed to be complete, then the production operation is simplified, but hydrocarbon loss occurs due to fluid diversion between layers
Solution Approach 1:
The patent employs feedback by using pressure transient test results to evaluate the actual effectiveness of zonal isolation. The analytical model compares observed pressure behavior with expected behavior under perfect isolation, providing feedback on the true state of zonal isolation. This allows operators to identify and address behind-casing flow issues, preventing hydrocarbon loss while maintaining operational simplicity
Solution Approach 2:
The patent applies preliminary action by conducting pressure transient tests and analyzing behind-casing flow potential before making production decisions. This advance assessment allows operators to take preventive measures such as remedial cementing or production strategy adjustments before significant hydrocarbon loss occurs, rather than reacting to loss after it has happened
Data Source
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AI summary
A measure of the hydraulic conductivity, F c , is obtained to characterize the leaky medium behind well casing between adjacent hydrocarbon producing layers is a subsurface reservoir. The value of F c can be utilized in estimating the rate of flow from a secondary reservoir layer contributing to the total production through the wellbore based on the respective well pressures at a given time. The well pressures are calculated from a model based on the individual properties of and the amounts of fluid produced from these layers. Once there is a reasonable match between the calculated pressures and the measured pressures during a transient test, the parameters that have been used in calculating the model pressures are stored as characteristic parameters of the reservoir system. Such characteristic parameters are utilized in assessing the commercial producibility of the reservoirs.