Fractured-Vuggy Well-Wall Collapse Detection via Productivity Index
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Solution Overview
Problem
Existing methods for determining well wall collapse in fractured-vuggy reservoirs are inadequate due to the complexity of pore structures and fracture networks, which are not accurately represented by core experiments, and the difficulty in obtaining formation pressure in actual production processes.
Innovation Solution
A method is developed to determine well wall collapse by establishing an optimization model using a material balance equation and production performance, which calculates the change in oil productivity index to find the critical differential pressure during well wall collapse.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If core testing method is used to determine well wall collapse, then mechanical parameters can be obtained, but the complex pore structure and fracture network of fractured-vuggy reservoir cannot be fully represented
Solution Approach 1:
The patent uses production performance data as a copy or proxy for the complex in-situ conditions that cannot be replicated in core experiments. By analyzing production differential pressure and oil productivity index trends, the method infers well wall collapse characteristics without requiring physical core samples that would fail to represent the fractured-vuggy structure.
Solution Approach 2:
The patent introduces production performance parameters (oil productivity index, production differential pressure) as intermediary variables that link the complex reservoir conditions to measurable well performance. These intermediaries allow indirect assessment of well wall collapse without direct measurement of the complex pore-fracture system.
2Measurement precision
If production statistics method is used to monitor well wall performance, then flowing pressure can be monitored, but formation pressure is very difficult to obtain in actual production process
Solution Approach 1:
The patent establishes a feedback relationship between production differential pressure and oil productivity index. By continuously monitoring production performance and comparing against theoretical models, the method infers formation pressure conditions and well wall collapse states without requiring direct formation pressure measurement.
Solution Approach 2:
The patent replaces the mechanical/physical measurement system (direct formation pressure gauges) with a computational approach using production statistics and material balance equations. This substitution allows formation pressure inference through mathematical relationships rather than direct physical measurement.
3Measurement precision
If core experiments are conducted to study rock properties, then mechanical parameters can be obtained, but the experiments cannot fully simulate the occurrence and evolution of well wall collapse in the reservoir
Solution Approach 1:
The patent allows the reservoir itself to provide the data needed for assessment through production performance monitoring. Instead of relying on external core experiments, the actual production process generates the information (production differential pressure, oil productivity changes) needed to detect well wall collapse in its natural setting.
Solution Approach 2:
The patent transitions from static core sample measurements to dynamic production performance monitoring. By tracking changes in oil productivity index and production differential pressure over time, the method captures the evolving conditions of well wall collapse as they occur during production, rather than using fixed core sample properties.
Data Source
AI summary
A method for determining well wall collapse of a single well for a fractured-vuggy reservoir is provided. The method includes following steps: S1, treating the single well of the fractured-vuggy reservoir as an isolated reservoir; S2, calculating a water influx rate for the fractured-vuggy reservoir; S3, substituting a formula of the water influx rate into a material balance equation; S4, calculating a change of an oil productivity index without considering the well wall collapse; S5, establishing an optimizing model for obtaining the oil productivity index; S6, calculating the formation pressure at any time in production through step S3; S7, calculating the oil productivity index at any time through the formation pressure, and establishing an optimal objective function; and S8, calculating a difference between the oil productivity index at any time and the theoretically calculated oil productivity index at any time, and determining whether the difference meets an accuracy requirement.