Well Shut-in Pressure Calculation Using Casing Wear Coefficients
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Solution Overview
Problem
Current methods for determining well shut-in pressure in oil and gas well drilling are inaccurate due to neglecting the heterogeneity of casing strings and wear caused by mechanical operations and corrosion, leading to safety risks such as wellhead explosions and blowouts, especially in sour gas wells.
Innovation Solution
A method and system using a processor to calculate the maximum well shut-in pressure by incorporating wellbore structure, drilling fluid, and casing string parameters into a pressure calculation model, accounting for factors like formation depth, internal pressure strength, and material stress-strain characteristics to provide a more accurate safety threshold.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the maximum well shut-in pressure is determined based on minimum rated pressure values and formation rupture pressure, then the calculation is simple, but the accuracy is insufficient due to neglecting casing string heterogeneity and wear
Solution Approach 1:
The patent changes the parameters used in the pressure calculation model from simple rated pressure values to include heterogeneity coefficients, wear coefficients, and mechanical operation factors. This transforms the calculation into a more comprehensive model that accounts for real-world degradation and variability in casing string properties, thereby improving accuracy without entirely redesigning the computational framework.
Solution Approach 2:
The patent applies preliminary assessment of casing string conditions by evaluating heterogeneity and wear coefficients before determining the maximum well shut-in pressure. This preliminary characterization of the casing string state allows for more accurate pressure calculations to be performed subsequently, as the degradation factors are established in advance based on operational history and material properties.
2Stress or pressure
If the casing string is subjected to mechanical operation and corrosion in high-pressure sour gas wells, then the well can operate under high pressure, but the casing string experiences wear and strength degradation
Solution Approach 1:
The patent applies preliminary anti-action by introducing wear coefficients and corrosion factors that counteract the degrading effects of mechanical operation and chemical corrosion. These factors are determined based on the well's operational history, fluid composition, and environmental conditions, and are used to reduce the casing string's effective strength in the pressure calculation, thereby preventing overestimation of safe operating pressures.
Solution Approach 2:
The patent incorporates feedback mechanisms by using operational parameters such as number of mechanical operations, exposure time to corrosive fluids, and temperature history to continuously update the wear and corrosion coefficients. This feedback loop allows the casing string strength assessment to reflect actual condition degradation over time, enabling dynamic adjustment of the maximum well shut-in pressure.
Data Source
AI summary
Methods and systems for determining a well shut-in pressure of oil and gas well drilling are provided. The method comprises: obtaining, by a first processor, a basic parameter of a target oil and gas well, the basic parameter including at least one of a wellbore structure parameter, a well drilling fluid performance parameter, or a casing string parameter; obtaining, by the first processor, a pressure calculation model; and determining, by the first processor, a maximum well shut-in pressure during well drilling of the target oil and gas well based on the pressure calculation model and the basic parameter.