深水油气含水合物地层固井过程数值模拟分析及工艺参数优化研究

Numerical Simulation Analysis and Optimization of Process Parameters in the Cementing Process of Gas Hydrate-bearing Sediments in Deep Water Oil and Gas Wells

摘要:

南海地区被证实富含油气资源和天然气水合物资源，然而在油气钻井过程中常钻遇水合物地层。固井作业是油气开发的重要环节，然而在深水钻井中，固井过程中水泥水化放热可能引发水合物的分解，降低地层稳定性，甚至影响固井质量。本研究采用数值模拟方法，以南海神狐海域GMGS-1工程SH7站位水合物地层为对象，建立了固井数值模型，分析了固井过程中水泥浆侵入水合物地层所引发的问题及固井工艺参数的影响。研究发现，水泥水化放热速率的增加会显著提前反侵现象的发生时间，增加反侵量；固井压差对反侵现象影响较小，但超过一定阈值后会抑制反侵；延长保压时间会显著推迟反侵的起始时间，减少反侵量。因此，在实际工程中，建议采用低水化热水泥，适当延长保压时间，并在早期阶段避免过高的固井压差，以减少水合物的分解，降低反侵现象的发生。本研究为水合物地层的固井作业提供了理论基础，对提高固井作业的安全性和效率具有重要意义。

Abstract:

The South China Sea has been confirmed to be rich in oil and gas resources as well as natural gas hydrate resources. However, hydrate-bearing formations are often encountered during the drilling of oil and gas wells. Cementing is a critical step in oil and gas development. In deepwater drilling, the heat released during cement hydration can potentially induce hydrate decomposition, compromising formation stability and even affecting cementing quality. This study utilized numerical simulation methods, focusing on the hydrate-bearing formation at the SH7 site in the Shenhu area of the South China Sea GMGS-1 project. A numerical model for cementing was established to analyze the issues caused by cement slurry invasion into hydrate-bearing formations and the impact of cementing process parameters. The study found that an increase in cement hydration heat release rate significantly advanced the onset of gas and water influx, as well as increased its volume. The cementing pressure differential had a minor impact on the influx phenomenon, but it suppressed the influx when exceeding a certain threshold. Prolonging the pressure maintenance period significantly delayed the initiation of influx and reduced its volume. Therefore, it is recommended in practical engineering to use low-heat cement, extend the pressure maintenance period, and avoid excessively high cementing pressure differentials in the early stages to minimize hydrate decomposition and mitigate the occurrence of influx. This research provides a theoretical foundation for the cementing of hydrate-bearing formations, which is of great significance for enhancing the safety and efficiency of cementing operations.