| 准噶尔盆地吉木萨尔凹陷二叠系超压成因及分布预测 |
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| 关键词:Jimusar Depression Permian mechanism of overpressure generation disequilibrium compaction hydrocarbon-generating supercharging pore pressure prediction grain stress |
| 基金项目:中国石油天然气股份有限公司科技专项“吐哈探区石炭系石油地质条件与勘探方向选择研究”(编号: 2021DJ0306)；“北疆海相泥盆-石炭系油气地质研究”(编号: 2022DJ0507) |
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| Mechanism of Generation and Prediction of Distribution of Overpressure within the Permian Strata in the Jimusar Depression, Junggar Basin |
| Abnormal pore pressure, developed in Permian strata throughout the Jimusar Depression, eastern Junggar Basin, is recognized as the key factor affecting the safety and efficiency of the drilling process and evaluation of the dynamic conditions of hydrocarbon accumulation. However, the causes of overpressure have still not been studied systematically, the accuracy of traditional overpressure calculation methods remains insufficient due to its deep burial, and the distribution law requires improvement. In this study, the current measured pore pressure features of the target layer were analyzed based on drilling, logging, and formation testing data, in combination with the compaction characteristics of the mudstone, organic geochemical characteristics, and present tectonic setting. Then, the mechanisms of overpressure generation were evaluated. Furthermore, based on the static equilibrium principle of formation, the pore pressure prediction model was improved theoretically. In addition, a new method suitable for the study area was developed considering the overpressure generation mechanism, and the pressure distribution in the study area was predicted. The study produced several interesting results: (1) High-amplitude overpressure is generally developed in the Permian of the Jimusar Depression, and the pressure coefficient of the Lucaogou Formation is as high as 1.8. (2) The overpressure of the Permian in the study area is caused mainly by disequilibrium compaction and hydrocarbon-generating supercharging, but a hydrothermal mechanism may also exist. (3) Traditional pressure prediction models have extremely strict assumptions and low accuracy. Therefore, based on the principle of the static equilibrium equation, grain stress parameters were introduced to eliminate the defects of the Terzaghi model, and a new pressure calculation model with significantly improved accuracy was proposed. (4) The overpressure is mainly developed in the western deep sag and the central-western slope zone, the high-pressure coefficient is mainly located in the J36 well area, which is controlled by the hydrocarbon-generating depression. The aforementioned results and implications have important guiding significance for drilling in the Permian and evaluating hydrocarbon exploration in the Jimusar Depression. |
| LI Xinning,LIU Zhen,MA Xinruo,JIAO Lixin,ZHOU Zhichao,XU Xianjing,YANG Yuzhong.2024.Mechanism of Generation and Prediction of Distribution of Overpressure within the Permian Strata in the Jimusar Depression, Junggar Basin[J].Acta Geoscientica Sinica,45(6):953-964. |
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