库车坳陷克拉苏—依奇克里克构造带构造挤压型超压识别与计算

Identification and calculation of tectonic compression overpressure of Kelasu-Yiqikelike tectonic belt in Kuqa depression

强烈的构造挤压对地层超压的形成和演化具有重要影响,对构造挤压型超压的判识与估算有待进一步深入研究。综合岩石力学特征与储集物性参数的相关性,系统分析了相同应力条件下,构造挤压型超压地层和静水压力地层在垂向有效应力、声波速度、密度测井响应等方面的差异,建立了构造挤压型超压的识别模版。依据孔隙弹性理论,改进了传统的等效深度法并提出了构造挤压型超压的计算方法——平均应力法。综合实钻压力、区域地质资料和泥岩综合压实特征,在库车坳陷克拉苏—依奇克里克构造带识别出不同强度的构造挤压型超压。基于三维主应力计算,定量评估了构造挤压引起的增压量。构造挤压是克拉苏—依奇克里克构造带地层超压的重要成因机制,其对地层超压的贡献率与构造强度具明显正相关性,在克拉苏构造带KS6井区,构造挤压对超压的贡献率为43.2%~44.4%,在DB6井区的贡献率为34.1%~39.3%;在依奇克里克构造带YS4井区,构造挤压贡献率为32.8%~34.7%,在TX1井区的贡献率为21.1%~22.0%。研究方法与认识可以为预测构造挤压型盆地的地层压力提供研究思路、为有利储层的寻找提供理论指导。

Strong tectonic compression has an important influence on the generation and evolution of formation overpressure, and the identification and estimation of tectonic compression overpressure need to be further studied. Based on the correlation between rock mechanics characteristics and reservoir physical property parameters, This paper systematically analyzes the differences of vertically effective stress, acoustic velocity and density logging response between tectonic compression overpressure formation and hydrostatic pressure formation under the same stress condition, and establishes the identification template of tectonic compression overpressure. According to the pore elasticity theory, the traditional equivalent depth method has been improved, and the calculation method of tectonic compression overpressure(mean stress method) is also proposed. Based on actual drilling pressure, regional geological data and comprehensive compaction characteristics of mudstone, the paper identifies the tectonic compression overpressure with different strengths in the Kelasu-Yiqikelike tectonic belt of Kuqa depression. Based on the calculation of three-dimensional principal stress. Then a quantitative evaluation is performed on the pressurization caused by tectonic compression. Tectonic compression plays an important role in the genetic mechanism of formation overpressure in Kelasu-Yiqikelike tectonic belt, and its contribution rate for formation overpressure is obviously positively correlated with tectonic strength. The contribution rate of tectonic compression in Well KS6 area of Kelasu tectonic belt ranges from 43.2% to 44.4%, and that in Well DB6 area is from 34.1% to 39.3%. The contribution rate of tectonic compression in Well YS4 area of Yiqikelike tectonic belt ranges between 32.8% and 34.7%, and that in Well TX1 area is between 21.1% and 22.0%. The research methods and understanding will provide research ideas for the formation pressure prediction of tectonic compression basins and a theoretical guidance for seeking favorable reservoirs.