准噶尔盆地南缘中段深层—超深层超压成因机制及其与成藏的关系——以HT1气藏为例

Overpressure formation mechanism in deep and ultra-deep layers in middle section of southern margin of Junggar Basin and its relationship with reservoir formation: a case study of Hutan 1 gas reservoir

田志新 刘刚 彭叙凯 范昌育 王刚

TIAN Zhixin LIU Gang PENG Xukai FAN Changyu WANG Gang

西北大学 地质学系, 西安 710069 中国石油勘探开发研究院, 北京 100083 中国石油 长庆油田分公司 第一采油厂, 陕西 延安 716000

Department of Geology, Northwest University, Xi'an, Shaanxi 710069, China PetroChina Research Institute of Exploration & Development, Beijing 100083, China The First Oil Production Factory, Changqing Oilfield Company, PetroChina, Yan'an, Shaanxi 716000, China

近年来，准噶尔盆地南缘深层—超深层油气勘探不断取得突破，该地区深层—超深层普遍发育超压，明确超压成因机制及其与油气富集关系，对深层—超深层的油气勘探具有指导意义。利用DST实测压力资料分析了南缘深层—超深层压力分布特征，通过综合泥岩压实曲线、VES-VP交会图版、DEN-VP交会图版综合判识了HT1气藏复杂超压成因，并结合声发射实验及应力场模拟等技术方法，分析讨论了HT1气藏超压与油气成藏的关系。分析认为：(1)南缘深层—超深层除山前第一排冲断带外，普遍发育压力系数达2.0以上的极强超压。垂向上超压分布在吐谷鲁群厚层泥岩及其之下地层中，平面上强超压主要发育在南缘中段山前第二、三排构造带及西段四棵树凹陷内；(2)综合识别出HT1气藏发育欠压实成因及构造挤压成因超压，其中区域性厚层泥岩快速沉积造成欠压实超压产生，而喜马拉雅运动晚期天山隆起对南缘形成的N-S向强挤压应力是深层—超深层构造挤压超压形成的原因；(3)深层流体超压的形成，一方面促进了HT1气藏清水河组背斜圈闭的褶皱变形，形成油气优势汇聚部位，另一方面改变了呼西背斜周缘的流体动力场格局，使得气势梯度增加，增强了天然气运移动力，为油气在呼西背斜的富集提供了良好的动力条件。

In recent years, breakthroughs have been continuously made in deep and ultra-deep oil and gas exploration in the southern margin of the Junggar Basin. Overpressure is commonly developed in the deep and ultra-deep layers of this area. Clarifying the overpressure formation mechanism and its relationship with oil and gas enrichment is of great significance for guiding oil and gas exploration in these areas. In this study, the pressure distribution characteristics in the deep and ultra-deep layers of the southern margin were analyzed using drill stem test (DST)-measured pressure data. The complex overpressure formation mechanism in Hutan 1 (HT1) gas reservoir was identified through comprehensive analysis of mudstone compaction curves, VES-VP cross-plots, and DEN-VP cross-plots. Based on the acoustic emission experiments and stress field simulations, the relationship between overpressure and oil and gas accumulation in HT1 gas reservoir was analyzed and discussed. The analysis showed that: (1) Except for the first row of thrust belts at the mountain front, extremely strong overpressure with a pressure coefficient greater than 2.0 was widely developed in the deep and ultra-deep layers of the southern margin. Vertically, overpressure was distributed in the thick mudstone of the Tugulu Group and its underlying strata. Horizontally, strong overpressure mainly developed in the second and third rows of structural belts at the mountain front in the middle section of the southern margin and in the Sikeshu Sag in the western section. (2) Comprehensive analysis identified that the overpressure in HT1 gas reservoir was caused by undercompaction and structural compression. Regional rapid deposition of thick mudstone caused undercompaction-associated overpressure, while the strong north-south trending compressive stress exerted by the Tianshan uplift during the late Himalayan Movement onto the southern margin caused structural compression overpressure in the deep and ultra-deep layers. (3) The formation of fluid overpressure in the deep layers promoted the folding deformation of the anticline trap in the Qingshuihe Formation of HT1 gas reservoir, forming an optimal area for oil and gas accumulation. Meanwhile, it changed the fluid dynamic field pattern around the Huxi anticline, increasing the gas potential gradient and enhancing the natural gas migration dynamics, thus providing favorable dynamic conditions for oil and gas enrichment in the Huxi anticline.

中国石油勘探开发研究院测试分析项目“准噶尔盆地南缘中下组合声发射及构造应力压力分析” RIPED-2021-JS-710

https://doi.org/10.11781/sysydz2024061166