渝东南南川地区五峰组—龙马溪组页岩气层地应力数值模拟及有利区预测

Numerical modeling of in-situ stress and prediction of favorable area of shale gas layer in Wufeng to Longmaxi formations, Nanchuan region, southeastern Chongqing

刘明 杨瑞青 杨风丽 刘昊娟 张志萍 王玮 户盼盼

LIU Ming YANG Ruiqing YANG Fengli LIU Haojuan ZHANG Zhiping WANG Wei HU Panpan

1. 中国石化 华东油气分公司 勘探开发研究院, 南京 210000; 2. 同济大学 海洋与地球科学学院, 上海 200092

1. Research Institute of Exploration and Development, SINOPEC East China Oil & Gas Company, Nanjing, Jiangsu 210000, China; 2. School of Ocean and Earth Science, Tongji University, Shanghai 200092, China

南川地区上奥陶统五峰组—下志留统龙马溪组作为重要的页岩气产能层，具有页岩层厚度大，埋藏较深，地应力复杂、方位变化快的特点，地应力场研究对于该区页岩气的有效开发具有重要作用。为明确研究区地应力场特征及展布，通过采用SHELLS有限元应力场模拟方法，以研究区断裂、地形、热流值、岩石物性参数和边界条件为约束，开展了南川地区五峰—龙马溪组的应力场有限元数值模拟研究。结果表明，南川地区最大水平主应力性质以挤压性质为主，总体上存在NW-SE、NE-SW、近EW和近SN四个主应力方向和区域；应变率整体以压应变为主，存在低应变率(数量级别≤-18)、中应变率(数量级别介于-18~-17.6)和高应变率(数量级别≥-17.6)三类区域及相应的NE-SW、NW-SE、SN和EW展布方向；断裂滑移速率性质总体以逆断层性质为主，速率介于0～0.001 2 mm/a之间。将本次模拟的最大水平主应力方向、块体应变率和断裂滑移速率结果分别与实测的钻井最大主应力方向、黔渝地区应变率性质和数量级别、区域断裂发育等数据进行对比，展现出模拟结果与实测结果较高的数据吻合度，说明了模拟结果的准确性。最后，基于模拟结果揭示出的裂缝开启性、裂缝发育情况的信息，对南川地区裂缝储层有利发育区进行了评价，预测了Ⅰ、Ⅱ两类进一步勘探和开发的页岩气裂缝储层有利发育区块。

Upper Ordovician Wufeng to Lower Silurian Longmaxi formations in Nanchuan region, as an important shale gas productive layer, is characterized by large shale thickness, deep burial depth, and complex in-situ stress with rapid direction changes. Therefore, the study of in-situ stress field is of significance for effective deve-lopment of shale gas in the study area. In order to clarify the characteristics and distribution of the in-situ stress field, the SHELLS finite element stress field modeling method, with faults, topography, heat flow, petrophysical parameters and boundary conditions as constraints, was used in the study of the stress field in the Wufeng-Longmaxi formations in the Nanchuan region.The results indicate that the maximum compressive horizontal principal stress is in thrust regime and that there are four principal stress directions and regions in general: NW-SE, NE-SW, near EW and near SN. The strain rate is in thrust regime, with three regions of low strain rate (magnitude ≤ -18), medium strain rate (magnitude between -18 and -17.6) and high strain rate (magnitude ≥ -17.6) and their corresponding NE-SW, NW-SE, SN and EW spreading directions. The fault slip rate regime is in thrust, the fault slip rates range from 0 to 0.001 2 mm/a. The modeled results of the maximum compressive horizontal principal stress, the strain rate and fault slip rate were compared with the measured data respectively, including the maximum compressive horizontal principal stress directions measured in drilled wells, the regime and magnitude of strain rate in Guizhou and Chongqing, and the properties of regional faults. The modeled results showed high agreement with the measured data, indicating the accuracy of the predicted results. Finally, based on fracture openness and fracture development revealed by modeled results, favorable fractured reservoir development zones for shale gas was evaluated, and class Ⅰ and Ⅱ zones for further exploration and development were predicted.

国家自然科学基金重大研究计划重点项目 (92158207)和中国石化华东油气分公司科研项目(34600020-22-ZC0607-0001)联合资助。

https://doi.org/10.11781/sysydz2023061178