致密油储层地应力特征及其对物性的影响——以鄂尔多斯盆地上三叠统延长组为例

Characteristics of in situ stress of tight oil reservoirs and its influence on petrophysical properties: a case study of Upper Triassic Yanchang Formation in Ordos Basin

高毅 林利飞 尹帅 胡国祥 马绒利

GAO Yi LIN Lifei YIN Shuai HU Guoxiang MA Rongli

延长油田股份有限公司 开发部, 陕西 延安 716000 西安石油大学 地球科学与工程学院, 西安 710065 山东科技大学 地球科学与工程学院, 山东 青岛 266590

Yanchang Oilfield Co., Ltd., Yan'an, Shaanxi 716000, China School of Earth Sciences and Engineering, Xi'an Shiyou University, Xi'an, Shaanxi 710065, China College of Earth Science and Engineering, Shandong University of Science and Technology, Qingdao, Shandong 266590, China

致密储层物性及流体赋存状态均受现今地应力的影响。以往对于鄂尔多斯盆地中西部地区上三叠统延长组的岩石力学性质及地应力研究较少，制约了致密油气的高效勘探、开发。以鄂尔多斯盆地吴起、志丹及定边地区为例，利用大量薄片、物性、岩石力学、声学、全波列阵列声波测试及压裂测试资料，对3个地区长6—长8油层组的岩石力学性质、地应力特征及其对储层物性的影响进行了评价。利用测井方法识别出3种地应力状态：吴起地区长6—长8的变化不大，其现今的应力活动性较弱；志丹地区的水平应力活动性深层要大于浅层，较强的水平应力强度主要集中在长73及长8；定边地区的水平应力活动性从长6到长8整体较强，浅层的水平应力强度要略强于深层。研究区水平应力梯度有从西北向东南逐渐递增的趋势；水平主应力差的增加不是一定使岩石减孔，其造成的应力平面非均质性会使岩石孔隙度变化出现3种不同的路径；而水平主应力差的增加会造成岩石渗透率的降低，但影响并不显著。

The petrophysical properties of tight reservoirs and the state of fluid occurrence are affected by current geostress. In the past, there were few studies on the rock mechanical properties and in situ stress of the Yanchang Formation in the central and western regions of the Ordos Basin, which restricted the efficient exploration and development of tight oil and gas. A systematic study was carried out on the rock mechanical properties, in situ stress characteristics and their effects on the petrophysical properties of the Chang 6-Chang 8 reservoirs in the Wuqi, Zhidan and Dingbian areas in the Ordos Basin. A reliable method of in situ stress logging interpretation using fracturing methods and logging models was established. The Chang 6 to Chang 8 in Wuqi area is not significantly stressed. The horizontal stress activity deep in the Zhidan area is greater than that in the shallow layers, with the strong horizontal stress intensity mainly concentrated in Chang 73 and Chang 8. The horizontal stress activity of the Dingbian area is relatively strong from Chang 6 to Chang 8, and the horizontal stress intensity of the shallow layer is slightly stronger than that of the deep layer. The stress gradients in the three work areas are determined. The horizontal principal stress gradient gradually increases from northwest to southeast. Finally, the influence of horizontal compression stress on the path of rock compaction and the petrophysical properties of the reservoir are systematically discussed. It was found that the increase of σH-σh did not cause the loss of rock pores alone. The stress plane heterogeneity will cause three different paths of rock porosity changes. However, the increase of the horizontal principal stress difference will mainly cause a decrease of rock permeability.

延长油田开发部项目 ycsy2018ky-B-04;山东省重点研发计划（公益类） 2019 GGX103021

https://doi.org/10.11781/sysydz202102250