尖北气田基岩构造裂缝特征及其对储层的影响

Structural Fracture Characteristics of Basement Rocks in Jianbei Gas Field and Its Reservoir Improvement Effect

程鑫 柴小颖 杨会洁 王海成 肖鑫

CHENGXin CHAIXiaoying YANGHuijie WANGHaicheng XIAOXin

中国石油青海油田分公司勘探开发研究院, 甘肃 敦煌 736200 北京阿什卡技术开发有限公司, 北京 朝阳 100101

Research Institute of Exploration and Development, Qinghai Oilfield Company, PetroChina, Dunhuang, Gansu 736200, China Beijing ESSCA Co. Ltd., Chaoyang, Beijing 100101, China

裂缝是影响基岩气藏高效开发的关键因素。综合岩芯、薄片及成像测井资料，分析了尖北基岩气田构造裂缝分布规律，探讨了裂缝对储层质量的控制作用。构造裂缝以直立-高角度半充填-未充填缝为主，开启缝占比63.3%；裂缝走向主要包括近EW向、NW-SE向、NE-SW向和近SN向4组；上部层位以近EW向为主（占比80%），裂缝密度高、开度大，下部层位的裂缝多为NW-SE向和NE-SW向，裂缝发育不均，开度一般偏小；背斜高部位裂缝最发育，其次为构造斜坡和鞍部，断层控制区有效裂缝发育差。构造裂缝促进基岩风化淋滤作用，有效沟通次生孔隙，提升储层渗透率1~2个数量级，在基岩不整合面之下形成厚约40~150 m的优质储层。综合分析认为，构造高部位优质储层厚度大，控制了气井高产，是勘探开发部署的有利区，基岩不整合面下40 m之内风化淋滤作用强，是水平井钻探的有利靶区。

Fracture is the key factor affecting the development of basement rock reservoir. Using core, thin section and imaging logging data, the characteristics of structural fractures in bedrock reservoir of Jianbei Gas Field is analyzed, and the improvement effect of fractures on reservoir properties is addressed. The structural fractures are mainly vertical-high angle and semi-unfilled, with open fractures accounting for 63.3%, mainly showing near EW, NW–SE, NE–SW and near SN orientations. The dominant orientation of fractures in the upper layer of basement rock is near EW (accounting for 80%), with high fracture density and large aperture; while most fractures in the lower layer are NW–SE and NE–SW, with heterogeneous distribution and generally small aperture; On the plane, the fractures in the high part of the anticline have the greatest liner density and aperture, followed by the those in the structural slope and saddle, and the effective fractures in the fault control area have relatively low liner density and small aperture. Structural fractures promote weathering and leaching of basement rock, and effectively communicate secondary pores, improve reservoir permeability by 1~2 orders of magnitude. Fracture development results in the formation of high-quality reservoir with a thickness of about 40~150 m below the unconformity surface. The comprehensive analysis shows that the highquality reservoir in the high part of the structure has a large thickness, which controls the high productivity of gas wells and is favorable for exploration and development deployment. The 40 m thick reservoir section under the basement unconformity has experienced strong weathering and leaching and has good properties, which is a favorable target for horizontal well drilling.

10.11885/j.issn.1674-5086.2021.12.21.02