基底变质岩深部潜山储层构造裂缝发育特征及主控因素——以渤海湾盆地渤中B区块为例

Characteristics and main controlling factors of structural fracture development in deep buried hill reservoirs of basement metamorphic rocks: a case study of B block, Bohai Bay Basin

施宁 刘敬寿 张冠杰 程奇 张雷 刘文超

SHI Ning LIU Jingshou ZHANG Guanjie CHENG Qi ZHANG Lei LIU Wenchao

1. 中国地质大学(武汉) 资源学院, 武汉 430074; 2. 中国地质大学(武汉) 构造与油气资源教育部重点实验室, 武汉 430074; 3. 中海石油(中国)有限公司 天津分公司 渤海石油研究院, 天津 300459

1. School of Earth Resources, China University of Geosciences (Wuhan), Wuhan, Hubei 430074, China; 2. Key Laboratory of Tectonics and Petroleum Resources of Ministry of Education, China University of Geosciences (Wuhan), Wuhan, Hubei 430074, China; 3. Bohai Oilfield Research Institute, Tianjin Branch, CNOOC China Limited, Tianjin 300459, China

构造裂缝是改善基底变质岩潜山储层物性、提高油气产能的关键因素，但对于基底变质岩潜山储层构造裂缝的发育特征及主控因素的多尺度综合研究较少。以渤海湾盆地渤中B区块为例，综合利用薄片、岩心和成像测井资料，系统总结了基底变质岩潜山储层构造裂缝的特征，明确了主控因素，揭示了构造裂缝有效性影响因素和发育模式。研究区构造裂缝主要发育剪性裂缝，张性缝次之，斜交缝和直立缝较发育；裂缝整体充填程度高，主要充填物为泥质，其次为碳酸盐类；识别出近EW向、NE—SW向、NW—SE向和NNW—SSE向四组构造裂缝，其中近EW向裂缝较为发育，说明印支早期的强挤压作用环境是裂缝大规模发育的关键时期。研究区构造裂缝主要受岩石力学性质、构造作用、风化作用、储层物性和岩性控制。构造裂缝有效性主要受控于最大水平主应力方向与构造裂缝走向的夹角、构造运动、裂缝充填以及溶蚀作用等因素。纵向上基底变质岩深部潜山的构造裂缝随着深度增加所受风化作用减弱，在内幕带中沿断层局部发育溶蚀孔隙；不同岩石力学性质的岩石发育裂缝程度不同，脆性指数较大的岩石裂缝发育程度较高。横向上背斜核部的构造裂缝线密度大于翼部，当储层孔隙度和渗透率处于合适范围时有利于构造裂缝发育。

Structural fractures are pivotal in enhancing the physical properties of buried hill reservoirs within basement metamorphic rocks, thereby increasing oil and gas productivity. However, there is limited comprehensive, multi-scale investigations into the development characteristics and main controlling factors of such fractures. Taking B block in the Bohai Bay Basin as a case study, this research systematically synthesized thin-section, core, and imaging logging data to delineate the characteristics of structural fractures in buried hill reservoirs within basement metamorphic rocks. This study identified the principal controlling factors and revealed the influencing factors and development patterns of these fractures. The study area mainly developed shear fractures, followed by tensile fractures, with lesser occurrences of oblique and vertical fractures. The fractures exhibited a high overall filling degree, primarily filled with mud followed by carbonate. Four groups of structural fractures in near-EW, NE-SW, NW-SE and NNW-SSE directions were identified. Among them, the near-EW fractures were more developed, indicating that the strong compressive environment during the early stage of Indosinian was crucial for widespread fracture development. The development of structural fractures in the study area was mainly controlled by rock mechanics properties, tectonic activity, weathering processes, reservoir physical properties, and lithology. The effectiveness of structural fractures was mainly controlled by factors including the angle between the maximum horizontal principal stress direction and the orientation of structural fractures, tectonic movement, fracture filling and dissolution. Vertically, the influence of weathering decreased with depth in buried hill reservoirs, with local development of dissolution pores along faults in the internal zones. Rocks with different mechanical properties showed different degrees of fracture development. Rocks with higher brittleness index exhibited higher degree of fracture development. Laterally, the line density of structural fractures in the core of the anticlines was greater than that in the flanks, providing favorable conditions for the development of structural fractures when reservoir porosity and permeability were within suitable ranges.

国家自然科学基金项目(42102156,42072173)、山东省自然科学基金项目(ZR2020QD035)和中国地质大学(武汉)“地大学者”人才岗位科研启动经费(2022046)联合资助。

https://doi.org/10.11781/sysydz202404799