风化壳古岩溶型碳酸盐岩储层成岩作用与成岩相

Diagenesis and diagenetic facies of crust-weathered ancient karst carbonate reservoirs

何江 冯春强 马岚 乔琳 王勇

He Jiang Feng Chunqiang Ma Lan Qiao Lin Wang Yong

成都理工大学 地球科学学院, 成都 610059 2. 西南石油大学, 成都 610500 3. 中国石油 西南油气田分公司, 成都 610051

College of Earth Sciences, Chengdu University of Technology, Chengdu, Sichuan 610059, China 2. Southwest Petroleum University, Chengdu, Sichuan 610500, China 3. PetroChina Southwest Oil and Gas Field Branch, Chengdu, Sichuan 610051, China

以鄂尔多斯盆地靖边气田北部马家沟组马五41小层为例,通过详细的井下地质调查、典型成岩特征写实、系统取样和室内测试等研究,以地质背景和古岩溶岩石学特征为主线,精细解剖风化壳古岩溶型碳酸盐岩储层成岩作用特征,并进行成岩相识别.研究发现:马五41小层海水成岩环境以白云岩化作用和硬石膏化作用为主,受控于古地理格局;表生成岩环境发育溶孔缝型和溶洞型溶解充填作用,受控于古岩溶地貌;埋藏成岩环境常见扩溶型溶解作用.基于成岩作用与孔渗网络耦合关系,采用"海水成岩环境成岩作用+表生成岩环境成岩作用"组合原则划分出4种典型成岩相类型:(Ⅰ)硬石膏小结核白云岩化—溶孔缝型中—弱充填相,(Ⅱ)硬石膏小结核白云岩化—溶孔缝型中—强充填相,(Ⅲ)白云岩化—溶洞型强充填相,(Ⅳ)硬石膏岩化—溶孔缝型强充填—溶洞型强充填相.其中Ⅰ类相区优质储集岩类发育,岩溶强度适中,(沉淀)充填中—弱,易形成裂缝—溶(孔)洞型储层,是为最有利的成岩相区.

In the north of the Jingbian Gas Field in the Ordos Basin, a case study was made of the first section of the fourth sub-member of the fifth member of the Majiagou Formation (M541). Through detailed subsurface geological analysis, a realistic description of typical diagenetic features, systematic sampling and laboratory testing, with geological background and petrological characteristics as main clue, the diagenesis characteristics of crust-weathered ancient karst carbonate reservoirs were analyzed, and the diagenetic facies were recognized. The marine diagenetic environment of M541 was influenced by dolomitization and anhydritization, and was controlled by the palaeogeographic framework. As to the epidiagenetic environment controlled by ancient karst physiognomy, dissolution and packing effects of dissolved pore, fracture and cave types took place. For the buried diagenetic environment, extensive dissolution was common. Based on the coupling relationship between diagenesis and porosity-permeability network, a "diagenesis in marine diagenetic environment + diagenesis in epidiagenetic environment" combination principle was adopted to divide the diagenetic facies into four typical types: (Ⅰ) medium-weak filling facies of anhydrite small nodule dolomitization-dissolved pore and fracture type; (Ⅱ) medium-strong filling facies of anhydrite small nodule dolomitization-dissolved pore and fracture type; (Ⅲ) strong filling facies of dolomitization-dissolved cave type; and (Ⅳ) strong filling facies of anhydrite lithification-dissolved pore and fracture type, and strong filling facies of dissolved cave type. With well-developed premium reservoir rocks, moderate karst intensity and medium-weak (deposition) filling, the type-Ⅰ area was favorable for fracture-cave reservoir development.

国家油气重大专项"岩性地层油气藏成藏规律、关键技术及目标评价"(2011ZX05001)资助.

https://doi.org/10.11781/sysydz201501008