四川盆地海相碳酸盐岩储层成因及特征

Genesis and characteristics of marine carbonate reservoirs in Sichuan Basin

根据四川盆地海相碳酸盐岩储层的岩石学、地球化学等特征,结合储层发育分布规律,提出储层成因综合分类:指出四川盆地海相碳酸盐岩储层分为礁滩储集层、表生岩溶储集层、白云岩储集层三大类。三个大类进一步分为了7个亚类。礁滩储集层发育的最主要控制因素是沉积相带,即礁、滩相沉积控制优质储层规模发育,也控制了后期的白云石化作用和岩溶作用;依据沉积特征,将礁、滩储集层分为台缘礁储集层、台缘颗粒滩储集层、台内颗粒滩储集层3个亚类。岩溶作用的强度和对储层的改造效果受岩石成分和岩石组构控制,形成不同类型的表生岩溶储集层;依据储层特征,将表生岩溶储集层划分为白云岩风化壳储集层、石灰岩风化壳储集层2个亚类。白云岩储集层主要受控于白云石化作用和与白云石化流体相关的溶蚀作用。储层成因及地质特征的认识对于四川盆地寻找规模碳酸盐岩储层的油气勘探具有重要借鉴作用。

According to the petrological and geochemical characteristics and the development distribution laws,the marine carbonate reservoirs in Sichuan Basin may be divided into three types from their genesis,including bioreef—shoal reservoirs,supergene karst reservoirs,and dolomite reservoirs.Moreover,these three types of reservoirs can be subdivided into seven subtypes.For the bioreef—shoal reservoirs,the most important factor controlling their development is sedimentary facies belt,in other words,both bioreef—and shoal—facies sediments affect not only the large—scale development of quality reservoirs but also the later dolomitization and karstification.Based on sedimentary characteristics,this type of reservoirs may be subdivided into three subtypes,i.e.platform margin bioreef reservoirs,platform margin grain shoal reservoirs,and intraplatform grain shoal reservoirs.The karstification intensity and its effect on reservoir reformation are controlled by rock composition and framework to form different types of supergene karst reservoirs.In addition,on the basis of reservoir characteristics,the supergene karst reservoirs may be subdivided into two subtypes,i.e.dolomite weathering crust reservoirs and limestone weathering crust reservoirs.The former is mainly affected by dolomitization and dissolution associated with dolomitized fluid.These geological understandings on reservoir genesis and characteristics may provide important reference for seeking large—scale carbonate reservoirs in Sichuan Basin.