四川盆地下组合(震旦系至石炭系)的震旦系至奥陶系碳酸盐岩中发育三种成因类型的岩溶,即构造不整合面岩溶、准同生期沉积间断岩溶和同生期岩溶.受多期区域性构造抬升作用的影响,下组合中形成多个区域性构造不整合面,之下的碳酸盐岩发育不整合面岩溶型储层.在碳酸盐岩沉积后的准同生浅埋藏阶段,受到局部短期构造抬升作用而暴露至地表,发生沉积间断和岩溶改造,从而在相对较为连续的厚层碳酸盐岩中发育多层的沉积间断岩溶型储层.受短期相对海平面下降影响,下寒武统龙王庙组颗粒滩相白云岩暴露至海平面之上,遭受同生期的大气降水岩溶改造,在相对海平面上升—下降频繁变化作用下,发育多层同生期滩相岩溶型储层.由于构造抬升作用以及相对海平面下降而形成的不同级别层序界面,决定了该级别层序界面之下岩溶型储层发育的分布范围和强度,并且多种成因类型的岩溶从早至晚依次叠置和复合改造,构成了下组合岩溶型碳酸盐岩储层在垂向和横向上广泛发育的格局.

the Lower Assemblage refers to the whole thick pre-Mesozoic formations from Sinian system to Paleozoic Carboniferous system in Sichuan Basin. Three types of karst reservoirs develop in Sinian-Ordovician Carbonate rock in the Low Assemblage, which are tectonic unconformity karst, penecontemporaneous hiatus karst and contemporaneous karst reservoirs. Having been affected by long-term regional tectonic uplifts and frequent sea level eustasies, several regional tectonic unconformities, including ?1/Z2dy, O1/?2-3, S1l/O2b and P1/Z unconformities, and sequence boundaries formed and several contemporaneous shoal facies karst reservoirs developed under these unconformities. Superimposition and repeated reformation of multi-genetic karstification from early to late is the reason why carbonate karst reservoirs widely develop in horizontal and vertical extents in the Lower Assemblage.