鄂尔多斯盆地西南缘奥陶系碳酸盐岩储层主控因素分析

鄂尔多斯盆地西南缘奥陶系碳酸盐岩在地质演化过程中形成了以次生成因的孔、滑、缝为主要储集空间类型的储层。该套储层是在沉积环境、成岩作用和构造作用的相互作用下形成的,其中沉积环境是基础,影响着储层的基本形态,有利于储层形成和发育的沉积环境为碳酸盐岩斜坡、潮坪和台内浅滩;成岩作用决定了储层的最终分布形态、范围和储集空间特征,对储层物性优劣起主导作用;有利于储集空间发育和扩大的成岩作用主要有白云石化作用、溶解作用和压溶作用。构造作用主要是构造抬升可形成沉积间断面和不整合面,促进了与岩溶作用有关的岩溶型储层和各种类型的节理、裂缝边溶孔的发育。

Analyses on main controlling factors of carbonate reservoirs of Ordovician system in the southwest margin of Ordos Basin

During the geological evolution, carbonate rocks of Ordovician system in the southwest margin of Ordos Basin formed a kind of reservoir whose reservoir space type is mainly secondary origin voids, vugs and fractures. This set of reservoir was formed by mutually interaction among sedimentary environment, diagenesis and tectonism. Sedimentary environment is the basic factor that controls the primary form of the reservoir. Carbonate slope, tidal flat and shoal in the platform are the favorable sedimentary environment for the formation and development of reservoir. Diagenesis which played cardinal role in the quality of reservoir physical property determines the final distribution form, scope and space characteristics of reservoir. The main diageneses which are beneficial to the development and extending of reservoir space are dolomitization, karstification and pressure solution. Tectonism, under which depositional break and unconformable surface were formed through tectonic uplifts mainly, promoted the development of karst reservoir and all kinds of solution voids pores near the joints and fractures.