歧口凹陷沙一下亚段白云岩分布广泛,白云岩可以发育物性良好的储层。根据钻井岩心、地球化学特征、扫描电镜、电子探针及物性资料,确定了该套地层白云岩储层的主要岩石类型及储集空间类型:岩石类型可分为微晶白云岩、泥晶白云岩、砂质云岩、灰质云岩和云质灰岩;储集空间有晶间孔、粒间孔、溶蚀孔、构造缝、溶蚀缝等,主要以次生孔隙和裂缝为主。微晶白云岩储集物性较好,主要为晶间孔、粒间孔及裂缝,为较好的储层。分析了目的层白云岩储层的主要成岩作用及期次,主要有胶结作用、压实、压溶作用、白云岩化作用、溶蚀作用等。明确了改善及破坏白云岩储集性能的成岩作用类型,其中对储集性产生积极影响的有溶蚀作用、白云岩化作用,消极影响的有压实、压溶作用、胶结作用。建立了歧口凹陷沙一下亚段白云岩化作用影响储层物性模式,稀土元素Eu异常特征揭示了本区白云岩化作用的两种成因环境:准同生期的回流渗透白云岩化作用和成岩期的埋藏白云岩化作用,通常准同生期的回流渗透白云岩经过深部热液流体的改造,发生埋藏白云岩化作用,多见于裂缝发育区,后者较前者对白云岩储层的改善作用更为明显。
The depression of sand about Qikou is widely distributed in the sub-section of dolomite, which can develop good reservoir properties. With core drilling, geochemistry, scanning electron microscopy, electron probe data and physical properties, the major rock and pore types of dolomite strata are determined. They can be divided into microcrystalline dolomite, clay dolomite, sandy dolomite, gray dolomite and dolomitic limestone; reservoir intergranular pore space, intergranular pores, solution holes, construction joints, corrosion and other joints, mainly in the secondary pores and cracks. Dolomicrite has good reservoir properties, mainly with intergranular pore, intergranular pores and cracks in the reservoir. The dolomite diagenesis and the stages of reservoirs in the main target zone are analyzed, including the main cementation, compaction, pressure solution, dolomitization, dissolution and so on, to make clear which reservoir types improve or damage the performance of dolomite, in which the dissolution has a positive impact on dolomitization, and the compaction, pressure solution, cementation have negative effects. Sha Qikou depression is established as a sub-section of dolomitization of reservoir property model, and the rare earth elements Eu are found in anomaly zone dolomitization, which reveals two causes of the environment: the return of penecontemporaneous penetration of dolomitization and burial diagenetic dolomitization, usually on the back penecontemporaneous dolomite infiltration of hydrothermal fluid through the transformation of deep burial dolomitization occurs, as is more common in the fracture zone, with more obvious improvement of dolomite.