Characteristics And Distribution Of The Karst Reservoirs Of The Ma5₁₊₂ Multi-stage Superimposed Weathering Crust In The Eastern Ordos Basin

In close combination with the actual exploration, in Ordos Basin weathering crust of Ordovician in eastern Ma51+2 as the object, to multidisciplinary geological theory and method as a guide, making full use of drilling coring, thin section identification, logging, core observation and analysis of matching test data, and make a deeply stuy to the characteristics and distribution of karst reservoir in multi stage superimposed weathering crust.the reservoir rock type of Ordovician Ma51+2 is diversiform, including plaster mould hole micrite dolomite and particle dolomite, algal lattice frame dolomite and karst alteration rock; reservoir space mainly include gypsum mould hole, intergranular dissolution pore, moldic pore, algae framework pores and intergranular (solution) hole and karst system in carbonate sand holes between reservoir types. The reservoir type is mainly pore type reservoir with fracture, also see a small amount of hole type reservoir; reservoir set performance with gypsum mould hole micrite dolomite best. Clear the area through Ordovician Ma51+2 Atmospheric freshwater karstification type, identification is the basis and effect on reservoir. It is pointed out that there are two phases of atmospheric water dissolution, the early diagenetic stage of karst and the late diagenetic stage of karst. The early diagenetic stage of karst and filling for the storage layer, the overall performance of the constructive role, and late diagenetic stages of karst especially mud filling of reservoir mainly damage. Through the observation and analysis of cores, ploting typical karst single well and connecting well section of Ma51+2, clear the area of karst with multi period, frequent, and multilayer bedding filling developmental characteristics of cave collapse, found that there is a close correspondence between the early diagenetic stage of cave development period and granular-beach weakly consolidated porous layer belonging to the facies controlled karst, late diagenetic stage of karst is relatively stable subsurface karst zone and mainly developed in Ma514 small layer at the bottom, also developed along the previously cave superimposed along the layer in the cave. However, the distribution of irregular. Based on the ancient karst landform analysis, it is found that the area in order to smooth the solution hills and plain features, which belongs to the karst slope areas, due to things to the valley extends the impact, division are Karst Hilly, karst hill slope and gully three geomorphic units, which dissolved mound and karst hill slope is the most favorable reservoir zones. Considering the favorable sedimentary geomorphology, sedimentary facies and karst landform, and calculate the favorable reservoir area...