Study On Sedimentary Facies And Reservoir Characteristics Of Ma5₁₊₂ Of Majiagou Formation Of Ordovician In Gaoqiao Area

Based on the results of previous studies, and by means of observing cores, test analysis and comprehensive study, this paper comprehensively and systematically studies the sedimentary facies and reservoir layer characteristics of Ma51+2 member of Ordovician in Gaoqiao.Firstly it studies the types and characteristics of sedimentary facies of Ma51+2 member in Gaoqiao area Systematically. Influenced by the central palaeo-uplift, Gaoqiao area belongs to the Epicontinental carbonate platform evaporative tidal phase. According to petrology and sedimentary tectonic, this paper divids the sedimentary system of the area into 3 types of sedimentary subfacies which is supratidal zone, intertidal zone and subtidal zone and 20 sedimentary microfacies. The main depositional environment is supratidal-intertidal zone that widely developed the supratidal gypse-dolomite ground and thesupratidal gypseous-dolomite ground,which is the material base of karst reservoir. In the later period ,Gaoqiao area uplifted massively affected by Caledonian movement ,the top of Ma51+2 suffer weathering and erosion and formed dissolution pores, intergranular pore, intergranular pore solution, cream bores and cranny as a result of superposition of multiple karstification , which provide the channel and space for the late migration and storage of gas.Secondly, based on rebuilding Palaeogeomoprhology, this paper believes that Gaoqiao area is a Dipping low-lying land of southeast area, Jingbian and with strong dissolution in the top of the Ordovician,which favored the growth of weathering crust reservoir. Karst Heights and Karst inclined are the most developing position of the Karst reservoir as well as the relatively developed parts—near groove, where there are many prolific wells. The Reservoir area where upto Subsurface diffuse band region has high Dissolution rate,low Filling rate and well developed reservoirFinally, it studies the reservoir characteristics of Ma51+2 member in Gaoqiao area comprehensively. The reservoir rock includes dissolved pores mainly dolomite,dolomite cement powder, granular dolomite andbrecciated dolomite, the reservoir pore types includes dissolution pores, intergranular pore,between the solution pores, gypsum mold holes and cracks. Physical properties shows low porosity and low permeability. based on the above Information Evaluation, this paper evaluates reservoirs and filter favorable block. The results showes that the reservoirs of Ma51+2 member in Gaoqiao area is Low porosity and low permeability reservoirs, which has high heterogeneity.Finally,on the basis of lots of data of core porosity, permeability, effective thickness, open flow potential, pore structure characteristic, we select and classify the range of profitability in the area ,which type is manily typeⅡand typeⅢ.