Research On The Micro Geological Characteristics And Remaining Oil Distribution Of Chang 6₃ Reservoir In Hua Qing Oilfield

Based on collecting relevant information, from the point of geology, using several experimental methods, such as core observation, physical properties analysis, casting thin sections, scanning electron microscopy, high-pressure mercury injection, constant velocity mercury injection and so on, to qualitatively and quantitatively analyze the types of reservoir pore and combination,the microscopic pore structure characteristics in study area, the Chang 6₃ group's tight sandstone; at the same time, combined with the real sandstone model of water flooding experiment and the dynamic production data, to analyze the different pore combination's water flooding characteristic, type of residual oil and formation mechanism, and further analyze the distribution and influencing factors of residual oil. The main conclusions are listed as follows:?1?The types of reservoir sandstone in study area are mainly grey, taupe lithic feldspar sandstone and arkose; rock particles are poor roundness, compositional maturity is medium to low; cements are mainly the types of clay?carbonate and siliceous. The clay minerals are mainly illite?6.7% on average? and chlorite?2.4%?, kaolinite is less developed; the carbonate minerals are mainly ferrocalcite ?2.7% on average? and ankerite ?1.5%?; the siliceous minerals are mainly quartz secondary overgrowth; the reservoir physical property is poor as a whole, and the heterogeneity is a little strong, each layer has little difference. It belongs to a low porosity?super low porosity-super low permeability reservoir.?2?Pore types are mainly intergranular pore?1.76%?? feldspar dissolved pore?1.02%?; the pore combination types are mainly intergranular-dissolved pore?40.11%??micropore?32.53%? and dissolved pore?14.46%?, the main types of throat contain laminated throat, the curved lamellar throat, and the control shape throat; pores and throats are uneven distribution, the particle size is differ, but small pore and micropore are dominating, and the connectivity between pores and throats is poor.?3?The types of water flooding are mainly combined-type, single displacement type consists of uniform displacement, finger displacement and mesh displacement; samples with dissolved-intergranular pores are mainly mesh displacement and finger-mesh displacement, the oil displacement efficiency is high?37.75%?; samples with dissolved pores are mainly mesh displacement and uniform displacement, the oil displacement efficiency is slightly high?34.75%?; samples with micropores are mainly finger displacement, the displacement pressure?180Kpa? and time?6 days? are the largest, oil displacement efficiency is the lowest?33.12%?.?4?The existence types of microscopic residual oil are mainly blocked?oil slick?the corner, detour flow in a small or a large scale, the blocked and detour flow are primary existence types in study area; the distribution of residual oil in macroscopic view is:? Laterally, the residual oil is mainly distributed in the reservoir with better physical properties, especially the E and F types flow units;?Lengthways, the residual oil appears mainly in the Chang 6₃¹ single layer and the upper of the positive rhythm sandstone, the content of residual oil in the Chang 6₃² and Chang 6₃³ is less and the differences between them are not obvious.?5?The reservoir's oil displacement efficiency?types and distribution of residual oil in study area are mainly controlled by geological factors?sedimentary?structure?diagenesis and so on? and exploitation factors?water injection models?pressure?well pattern, etc?, and the effects caused by sedimentary and diagenesis, resulting in the stronger reservoir microscopic pore structure heterogeneity, lower oil displacement efficiency and complicated distribution of residual oil, are more obvious.