Evaluation Of Reservoir Character Of Majiang Paleo-oil Reservoir In Depression Of South Guizhou

Due to the impact of multiphase uplift tectonic movement after forming, Majiang paleo-oil reservoir was exposed to the base level eroded, and the upper stratum and overlying formations were denuded or were exposed surface. So Majiang paleo-oil reservoir was broken up, and formation of Cambrian and Sinian had been exposed in the core of the paleo-anticline, where reservoirs were distributed and were remained in the sinks.The exploration practice confirmed that the region is a exploration area with very complexity, difficulty and high risk. Therefore, it should strengthen research of Reservoir character,point out favorable development zone,and evaluate preservation conditions latter. So it is of great practical significance to guide further work of exploration and development and to achieve breakthroughs in oil and gas exploration.On the basis of previous studies, summing up investigation findings and combining findings in exploration drilling,it is concluded that main reservoirs are limestone strata of honghuayuan formation in Ordovician and sandstone formation of wengxiang formation in Silurian, the main sedimentary character is researched, according to the lithology character, sedimentary structure and paleontology combination and so on, and sedimentary facies is divided initially.Then reservoirs are classified after the research of the types of the pore space, the character of porosity and permeability, and the character of pore structure, affecting factors of which are pointed out, and distribution of reservoirs is evaluated. With ground surveys of oil and gas, tests of residual oil saturation, and the discovery of oil and gas in drilling, oiliness of reservoirs is analyzed.The preservation conditions are evaluated, by analyzing the production formation of water, oil, and gas. Finally, the further plan for the exploration and development is proposed. Through studying above, the main pore types of honghuayuan limestone reservoir is dissolution cave,development of limestone reservoir in honghuayuan formation is controlled mainly by crust of weathering of fassil karst formed by uplift movement in the end of the Caledonian. The main pore types of wengxiangqun sand reservoir are the mainly residue original interganular pore and the dissolved pores between grains, the average porosity is 11.51% and average permeability is 69.92×10^-3μm², the pore structure is good to medium. The favorable reservoirs are mainly distributed in Kaili and Danzhai region. Oiliness of reservoir is controlled mainly by the ancient anticline and fault. The residual oil saturation of wengxiangqun sand reservoir is poor, the average of it is 10.07%, the residual oil saturation of Kaili area where is the north limb of Majiang paleo-oil reservoir is the highest the average of it is 14.06%. Region of interest is characterized with opening totally and close partly after multiphase destruction. It is possible to remain reservoir somewhere, and the wings of anticline and the fault screened reservoir are well preserved..From the results of the exploration made, the Huzhuang and Yudong are the best area for exploratory and development, and wings of anticline and the fault trap are the favorable structure.