Study On Reservoir Characteristics Of Chang8Group In Yanchang Formation Of Zhenjing Area In Erdos Basin

Erdos basin is one of the basins in which founded oilfield at the earliest in our country. It’s oil&gas exploration and exploitation have got a series of important breakthrough after hard work of serious generation.The location of Zhenjing oil field is at the southwestern of the basin, the potential of exploration is huge. Although there are some negative factors such as low exploration degree, bad reservoir physical property and so on in Zhenjing area, the objectives factors have limited the exploration degree in Zhenjing area. This paper studies on the Chang8group thoroughly aimed at the characteristics, and makes the exploitation degree go into a new stage.This paper study on the reservoir characters of chang8group of Yanchang formation in Zhenjing area systematacially through observing outcrops, analysing and observing of cores, identifying thin slices and so on. Contrasting sublayer sand body by guiding of high definition sequence stratigraphy to confirm communication between sand bodies and plat the sand body spread. Confirm the main depositional system is the front braided channel delta depositional. And five microfacies have identified:undersea distributary channel, undersea natural levees, distal bar, mouth bar and undersea split between bays. Predict the plane spread of sedimentary facies after studying on sedimentary characteristics of every microfacies and section structure.After studying on reservoir by using logging data and the testing results, it shows that the main reservoir lithology is miliary arkose-quartz sandstone, and with medium-grained sandstone, little microgranular sandstone. The main pore types include primary intergranular pore, secondary intergranular pore, dissolved pores in grains, dissolved pores in feldspar, moldic pore and microfracture. The main clast psephicity types is angularity-underangularity, with underangularity-underound. The main cemented types is pore style, the main cementing material is calcite and kiesel, with dolomite and kaolinite. The porosity distribute is from4.5%to17.9%,the average is9.6%;the permeability distribute is from0.067to6.909xl0"3um2, the average is0.34md. Setting the reservoir lithology lower limit is fine sandstone and oil lower limit is oil slick by using logging and lithology data; the reservoir lithology lower limit is that porosity is9%and the permeability is0. lmd.According to the classification and evaluation of physical parameters characteristics of the Chang8reservoir, come to class II reservoirs have good ability of preserve and permeate. They are important reservoirs of the study area. Porosity is between10%to12%. Permeability is between0.2xl0"3um2to0.8xl0"3um2.Class III reservoirs are the main reservoir of the study area. Porosity is from9%to10%. Permeation is from0.1xl0"3um2to0.2xl0"3um2. Sedimentary facies and sand body distribution as the basis for the prediction of favorable reservoir zone, consists of three blocks, mainly belonging to the class III favorable exploration area.