Research On The Reservoir Characteristics Of The Chang-8 Member And Prediction Of Dessert In Jinghe Oilfield

Jinghe Oilfield is located in the southern edge of the Ordos basin, after the early exploration, a number ofhigh oil flow is tried out in the Producing layer, which shows that this region has the exploration and development prospects of oil and gas, there exist relatively high porosity and permeability sandstone in the low porosity and permeability reservoirs. Jinghe region has the low degree of research, the regularity of oil and gas enrichment is complex. The main Oil production horizon of Chang-8 is Chang-81-1 and Chang-81-2, In this paper, combined with logging, core, seismic data and the corresponding experimental data, we studied the provenance direction, sedimentary facies, reservoir, controlling factors and accumulation models of high capacity wells (dessert) of Chang-81, which provides geological basis for the next development and horizontal well deployment of Jinghe region.The rock types of Chang-8 oil-bearing Formation in Jinghe Oilfield are feldspathic lithic sandstone and lithic sandstone, and the cementation types are calcite and dolomite cementation. The reservoir space is not well developed, mainly composed of residual pore, dissolved pore and microcrack and generally filled with kaolinite and chlorite and occasionally with deformed mica, illite-smectite mixed layer, illite and authigenic quartz. The average effective porosity of Chang-8 in study area is 6%-12% and mean permeability is 0.37×10-3μm2, which means that Chang-8 is low-porosity and extra-low permeability reservoir.Chang-81"1 and Chang-81-2 develop small sand bodies which belong to northeasterly distributary channel and mouth bar. From Chang-81"2 to Chang-81-1 there is a prograding process from fluvial facies to delta-shallow lake and the reservoirs are mainly sandstones of delta plain distributary channel and front mouth bar. Studies on seismic foreset sandbody reflection and light-heavy minerals in sandstones show that the provenance is from southwest and the sand bodies stretch in northeast direction.The Zhangjiatan shale, whichis the main source rock in study area is 8m-16m in thickness, it is also the sign layer and the cap layer of the well logging and seismic reflection in the region. The argillaceous interlayer, at the top of Chang-81-1, prevents the downward migration of oil and gas. The fault through the barrier argillite, as a hydrocarbon migration path, is one of the important conditions for the Chang-8 sandstone reservoir. Four North-east trending echelon faults (a, b, c, d) occurred from west to east. In the 17 district of the Jinghe well region, a V-shaped double fracture is one of the main factors of the high production. The fault break-off from the 10ms-30ms, the horizontal spacing 400m-600m, and the section angle greater than 80 degrees. The plane opposites to the tilt and extends more than 20 km.The High-yield wells in the study area distribute along the thick sand body (main channel sand) near the fracture. The fracture in the two-dimensional seismic zone to the south Jinghe River is similar to the northern three-dimensional zone, in which, the vertical fault cut the deeper formations. The length of the rupture Smaller-scale in two-dimensional fracture zone is only about one-third to the half than that of three-dimensional. However, the density of the two-dimensional fracture region increases more. With the limited capacity in thin hydrocarbon source rocks and the surrounding of the Yanchang 8th, the "dessert" has been controlled by a certain size fault and thick sand.