Reservoir Characteristics And Distribution Of The Ordovician Yingshan Formation In The Lugu 7 Well Area

The main problems are reservoir heterogeneity, diverse control factors and reservoir distribution of the Yingshan Formation in Lungu 7 Wellblock. Guided by reservoir geology, karst geomorphology, logging geology and other disciplines, and according to using core, conventional logging, imaging logging, drill logging, production dynamics, and seismic data, the paper analyzes the basic characteristics of the reservoir, then summarizes the rock characteristics, reservoir space types, reservoir characteristics and reservoir types. Furthermore, describes its distribution in the vertical and horizontal direction. Analysis the controlling factors of reservoir development from the main lithological facies, weathering crust karst, fracture and corrosion buried these dimensions to predict favorable reservoir development area. The main conclusions are as follows:The Yingshan Formation of Ordovician in Lungu 7 Wellblock can be divided into four Segments from top to bottom, and the main lithology includ bright crystal grain limestone, micritic limestone, dolomitic limestone and karst rock. The reservoir rock of the study area with the matrix porosity distribution range of 0.2% to 7.0%, the average is 1.26%, permeability distribution of 0.02×10-3um2?376.78×10-3um2, the average is 0.32×10-3um2 concentrated in 0.01×10-3um2?1×10-3um2, the whole reservoir physical parameter is low porosity and permeability. According to relations of the hole, cave and fracture, the reservoir types can be divided into fractured, holes and cave holes and cracks those four categories; wherein the fractured reservoirs in the study area is the most developed one, accounting for 37.7%, followed by the cave-type, accounting for 26.4%, hole type 19.6%,16.3% crack hole type.In the longitudinal direction, within 160m from the top of the range, there are four sets of reservoir in top-down direction, The first set is in the range of 0-30m, and the second set is in the range of 40-60m, and the third is set in the range of 90-120m, the fourth set is in the range of 140-160m, Wherein the first set and the third set is the best reservoir properties, the holes porosity of the first set of the distribution at 0-15%, average is 6%, the third set at 0-14%, average is 4%, then followed by the second set of holes porosity at 0-15%, average is 3%. In the transverse direction, in the upper part of Yingshan Formation the reservoir developed, and it has good lateral continuity, the lower part of the formation the reservoirs developed in some local area, and has poor continuity.Divide those wells in the block into epikarst zone, vertically filtering zone and horizontal flowing zone. With the seismic data, restore the ancient landscape before Carboniferous, the study area can be divided into depressions dissolved mound depressions and valleys fengcong mound these three three geomorphic units. In different landscape units, each karst with a varies degree of development, and the epikarst is controled by the microgeomorphology. According to the development characteristics of cave-cleft, sub landscape-units and karst with different types of fractured body for statistical analysis, showed that surface cave-cleft is most developed, and the main cave-cleft is fractured.According to the study of the different reservoirs types of drilling rate and where the monadnock is, found that in lg7-4, lg3, lg7, lg7-5-2,lg701,lg 7-10,the reservoir is most developed, and the class ? monadnock is the most developed one, and obviously the monadnock drilled core part is higher than monadnock slope.The large thickness, widely distributed beach subfacies in the open platform, rocks are the lithology limestone, which can be high-speed dissoluted to form a large number of dissolution bores, cavities and fractures, which is the material basis of reservoir development. Fracture can be as a reservoir space and flow channel, and it is conducive to the karst, to form a unified hole, cave, slit system. The solution expansion joints and expansion cave of burial dissolution, increased the reservoir space, and improved the reservoir performance. According to the seismic data, the karst reservoir is mainly distributed in the solution mound depressions which near the fault location and along the fault west which controlled by the fracture.