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Study On Fine Description Of Extra Low-permeability Reservoir Of Member C4+5 In Majiashan Area

Posted on:2011-06-27Degree:DoctorType:Dissertation
Country:ChinaCandidate:Y M TangFull Text:PDF
GTID:1220360302492996Subject:Mineral prospecting and exploration
Abstract/Summary:PDF Full Text Request
Because of the complex geological characteristics of extra low-permeability reservoirs, the prediction and exploitation of the reservoirs are difficult. The research object, Majiashan area, belongs to Jiyuan Oil-filed in Ordos Basin. At present, the blocks of G117, G63, and G116 in the area are being developed. The target formation, C4+5 oil-bearing formation of the Upper Triassic Yanchang Formation, belongs to extra low-permeability reservoirs, and the geological characteristics change a lot. With gradual developing, many problems have arisen, such as the low output of single well, water breakthrough in some parts of the area, the great differences of development effect among the different blocks, the great pressure to stabilize outputs of the reservoirs. To solve these problems, the author conducted intimate researches of reservoir description with the latest static and dynamic data, deeply analyzed the geological characteristics and the key factors which control the output differences of the reservoirs from macroscopic and microscopic aspects. With the limited data, the author managed to study the effect of natural fracture to the reservoir, and planned pertinent policies of development technology based on numerical simulation results.With the guidance of high resolution sequence stratigraphy and sedimentology, the author conducted systematic studies of the geological characteristics of the extra low-permeability reservoir of member C4+5 in Majiashan area, and established the isochronous stratigraphic framework. Then the author studied the rules of sand body distribution and the characteristics of reservoir heterogeneity in detail, and discussed the reservoir differences of C4+5 in different blocks based on geological background.For the first time, the author innovatively introduced Monte Carlo technology into fracture-identifying by conventional well logging, and studied the characteristics of natural fracture distribution. The method can improve the accuracy to identify fracture with conventional well logging curves in the extra low-permeability reservoir, which is great significant to identify fracture in development areas lacking of image logging data. The study shows that natural fractures are most abundant in G116 block and subsequently in G63 block. Natural fractures are not relatively abundant in G117 block. The main direction of abundant fractures is NE, and the next is NW.Because the fractures were dynamically changed by artificial hydraulic fracturing, the author selected five parameters, such as reservoir thickness, oil well waterflooded time, water-bearing rising speed per month, the ratio of fluid production index over porosity, fracture-identifying factor by conventional well logging curves, and set up special fracture-identifying method with gray relationship analysis technology, which combined dynamic data with static data to lead the fracture-identifying more reliable and conformable to the geological facts.The analysis of dynamic development shows that the development effect of G116 block is worse, which possesses the strongest reservoir heterogeneity and most abundant fractures. According to the studies of the development technology policy of reservoir C4+5 in Majiashan area by the techniques of reservoir engineering and mathematical statistics, the author designed pertinent optimization plans of injection-production pattern. The studies based on the technology of reservoir numerical simulation show that the well pattern density of the three blocks should be improved, and the diamond-shaped inverted nine-spot well pattern should be selected. The major axis direction should be identical to the main direction of abundant fractures, reducing the distance of injection-production well-drain and expanding the distance of production well-drain in the same direction of fracture. The reasonable distance of well-drain should be 500mxl50m in G117 block, 520mxl30m in G116 block, 520m×150m in G63 block. At the same time, injection-production ratio should be reduced to control injection strength, and the speed of fluid production should be improved. By these means, the increasing speed of water content can be controlled, and the aim of improving recovery ratio can be reached.
Keywords/Search Tags:Extra low-permeability reservoir, Monte Carlo, Fracture, Optimization of injection-production pattern
PDF Full Text Request
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