Study Of Economical Development Mode And Principle For Offshore Low Permeability Reservoir

Marine low permeability reserves have the characteristics such as deeply buried depth, poor reservoir properties, strong heterogeneity, the existence of start-up gradient, and also face many unfavorable condition like marine environment, limited platform space and load-bearing, that make it difficult to establish effective Injection-production system.Based on the combination of geological reservoir, development technology and economic factors, focused on the effective development of low permeability reservoir, the author established the theory of effective water injection development in marine low permeability oilfield which considering the influence of starting pressure gradient, and studied the rational well type, well pattern, well spacing, fracture parameters for the effective water injection development of the target block, A method of establishing effective injection production and effective control reserves under the condition of the offshore fewer well was put forward. Based on many factors influencing the low permeability oil reservoir, the effective development limit chart was established. The comprehensive evaluation coefficient of well group reserves quality and reserve scale was combined. The effective development model of low permeability oil field was put forward.(1)Based on the geological characteristics and low permeability oilfield development characteristics, the author analyzed the general and special problems of effective development of marine low permeability oilfield, thus proposed three basic ideas to solve effective development problem of marine low permeability oilfield:Based on the geological reservoir as the core, strengthen the basic research of geological reservoir and combine technology and economic conditions in order to seek a breakthrough method and combine the technology of onshore oil field development with the conditions of offshore oil field development; strengthen the basic research of geological reservoirs; strengthen technology research; establish the pilot test area; explore economic development mode.(2)Using complex function theory and transforming the horizontal wells on the Z plane to drainage radius circular tunnel on the plane W by inversed joukowski function, this paper analyzed the seepage characteristics of deviated wells injection- horizontal wells production system, discussed the research method and impact factors of limited injection-production well spacing and the effectively impacted scope of water injection, and then established the corresponding plate. Based on the above discussion, the author analyzed the longitudinal producing ratio with the limit of limited injection-production well spacing and the required hydraulic fracturing scale.(3) Based on reservoir engineering optimization method and threshold pressure approximate simulation start pressure, considering the influence of well pattern, well spacing, row distance factors, the orthogonal experiment design of the mixed well pattern, the mixed well pattern is designed by orthogonal experiment. From the comparison of the different programs to the simulation results, the optimized well pattern and the corresponding fracture parameters are obtained.(4) Based on the development mode of multiple-stage fracturing with horizontal well, the optimal parameters of hydraulic fracture are obtained with the calculation model considering starting pressure grediant.(5)Through the analysis of lowest single well economic yield of Marine low permeability oilfields restricted by multiple factors, based on multiple factors of principles and methods, the author established effectively water flooding developed line plate on the basis of marine low permeability oilfield. Specifically including: ?The limit under whole cost development with onshore terminal and offshore FPSO; ?The limit under partial cost development tied to existing oilfield around.?The influence of heterogeneity on oilfield development using the permeability variation coefficient.?The influence of buried depth on the development of reservoir limits considering the drilling cost change with drilling depth. ? Impact of development cost reduction on development limits based on the technical improvement and management improvement. ? The influence of applying for derating state tax on the development of reservoir limits.(6)Defying the comprehensive evaluation coefficient of well group reserves and obtaining the threshold value of comprehensive evaluation coefficient, based on the scale of reserves this paper first put up with the effective development mode decision table for different types of marine low permeability oilfield.