Study On Optimization Of Steam Flooding Development Policy For Heavy Oil Reservoir In Cretaceous G Formation In Eastern Area Of S Oilfield

Formation G in Eastern Area of S Oilfield in Kazakhstan is a structural-lithologic heavy oil reservoir with medium-high porosity and permeability.Its sedimentary type belongs to littoral and shallow delta front subfacies.At present,there are some problems in the reservoir,such as the factors affecting productivity are not clear,steam injection parameters have not yet been optimized,steam channeling is serious,insufficient understanding of remaining oil distribution and formation causes,and unknown feasibility of infilling well pattern to improve productivity.In this paper,the existing problems are studied by means of reservoir dynamic analysis,grey correlation analysis,numerical simulation,specified oil recovery index and oil production rate analysis.Based on the research results,the development policy of steam flooding in G formation of eastern area of S oilfield is optimized and adjusted from the aspects of steam injection parameter optimization,cycle shutdown adjustment of steam channeling wells,and well pattern infilling of steam flooding.The results show that the main reservoir factors affecting the steam flooding productivity of G formation in the eastern area of S oilfield are reservoir thickness and oil saturation.The main steam injection parameters affecting productivity are steam injection speed and steam injection dryness.The optimized steam injection speed is 60t/d and the steam injection dryness is 50% by numerical simulation;In view of the serious problem of steam channeling in this reservoir,the cyclic control and adjustment of easy-to-steam channeling wells in the simulation area are carried out.The results show that periodic shutdown the easy-to-steam channeling wells for one month will have the best development effect,and the economic recovery degree can reach 35.11%,the scheme can effectively alleviate steam channeling;Through comprehensive analysis of the horizontal and vertical distribution of remaining oil,it is found that the distribution of remaining oil in this reservoir conforms to the enrichment mode of physical property separation remaining oil,and the remaining oil is mainly inter-well residual oil which is not affected by steam flooding;Under the present situation of remaining oil distribution,the production rate can be greatly increased by infilling the well pattern into anti-nine-point steam drive pattern which well spacing is 106m×150m,and the degree of economic recovery can reach 38.9%,which is 3.79% higher than that of cyclically controlled easy-to-steam channeling wells.Therefore,it is feasible to increase the productivity by infilling well pattern.It is suggested that infilling well pattern test should be carried out in a small scale first.