Study On The Fine Description Method For Wuerhe Low-permeability & Difficult Recovery Reservoir In Xinjiang Junggar Basin

At present, it is an urgent problem for us to develop some advanced and practical fine description techniques for the low efficient and complex reservoir with low-permeability and difficultly movable reserve in our petroleum industry.The reservoir in Kelamayi & Baikouquan formation of Triassic zone in Wuerhe oilfield is a typical low-efficient reservoir. Based on the study on fine reservoir description of this reservoir, the results not only provide more information of this low efficient reservoir, but help to establish the efficient development model and exploitation techniques. And the results also ensure that Wuerhe has high and stable production and high-efficient development, which can enhance its exploitation technology and provide very important and valuable instructions to the other entire low-efficient oilfield of Junggar basin.Aimed at the problems in the reservoir description of Wuerhe oilfield, the investigating is focused on the Kelamayi and Baikouquan formation of Triassic zone of Wu5 and Wu16 areas. The research integrates all of data, such as core, well logging, seismic, dynamic information while production and etc., and adopts many novel methods. The main contents include the following 7 aspects: (1) stratigraphic division and correlation and establishment of the formation thickness model,(2) intensive interpretation of faults and study on the micro-structure model, (3) Identification of sedimentary microfacies and establishment of distribution model of that, (4) precision processing of well logging data, (5)foundation of quantitative geological model of formation and analysis of formation characteristics, (6) research of the oil-water distribution and establishment of distribution model of storage capacity, (7)study on the development program.Formation sequence (depth interface) of T₂k- T₁b, including 20 sand layers, is determined through stratigraphic division and correlation with several methods, and the results are approved and adopted by this oilfield. From this data, the formation structure model of this area is established successfully.The characteristics of faults are made sure based on the fine interpretation of seismic data and analysis of dynamic information, and the structure distribution models of the top of 20 layers are founded. The fault F5, F12, F13, F14 and F16 are validated, but the position of F5 on the plane is as almost same as the F10, which was marked in 1999, the only difference is the length of F5 is smaller than that of F10. Positive and negative micro-structures with different scale exist at nose structure, which makes oil and water more complex relationship.The microfacies of this reservoir are identifying quantitatively by integrating the faces signs, sediment logy and pattern recognition techniques, and then 3 subfaces and 13 microfacies are marked. Based on the analysis of microfacies of single well and profile microfacies ofmulti-well, the model of microfacies distribution is established. The most profitable microfacies are braided channel of fan delta plain, sub-aqueous distributaries channel and river mouth bar of fan delta front of fan delta sedimentation.The vital technology is the comprehensive interpretation and intensive processing of log data. According to the corresponding characteristics of complex lithology and low permeability reservoir, and the principle of core calibrating log, the charts for the interpretation of reservoir parameters and fluid-face are found by using neural network and multi-parameter cross-plot. Based on these, the data are processed for 324 wells, and the cutoffs of each parameter are set. Optimal interpretation based on multi-mineral model is adopted to solve the complicated oil/water zone with low permeability and water-flooded oil zone. Serial methods, much fit for the fine processing of low-efficient reservoir, are formed.The distribution characteristics of oil and water and the reservoir reserve is made sure completely. From distribution model of this reservoir reserve, the geological reserve of oil of this oilfield is 39.38 million ton, and that of solution gas is 1.6808 billion cube meter, the reserve abundance is 1.3083 million ton per square kilo-meter. So this reservoir is middle-low reserve abundance oilfield.Based on the fine description of this reservoir and study of reservoir engineering, a serial suitable technique is presented and set up for us to develop highly efficient this reservoir.From the above research, a serial of methods for this reservoir fine description and study is formed, which will be most helpful to increase reserve and enhance production and design effective development plan of other low-efficient reservoir in China.