Geological Modelling Study Of Low Porosity And Low Permeability Fractured Sandstone Reservoir In Dabei Gas Field

This paper is mainly based on sedimentology, sequence stratigraphy, petroleum geology and geostatistics to build geological model. According to cores observation, seismic data, log information and achievement of previous studies, Bashijiqike formation of Cretaceous which is in Dabei gas field of Kuqa Depression can be divided into 6 groups containing 21 single layers. Combining with regional sedimentary background, facies model of Dabei gas filed is built by analyzing facies marks. It shows that the second member of Bashijiqike formation is braided river delta front sub-facies while the third member is fan delta front sub-facies. Based on the characteristics of logging curve, logging facies model is built, and the micro-facies of core sections are identified. It shows that the channel sands of the second member appear more than the third one, so they are main reservoir sands of DaBei gas field.On this basis, the other basic geological reservoir studies, including determining petrophysical parameter cutoff, identifing interlayer, and analying depth of water interface along with type of gas reservoir, are carried out.The structure models of the study area are built with analysis of seismic information and data of single layers. Then attributes geological models (including porosity, permeability, effective thickness, N/G, and so on) are built by using the method of sequential Gaussian stochastic simulation in the Petrel 2008. After that, fine attribute models are coarsened and tested in accordance with the needs of numerical simulation and tectonic stress field analysis. If they are tested appropriate, the grid data will be used in the tectonic stress field analysis for fractures prediction.With fracture porosity and permeability date from the tectonic stress field analysis acting as constraints, fracture porosity and permeability models of all blocks can be built by using the method of sequential Gaussian stochastic simulation according to the data of the single well imaging fracture porosity and fracture permeability.After several tests and adjustments, the petrophysical parameters of the geological model can achieve meet the needs of reservoir simulation.