The Study On Conceptual Model Of Heterogeneity In Braided River Reservoirs

Reservoir heterogeneity is the major factor to influence on the seepage flow and driving of petroleum, which plays an important role in the distribution of remaining oil. Palogue oilfield locating in the north of Melut Basin in 3/7 area of Sudan, which is still under the stage of field evaluation. Results of regional research show that the reservoir of Palogue oilfield belongs to continental facies sedimentary strata predominated by braided rivers. The reservoir has the typical characteristics of good development of sand body , high porosity, high permeability, and the reservoir physical property is good.The paper focuses on the evaluation of heterogeneity, using different theories and techniques of many subjects including sedimentary, petroleum geology, development geology, modeling of geology and so on, to do the research about reservoir in-layer heterogeneity, interlayer heterogeneity, plane heterogeneity and microscopic heterogeneity. On the base of basic geological study, it builds the heterogeneity conceptual model by using reservoir stochastic simulation technology. The model shows the characteristics of reservoir heterogeneity objectively, correctly and externally.Research shows that the reservoir of Palogue oilfield is characterized by high porosity and permeability. The reservoir interlayer heterogeneity research observes that the stratification is weak according to low stratification coefficient, interlayer heterogeneity between the various sand groups is weak, and it does not produce interlayer interference in sand group. But the heterogeneity between the single sand is quite serious in the scale of entire oil-bearing series. In the layer, the complexity of cross beddings and interlayers affect the permeability anisotropy, research shows that the in-layer heterogeneity is medium. In the plane, the main study area has high permeability of the single sands. The reservoir is characterized by great plane discrepant distribution of permeability, especially along the direction of northeast-southwest, the permeability variance is the most remarkable. Sedimentary microfacies is the most important factor to impact reservoir heterogeneity, the horizontal distribution of reservoir parameters is fairly well correlated with the planar distribution of the microfacies. On the base of research on reservoir micro-characteristic, such as lithologic property, types of pore and throat, pore throat distribution and so on, reservoir microscopic heterogeneity is introduced. Reservoir of Yabus Group is characterized by coarse pores, fine throat, weak separation of pore and throat, which indicates that the micro heterogeneity is serious.According to the results of reservoir heterogeneity research, with the software of Petrel 2007,established the heterogeneity conceptual model of braided river reservoirs in Palogue oilfield, which include sedimentary facies model, flow unit model, porosity model and permeability model. The simulation results accord with the geological knowledge, and reflect the heterogeneity of Palogue oilfield exactly.Based on the above researchs, the paper gets a comprehensive evaluation for the heterogeneity of the braided river reservoirs in Palogue oilfield, and has the great significance to oilfield development.