Study on reservoir heterogeneity with Analytic Hierarchy Process based sedimentary micro-facies

The heterogeneity of hydrocarbon reservoir manifests itself in terms of variable rock and/or fluid properties and may be observed in the lateral and vertical directions. The heterogeneity, influenced by depositional... [ view full abstract ]

The heterogeneity of hydrocarbon reservoir manifests itself in terms of variable rock and/or fluid properties and may be observed in the lateral and vertical directions. The heterogeneity, influenced by depositional environment, diagenesis and tectonism, is one of the key factors which impact motion state of fluid and the ultimate recovery of oil and gas. In addition, the study of reservoir heterogeneity also is the core content of reservoir description. Therefore, it is critical to exploration and development of oil and gas that making a study of the reservoir heterogeneity.
Wangguantun oilfield with total area of about 70 km2 is located in the southwest of Huanghua depression of Bohai Bay Basin , eastern of China. As the major target layer, the first member of the Kongdian formation consists of various types of sand body deposited under continental sedimentary environment, with the burial depth of 1800 ~ 2500 m. Based on the data of core analysis, seismic and well logging, the reservoir was divided into three sedimentary micro-facies (braided channel, diara and interchannel sludge), then a three-dimensional model of sedimentary microfacies was established.
The previous heterogeneity parameters are one-sided and contradictory sometimes. In order to overcome the defects, the Analytic Hierarchy Process (AHP), a practical method to determine the weight of each parameter in the complex problem based on the experts’ experience, is put forward to calculate integrative index of reservoir heterogeneity. The integrative index calculated in wells are taken as hard data, and the three-dimensional model of sedimentary micro-facies are taken as constraint condition between wells because different sedimentary microfacies show diverse heterogeneity, finally a three-dimensional model of integrative index was established based on Sequential Gauss simulation method. Thus the three-dimensional distribution of reservoir heterogeneity has been predicted well. Results indicate heterogeneity of reservoir can be studied better and the disadvantages of single parameter mentioned above can be overcomed by the application of integrative index.