The Discrete Numerical Models and Transient Pressure Curves of Fractured-Vuggy Units in Carbonate Reservoir

Fractured-vuggy carbonate reservoirs have various types of units, and making full use of the well test data to study reservoir characteristics is quit important to enhance oil production. However, conventional analytical well test model cannot consider the positional relationship of well and fractured-vuggy units. According to the distribution of well and fractured-vuggy units, two kinds of discrete numerical models of WIC and WOC are given, and these models are solved by the finite element method. The influence of cave volume and the distance between cave center and well are analyzed. The measured data of 65 Wells in Hala Hatang oilfield is summarized and interpreted, and the classification of the reservoir units and identification methods are analyzed. Their well test double logarithmic curves are divided into five types corresponding to different reservoir units characteristics.. : The oil well is not drilled in any fractured-vuggy unit, but abundant fractured-vuggy units exist in the reservoir. II : The oil well is drilled in the fractured-vuggy units, and many fractured-vuggy units exist in the reservoir. III: The oil well is drilled in multiple connected caves..: Carbonate reservoirs contain primarily matric. V: The oil well is drilled in some individual caves, but the fractured-vuggy units do not develop.