Study Of Reservoir Engineering Methods For Fractured-Vuggy Carbonate Reservoirs

Fractured-vuggy carbonate reservoirs exist widely in the world with massive reserve and production of petroleum stored in it. The reservoirs in District IV of Tahe Oilfield are typically the fractured-vuggy ones with high heterogeneity. With complex geological condition and variable pore structure they are neither the same as the normal sandy reservoirs nor the fractured carbonate reservoirs. It is very difficult to manage the production, to predict and analyze the performance index, even to make the decision.The research in reservoir engineering for fractured-vuggy carbonate reservoirs is at the groping stage home and abroad. It is an urgent need to conduct the corresponding theoretical study. Based on the research of the production performance of District IV in Tahe oilfield the typical geological model were abstracted where various testing information and geological results were employed adequately. The effects of various factors on the development index were studied and the calculation methods of the development index and the decision-making methods of rational development policies were discussed through the analytical technique and reservoir numerical simulation. The partition method of fracture-vug unit and different development policies for different kinds of unit were put forward due to the high heterogeneity. Based on the results of study of fluid flow mechanism, combined with the theory of seepage and theory of fluid flow the equivalent permeability methods were established for small fractures, small vugs, big fractures and big vug and even the different situation that the well were drilled respectively. The law of variation of reservoir pressure, water cut and production rate of typical units were studied systematically. Four kinds of typical bottom reservoir model with block shape were abstracted on the comprehensive consideration of geological results. The calculation method of water cut and decision-making method of other corresponding performance index were gained. At the same time the quantitative relations between rational well space, perforation ratio and production rate were decided for this kind of reservoirs. According to the special relative permeability relation the water flood characteristic curve were deduced for two kinds of fractured-vuggy reservoirs and the calculation method of the well shut in time was got for injecting water replacing oil project for fracture-vug unit with fixed volume.The decline of production rate accorded with log law for the fracture-vug unit through the research of the main unit which provided a new and prompt method for the prediction of the development index of the oilfield. The law of water cut variation was studied for three kind of typical model with different combination of big vugs, faults, impermeable barrier and wells. The mechanism of effect of various factors and efficient method to control water cut were decided. The deficiency of the analytical method was compensated. The rational development policies of various kinds of unit were studied and discussed based on the appraisal of the development policies implemented. The development polices which are instructional and can be operated easily were put forward.The innovation of this paper are calculation method of equivalent permeability for fractured-vuggy reservoirs, the calculation method of performance index for bottom water reservoirs with block shape, establishment of quantitative relations between ration well space and perforation ratio and establishment of water flood curve and well shut in time for injecting water replacing oil project.