Study Of Areal Sweep Efficiency Of Fractural Low-permeability Reservoir

The previous studies of areal sweep efficiency of well pattern were researched in this dissertation. How to enhance the development efficiency of low-permeability reservoir was realized. It is prerequisite to arrange the well pattern and study the seepage flow of water-oil displacement. The areal sweep efficiency of square inverted nine-spot pattern and rhombus inverted nine-spot pattern was studied by plane visualization models and reservoir engineering methods, as well as some adjustment patterns of this two basic well patterns. After analyzing and comparing of these well patterns, the best well pattern applied to low-permeability reservoir with fractures was selected.By comparing square inverted nine-spot pattern and rhombus inverted nine-spot pattern, the rhombus inverted nine-spot pattern was more satisfied with the development of low-permeability reservoir with fractures and the areal sweep efficiency was enhanced effectively. The effect of oil well was well-distributed and the water-out time was postponed when well spacing which paralleled to the direction of fracture was increased and the well spacing which was perpendicular to the direction of fracture was shortened. In the later stage of production, the high water cut corner well of basic well pattern was forced to converted in order to keep the production of oil field and enhance the efficiency of oil wells.The area sweep efficiency of row well pattern which was shown by visual physical modeling was higher than inverted nine-spot well with small pattern spacing by comparing these two types of well patterns which both were adjust transformations of inverted nine-spot well. Areas arranged with square inverted nine-spot well pattern should be optimized by infill wells paralleled to the waterline and fracture direction. The direction of well array should be consistent with the direction of fracture, while keeping an appropriate proportion between well spacing and row spacing.The formula of areal sweep efficiency and water breakthrough time of square inverted nine-spot well pattern and rhombus inverted nine-spot pattern with fracture were given by reservoir engineering method considering the model of single-flow-tube with starting pressure gradient, while the influence of injection-production pressure and the well spacing to areal sweep efficiency were studied. Some dead oil was left after the initial development phase. Accompanying with the increasing of injection-production pressure, adjustment of well pattern should be applied in order to improve the production. The formulas of areal sweep efficiency of different units of particular row pattern based on experimental result were also given in this dissertation, which would be a supplementary method to calculation of efficiency in fractural low-permeability reservoir.