The Study Of Method For Evaluating The Development Performance Of Waterflooding Sandstone Reservoirs

After long--term waterflooding processes,so many major oilfields in china have already went into the latter development stages of high water-cut.With increasing the recovery percentage of reserves, water-cut raising rate and production decreasing rate goes fast, meanwhile, the underground oil-water relation and the distribution regularity of remaining oil become more and more complicated. It is very difficult to achieve oilfield stable production over a long period of time.Cha 30-faultblock is a small complex fault block reservoir which lies in the northern part of Chaheji oilfield . Cha 30-faultblock began to develop by means of waterflooding in 1984, until the year of 2005, its yearly oil recovery rate is below 0.31%, the water cut above 77.89%, the current recovery percentage of reserves only arriving at 21.80%.For improving the waterflooding efficiency and ensuring the oilfield long-term stable production, firstly, it is necessary to evaluate the development performance of waterflooding; secondly, based on the result of evaluation, it is necessary to find out the problem and make some comprehensive adjustment policies. For evaluating the development performance of waterflooding, the following five aspects are studied in this paper: reserves change trend and reserves producing degree、the trend and regularity of production change、the level of formation pressure、the regularity of water-cut change、the utilization efficiency of injection water.Considering above mentioned five aspects, so many single-factor indexes are selected to evaluate the waterflooding development performance, such as: recovery ratio and recoverable reserves、controllable degree of water drive、producing degree of water flooding、oil production rate of remaining recoverable reserves、composite decline rate of annual oil production、production decline rule、the level of formation pressure、water-cut and water cut increasing rate、water storage rate、water drive index、water consumption index and so on. Based on the evaluation result of all the single-factor indexes ,by means of principle of oil-industry standard comparison and similar oilfield development index comparison, the waterflooding development performance of Cha 30-faultblock is systemically evaluated.According to the study result, the conclusions are made as the following: the evaluation result of reserves change trend and reserves producing degree is poor; the production decreasing rate and water-cut raising rate goes fast; the utilization efficiency of injection water is low. Combining with the principle of oil-industry standard comparison and similar oilfield development index comparison, we can make the final conclusion: the waterflooding development performance of Cha 30-faultblock is poor.