The Study On The Evaluation Method Of Reservoir Pressure In Extra High Water Cut Stage

Daqing Oil field has entered the extra high water cut stage, injection-production ratio is greater than 1 while formation pressure decreases gradually. Actual production condition is inconsistent with the principle of material balance. In addition, liquid production capacity of oil field is high while formation pressure is low significantly, liquid production capacity is inconsistent with liquid production capacity and the present formation pressure level is contradictory. Therefore, the present formation pressure assessment method is unable to reflect the real producing energy level and also brings very major difficulty for future oil field development and adjustment work. In view of the characteristic of extra high water cut oil reservoir, this article proposes a comprehensive formation pressure evaluation method, combining well test method, numerical simulation method and empirical method.This work took Xing 1-3 block as the research object, oil well pressure, water well pressure and average formation pressure are calculated by well test method and separated layer water flooding numerical simulation method, the calculation results of the two methods are contrasted. The results indicates: coincidence rate of formation pressure of the basic well pattern calculated by these two methods achieves 100% basically; coincidence rate of oil well formation pressure of the fist adjustment well pattern achieves 73.53%, that of water well formation pressure of the first adjustment well pattern achieves 78.75%; coincidence rate of oil well formation pressure of the second infilled well pattern only achieves 53.45%, that of water well formation pressure of the second infilled well pattern achieves 78.75%; and oil well test interpretation formation pressure of the second infilled well pattern is generally somewhat low while water well test interpretation formation pressure is generally high, this mainly due to each method. The primary factors that affect the precision of well test interpretation of average formation pressure are analyzed and corrected later. The research discovered that the main factors affecting the formation pressure include injection-production ratio, oil-water well number ratio, reservoir properties and water content and the correction method for each influencing factor is given in this study. Finally the above research is taken as the foundation, and then the comprehensive evaluation of formation pressure is given and compared with the existing evaluation methods. Comprehensive evaluation method gives the average pressure closest to the numerical simulation results, moreover each year's difference scope is small. Average pressure given by the comprehensive evaluation method and the numerical simulation results have good uniform. The results given by this work have high confidence level.