A Comparative Study of Reservoir Average Pressure Calculation, Using Flowing Pressure Data andWell test Analysis, in one of the Southwest Iranian Carbonate Fractured Oil Reservoir

High operating costs associated with build-up tests and periods of shutting the well sometimes lead petroleum producing companies to avoid performing tests which require ceasing the production. In material balance equations the value of average reservoir pressure in different periods is a critical parameter to find the oil/gas in place. To measure this value, oil companies have to shut the producing well and stop oil production for a while, which is economically not recommended. On the other hand, such a parameter is critical in reserves estimation. By applying a method so called Dynamic Material Balance, it would be possible to calculate the average reservoir pressure by production data without the need to shut the well, thus decreasing the OPEX associated with the test as well as keeping the well on production. This method is applicable to both fixed and variable flow rates. Having obtained the average reservoir pressure, other calculations can be handled by the Conventional Material Balance. However, an important factor is the accuracy of this method and its reliability. In this paper, the formula conforming to the methodology mentioned above has been established, then it has been demonstrated that the reservoir was in its pseudo steady state stage of life, using the results of RFT and static data, finally the average reservoir pressure has been calculated from bottom hole flowing pressure data using Dynamic Material Balance then build up test analysis results from six wells have been compared with the results obtained from this method and their accuracy will be discussed. A good agreement has been observed between results obtained from this method and pressure build up test mentioned in the wells studied in this work.