EVALUATING THE FACTORS EFFECTING PRESSURE BUILDUP TEST IN FRACTURED RESERVOIRS WITH GAS INJECTION DRIVE MECHANISM

Many factors can influence the shape of a pressure build up curve. An unusual shape may require explanation to have a appropriate analysis, or it mayprevent a proper analysis. In addition to wellbore storage effects, hydraulic fractures and natural fractures can have a major effect on build up curveshape and analysis. The shape of the pressure buildup curve also can be affected by fluid and rock interfaces, water-oil contacts, layering, and lateralfluid or rock heterogeneities. Wellbore storage, wellbore damage or improvement, and geometry of the drainage area can also affect the shape of abuildup curve. Additionally, wells with a high gas-oil ratio can show humping during pressure buildup, in such cases, the bottom-hole pressure increases to apeak and after a period of time decreases. In this paper, a well is selected in Haft kel oil field and its build up test have been analysed during 20 years andin three periods from 1990 to 2010. The conditions of well in each period has been analysed and the resultsshow that in addition to wellbore effects, some reservoir effects may influence the build up test in this well.