Hydraulic fracturing in condensate reservoirs: A simulation study

摘要

In gas condensate reservoirs, because of the retrograde condensate, while the bottom hole pressure drops under the dew point, intermediate components go to the liquid state, so the condensate accumulation will be occurring into the porous medium. Practically, we are not able to produce the valuable liquefied components by decreasing the reservoir pressure forever. Besides, by increasing the saturation of these liquids around the production well (condensate blockage), a decrease in gas production rate occurs. So far, many methods have been applied to prevent these condensates inside the reservoirs. However, in these traditional methods typically it is required to inject another fluid into the reservoir to prevent pressure depletion such that the pressure distribution profile inside the reservoir is maintained above the dew point. Generally, in this method, it is assumed that the pressure distribution profile has a continuous logarithmic trend from the hole to the reservoir boundary. In the present study, a new approach is taken to change the pressure distribution profile inside the reservoir through creating a hydraulic fracture around the production well. In this way, a lower bottom hole pressure drop would be required for producing a certain amount of fluid. As a result, liquid accumulation around the well is prevented. In other words, a change in the profile of reservoir pressure distribution would occur in the areas near to the well, leading to a remarkably higher well productivity index. However, this method affects productivity index of the well rather than prevention of condensate trapping. In this paper, the impact of hydraulic fracturing on preventing the amount of condensate accumulation in the reservoir is investigated using simulation of a synthetic model. Three scenarios are considered; natural depletion, injection of water into the reservoir and producing by a hydraulic fractured well. Then, a sensitivity analysis is conducted on production and injection rate as well as fracture permeability to achieve the best scenario. The results show that hydraulic fracturing reduce the bottom hole pressure for a certain production rate, by the way it prevents the pressure to drop less than dew point, so it prevents the formation of condensate around the wells which result in improve well productivity index.