Investigation of Gas-Cap Effects on Pressure- Transient Response in Naturally Fractured Reservoirs

Well testing is performed to obtain different information about the well and reservoir. In order to obtain this information, the flow rate of the well is changed and these changes cause pressure turbulence in the reservoir. Measuring pressure changes over time and interpreting these changes give us information about the well and reservoir. Other effective parameters such as inter-porosity flow coefficient and storativity ratio are also very important.In this study, a naturally fractured reservoir with gas cap has been simulated in three senarios of oil production, oil and gas production and gas production using Eclipse reservoir simulation software. In order to investigate the effect of gas cap on parameters that mentioned before Saphir well testing software has been used and pressure build up and draw down tests in various time periods conducted.The results of the analysis showed that in the case of presence of a gas cap, the behavior of the naturally fractured reservoirs is in contrast to the presented models, meaning that in the early times the reservoir will not produce only from the fractures and Gas cap will also be involved in the production. The involvement of gas cap in production changes the values of the inter-porosity flow coefficient and storativity ratio and causes the dual porosity naturally fractured reservoir to behave like a triple porosity reservoir.

Keywords:

Simulation , well testing , Naturally Fractured Reservoir , Dual Porosity , Pressure Derivative type Curve