Production performance analysis for horizontal wells in gas condensate reservoir using three-region model

Abstract

Gas condensate reservoir is a special kind of oil and gas system that involves two-phase flow during production, because oil condensation occurs when reservoir pressure drops below the dew point pressure. It is of great importance to develop some well testing models for the gas condensate reservoir, yet there exists no analytical well-testing model for horizontal well in such formations. This paper proposes an analytical model for the production performance analysis of horizontal well in gas condensate reservoir. The three-region model is employed to characterize the flow and production of gas condensate, and the three regions are: region-1 in which oil and gas are both mobile, region-2 in which only gas is mobile whereas the oil cannot flow, and region-3 in which only the gas phase exists. To solve the proposed model, Laplace transformation and Cosine transformation are applied to change the partial differential equations to ordinary differential equations. Then, Stehfest numerical inversion technique is used to convert the solution of the proposed model into real space. Afterwards, the pressure response type curve is obtained and nine flow regimes are identified. Subsequently, sensitivity analysis is carried out to investigate the influence of several factors on production performance. Finally, field application is carried out to validate the accuracy of our model, and it is shown that the model prediction result is in accordance with the real production data. The proposed model provides some insights toward the production behavior of horizontal well in gas condensate reservoir, and can be used to evaluate the horizontal well productivity of the such reservoirs.