Well Test Analysis of Horizontal wells in Gas-Condensate Reservoirs

Abstract

Abstract Gas condensate reservoirs usually exhibit complex flow behaviors due to the build-up of condensate banks around the wells when the bottomhole pressure drops below the dew point. The formation of this liquid saturation can lead to a severe loss of well productivity and therefore lower gas recovery. Several studies have examined various ways to minimize the pressure drop in order to reduce liquid drop-out and related problems. One solution implemented over the past decade is the use of horizontal wells. There is a lack of published knowledge on the flow behavior of horizontal wells in gas condensate reservoirs. The limited studies in this area1-3 focused on well performance rather than on well test behavior. There has been no evidence of condensate drop out effects in published horizontal well tests data. This paper presents preliminary results from a study aimed at establishing an understanding of the near-wellbore well test behavior in horizontal wells in gas condensate reservoirs, with a focus on the existence of different mobility zones due to condensate dropout. We used a 3D fully compositional model to develop derivative shapes to be expected from horizontal well test data in gas condensate reservoirs below the dew point under various conditions. We then analyzed actual well test data that exhibit such derivative characteristics. Finally, we used a compositional model to verify the results obtained from conventional well test analysis. It was found that condensate deposit near the wellbore yields a well test composite behavior, similar to what is found in vertical wells, but superimposed on a horizontal well behavior, which makes it much more complex.