Gas-condensate well test results interpretation at Helang field

Abstract

Gas condensate reservoirs exhibit a complex behavior caused by the existence of two-fluid system, reservoir gas and liquid condensate, around the well when bottomhole pressure drops below the dew point. Numerous published literatures (Gringarten et al., Marhaendrajana, Raghavan) based on field data have demonstrated that when this happens, two different mobility regions can be observed in the pressure derivative response in well test data. These two mobility regions are (1) an outer region away from the well, with initial liquid condensate saturation and (2) a region near to the well, with increasing condensate saturation and corresponding lower gas mobility. Some laboratory/theoretical data (Boom et al., Mott et al.) even showed an additional third region : (3) a region in the immediate vicinity of the well with high capillary number corresponding to reduced condensate saturation and higher gas mobility.In Helang gas condensate field, offshore Sarawak, East Malaysia, multiple wells were tested in year 2004 and again in year 2005. Modified isochronal tests (MIT) were conducted in each productive zone with bottomhole shutin condition. This report investigates the identification of 2-region radial composite model from the analyses of Helang field 2004/2005 well test data. Furthermore, the existence of the high capillary number region (region 3) is also investigated from the well test data. With the availability of well test data from two time periods, this report also examines the possible growth of the liquid condensate drop-out region versus time.