On the appraisal and development of ST-X field: uncertainties and challenges

Abstract

This paper summarizes theuncertainties and challenges in appraising and developing the ST-X gas condensate field, which is offshore Vietnam in Block 15-1. Drill Stem Test (DST) results show that the ST-X field has moderate to low permeability, multiple flow boundaries/barriers, and at least 2 PVT regions. To understand the impact of these and other important reservoir parameters on ultimate gas and condensate recovery and well count, a reservoir simulation study was performed. The study demonstrates that there is a wide range of possible ultimate gas and condensate recoveries and well counts. The top causes for this wide range are the heterogeneity in permeability distribution and flow boundaries/barriers. In addition to the subsurface risks, drilling cost of a ST-X well is very high. The high well cost in combination with the field being offshore, having low permeability and possibly numerous reservoir compartments dramatically increase the risk of a full field development.