Core Testing Provides an Engineered Approach to Underbalanced Drilling in Tight Gas Reservoirs

Abstract Core analysis of tight gas reservoirs can provide an engineered approach to the selection of underbalanced pressures required to drill tight gas reservoirs and thus avoid imbibition. A small number of core samples from the Ordos tight gas basin in China were tested for imbibition and phase trapping. The analysis conducted on these cores provided a direct indication of the level of underbalanced pressure required to avoid imbibition in this tight gas reservoir. This paper will highlight the techniques used on the cores to establish the imbibition effect and the level of underbalanced pressure required to avoid the imbibition effects. The paper will then highlight some of the additional challenges that are encountered when conducting underbalanced drilling operations in tight gas reservoirs. The paper will discuss the significant benefits of underbalanced drilling in tight gas reservoirs and highlight why underbalanced drilling technology is extremely well suited to the successful development of tight gas reservoirs. The paper will further discuss the challenges that need to be addressed when considering the development of tight gas reservoirs through the use of underbalanced drilling.