TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractThe Tapis field, located offshore peninsula Malaysia, has been producing since 1978 and about 90% of the original development estimated recoverable oil has been produced. Large gas caps remain for future development. Recovery to date has been primarily from line drive pattern waterflood. Continuous implementation of improved oil recovery (IOR) strategies has increased the recoverable reserves and production capacity for economic operation of the field. This paper describes technical studies completed at Tapis and the results of recent IOR work programs that added more than 20 million barrels of reserves. In addition, enhanced oil recovery techniques currently under evaluation for Tapis are described.

TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractThe Guntong field is one of the largest oil fields in the Malay Basin. With almost twenty years of production history and currently at 80% depletion, Guntong production has been on the decline since the late 90s. Despite the complexities resulting from its multiple stacked reservoirs that are developed by 150 wells, and the challenges of maximizing oil recovery from a mature offshore field, the various oil recovery improvement measures implemented at Guntong have successfully resulted in the addition of almost 80 million barrels of oil to the overall field recovery within the last five years.This paper is an overview of these initiatives which include workovers to decommingle selected reservoirs and perform acid stimulations, in addition to three infill drilling programs that were conducted within a span of three years. A fourth infill program, requiring a new satellite platform, is scheduled for completion in 2005. Positive results were also achieved by revising the field's reservoir pressure maintenance program along with optimizing reservoir management strategies such as water injection patterns.The underlying key to the success of these efforts has been the holistic approach in analyzing the field data. A more comprehensive understanding of the reservoir behavior was achieved by integrating production data, geology, reservoir engineering as well as findings from the recent infill programs. A more accurate representation of the reservoir behavior was attained through iterative comparisons between the geologic description updates and the results derived from the reservoir simulation models. Predictions from these models, which were further supported by seismic timelapse and AVO analyses, have led to the successful identification of bypassed oil regions within the field. Moreover, the availability of reliable simulation models was also instrumental in testing out and fine-tuning reservoir management strategies before their implementation.