The 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. The Tapis structure is an east-west trending anticline, approximately 16 km long and 7 km wide. Initially, only the northern and eastern areas were developed from four platforms. The other areas were only developed in recent years following studies to re-assess recovery from poorer quality reservoirs and application of more cost-effective technologies to commercialize them. This led to a fifth platform that developed the western area of the field. Recently, the southern flank with marginal reserves was developed from a sixth platform, which adopted the minimal facilities satellite platform concept. Reservoir risk for this development was mitigated by additional exploration/ delineation and development well data. The data confirmed that the reservoirs are oil-bearing and productive. This marginal development was a challenge due to reservoir quality uncertainties (extensive bioturbation), structural complexities (steep bed dips, close to a major reverse fault), and fluid contact uncertainties caused by production. Reservoir simulation study was carried out to address these uncertainties to aid development planning. Reservoir simulation study has also identified the potential for infill drilling and workovers to further improve recovery in the eastern area. This latest simulation study was conducted using finer layers, unstructured grids, and incorporated over 25 years of history matching. Given the advanced state of field depletion, early assessment utilizing compositional simulation model and laboratory tests are being carried out to investigate the potential for enhanced oil recovery processes. Processes under evaluation include double displacement and water alternating gas (WAG) displacement using various types of gas. Introduction The Tapis field was discovered in May 1969 in an average water depth of about 64 meters. It is located in the southern part of the Malay basin as shown in Figure 1. A total of fifteen exploration and delineation wells have been drilled to-date. Hydrocarbon bearing reservoirs are in the Group I, J, and K sandstones as shown in Figure 2. This paper focuses on the oil development in the Upper and Lower J reservoir groups only, which contain about one billion barrels of oil or 90% of the field's original oil in-place. The assessment and application of IOR started early and have been a continuous process; several IOR assessments have been conducted and associated work programs have been implemented. The application of Enhanced Oil Recovery (EOR) has also been evaluated in the past. These were mostly simple screening level assessments. A more detailed evaluation involving laboratory tests and compositional models has recently been initiated.

This paper focuses on how the integration of technologies such as sequence stratigraphy, log analysis, 3D seismic, reservoir simulation and drilling have helped in overcoming the many challenges, and increased Tapis field's reserves by about 30 percent. The work program for realizing these reserves includes rig workovers, infill/step-out drilling from existing platforms, and installation of a new satellite platform. To date, the rig workovers and most of the infill drilling have been completed, and results have been mixed but overall, encouraging. The new satellite platform was installed in third quarter of 1998 and development drilling off this platform is now underway. The experience at Tapis demonstrates the value of looking for new opportunities in mature fields.