Technology Advancement Against Nature: 3D 4C OBC Seismic In a 40-Years Producing Field Unleashed Reservoir Potential
Authors: Hassan Siti Normaizan , Latif Nurlizawati , Ashqar Ayham 
Published: January 2020

To further develop and recover reserves volume from a major oil field in Malaysia utilizing the latest and most premium seismic technology 3D 4C OBC. The overall field development was imposed due to a disappointing drilling results.
Field A, located offshore West Malaysia, is a laminated Lower Coastal Plain sandstone deposited with occasionally marine transgressions. A highly complex, elongated anticline structure that possess over 330 interpreted normal, reverse and and wrench faults (normal, reverse and wrench). Production started in 1979. Despite the strong and consistent production, the Recovery Factor (RF) remains at 19% indicating potential remaining value.
The time-consuming and costly azimuth 3D 4C OBC was acquired in 2015, to benefit from its capability in mapping hydrocarbon and water as well as lithology identification (sand/shale/coal). The 4C data was processed using 3D pre-stack. An improved continuity and sharpness of the main reflectors on the P/Z cube was clear to allow an efficient brown field redevelopment analysis specifically in the areas of infill and injectors well placements. Attributes maps were calibrated with newly acquired logs, and combined with re-evaluation of existing well logs and production data to ascertain development areas, and potential secondary recovery mechanism. Results were translated to static and dynamic models where possible, with 2D volumetric exercise for the smaller, and non-producing reservoirs. The opportunities identified were classified according to risk matrix, and uncertainties, an overall full-field redevelopment plan was proposed including an aggressive project tiring approach with fast execution process and higher risk appetite.
Results coming from PP PSDM and PS PSDM confirmed the reasoning behind unsatisfactory outcome of 2015 infill campaign. The previously high uncertainty in sand distribution and reservoir extensions were clarified and confirmed with the new seismic interpretation result. Two wells were suspended based on the indicative result that showed addition of fault planes within the area. Subsequently, moving forward a total of 85 areas of new opportunities were identified and tiered based on technical confidence and risk appetite. A roadmap consists of detailed development strategies spanning over 5 years and beyond associated with ~100MMstb reserves value that will bring the RF to 31% were proposed and proceeded towards project sanctioning. The first four wells of its campaign was sanctioned, executed and spudded in August 2018.
The objective while developing existing producing area is to target virgin location for additional data and to de-risk the undeveloped areas. The results from the first two wells allowed clearer picture of the complexity of the fields with mixed results combined with the operational challenges due to unexpected reservoir losses. Immediate recovery plans and decision matrix were quickly devised and re-entry and deviations were made to the original plans.
The completed wells successfully produce up to 1100 stb/d, which was higher than the planned 750 stb/d. In addition to the completed targets, 6 BCO targets were also identified for future production enhancement activities.