Formation evaluation quality and cost efficiency are crucial in ultra-deepwater reservoir evaluation. Reservoir properties such as fluid composition, formation pressure, and sand producibility are critical in the exploration and appraisal phases of the well life and represent a key input to comprehensive production and reservoir engineering studies in the development phase. In addition, contaminants measurement including hydrogen sulfide (H2S), carbon dioxide (CO2), and mercury are important to address challenges in the planning and utilization of equipment and production facilities. This work is based on recent experience in South-East Asia that demonstrate prudent operatorship in maximizing value of information (VOI) from exploration drilling and evaluation. These formation testing is conducted to address the inherent uncertainty in reservoir characterization; particularly reservoir connectivity, producibility and presence of fluid's contaminants. Integrated measurements such as core data, log analysis, image logs, pressure data and fluid sampling were utilized to better characterized the reservoirs. Advanced sampling method was conducted to evaluate presence of contaminants including H2S, CO2, and mercury in the reservoir. Onsite lab services were utilized to handle and analyze the captured sample on location for better contaminants evaluation. In addition, formation mini-DST testing was also conducted to further understand interval rock and pressure properties at larger scale. The application of this proposed approach is critical to reduce the subsurface uncertainty especially on reservoir and fluid properties; which inputs are used to prudently design future field development facilities. Field data and workflow demonstrating formation evaluation techniques will be presented in this paper. Lesson learned and best practice will also be explained supported by lab analyses and results.

Proper and reliable resource assessment of hydrocarbons in-place and recoverable volumes is one of the key factors in field development planning (FDP) and determines the commitments made to the host government for the reserves to be developed (RTBD). Many times, it is critical to update the resources and reserves of a producing asset through full field reviews (FFR) to gauge the production attainment and success of initial forecasts in FDP and also to locate any upside/locked-in potential. Often uncertainties in the field development are expected to reduce as the field produces, but in many cases the results show otherwise due to lack/ inaccuracy of data or existing reservoir complexities. This paper elaborates how an integrated approach utilizing analytical methods (material balance, pressure and rate transient analysis) combined to numerical reservoir simulation is used for accurate resource assessment of an over-pressured gas condensate reservoir that suffers from lack of geological and petrophysical data, faulty production data measurement system and complex fluid and pressure behavior. A comprehensive workflow comprising of different methodologies is used to harness the available geological, petrophysical, production and pressure data. Over-pressured and compressibility corrected gas material balance and pressure and rate transient analysis (RTA) are conducted using static and flowing data to encompass the existing uncertainties on resource numbers and generate low, base and high cases. The results of these methods are then successfully utilized to construct the dynamic reservoir model for evaluation of the upside and near field exploitation (NFE) potential. The results of the full field review lead to a 50% increase in the gas initially in-place compared to FDP volumes and a significant addition in the proven reserve. This increase in volumes was investigated through proactive surveillance for a period of time and was well supported by the reservoir and well performance. A novel approach to numerically model the over-pressured gas reservoirs is developed using a simple concept of compressibility modifications supported by production data history match and analogue core data. The results of the study greatly benefited the production sharing contract (PSC) and lead to production enhancement from the field through a proper debottlenecking project.