Identify the Key Uncertainties Which Influence Production Performance and Recovery by Using Global Analogs

Limited data is available for a new discovery at the preparatory stage for the plan of development (POD). Uncertainties exist such as the depositional environment of the reservoir and individual sandbody type, reservoir heterogeneities and fluid properties. This paper presents an innovative and unique method for the qualitative and quantitative evaluation of the influences of these uncertainties on production performance and final recovery factor.The developed methodology enables reservoir engineers and development geologists to conduct uncertainty assessment on production performance and final recovery factors by using a global analogs database and proprietary analytical software tools, including performance forecasting, characterization and attribute cross plotting, etc. The process consists of four steps: (a) selection of the analog reservoirs, (b) performance forecast, (c) uncertainties evaluation, and (d) analysis of key drivers impacting performance and recovery factor. In our case study, Field A is in its POD study stage. Based on available information, reservoir sand in Field A potentially consists of sandbodies of either fluvial channel (FC), distributary channel (DC) or combined fluvial and distributary channels (CFDC). Uncertainty evaluation results indicate that the sandbody of FC, DC and CFDC will produce ultimate recovery factors of 35.9%, 37.9% and 39.7% respectively for the medium-case scenario and 52.4%, 54.3% and 59.2%, respectively for the high-case. The various sandbody types also have a great influence on performances of life-cycle production profile, peak production rate and water-cut variations. Analog analysis of the same sandbody type reveals the impact of three group specific attributes on the ultimate recovery.Compared with the normal approach of conventional geological modeling and reservoir simulation, the analog solution using the proprietary software tool is an efficient process and provides reasonable results.