The Third Sand Middle of the Greater Burgan field is a massive sandstone reservoir with a strong bottom water drive. It has been on production since the last six decades. During this period, the dynamics of fluid movement have resulted into highly uneven remaining oil columns throughout the reservoir. These remaining oil columns are the key parameter to the placement of infill wells. The structural configuration of the reservoir is well understood with the help of 3D seismic. Thus, the determination of the remaining oil column hinges mainly on the current OWC surface. To build the current OWC surface, a large set of PNC data has been used.
Conditional simulation using Sequential Gaussian Simulation is used to assess the degree of uncertainty associated with distribution by randomly sampling the spectrum of possible solutions. Stochastic realizations of the surface are generated by changing the seed on each pass through the loop of SGS workflow. Annual fluid production map surfaces have been generated for the last four years. A volume-height map for remaining oil in place has been generated using a coarse single zone stratigraphic model. Based on these surfaces, water rise velocity surfaces have been computed for the last four years. The simulated current OWC surfaces are used in conjunction with the structural top surface to generate the remaining oil column map. This has been, in turn, used to identify new infill well locations with greater confidence and less risk.
The water encroachment in the Third Sand Middle reservoir of Greater Burgan field has been very complex due to its complex reservoir architecture and a six-decade long history of fluid withdrawals. The Pulsed Neutron Logs are taken in nearly 8% of the wells every year and provide reliable current oil-water contact in the massive Third Sand Middle reservoir at the well location. However, this poor coverage does not provide adequate information for the field that is of the size of Greater Burgan, Some additional information is available from the oil-water contacts based on open-hole logs taken in the new infill wells that are being drilled every year. In order to have better estimates of current oil-water contacts, this work focuses on the use of robust analytical tools to supplement the measurements using cased/openhole logs. With more accurate values of COWCs (current oil-water contacts), the remaining oil columns can be estimated with more confidence and the infill well placements become more target-oriented.