The Duri steam flood is currently the largest thermal enhanced oil recovery project in the world. The field is approximately 18 km long by 8 km wide with more than 7000 wells in an existing developed area of about 25,000 acres. The original oil in place is about 6 Bbbls with to date total cumulative production of 1.8 Bbbls mainly from the South Area. After 48 years of primary and enhanced recovery, production is relatively stable at approximately 200 MBOPD recently.
The north part of the field is currently under primary development only. The North Area reservoirs are depositionally more complex and highly faulted compared with other areas in the Duri Field. To better predict reservoir performance under the upcoming steam flood project, the team identified key subsurface uncertainties in the North Duri Development Area, including bottom water, rock and fluid characteristics, synthetic logs and reservoir model validity, velocity model, reservoir compartmentalization, hydraulic flow units, and faulting characteristics.
Twenty new wells with more complete log suites were drilled in 2004-2005, and the existing 3D data was reprocessed to result in a new interpretation of the structure. Five wells were cored over the complete reservoir interval which is three of them were cut in mature steamed reservoir from the existing steam flood area. Specialized logs were collected in some of the new wells to help better petrophysical analysis and confirm principle stress directions in the field. This information was combined with the new fault framework interpretation to better qualify the sealing capacity of faulting, which will have an impact on steam efficiency within the patterns.
A reservoir model was built using new stratigraphic framework, new structural framework and new estimates of oil saturation and porosity, narrowing the ranges of uncertainty for key subsurface parameters and improving the input for flow simulation and performance forecasting. The new North Duri reservoir characterization has helped the team evaluate development alternatives adjusted for high potential trends in the flow units and possible impacts of faulting and bottom water on steam management.
Authors : Deborah Wechsler & Abdullah Faisal Talib