Publications

The Telisa Kaji formation is a tight shaly sandstone reservoir with kaolinite as the dominant clay. It has low permeability (5 mD) and low resistivity (3 ohm-m). Gas solution is the main drive mechanism and the field has been producing since 2003. Hydraulic fracturing with a certain concentration of proppant was introduced to provide cross-flow from a low-permeability reservoir into the created fractures. By this stimulation, oil recovery of up to 9.3% is expected. The initial reservoir pressure was about 1230 psia, declining rapidly to about 370 psia after four years production. Therefore, pressure maintenance needs to be implemented. Based on an integrated GGR study, it is found feasible to implement pressure maintenance with water injection to arrest the rapid reservoir pressure decline and to increase the oil recovery factor. A compatibility test on core and injection water showed no change in the clay composition, which means no indication of clay swelling and minimal signs of fines migration. Furthermore no tendency of new deposits and scaling was found from scaling tendency analysis. A pilot water injection was conducted from 2009–2010. A positive response was observed in the form of an increasing static bottom hole pressure in the surrounding wells (around 20 psi in first semester), which is expected to increase by as much as 200 psi for full-scale injection. A positive production response was also observed on the surrounding wells, where the oil recovery factor increased to about 10.1%. The water injection well conversion is being conducted to reach full-scale injection. Based on current production performance, the oil recovery factor is about 12.5%, and is expected to increase to 13.4% after full-scale injection is completed. Currently, the average static bottom-hole pressure of the formation has increased to 400–500 psia, and the plan is to run a tracer survey to identify the injected water flow path.