Successful Co-Development of Oil and Gas Reservoirs, A Case Study

AbstractJake field, discovered in July, 2006, contains 10 oil-producing and 12 condensate gas-producing zones. The total number of drilled was 19, including 5 updip wells penetrated oil and gas zones, the remaining 14 downdip wells completed at principal oil zones. A unique co-development project of oil and gas had been performed since the start-up of field in July, 2010, including three phases:Phase I: Prior to start-up of the field, In-situ gas injection was initiated. Single tubing string completion was utilized in updip wells, packer isolated oil and gas zones so that high-pressure gas could produce from the tubing and oil could produce from the annulus. After commencement, gas from updip wells was injected into downdip wells to maintain reservoir pressure and minimize water influx. The remaining gas was used to gas-lift at updip wells.Phase II: Following pressure depletion of oil and condensate gas zones, gas-lift wells became inefficient. The packerless tubing string was extended to the bottom of perforations for commingling production of oil and gas condensate zones at updip wells. Well stream was produced from the casing annulus while recycling gas was injectied from compressors into the tubing for gas lift. Nitrogen injection was conducted at downdip wells.Phase III: After water breakthrough, infill wells between updip and downdip wells were drilled for nitrogen injection to mitigate the water cut rising trend.Actual production performance of oil and gas co-development is better than sequential production of oil and gas. Initial well production at two producers reached over 10,000 BOPD, Current recovery factor for oil is 25% and gas is 36%. Oil is producing at the level of 18,000 BOPD with average offtake rate of 5.8%. Simulation confirmed that ultimate recovery factor for oil could be over 50%.