Enhancement of Oil Production in an In-Situ Combustion Process through Unconventional and Innovative Approaches: Case Study from Lanwa Field, Cambay Basin, India

Abstract

Abstract The objective of the paper is to demonstrate the 30% rise in oil production through unconventional and innovative methods in a heavy oil field "Lanwa" (oil viscosity: 1000-1500 cP) supported by active edge water drive. The non-conventional techniques involves, Water shut off (WSO) with Gravel pack in place, Aquifer management by flue gas trapping, Optimization of air injector- producer combinations in ISC affected areas and restoring the productivity of 6 horizontal wells through foam jobs by Coiled tubing. These efforts were made by revisiting the existing practices and improved technical understandings of the field. Results of field implementation of these activities helped in increasing the oil production of the field by ~ 62 m3/day. Water Shut Off (WSO) is being done to reduce the effect of water fingering due to adverse mobility in Lanwa field. Conventionally, WSO jobs were done by fishing out the Gravel pack (GP) assembly followed by polymer squeeze, Zone optimization and reinstalling the GP. To avoid the complicated workover operations, Rigless polymer squeeze through Gravel pack was experimented and desired reduction in water cut is observed. The rigless polymer squeeze resulted in reduction in water cut to 60% from 90-95% and remained low for 1.5-2 months and in some cases for a longer duration. The new process of WSO is very easy to execute and requires very less expenses which facilitates the increased number of WSO jobs. The number of annual WSO jobs in the field increased by 8 times. A total of 35 jobs were carried out in a year and resulted in incremental gain of 20 m3/day of oil. Insitu combustion process in part of the field is operational since 2010. Idea of trapping the flue gas to form a secondary gas cap to counter the aquifer encroachment was tested by closing/reducing bean size in high GOR wells. Flue gas production was reduced by 50%, which helped in expansion of secondary flue gas cap which in turn resulted in reduced aquifer activity in extremely adverse mobility conditions. Around 22 m3/day of oil gain has been observed in 4 oil producers along with the stability of water cut in down dip wells. To capture the mobilized oil from the ongoing ISC process, air injector to producer distance was optimized through shifting of injectors. Drain hole of the horizontal producers were cleaned by rigless foam jobs through Coiled tubing which resulted in regaining the productivity of horizontal wells. Optimizing the injector to producer distance and productivity improvement in horizontal wells resulted in oil gain of 20 m3/day. Performance of Insitu combustion process can be improved by trapping the flue gas and by proper placement of air injectors. Issue of circulating fluid loss while clearing the drain hole can be eliminated by the use of foam as circulating fluid during Coil Tubing operation (CTU-Foam). As the performance of water shut off with GP inplace was found encouraging, the same can be done through rig-less approach.