Optimising Exploitation Strategy of Multi layered Reservoir for higher recovery – A Case Study of an Aging Field, Cambay Basin, India

Abstract

The HC field was discovered in 1972 and put on commercial production in 1974. The field’s oil production reached life-time high of 461 tpd (tonnes per day) in June, 2006. However, soon the production started declining, rather rapidly, and average production during 2009-2010 was mere 220 tpd, which necessitated an integrated review of the field, combining geosciences, reservoir engineering and production technology. Study started with organizing abundant and scattered field data, recording of Cased Hole Formation Resistivity (CHFR) / Reservoir Monitoring Tool (RMT) and Cased Hole Compensated Neutron (C/H CNL) logs in key wells, which tagged shifted fluid contacts and modified saturations. Past performance of the sands was studied and reservoir simulation carried out for obtaining suitable perforation policy for sands with GOC and OWC. Shale/coal barriers were identified and their reliability was tested for two reservoir units, which helped in putting the rim of oil between GOC and OWC on production. Based on the integrated study, opportunities were identified and well interventions through work-over jobs were carried out for recompletion, zone transfer and water shut-off. Geology of the main block was redefined integrating seismic and new data gathered from four strategically newly drilled wells. Further, a strategy was firmed up for rational exploitation of all sands in the multi-layered block aiming at maximising recovery and minimizing development and operating cost. Implementation of the study augmented field’s production to a second plateau with increase in production from 220 tpd to 375 tpd.