Dumpflooding technique is defined as intentional cross-flow of water from a high pressure layer into depleting oil producing zone for the purpose of pressure maintenance. It is a highly economical method to improve oil recoveries as it requires no capital and operational expenses. After implementation, however, it is challenging to maintain optimal injectivity in dumpflooded potential oil zone given the nature of its subsurface process without direct measurements and monitoring.

This paper describes a case study of oil field discovered in 1993 by drilling of N-1 well which successfully penetrated two Sandstone reservoirs (B & C Sands). Open-hole logging and formation testing confirmed presence of oil in both Sands. Pressure production history of N-1 and subsequently drilled three developments wells determined C Sand to be moderate-tostrong water drive reservoir, whereas, B Sand witnessed poor pressure support with faster decline in oil production. Due to remote nature of this field, a full-fledge water injection project did not attract economics. In order to improve recovery of B Sand, it was evaluated to initiate dumpflood at the third development well, N-4, where C Sand was watered out. Geological analysis of the logs/core data suggests B Sand to be a laterally extensive Sand body, supporting the use of the dumpflooding technique in the given area. Engineering analysis was carried out using nodal analysis and tank models to estimate injection rates and additional recovery. After evaluating technical feasibility, dumpflooding was recommended and implemented at N-6, most downdip well located at Northern structure. The impact of dumpflood was realized on liquid withdrawals as well as pressures of B Sand. The injection performance of N-4 was routinely monitored and maintained through remedial measures. This way, the successfully implemented and well managed dumpflood process achieved significant increase in oil recoveries of the field.

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