Abstract

The reservoir performance and management of the Bombay High field with 25 years of production history has been reviewed. Bombay High is one of the most complex fields in terms of reservoir heterogeneity. The major reservoir (L-III) is multi-layered with 10 limestone layers of 5–10m thick which are separated by 2 to 5m shale. More than 600 development wells, both producers and injectors have been drilled. The very nature of this giant field and large and aging facilities have necessitated frequent reviews and changes in the development strategy of the field. The field is in the decline phase and has associated problems like increase in water cut and high GOR, which in-turn is effecting the oil production. Pressure maintenance by water injection is uneven in the reservoir due to heterogeneity. Problems being faced are differential depletion of sub-layers and associated poor primary cementation and mud losses during drilling of infill wells.

Infill drilling through available spare slots and side-tracking/re-drilling of the existing wells, drilling of horizontal wells, drainholes and ERD have been taken up to increase the production and also to augment the water injection. Massive well intervention programs like water shut off and gas shut off are being taken up to reduce the excess water and gas production. The paper also discusses, the utilization of tools like Downhole video and PLT for problem identification, Ball sealer for selective stimulation and Gel treatment for controlling excessive water and gas production, water flood surveillance programs and facilities optimization.

Sectorial approach, adopted for reservoir management has helped, in better well level monitoring, which becomes very essential in mature fields like Bombay High, in the identification of pressure sinks and better voidage compensation, fluid movements and design of well intervention programs and facilities optimization.

A multi-disciplinary team concept has been embraced for better reservoir management. The advantages of multidisciplinary teams, which are working for the re-development plan, with detailed/improved reservoir characterization, incorporating the 3D seismic data and reservoir simulation model, is highlighted.

Introduction

The Bombay High field is located 160 Km W-NW offshore from Mumbai (Bombay) in Western Coastal shelf of India at a water depth of 75m. It was discovered in 1974 and was put on production in May 1976. The field has large areal extent of about 1200 Sq Km and is a giant field. It is divided into Bombay High North (BHN) and Bombay High South (BHS) by a narrow east-west graben. (Fig.-1). The field production of BHN @120575 bopd and BHS @308097 bopd peaked during 1985 and 1989 respectively. The water injection started in 1984 and 1987 in BHN and BHS respectively. The field maintained the plateau rate of production of about 19.0 MMt for about 7 years i.e. from 1984 to 1990. It has passed the mature stage of its producing life and has entered into the decline phase.The field is fully developed with 660 wells (690 strings), with complete facilities for production, processing, evacuation and sale. Over 50% of the facilities are approaching their originally designed life. The present paper discusses about the development stages and reservoir management of the field.

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