Banzala Field Development: Technical Maturity of Individual Reservoirs Drives Phased Development Approach
Authors: Gaon M.T. , McCartney M.J. , Whatley C.P. , Rieken M.K. 
Published: October 2008

The Banzala Field is located offshore Cabinda, Angola, in Area A of the Cabinda Block 0 Concession. Banzala Field is an anticlinal structure with three primary reservoirs: the Mesa, Lago, and Azul members of the Cretaceous labe Formation. The current reservoir model shows varying levels of technicalmaturity associated with these three reservoirs. Due to varying levels of technical maturity associated with each ofthe Banzala reservoirs, a phased development approach will be utilized to develop the field. Phase I development will focus on the Mesa reservoir, utilizing a single 20 slot wellplatform. Phase 2 will allow development of the remainder of the field, and will most likely consist of a gathering stationand 3 additional 20 slot well platforms.

Introduction

The Banzala Field is located in Blocks 34, 35, 45, and 46 in Area A of the Cabinda Block 0 Concession (Figure 1), and is being developed on behalf of the Cabinda Association (Sonangol, Chevron, Elf, and Agip) by Cabinda Gulf Oil Company Limited. Water depth ranges from 125 ft. to 175 ft. The hydrocarbon accumulation at Banzala occurs in shallow marine clastic and carbonate reservoirs of the Late Cretaceouslabe Formation and is approximately 500 ft. thick. The reservoirs are shallow, with the deepest oil/water contact at 1,990 ft. tvdss. The current estimate of original-oil-in-place(OOIP) for all three reservoirs combined is 1.8 billion barrels.

Although the field was discovered in 1981, appraisal has been complicated and delayed by the shallow Landana gas hazard overlying the Banzala oil reservoirs. Four appraisal wells were drilled in 1997 to obtain the necessary data to complete the reservoir characterization. The first 1997 well provided enough additional data to adequately characterizeand plan development of the areally limited Mesa reservoir (Phase 1) and formulate a preliminary full field development plan (Phase 2). Because of the large areal extent of the Lago and Azul reservoirs, the Phase 2 portion of the development plan will be refined and updated by incorporating data from all four of the 1997 appraisal wells before additional development proceeds.

Phase 1 will primarily develop the Mesa reservoir, consisting of a single 20 slot well platform along the northeast flank of the structure. Phase 2 will develop the remainder of the field, and will most likely consist of a 75,000 BPD gathering station and 3 additional 20 slot well platforms. Additional information from 1997 appraisal well analyses, reservoir studies, and production information from Phase 1 will be utilized to update the reservoir and simulation models, and optimize the Phase 2 development.

Field History

Banzala was discovered by exploratory well 45-2x in 1981. The well blew out while tripping out of the hole for logging. The Mesa, Lago, Azul reservoirs were exposed during the blowout. Several relief wells were drilled in 1981 and 1982 to control the blowout. Two delineation wells were drilled in 1983 and 1984 to delineate and appraise the Mesa, Lago, andAzul reservoirs.