Maximizing Production Capacity With Intelligent-Well Systems in a Deepwater West Africa Field

This article, written by Technology Editor Dennis Denney, contains highlights of paper SPE 103308, "Maximizing Production Capacity Using Intelligent- Well Systems in a Deepwater, West Africa Field," by D.J. Goggin, M.A. Ovuede, N. Liu, SPE, U. Ozdogan, SPE, P.B. Coleman, SPE, and D.P. Meinert, SPE, Chevron; I. Nygard, Statoil; and J. Gontijo, Petroleo Brasileiro Nigeria, prepared for the 2006 SPE Annual Technical Conference and Exhibition, San Antonio, Texas, 24–27 September. Large, deepwater fields with a limited number of wells may require intelligent-well systems to maximize production capacity under facility constraints. Agbami field, a highly dipping reservoir with many producing zones and few wells, will use intelligent-well systems consisting of interval-control valves (ICVs) and many sensors to monitor, analyze, and control (MAC) injection and production at the zonal level. Introduction A key objective for optimizing asset performance is maximizing and accelerating recovery by producing wells at optimal rates, which will delay the arrival of water and gas while honoring the mechanical limitations of the production network (e.g., flowlines, manifolds, risers, and separators). The challenge for operators is to know where the excess production capacity exists in the network at any given time and what control settings can be adopted if well failures occur. Therefore, a MAC process is used to respond to unplanned operational interruptions and to be prepared for longer-term reservoir behavior caused by geologic uncertainties. Reservoir Description The overall field structure is a northwest/southeast-trending four-way-closure anticline on the Niger delta front, approximately 65 miles offshore Nigeria in the Gulf of Guinea. The anticlinal structure has dip angles as steep as 30° on the northeast and southwest flanks. From 3D-seismic data, several faults have been mapped across the anticlinal structure. A major thrust fault divides the Agbami field into inboard (northeast) and outboard (southwest) halves. Normal faults further subdivide the field into eight potentially noncommunicating areas. The high structural dip and the fault compartments are important factors in the well-placement strategy, injection patterns, and oil-recovery expectation. The field has four stacked reservoirs with distinct pressure profiles. The current geologic model includes three of these reservoirs designated as 14MY, 16MY, and 17MY. The 17MY reservoir contains 80% of the total-field oil-in-place of approximately 2 billion bbl. Field-Development Plan and Production Network The field-development plan recommends midflank oil production with crestal gas injection and peripheral water injection as the primary oil-recovery, pressure-maintenance, and gas-disposition scheme in the 17MY units. Oil properties of 47°API gravity and 0.23-cp viscosity are favorable to a combined crestal miscible-gas drive and peripheral water-injection scheme in a highly dipping reservoir. Thirty-eight wells are planned in three drilling stages. Plans include 17 Stage-1 wells drilled and completed before first oil production, comprising 10 producers, four water injectors, and three gas injectors. Stages-2/-3 drilling occurs after first oil production.