Decision-making in an uncertain world
A Chevron case study

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Page 3: Development

Chevron 4 Image 4Ever since its discovery in 1984, it was clear that drilling for Alba’s oil was not going to be easy. The geology of the area was particularly difficult and the total 750 million barrels of crude oil in the field were held in loose, unconsolidated sands. To make matters worse, the reservoir was long, thin and shallow, with a large volume of water underlying the oil. However, nearly 400 million barrels of the original reservoir oil were deemed recoverable – fairly good by industry standards.

With the drilling technology of the day, one way to reach into both the southern and northern extremities of the field would have been to construct a vast central platform - and then face uncertainties over the ability to produce the heavy, sluggish oil from the furthermost points. Chevron decided on a phased development process because of uncertainties about the performance of the oil reservoir and the processing of Alba fluids.

Phase I – Northern Platform and FSU

Phase I involved the installation of a platform with integrated production, drilling and living quarters, Alba Northern Platform (ANP), over the northern part of the field, together with the FSU.

ANP was expected to produce 227 million barrels of oil from 20 production wells (of the then-estimated total 385 million barrels recoverable from the whole field). The oil was to be extracted by conventional angled and horizontal wells. This was to be supported by the use of submersible electrical pumps. Meanwhile a number of highly deviated (i.e. at a high angle from vertical) wells are used to inject water from the platform to maintain the pressure in the reservoir and help drive the crude oil to the surface.

Chevron’s initial plan was to complement the Northern Platform with a Southern Platform which would be installed five years later. By operating from two platforms it would be possible to reduce the angle of the wells and this would reduce costs. Technology at the time would, anyway, limit the drilling radius to only 9,500 feet (under two miles).

Chevron | Decision-making in an uncertain world