This paper presents general guidelines to determine the feasibility of offshore petroleum projects in terms of field appraisal, subsurface development planning, and facilities options. It also illustrates the multidisciplinary nature of various tasks and includes examples for illustration. The emphasis is on oil fields, particularly marginal fields.
The life of every oil and gas field begins with its discovery. Almost immediately, we want to know what its potential is (in terms of reserves and monetary value) and what the development options are in terms of subsurface plan and facilities.
To answer these questions, a systematic approach is required to evaluate the discovery, to forecast the reservoir behavior under expected producing conditions, and to design the optimum facilities to meet forecasted production. This paper outlines the required process for studying the feasibility of developing offshore petroleum fields.
A petroleum development project typically is divided into a number of major phases: exploration (including permit acquisition), field appraisal (primary and possibly secondary), feasibility study, project implementation (construction), and field production (operation and maintenance, management, and facilities upgrades, including secondary development phases). Different technical departments, each with specific aims, usually manage these phases (Fig. 1).
While the development sequence is similar for all fields, there are notable differences between onshore and offshore projects. Most significantly, the engineering requirements and capital expenditure tend to be one or two orders of magnitude greater for offshore projects than onshore developments. Furthermore, offshore developments tend to have a much longer development schedule before they come on stream. Reserves and well productivity need to be substantially greater for offshore projects to cover the greater capital expenditure and operating cost, respectively.