Gasfield Development-Reservoir and Production Operations Planning
Authors: Simpson R.E. , Weber A.G. 
Published: December 2007

Efficient development of natural-gas reservoirs requires the participation of many engineering planning and implementation disciplines. participation of many engineering planning and implementation disciplines. When development involves large, remote, offshore gas reservoirs with high H2S and CO2 content, planning and coordination problems increase rapidly. This paper discusses the time/planning relationships in the evaluation and definition phases of a generalized major gas project typical of resources currently being evaluated in many locations. Project development planning requires an extensive drilling appraisal program to define gas in place, gas productivity, and gas quality. With program to define gas in place, gas productivity, and gas quality. With this information, marketing potentials can be established, and the interrelated planning and design steps to define commercial feasibility can be undertaken. These steps include gas process optimization studies necessary for project definition and continued reservoir assessments, progressing into early multidimensional analyses. This effort assists in progressing into early multidimensional analyses. This effort assists in establishing well count, well spacing, and platform siting to yield production performance consistent with equipment constraints and delivery production performance consistent with equipment constraints and delivery requirements. This study does not discuss the execution phase of the project, but it does stress the importance of having a qualified, multidiscipline project organization to complete the evaluation and definition phases and to serve as the basis of the fully staffed project management team necessary to complete the detailed design and construction phases of the project.

Introduction

Many steps are involved in planning the development of a generalized major gas project. The following discussion is based on studies of several large projects from which a composite hypothetical reservoir was constructed to illustrate the problems typically encountered. This composite reservoir is analogous in many respects to larger structures in the Khuff formation in the Middle East. Although project activities overlap in timing and manpower requirements, overall development planning may be subdivided into six phases (also shown in Fig. 1):

Phase 1-exploration and pre-evaluation; Phase 2-evaluation; Phase 3-definition; Phase 4-design; Phase 5-construction; and Phase 6-operations.

Other groups may use different terms, but the activities are similar. This paper is concerned only with the first three phases. During the completion of these steps, a number of activities must be performed in parallel, including exploration drilling, resource evaluation, assessment of oceanographic and geotechnical factors affecting design, and environmental impact evaluation. Preliminary planning must be initiated to anticipate requirements for structures, developmental drilling, production/treating facilities, pipelines, terminals, and marketing. The ultimate objective is to generate an overall project plan applicable to a deep, high-pressure, sour-gas reservoir in an offshore environment.

Pre-Evaluation Phase Pre-Evaluation Phase Minimum time is available for this evaluation. To assist in prompt, accurate reviews, the value of having well-organized project development planning and cost data cannot be overemphasized. The location of the discovery in a typical exploration contract area is shown in Fig. 2 in relation to a nearby shoreline. Some of the more significant steps to be taken in this period include the following.Preliminary assessment of potential recoverable reserves, development costs, and profitability of the prospect.Preparation of a delineation well-drilling program to defineadequately the gas reserves, gas producibility, and cost ofcarrying out such a program.Preparation of detailed study tasks for the evaluation anddefinition phases of the project, an estimate of the minimum timerequired to complete these tasks on the basis of completeddelineation well results, and the estimates of manpowerrequirements and costs for the studies.Management approval to undertake the additional delineation drilling and evaluation/definition study programs.

Although the circumstances of each project are different, the minimum time required to develop the detailed planning and estimates in this pre-evaluation period is planning and estimates in this pre-evaluation period is usually about 3 months but can take longer.

Evaluation Phase

With the approval of the proposed project study plan, the most important ingredient in project planning is the assembly of a qualified project organization.

JPT

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