This paper presents a systematic approach of identifying, selecting, developing, implementing, and operating a pressure maintenance scheme (PMS) for an offshore field. The paper discusses the design scheme through a five-phase, well organized process. The design is accomplished through an integrated approach involving geological, engineering, operational, and environmental aspects. In addition, the case history of a shallow water offshore Meren field is presented and analyzed. It covers the selection process that was used to determine the PMS, as well as the subsequent operational and performance histories over the past 17 years. The actual performance history is compared to the predicted performance and the lessons learned are summarized.
Although the methodology presented here is applicable to both onshore and offshore fields, the primary emphasis here is on the challenges posed by offshore fields. In both onshore and offshore development of pressure maintenance systems (PMS), the integration of the various multi-disciplinary teams (geophysical, geological, reservoir, drilling and completion, engineering and construction, operations, and environmental) is extremely important. However, in dealing with offshore fields, it becomes crucial very early on. This is due to the traditionally different approaches to PMS development for the onshore and offshore fields. While onshore, it is desirable to develop a field first, then produce and monitor its performance for awhile, prior to the selection of a PMS. However, in the offshore scenario, there is not enough time available to analyze the production performance data to ascertain the natural drive mechanisms before a decision is made regarding the pressure maintenance. The decision must be made before the reservoir drive mechanisms are fully understood so that the field can be developed at an economically optimum time and cost.
While many deepwater offshore field development plans are based upon multi-phase concepts, it is not uncommon for the field's "full life cycle asset management" to have been thoroughly forecasted and analyzed, well in advance of the multi-phase implementation. It is necessary for the teams to anticipate, identify, and manage all potential uncertainties relating to geological complexities, well placement, drive mechanisms, deliverabilities, and facilities early on - in order to take maximum advantage of the available resource.
Equally important to the success of the project is the full, effective involvement of partners and national oil companies, if applicable.
This section describes the design of a PMS in a five-phase process as follows: Phase 1 - Identification of Business Opportunities and Determination of Initial PMS Conceptual Designs The first step in a conceptual PMS design is to identify the business opportunities and goals at hand. In an offshore environment, the opportunities are typically based on: reservoir performance under primary depletion, potential to improve reserves and reservoir performance, and successful PMS in similar reservoirs. The establishment of goals should then be followed by the formation of an integrated task force to perform a quick PMS feasibility study to add probable reserves.