Defining the Optimum Well Completion for Marginal Field Development – An Approach

Marginal field development commonly face setback when it comes to an investment decision, which makes it technically and commercially very challenging to be developed. Technologies that usually applied in big fields may not be economically relevant to the marginal fields, despite require the same assurance and functionality. Well completion cost itself can take up to 50% of the total well cost, especially for fields that potentially must deal with sand production, high CO2 and/or H2S content, artificial lift, and multilayer zonal completion and isolation. This paper demonstrates an integrated approach to identify and define the optimum well completion strategy for such conditions in a Malaysian oilfield. The first step is to list all the operational issues and challenges of producing from the neighboring fault block and other analogue fields experience. Leveraging on the available data and types of completion that have been installed, a set of scoring is given to different completion type, considering the sand production control effectiveness, good well performance, and long well life span. The shortlisted completion types were further evaluated based on the following criteria: Production flexibility Early monetization Operation complexity (drilling and completion) Sand production management Sand control failure probability Associated Risks Stand-alone economic As a result, eight (8) completion strategies were investigated namely Monobore, Monobore wih resin, Cased & Perf, Cased & Perf with resin, Open Hole Stand Alone Screen (OHSAS), Cased-Hole Stand Alone Screen (CHSAS), Cased-Hole Gravel Pack (CHGP); using circulating method or frac pack. Different completion has its own advantages and disadvantages. Structured scoring system was again applied to guide the decision-making process. The key elements in the decision thought process are the associated cost of each option, the skin factor that affect the production and reserve estimation, and ultimately the Net Present Value (NPV) indicator. In conclusion, identifying the optimum well completion will never give a single solution answer. However, the most important thing is to consider all the decisive factors and properly evaluate all options. In our own real example, the option that gives the best NPV coupled with tolerable risk (HSE risk i.e. less issue at surface) was selected as the optimum well completion strategy to be used in the development plan.