Arun Indonesia: Big Bore Completion Tool Design

Abstract

ABSTRACT Although the current gross production average of the giant Arun gas field in northern Sumatra exceeds 3.3 BCFD, a number of projects were initiated in 1991 to increase field productivity, One of those projects, a monobore approach to completions, is being utilized to improve well performance on a series of ten 9-5/8-inch "Big Bore" completions. This is the first time a monobore completion has been utilized in the Arun field and, as far as we know, these are the largest bore producing gas completions in the world. Extensive tool development work, including detailed -design reviews, FEA modeling, and prototype testing, was required to ensure that the project's objectives of achieving operational tool reliability, improved equipment performance, and increased operational flexibility would be achieved. Six "Big Bore" wells have been successfully drilled and completed without any serious operational or equipment problems. All 9-5/8-inch completions will be drilled and completed by mid-year, 1993. The productivity improvements have far exceeded the rates originally expected (Fig. 1). INTRODUCTION The Arun gas field, located in the Aceh province (Fig. 2), is Indonesia's largest gas field currently on production. Several options were evaluated to improve field productivity to meet future LNG commitments, including large bore completions. The use of large tubing strings would satisfy the projected production needs at a lower cost per MMSCFD than the existing 7-inch tubing completions. Productivity projection for each Big Bore well was originally 120 MMSCFD. This projected production exceeded that of the existing 7-inch tubing completion (averaging 70 MMSCFD) by 71%. With the application of the monobore concept, full field development will be achieved with fewer wells. Although a significant opportunity, the application of the monobore completion technology in the severe Arun field conditions (Table 1) presented a major technical challenge. By applying several lessons learned during the initial Arun field development to the monobore program, significant expenses were saved during both equipment development and operations. The concept was originally considered in early 1990 and actual engineering design and manufacturing was initiated in 1991 after full project approval. All engineering design work, prototype testing and manufacturing was completed in approximately 11 months. The drilling and completion of the ten planned "Big Bore" wells was begun in early January, 1992 with the first 9-5/8-inch monobore well put on production in March of that year. Drilling and completion is expected to be completed by mid-year, 1993. The original projected well performance of 120 MMSCFD was far exceeded. Rates as high as 220 MMSCFD during high rate clean-up testing have been realized. Efforts to minimize well operational problems and provide maximum completion tool reliability have proven successful. COMPLETION OVERVIEW In early 1991, during the original 9-5/8-inch completion feasibility review, four separate options were considered. These included various combinations of conventional cased-hole tubing/packer and open hole tubing/packer completions. The monobore option, a fifth configuration, was identified and adopted. This includes a 9-5/8-inch tubing string in conjunction with a liner hanger, liner top packer and polish bore receptacle (PBR), as shown in Fig. 3.