Successful Installation of Elastomeric Packers/Expandable Sand Screen in Subsea Openhole Completions Offshore Nigeria

Abstract

Abstract The challenge posed by deep water field development particularly in complex geological architecture necessitates the application of new technologies to improve well performance/ultimate recovery and reduce well construction costs. Therefore, proper evaluation of a variety of new products is imperative so as to ensure selection of a purpose-fit technology. Additionally, a peer review process must challenge the execution plan and identify possible flaws. Then, risks can be assessed and adequate mitigation plans put in place to ensure success. In a first of its kind application in West Africa and probably in the world, Addax Petroleum employed a paradigm shift in zonal isolation in its subsea well construction; in 440ft of water, employing a combination of Elastomeric Packers and compliant Expandable Sand Screen (ESS), two 3-zone single string selective subsea wells in its OML-126 Okwori field have been completed, a feat that will potentially change zonal isolation equation in the industry. The cost savings include elimination of production casing; cementation, wait on cement, cement evaluation, associated loss circulation control, cased hole tubing conveyed perforation, perforation burr removal trip, extensive wellbore cleanup, brine filtration and Acid/Enzyme stimulation to treat post perforation lost control material (LCM). The Implementation included peer review Completing Well On Paper (CWOP) and Testing Well On Paper (TWOP), development of a risk log and following through with mitigation plans, lesson learned and close out meetings. The planning of the well to achieve a gun-barrel hole using state of the art synthetic base mud systems engineered to ensure a sleek hole helped to minimize hole problems. Rotary Steerable drilling was employed to minimize dogleg severity and reduce torque and drag to a manageable level. In spite of these measures however, the centralizers in the completion assembly tore apart while deploying the completion in well #1. Thus, the completion was unable to reach bottom depth and was pulled out and rerun. The two completions were subsequently run without centralizers. After deployment, the ESS was expanded without problem and then the rig moved off to install the completion assembly in Well#2. This allowed the Elastomeric Packers to expand for proper isolation in line with the design specifications. Extensive laboratory tests were carried out to design the right mud cake breaker recipe compatible with the filtering element corrosion limits. The initial production performance from Well#1 and #2 proved that Elastomeric Packers technology are effective in isolating the influx of water and gas. A surface Read Out (SRO) high resolution quartz gauge was used to measure real time drawdown and pressure buildup during initial flow tests. The analysis of the data showed that the productivity index (PI) from the two wells surpassed previous cased hole wells with the same ESS product.