Enhancing oil production from mature fields by focusing on well-intervention management: North Oman

North Oman comprises four mature assets, producing 90% of its oil from old wells. In the drive to enhance oil production of the existing well stock, while arresting the natural decline of oil rate through better Well and Reservoir Management (WRM), well intervention work has increased in importance in the Company's portfolio of activities. From 2003 a robust subsurface Well Intervention program is rigorously generated and vigilantly implemented and closely tracked. In 2005, some 3,600 well work activities were executed in the areas of Well Surveillance (well and reservoir data gathering); Well Optimization (oil generating activities, i.e. additional perforations, water & gas shut-off, stimulations, etc); Well Restoration (to maintain the old wells' oil potential by ESP replacements, tubing wash, re-dress Gas-lift valve, etc) and Well Integrity (production casing repairs, fishing operations, annulus pressure testing) activities. Implementation of this program calls for utilization of various types of intervention technologies such as work-over hoists, electric / normal coiled-tubing units, electric wireline units, slick-line units and non corrosive pumping units. The oil generating (optimization) activities delivered some 5.4%, while restoration and integrity repair activities safeguarded some 23%, of the total oil production from North Oman, there by arresting the natural oil rate decline during 2005, at a low unit technical cost per barrel. As the fields get older, the well intervention work is expected to grow in term of magnitude, complexities, need for new technologies, cost impact and new challenges. Hence, the directorate has foreseen a need for continued concentration on improving the management of the well intervention to maximize the value realized in terms of oil reward and arrest of the natural decline oil rate. This paper describes recent improvements to the Well Intervention Management Process in the North oil fields; fromranking of the activities, resource planning and optimization; activities planning and scheduling; execution of the plan, tracking of the operational / reservoir performance and feed back of learning for further improvement These improvements are described by real examples of well interventions and the results achieved from managing the overall well intervention operations. It will also discuss the current operational challenges and limitations, and new technologies needed to address the issues.