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; from ranking 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. Introduction North Oman, comprising four major mature assets (clusters), produces nearly 50% of Company's net oil. As the fields continued to age, oldest being over 40 years on production, wells management challenges from reservoirs to the surface.

TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractA new cost effective life-cycle profile control completion system has been developed to solve major problems associated with surveillance and interventions in horizontal and TAML level 2 multilateral wells completed with ESP. each other and can be selectively produced, shut-off or stimulated. The need for CT interventions for production logging and water shut-offs is removed. The water shut-off process offered by this technology is reversible.

Water production management starts to play a more important role as reservoirs mature. Production logging is required to identify watered out intervals in producers and thief zones in injectors. The interpretation of logs acquired in horizontal, barefoot wells in highly fractured, heterogeneous, carbonate reservoirs is challenging at least. Yet this technique has been successfully applied in Petroleum Development Oman (PDO) in the Yibal and Al Huwaisah fields (Fig. 1) and has lead to significant production improvements after the subsequent water shut off. Expandable Open Hole Clad (OHC) systems, with external seals, have been deployed to shut off water in both horizontal producers and injectors. The seal between the expanded pipe and the formation is further enhanced by elastomers with the ability to swell upon contact with formation fluids. Case histories are presented to demonstrate the viability of this new technology. Introduction As oil fields mature, production wells experience co-production of oil and water because of aquifer encroachment and/or water injection. Controlling the water production is one of the major challenges in reservoir management. Diagnosis of the zone of water influx in horizontal well bores, however, is not always straightforward and must certainly preceed any remedial water shut off treatments. This paper starts with a discussion on the water shut off technique using expandable tubulars, followed by two case histories in which more details are provided concerning production logging, expandable clad installation and production results. Technology Overview Previously published papers have discussed the concepts of Solid Expandable Tubular (SET) technology1 and the effect of the expansion process on the system's tubulars2,3 and connectors4. The specific system used in PDO, with the required adaptations, will be reviewed in this paper. The basic principle is the down hole enlargement (expansion) of a solid pipe. Expansion is achieved with a cone that can either be pushed (typically by hydraulic force) or pulled through the pipe. SET can be applied for both well construction and remediation5. Four general types of SET products can be identified:The Expandable Cased Hole Liner (CHL) is set in a cased hole environment and is typically used to isolate perforations or damaged or corroded casing.The Expandable Open Hole Liner (OHL) is used in the well bore construction process to provide an additional liner whilst minimizing Internal Diameter (ID) loss. This provides more options in the well design process to reach the required Total Depth (TD) without compromising hole size.