New completion techniques using expandable casing with swelling elastomers to seal the annulus, or just swelling elastomers used as packers are becoming available. Diagnostic services are required for these new completions such as evaluation of the annular seal, analogous to cement evaluation. Both conventional and new generation Wireline ultrasonic measurements have been used to characterize and possibly evaluate zonal isolation using swellable elastomers. So far, the following 360 degs circumferential measurements were studied: Ultrasonic radii, acoustic impedance (AI), as well as attenuation and third interface Echo (TIE) reflections from flexural wave data. Radii measurements show a "springback" effect, indicating that expansion against the formation has been achieved. Flexural attenuation has a much better dynamic range over the elastomer sections compared to the acoustic impedance measurements. Both measurements do not consistently distinguish rubber-backed casing with ordinary casing in our examples. The TIE from the latest generation imaging tool tracking the external rubber interface, may provide the measurement the industry needs. First results look promising and further experiments to characterize the tool response are ongoing. The casing geometry of expanded liners was also studied. Introduction The introduction of expandable metal technology and new "smart" materials like swelling elastomers will provide more options for well construction and completion:New techniques in zonal isolation are now possible for over - underpressured, fractured zones and zones with fluid losses [1], [2],Allowing monobore well design [3],Production of selected zones will be made easier, like selective perforation, completion, and stimulation [4],Multilateral junction sealing will be made easier. The effectiveness of zonal isolation and long-term well integrity for this new technology needs to be evaluated and proven. " Smart Material" - Swelling Elastomers Swelling elastomers are now offered by several service companies and have been used by operators for a variety of applications: As a means to establish zonal isolation in liner completions where conventionally a cement column would be used [5], as a production separation packer (swelling packers are used to replace conventional hydraulically or mechanically set packers) [6], and as an integral part of an expandable open hole clad [1]. By incorporating filler materials into an elastomeric matrix the material reacts or swells with time if in contact with water, depending on the elastomer and the requirements [7]. A water swellable elastomer swells through the absorption of (saline) water (osmosis process). An oil swellable elastomer swells primarily through the absorption of hydrocarbons (diffusion process). The typical swelling ratio is about 1.75 to 2.5 and swelling pressures are up to 150 bar. Swelling time is from 5–100 days depending on produced water salinity, temperature and oil viscosity and composition. The longevity of swelling elastomers still has to be quantified.

TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractPetroleum Development Oman (PDO) is planning a major brown-field re-development project. For that reason a waterflood appraisal drilling campaign has been executed. Drilling through fractured reservoir sections causes drilling losses that have to be cured prior to liner cementation. Liner cementation in wells with severe or heavy drilling losses has had limited success despite novel loss curing materials.Expandable tubulars with swelling elastomer seals have been applied in 8 wells as an alternative to cemented liners with the objective to • Provide zonal isolation, to • Attempt time savings by eliminating loss curing and liner cementation and to • Slim down the well design.The reservoir sections of 2 vertical water injector wells and 6 vertical oil producer wells were drilled with losses and lined with expandable casing. Elastomer seals isolate the multiple reservoirs from each other. Expandable casing enables a slim oil producer design still using a 2 7/8" gaslift string. 4 slim wells were drilled. Zonal isolation has been created without cement. This novel approach to drill fractured carbonate reservoirs has proven technically feasible in terms of installation operations, zonal isolation and slimming down well designs. The paper describes the experience with expandable tubular technology for waterflood well delivery.

fax 01-972-952-9435. AbstractThe Fahud water flood project is a major brownfield redevelopment project and a key component to PDO's future production plan. Key value drivers for the successful project delivery are selecting the right recovery mechanisms for the target reservoirs and achieving low-cost well delivery through standardization and technological innovations.The pilot program, which consists of drilling 39 vertical wells in PDO's Fahud field, commenced in April 2004 to gather data on four Natih target reservoirs. The data will be used to identify applicable recovery mechanisms for future field development. The recovery methods under review include the following: • Water flood • Gas-oil gravity drainage (GOGD) • Combination GOGD and water flood • Combination GOGD and depletion • Combination GOGD and gas flood Natih is a stacked layered reservoir. Natih A and C were developed by water floods in 1972-1980. These wells were unsuccessful due to early water breakthrough through fractures and karst parts of the reservoir. From 1984 to 1998 certain reservoir sections were developed by GOGD with 200+ development wells drilled. Since 1997, water flooding has been used to produce different zones in the Natih reservoir. Most of the drilling during this time consisted of horizontal wells with single or dual laterals.Although horizontal wells, in particular dual-lateral wells, provide excellent area data coverage, they also • Provide ambiguous production data from single zones.• Do not allow observation of reservoir behaviour in overand underlying zones. • Are costly to enter (hoist/coiled tubing).• Present a challenge to manage flow profiles.These issues led to the consideration of implementing alternative well designs. This paper will discuss the well planning, wellbore preparation and successful application of solid expandable tubular technology. These systems, combined with swelling elastomers, slim the well design and provide reliable isolation of the Natih sub-units to allow independent testing of the zones. The paper also presents the completion design planned for the test program and long term production.

TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractDrilling through weak formations with total losses, while concurrently controlling gas influx by pumping water down the annulus, is a situation often encountered in the main Northern Oman carbonate oilfields. Consequently cementing the intermediate liner and aiming to achieve total annular coverage for zonal isolation becomes a challenge.This paper describes a technique that has permitted the intermediate liner to be set and fully cemented while experiencing drilling fluid losses and formation flows. Using this technique, the liner packer is set before cementing, thus isolating the gas influx and removing the need to pump in the annulus during the cementation. Then by cementing using a foamed spacer and foamed cement in stages, the fluids can be effectively diverted up the annulus across the loss zones resulting in zonal isolation. For better control of the volumes, and to be able to react to a possible early increase in pressure, the inner-string liner method is used. This cement procedure has been employed on several wells and the cement bond log (CBL) results are very encouraging. Prior to employing this method, cement was only evident around the liner shoe joint. With this new method the total liner length has shown cement coverage from 80-100% with the top of cement (TOC) approaching the previous shoe. In addition this technique has resulted in economic gains by eliminating stage tools and annular packers.The drilling challenges of these fractured wells, the cementing requirements, the design notion of the foamed fluids, the operational execution, and the observed CBL results are all discussed. The value added by using this technique is also demonstrated.

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