TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractMatrix acidizing of horizontal and multi-lateral wells is a challenging task for several reasons. First, oil reservoirs are heterogonous in nature and the presence of high permeability streaks is common. Proper diversion technique is always required to better distribute the injected acid across the target zone. Secondly, stimulation of horizontal wells requires injection of large volumes of acids. This will require using an effective corrosion inhibitor package that can protect down hole tubulars and coiled tubing, especially in sour environments. Thirdly, recovering large volumes of spent acid is a concern, especially in tight formations. Acid treatments should be designed to address these issues in a cost effective way.Currently, there are a limited number of chemicals that can divert the acid into the formation. This paper introduces a new viscoelastic surfactant which was used to form stable foam during matrix stimulation of a seawater injector. The length of the target zone was 1,500 ft, and the average permeability of the carbonate was 700 mD. A 1.75-inch coiled tubing was used to better distribute the acid in the open hole section (6.125-inch in diameter).As with previous viscoelastic surfactant systems, the surfactant molecules form structures in solution in the presence of salts. These structures enhance the viscosity of solution significantly and can be broken by dilution with injection water or by adding mutual solvent (3-5 vol%) to the preflush/postflush stages.Unlike previous viscoelastic surfactant-based systems, the new surfactant builds viscosity faster and its gel breaks down in a shorter period of time.This paper examines the results of extensive lab testing that led to the development of this improved self diverting system. It will also give details of the first field application of this system. Following the acid treatment, the well injection rate improved by five folds, from 16,000 to 80,000 BPD. Benefits and improvements introduced by the new diversion technique will be discussed in detail.

TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractThe trial test of Wireline Retrievable Side Pocket Surface Read-Out Permanent Downhole Monitoring System (SPSRO-PDHMS) was successfully conducted in a newly drilled well in a giant oil field in Saudi Arabia. In the wireline retrievable PDHMS system, the downhole gauges sit in a side pocket mandrel; if the downhole gauges malfunction, they can be retrieved and replaced easily with wireline. Conventionally these gauges are run on tubing and in case of gauge failure, a workover rig is required to replace the malfunctioning gauge (there are 6 wells with malfunctioned/failed gauges in the operated field). The WL retrievable option would eliminate the $500,000 rig cost per well to replace malfunctioning or damaged gauges.

This paper discusses the first successful coiled-tubing-conveyed production logging operation in a short radius horizontal well in Saudi Arabia. The production logging tool (Polaris[TM]) was modified with knuckle joints to pass through the severe well dogleg of 58 degrees per 100 ft in openhole. Subsequently, the tool was conveyed an additional 1400 ft in the horizontal section. The logging objective was to determine the flow profile for oil and water and identify the water entry points. The major challenge was tool deployment in this short radius well to gain access to the horizontal section. Monitoring of short radius horizontals has been almost nonexistent due to high dogleg severity. Because of the rigid tool length of conventional production logging systems, tool modifications were crucial and extensive job planning preceded the operations. Planning included modeling maximum rigid tool length, tool modifications, simulations for job feasibility with 1.75 in coiled tubing, and tool string bending moment tests. Prior to the main run, a dummy tool was successfully conveyed through the high dogleg to determine the feasibility of the operation. The successful completion of the log allowed the generation of a flow profile and identification of the major fluid entry poiints. These will help determine the most efficient way of sidetracking wells in the Ghawar Field to maximize reservoir sweep efficiency and to aid in planning future short radius horizontal wells. Introduction As fields mature, short radius horizontal (SRH) wells become increasingly more important in maximizing oil recovery and prolong plateau production performance [1]. One of the main challenges for SRH wells is to obtain reliable formation or well evaluation data to analyze well performance. This type of data is crucial for optimization of oil production as it allows diagnosing any further remedial work such as possible water shut off or selective acid stimulation. During or after drilling SRH wells, only slim access openhole tools can be used to aquire formation evaluation data, due to dimension limitations of conventional LWD and wireline tools. Once SRH wells are put in production, teh tool diminsions of the conventional suite of production logging tools do not allow conveyance through the high dogleg interval of such wells. The well discussed in this paper was drilled as a SRH well with a maximum severe dogleg of 58 degrees per 100 ft. To analyze well performance, and existing horizontal production logging system (Polaris) was adjusted and modified with knuckle joints, allowingthe tool to pass through the severe dogleg and succeddfully log the horizontal well section. The conveyance method for this job was on 1.75 in. coiled tubing. This was the first time worlwide that the Polaris production logging system was used to evaluate flow performance and identify fluid entries in a SRH well.

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