Drilling new generation wells with longer horizontal sections, to maximize the reservoir contact, has brought many challenges to well interventions using Coiled Tubing (CT). In most cases, the complexity has pushed CT interventions to the limits, driving the development of new solutions to extend the reach to total well depth. The number of these extended-reach wells has grown significantly in recent years in Saudi Arabia, especially in this new development field where more than 120 extended reach water injection wells were placed in the reservoir flanks. The water injection wells in this study area are complex due to the combination of large bore tubular, lower reservoir pressure and horizontal openhole (OH) completion, with lengths from 3,000 ft to almost 5,000 ft. During the initial CT interventions in this field, several challenges were encountered, e.g., stuck CT differentials, slack-off weight through severe doglegs, tight spots, and other obstructions. Extensive knowledge was gained by performing an extensive simulation, studying the horizontal section geometry and analyzing the operational data. Based on the findings, combinations of techniques were introduced to the procedure to extend the reach and minimize the operational problems and costs. The key components of our new implemented strategy were buoyancy reduction by using nitrified fluids and new viscoelastic surfactant (VES) friction reducer or drag reduction agents. In addition, combinations of other techniques were employed, e.g., optimizing the pull tests frequency in the OH and improving CT movement practices. This paper discusses the difficulties and challenges of the initial stage of the stimulation campaign, performed in horizontal OH water injector wells using CT. Also, it presents the results and analysis of the effect of buoyancy, CT pipe size and new friction reducer for the referenced wells. The study leads to a new cost effective and reliable technique, which once implemented, conduces to maximize the CT reach without using mechanical devices, e.g., agitators or tractors. INTRODUCTION The study was performed in one of the new fields being developed in Saudi Arabia by drilling extended-reach horizontal water injection wells in the flank of the reservoir to help assure the effective water distribution, optimum sweep and adequate pressure support in the reservoir. Stimulation of the new water injection wells is a key factor for new increment success. The horizontal wells were acid stimulated, in order to remove formation damage and enhance the water injection. Distribution of treatment on the whole horizontal section is essential to implement the depletion strategy and maximize recovery factor. The length of horizontal OH section varies between 3,000 ft and 5,000 ft.

CO@~l199S, Sodety of Petroleum Engin6Ws, inc. Tf-Js paper was prspa-fifi-p-mmti~al me W9S ?iPE/OOE Improved Oil RecoverySYmpdum held in Tulsa, Oklahoma, 19-22A@ i998.This papar wss aelaclad for presentation by an EWE Program Committee followir!g review of hformation confalnad In an abstract submitted by the author(s). Ccntents of the wwr, aS prasanred, hava not i%6n"rW?ewedBy Ihe SZEf3W of Petroleum Enoin=s and are sub@t tO correction by the author~s]. The material, as presented, dcas not necessarily reflect any fxasflion of the Society of Petroleum Engineers, Its officers, or members. Papers presented a! SPE meatings sre sub&f 10 puiSicafimn rmiawlsy Editorial CommiWas of the Sodefy of Petroleum Engineers. Efactronic raprcductiom distribution, or storage of any part of this paper for commercial purpoaas wfthout the wiftsm ccmsant of the Sdety of Petroleum Enginaars is prohibited. Permission to reproduce in print h reatrfcfad to an abstracl of not more than 300 wrdq ilhsirattmns may not be copkd. The abstract must contain conspicuous acfmowiedgment of where and by whom the paper was preaen!ed. Write Liirarian, SPE. P.O. S0s S33S36, Ffichardaon, lX 75063-3&S6, U. S.A., fax 01-972-952-9435. AbstractWater shut-off treatments (WSOT) are routinely performed on wells in the carbonate formation, in one of Saudi Aramco's oil fields that are dead, have high water cut, or low-flowing wellhead pressure. WSOT using through-tubing bridge plugs ('ITBP) in both open-hole and cased-hole completions have been employed. Such a treatment was successfully applied in zones that are LOCYZO swept by the water flooding and are no longer contributing oil and in high permeability zones (super-K) located in the lower interval. These wells were then activated and have been placed on production. The field results horn 40 bottom water shut-off jobs, using 'ITBP technique, are presented. The 1990 -1 996 water shut-off jobs added a total of 88.0 MBD of producible potential. In addition, the application of TTBP method increased recoverable reserves and avoided expensive workover costs.This paper presents data to show that 'ITBP technique is very effective compared to other methods of water shut-off jobs. Significant cost reductions are realized. The success ratio of this treatment in the open-hole completion (OH) can be as high as the cased-hole (CI-1) completion, provided that a 'gauge' hole exists.

This paper describes the experiences of utilizing coiled tubing and its conveyed diagnostic tools, following a multi-stage plug and perf acid fracturing treatment performed in a highly deviated well. A downhole video camera and multi-arm caliper run on coiled tubing were used for the first time in Saudi Aramco gas wells. The well is a gas producing well in a thick carbonate structure and was drilled at a high angle to intersect several different porosity layers within the formation. The well was also drilled at 30 degrees to the minimum stress direction to allow the creation of transverse fractures from each frac stage. The final completion consisted of five frac stages spaced out along the interval separated by four bridge plugs. Following the completion of the fracturing operations the initial attempt to mill the plugs was unsuccessful as the milling tools were unable to reach the depth of the first plug. At this stage the well was potentially lost due to suspected damage or deformation to the liner caused during the fracturing. A series of diagnostic runs was performed with coiled tubing and a milling strategy formed from the results. The diagnostics included first time use in the area gas wells of a downhole video camera and multi-arm caliper conveyed on coiled tubing. The diagnostics were successfully completed and analyzed. From these results the required milling tool diameter was determined and a milling bottom-hole assembly was designed. Coiled tubing was re-mobilized and the plugs were successfully removed from the liner allowing full bore access and the well to be flowed back.

The design of fracture diversion in tight carbonates has been a challenging problem. Recently, a conceptual and theoretical workflow was presented using a β diversion design parameter that uses system volumetric calculations based on high-fidelity modeling and mathematical approximations of the etched system. A robust field validation of that approach and near-wellbore diversion modeling was conducted to extend the application. Extensive laboratory and yard-scale testing data were utilized to realize the diversion processes. Fracture and perforation modeling coupled with fracture diagnostics was used to define system volumetrics, defined as the volume where the fluid needs to be diverted away from. Multimodal particulate pills were used based on a careful review of the size distribution and physical properties. Bottomhole reactions and post-fracturing production for multiple wells and 100 particulate pills were studied to see the effect of the β factor on diversion and production performance. A multiphysics near-wellbore diversion model was used for the first time to simulate the pill effect. Representative wells were selected for the validation study; these included vertical and horizontal wells and varying perforation cluster design, stages, and acid treatments. A complex problem was solved with reaction modeling coupled with near-wellbore diversion for the first time based on given lithology and pumped volumes to match the treatment and diversion differential pressures. Final active fractures and stimulation efficiency were computed through etched geometry. The results showed a range of etched fracture length from 86 to 109 ft and width of 0.05 to 0.08 in. A similar approach was used for perforation system analysis. Diversion pills from 2 to 15 per well were investigated with a 5- to 12-bbl particulate diversion pill range. Finally, the β factor was calculated for each case based on the diversion material and system volumetric ratio. The parameter was plotted against the average diversion pressure achieved and showed an R2 of 0.87. Based on the comprehensive theoretical, numerical modeling, and field-coupled findings, a β factor of 0.8 to 1.0 is recommended for optimum diversion and production performance. For multiple cases, stimulation efficiency and production performance have been enhanced up to 200%. From the field results, it is evident that the design of near-wellbore diversion needs to be strategic. The unique diversion framework provides the basis for such a well- and reservoir-specific strategy. Proper and scientific use of diversion material and modeling can lead to advances in overall project management by optimizing the cost–efficiency–quality project triangle. Digital advancements with digitized cores, fluid systems, and advanced modeling have significant potential for the engineered development of tight carbonates.

Well integrity management (WIM) is an art of managing the well to reduce risk applying technical, operational and organizational solutions. With maturing fields and the evolution of advanced technologies, the industry has significantly improved in terms of WIM, though the art is still to be mastered. Nevertheless, WIM over the years has evolved and to some extent has become reliable enough to provide high confidence to operators to safely operate and manage matured fields. In spite of all the WIM practices in place, failure does happen. The root cause of the failure is carefully studied and necessary changes in process/technique are incorporated to ensure that such reoccurrences are not repeated.Well integrity management starts from the stage of designing a well and continues throughout the life cycle of a well. The risk management becomes intense and difficult as the well gets older. Investment in gathering valuable well data remains a key to mitigate from risk and to better anticipate potential failures. Classical approaches to WIM are mainly for detecting a failure. Now, there is a paradigm shift, thanks to advanced technology at our disposal, to go for a predictive approach in forecasting a problem before it happens.This paper describes the evolution story of proactive WIM at Saudi Aramco with emphasis on the utilization of corrosion monitoring tools as a predictive approach. The results of such a methodology can predict many "to-be" failures and allow for the timely resolution of expected integrity related challenges. The paper also narrates one case study for an oil well-A from Saudi Aramco, which developed a failure. The study of the root cause of the failure and lesson learnt were applied in improving the risk mitigating technique, and so inching toward complete WIM.