Increased water cut represents one of the biggest challenges to the oil industry, with more than 75% of the produced fluid being water that brings an increased cost per barrel of oil through water handling, scale deposition, corrosion, and mainly the bypassed oil reserve. Water shut off solutions range from mechanical solutions like bridge plugs to chemical treatments that include cement, resins and polymer gels. Cement applied as a plug or a squeeze treatment is often the preferred option to the operating company for isolating unwanted production intervals near the wellbore, and crosslinked polymer systems are also commonly used when deeper penetration is required. However, the success of these treatments often suffers from mixed fluid quality, zonal isolation (cementing quality), proper placement, numerous downhole conditions and more importantly backflow of unset cement slurry or immature gels while cleaning up leftover slurries in the wellbore or pulling out the work string after the treatment. In this paper, a new system based on a single nano-additive is described to shut off a water zone in a South Kuwait regional oil producer. The new system, which does not require curing but acts rapidly in porous media, addresses the concern of backflow associated with unset cement or crosslinked polymer fluids. The objective of this treatment was to seal off the upper zone that produces mostly water, reduce overall water cut from 90% to less than 10%, and test the productivity of the lower zone. The well configuration does not allow zonal isolation without a rig, so cement and other known chemical treatments were unsuitable for this application. Eighteen barrels of the water shut-off treatment was pumped through coiled tubing (CT) and injected into a 34 ft zone resulting in nearly immediate response through increased wellhead pressure. The injection was resumed every three to four hours to ensure a complete sealing of the target interval. The fluid starts workingupon injection into porous media but always remains as liquid phase when kept in the wellbore or surface tanks, so there is no concern about sticking or plugging the coil. The operational time was reduced compared to normal water shut off jobs, and the single additive fluid is low viscosity making surface mixing simple. The novelty of this water shut-off system is efficient sealing of a high permeability formation with minimal fluid and achieving a drastic water cut from 90% to1%. This new system, unlike polymer-based systems, doesn't degrade with temperature, water hardness or salinity, and plugging of the porous media works by acompletely different mechanism leading to a more robust barrier against water production with reduced interventional risk.
This paper presents a case history application of real-time fiber-optic technology in the Bahrah oil field, onshore Kuwait. A primary challenge during openhole swellable packer completion operations with multistage fracturing is understanding the number of fractures induced in the formation, particularly in heterogeneous formations where the fracture pressure energy will be distributed along the openhole section. Therefore, fiber-optic technology was selected for the Bahrah project. The application consists in diagnosing a tight carbonate reservoir after multistage acid fracturing and milling the baffles of a production sleeve completion to obtain a well production profile. This technology consists of a fiber-optic cable and a modular sensing bottomhole assembly (BHA). The fiber-optic cable provides distributed temperature sensing (DTS), whereas the BHA is used to monitor pressure, temperature, and the casing collar locator (CCL) in real time. The usual procedure when using conventional coiled tubing (CT) to stimulate a carbonate openhole section is to treat all pay zones with acid and diverter, which increases both operation time and operational costs. In addition, inadequate control of the treatment placement will often result in ineffective stimulation. When using the fiber-optic technology, monitoring is performed by analyzing the distributed temperature profiles both before and after stimulation; the BHA helps ensure that the optimum pressure is maintained and that the fluid is placed accurately through depth correlation sensors. All components of this intervention are performed in a single trip, which reduces both costs and operation time. This paper presents an application that uses the modular sensing BHA to improve the performance of milling balls and baffles in the horizontal production sleeve completion. Afterward, DTS is used to diagnose the reservoir performance after multistage acid fracturing to identify fracture initiation points (FIPs). This assists in design optimization, provides better understanding of formation properties, and helps determine the flow rate distribution of each stage across the entire lateral. Another application uses DTS to obtain the production profile of a 3,286-ft horizontal section while flowing back the well through an electrical submersible pump (ESP). The paper presents the methodology and results of these applications. Using this technology in the petroleum industry helps reduce operation time by up to 50% as a result of performing various CT activities in a single run. This eliminates the need for additional logging or slickline runs using the same BHA, after performing the milling operation to collect DTS data for FIPs and flow rate distribution analysis in the same run. It also reduces costs by enabling real-time decision-making capabilities and effective stimulation.
This paper presents the application of a unique gelling system for perforation shut-off operations that can help reduce operational time by 50% and can also be used as an effective water- and gas-migration control agent. The system combines a conformance sealant (based on an organically crosslinked polymer) with non-cementious particulates. The particulates provide leak-off control, which leads to shallow matrix penetration of the sealant. The filtrate from the leakoff is thermally activated and, as a result, forms a three-dimensional (3-D) gel structure that effectively seals the targeted interval after exposure to the bottomhole temperature (BHT). The traditional method for recompleting wells into newer layers, after the current producing zones have reached their economic limit, involves several steps. The first step is to squeeze off the existing unwanted perforations using cement, drill out the cement across the perforations, and then pressure test the squeezed zones to help ensure an effective perforation seal has been achieved. The new zones are then perforated and completed for production. The entire operation can require four or more days of rig time, depending on the success of the cement squeeze. In cases of cement failure, the required time can extend to over one week. Common challenges associated with cement-squeeze operations include leaky perforations, fluid migration (gas or liquid) behind the pipe, or compromises in the completion. Attempts to remediate these issues must be repeated until all objectives are met. The new perforation plugging system can be bullheaded into the well (spotted at a desired location in the wellbore), allowing for easy placement and calculation of the treatment volume. The limited and controlled leakoff into the matrix during the squeeze results in a controlled depth of invasion, which allows for future re-perforation of hydrocarbon-producing zones. The system can be easily washed out of the wellbore, unlike cement, which must be drilled out. The temperature range of the particle-gel system is 60 to 350°F, which makes it versatile. To date, more than 500 operations have been performed with this system globally. This paper presents the results obtained from laboratory evaluations, the methodology of the treatment designs, and four case histories from Kuwait. A salient case is the successful use of the sealant/particulate system, resulting in shutting off all perforations after six failed cement-squeeze operations. The prospect of reducing the required time to perform remedial cement-squeeze operations by 50%, as well as the ability to repair casing leaks and seal off thief zones, make this sealant/particulate system a valuable alternative to standard cement-squeeze operations.
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