Korchagina and Filanovskoe oil fields in the north Caspian Sea have many extended- and mega-reach wells that uses inflow control device (ICD) screen completions with sliding sleeves. This completion technique empowers the operator with the ability to shut off unwanted water/gas breakthrough and allows for more control of injection or inflow with unlimited number of stages or zones. This paper describes a new verified workflow to successfully intervene these wells and manipulate (open/close) these sliding sleeves using coiled tubing (CT). It has proven challenging to shift these sliding sleeves using conventional methods with CT owing to the limitation of available weight on bit (WOB) at the toe end of those extended-reach wells, even when using large-size CT strings. The new proposed workflow uses a well tractor operated in tandem with a hydraulic shifting tool to generate the required shifting force downhole. The bottomhole assembly (BHA) also includes a novel flow control sub, assembled between the shifting tool and the tractor, with the ability to control the flow to selectively activate the tractor, the shifting tool, or both, based on surface commands by manipulating pump rate. To verify the methodology, a realistic well scenario was simulated at a test site by installing two ICD screens with sliding sleeves at the end of a 1,000-ft-long horizontal flow loop. The sleeves on each ICD screen required approximately 4,000 lbf set-down force to open. The available WOB at the end of horizontal loop with 2-in. CT was only 1,000 lbf; applying more than 1,000 lbf set-down load could have detrimental effects, including CT buckling. The 3⅞-in. OD well tractor used for the job was able to generate 6,000 lbf of pulling force downhole, which was more than enough to shift the sleeves open. Both sleeves were successfully opened by tractoring down while maintaining both the tractor and the shifting tool in the on position, which was achieved by manipulating the flow control sub using pump rate cycles. Both sleeves were then successfully closed, one after the other, by pulling with the CT with the tractor turned off while maintaining the shifting tool in the on position, again achieved by manipulating the flow control sub. Live downhole pressure and force measurements were key in confirming proper functionality of the tractor and identifying different tool modes. Having real-time data is also crucial for proper depth correlation using casing collar locators (CCL) or gamma ray measurements to ensure activating the correct sleeves. This marks the first time that a workflow was verified on the use of pull force generated by a well tractor to manipulate completion accessories in extended-reach well interventions using CT. The technology, preparation, results, and prospects of implementation are discussed in this paper.
In 2015, LUKOIL-Nizhnevolzhskneft developed two intelligent multilateral (TAML 5) wells in the Korchagina field in the Caspian Sea—a first for LUKOIL and Schlumberger, the company's service provider. The development of offshore fields is difficult, requiring nonstandard procedures and solutions, including the use of new technologies to construct multilateral wells. This paper describes the approach to designing these wells with TAML 5 intelligent completions in conditions where there is a high risk of gas and water breakthrough. The main objectives for this type of completion were extending the production period before catastrophic gas breakthrough, increasing the drainage area by drilling several drains, and, as a result, increasing total oil recovery. The formation of Korchagina field is an oil rim with height of 20 m located between the massive (up to 90 m) gas cap and bottom edge water. In the majority of wells (usually extended-reach drilling (ERD) wells), the first three months of production see gas breakthrough, drops in oil production, and the gas/oil ratio (GOR) reaching values up to 5,000 m3/m3. To reduce the rate of gas breakthrough and delay water breakthrough, a new well design was proposed featuring the following technologies: dual-lateral production wells with a TAML 5 junction; active monitoring of inflows from each lateral in an interval of the junction by using multiposition valves hydraulically controlled from the surface; pressure and temperature sensor system that enables real-time tracking of the formation conditions in the drainage area of the laterals, estimates flow rate from each lateral, and interprets the obtained data to determine reservoir parameters. The first TAML 5 intelligent well had a very stable flow regime with a flow rate of more than 400 tons of oil per day. GOR and water cut showed a better dynamic when compared to offset wells in the field, where gas and water breakthrough was observed. One of the main reasons for this was the ability to control drawdown in each of the laterals by using multiposition valves installed in the pressure-tight junction. When compared to the standard monobore well drainage area, boundaries have been considerably extended. At the same time, production was achieved with much lower drawdowns than for wells with a single lateral, while maintaining the same flow rate. As a result of smaller reservoir and tubing pressure differences, the speed of the water and gas vertical movement significantly slowed down, even with the proximity of gas-oil contact (GOC) and oil-water contact (OWC) to the wellbores. The second TAML 5 well was sidetracked from the existing well. Prior to sidetracking, the well was producing with high GOR (more than 2,000 m3/m3) and low flow rate. After the sidetrack was drilled and completed, total GOR decreased by 75% while the production rate increased more than 3 times. The main reason for such a positive change was the increase in coverage ratio, as well as the redistribution of the drawdown between and along the laterals. In both wells, the intelligent completion enabled real-time drawdown redistribution to respond to changes in well production during the life of the well. The use of a pressure-tight TAML 5 junction is relevant for any field with an active gas cap. This manuscript provides the details of the development, justification, and field-testing of this new approach for the development of offshore fields by using multilateral intelligent wells and a pressure-tight TAML 5 junction to substantiate the advantages and benefits of this technology.
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