Integrated Approach to Drilling ERD Wells with the Innovative Reservoir-Scale Mapping While Drilling Technology on Korchagina Field (Russian)
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Cited by 5 publications
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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.
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.
Initial selection and further optimization of drill bits is one of the key factors of an effective drilling process, which is particularly important in high-cost projects. This article presents the incremental changes made to increase the ROP and mechanical efficiency of drill bits while drilling offshore extended-reach drilling (ERD) wells. With the implementation of the tasks based on a well-by-well analysis of bits, recommendations were developed for optimizing the design of drill bits. These recommendations were based on results of bit simulations in specialized software with correlation of proposed models and actual results. Simultaneous bit optimization was performed in conjunction with other elements of the BHA with the help of an integrated engineering analysis system. The result was the development of new bit designs and sizes designed for drilling specific rock in specific fields. In addition to the optimization of the drill bits themselves, a refined technological component was introduced: a real-time drillbit optimization system to enhance ROP, decrease bit wear while drilling, and ensure maximum run length via the optimization of drilling parameters. Application of the proposed technical and technological changes has increased ROP up to two times, and enabled a bit to drill a 4,900-m section in one run with minimum bit wear, leading to a reduction in the cost of the well. As a result, bits for ERD were optimized for each size, and a drilling parameters map was created. This map was updated based on the result of the construction of each well to ensure maximum efficiency with minimal bit wear during subsequent drilling. Additionally, one of the most important results was a 6-year record of no NPT associated with the drill bits. Experience gathered during the development of the bits using advanced modeling applications, together with real-time drilling optimization, will be applied on a nearby offshore field to minimize the time required to reach the optimal ROP. This article describes the selection, optimization, and continuous improvement of drill bits using the latest techniques and technologies, the use of which occurred gradually during development over several years. The above approaches can be applied to ERD and standard horizontal wells worldwide.
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