Today, when most reservoirs have low productivity, the question of whether hydraulic fracturing can be applied to the oil rims becomes very important. During hydraulic fracturing at Novoportovskoe field, the operator was faced with a complex geological model of the reservoir characterized by an absence of strong barriers and minor contrasts in stress between interlayers associated with high risks of breakthrough into the gas zone. An outstanding example of oil rim stimulation and application of new technology was a project in Novoportovskoe field where 30- and 27- stage multistage fracturing operations (MSF) were successfully performed with a shifting ports completion operated by coiled tubing. Currently, oil and gas companies are increasingly demanding technical and technological aspects of the MSF, where the determining factors are the efficiency of operations, the number of stages, the length of the horizontal part of the well, the possibility of refracturing, and ability to open / close sleeves after operation for water and gas shut-off. The experience gained shows the possibilities of modern technologies, where the use of coiled tubing enables meeting the high requirements and also expanding the boundaries of the application. The 30-stage boundary was successfully overcome and allowed to increase the formation coverage by means of more fracturing stages. At the same time, the completion method made it possible to perform MSF without pulling the coiled tubing out of hole and to use all the capabilities and benefits of CT in the case of a screenout (SO). The teamwork between the customer and several of the contractor's product lines enabled successful completion of the integrated project under the difficult geological and climatic conditions of the Novoportovskoe field, which is located beyond the Arctic Circle. An optimized concept of MSF with the use of re-closable full-pass hydraulic fracturing sleeves, operated by a single-trip coiled tubing-conveyed shifting tool was developed and implemented. The following results were achieved: In one week, 57 hydraulic fracturing stages were completed.Hydraulic fracturing stage time was reduced by 63%.The number of stages per well increased by 43%.The gas factor for storage was reduced from that of previous fracturing operations. The integrated method of multi-stage hydraulic fracturing allowed achieving effective fracture coverage to increase the recoverable reserves, while preventing fractures in the gas cap and bottom water. The sliding sleeves MSF technology, operated by coiled tubing without pulling it out of hole, is applicable to further operations in the region and worldwide. This paper describes the experience, lessons learned, and best practices gained at the Novoportovskoe field while deploying a novel application of MSF for oil rim deposits where CT was used as the key enabler. It also describes the first success worldwide in closing of sleeves after 1 year of well production. The well was completed in December 2017 with a 30-stages, and in 2018, after a year of production, logging showed a gas break through which required eight sleeves to be closed. All eight sleeves were successfully closed. This method can be applied to other oil and gas fields, where the construction of horizontal wells with MSF is the main development strategy.
Today, when most reservoirs have low productivity, the question of whether hydraulic fracturing can be applied to the oil rims becomes very important. In such environment, the challenge of this widespread method of production intensification is significantly increased risk of gas breakthrough. Another challenge that is faced primarily during development of oil-rim (sub-gas) reservoirs is the selection of the most suitable completion designs. An outstanding example of oil rim stimulation was a project in Novoportovskoye field where an operator faced with a complex geological model of the reservoir characterized by an absence of strong clay bridges and minor contrasts in stress between interlayers associated with high risks of breakthrough into the gas zone. In 2016, the Novoportovskoe field operator successfully performed a 20-stage fracturing job. An innovative optimized multistage fracturing (MSF) solution was used that employed shifted closable fullbore sliding sleeves operated by coiled tubing (CT) intermittently with fracturing operations. This method was used for the first time in the development of the hydrocarbon deposits of the Yamal Peninsula and is based on the use of sliding sleeves that allow opening and closing of separate hydraulic fracturing ports. Such a design allows, in the course of further operation of the well, to cutting off or separating ports to prevent the inflow of water and gas, or, at the same time, to conduct refracturing of certain parts of the formation if required. This technology, which optimizes the fracturing process by utilizing shifted closable fullbore sliding sleeves/ports consists of the following: Reclosable CT fracturing sleeve (fullbore cemented sleeve that could be opened/closed an unlimited number of times)Openhole hydraulic packers to isolate zones in case of uncemented completionCT shifting tool (CT/tubing conveyed)Multistage mechanical packer (optional, could be used in case of inability to close one of ports). The resettable packer could be activated in any part of liner with axial CT movements; 10 000-psi rated. The main risk for hydraulic fracturing, in the absence of barriers is the proximity of the gas and water layers. Breakthrough of a hydraulic fracture into a gas- or water-bearing zone leads to a significant reduction in oil production rates. Stimulation operations in such difficult geographic and geological conditions have shown opportunities for the oil industry in the Arctic.
The results of acid tunneling on carbonate reservoirs of the Orenburg region for the increase of drainage area are considered. Weaknesses of the technology are considered, ways to improve efficiency are proposed. The technology made it possible to obtain stable increments of oil production at pilot wells.
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