Coiled Tubing Boosts Efficiency of Multistage Hydraulic Fracturing Technique in Novoportovskoe Field

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.