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Hydro-slotting perforation technology is the process of opening the productive formation through the casing and cement sheath to produce the oil or gas product flow (intensification, stimulation). The process has been used for industrial drilling since 1980, and involves the use of an underground hydraulic slotting engine (tool, equipment). The technology helps to minimize compressive stress following drilling in the well-bore zone (which reduces the permeability in the zone). == Overview == Since ancient times, when there were the first coal mines, it was observed, that increasing the depth of the development the coal tunnel, under the action of overburden pressure, surrounding rocks become harder and little-permeable. To solve this problem they developed a cavern of a certain form in the rock. More modern mining geo-mechanics explain the reason for the occurrence of this effect in relation to drilling wells. During any drilling process in the well there is formed the annular compressive stress conditions around the wellbore zone. The deeper the well, the more overburden pressure, which means the greater the annular compressive stress conditions. On the rocks lying at depths of 3–5 km the compressive stresses may reach up-to 75–125 MPa. In the near-well zone, as a result of concentration these stresses increase and sometimes become equal to double 150–250 MPa. If the tectonic stresses is several times higher than stresses from the weight of rocks, the stresses in the near-well zone may be even greater. Under the action of stress conditions and high overburden pressure occurs a significant reduction in permeability in the near wellbore zone, in some cases close to zero. Oil or gas flow can not penetrate to the well. Traditional methods of opening the productive layer formation (cumulative, jet perforation, sand jet perforation, abrasive jetting perforation and other similar methods) did not consider this complicated situation in the near-well zone and therefore was not the effective. Porous and fractured formations are subjected to compression, that deforms the rock mass and reduces its permeability. The greater the depth, the stronger the effect can be. Hydro-slotting perforation is quite different from jet (hydro-jetting or sand-blast) perforation. The energy of working fluid, consisting from water (layer water) and sand (abrasive quartz sand) pressure in the hydraulic engine is divided into two components: five percent of energy goes to the creation of smooth uniform rectilinear motion of the working rod with the perforator and nozzles (between two and six nozzles) without participation in the process the multimeter tubing or coil-tubing. Ninety-five percent of energy is goes to the cutting of continued and geometrically correct deep slots (up to five feet deep and between three to five slots at the same time). Slot length is equal to the length of the working engine shaft, usually . The hydro-slotting perforation process does not deform the casing, does not create cracks in the cement, and does not clog-up the borders in the formation. The geometry and depth of the slots creates the conditions for occurrence of the effect of unloading the circular stress conditions in the near wellbore zone (from 50 to 100 percent) and accordingly the increase of permeability (up to 30 to 50 percent) in this zone. In addition to this it forms a large area of the penetration ( area for one cut with two nozzles only), that provides a very good hydrodynamic connection of the productive layer with the well. The cutting speed may be corrected with the temperature in the borehole, temperature of the working fluid, concentration, flow and pressure. (these components are enough to completely control the depth and length of the cut and thus forming the slots), to instantly cut through the steel casing, through the cement to delve into the productive formation and keep the jets in this state while moving along the borehole, keeping the same depth of cut. At the end of the cutting continuous slot process the engine is set up to the initial position and ready for the next cutting interval. The process of hydro-slotting perforation and the depth of cut is controlled by the working fluid supply, pressure and concentration. The equipment can be operated without lifting on the surface for 11–15 hours. Hydro-slotting perforation is the ecologically safe, environmentally friendly and effective affordable method for intensifying the operation in oil, gas, injection and hydro-geological wells. Now this method is widely used in Azerbaijan, Brazil, China, Eastern and Western Siberia, Jordan, Kazakhstan, Komi Republic, North Caucasus, Russia, Udmurtia, Ukraine, Urals, Uzbekistan and Yemen. The first mention regarding the hydro-slotting perforation in America, was in 1987 at the oil and gas conference in Texas. The first use of hydro-slotting perforation in the United States dates back to 1996, when together with Shell E & P Technology Company, discovered two wells (Abrasive Hydro jet Technology in Albert Load, Michigan). After that the hydro-slotting perforation was highly appreciated by the Department of Geophysics at Stanford University and by Division of Shell Exploration and Production by Shell E&P Technology Company. Hydro-slotting perforation was used in California, Kansas, Michigan, Montana, Nebraska, New York, Pennsylvania, Texas and Wyoming states. In Canada it has been successfully applied in Saskatchewan. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Hydro-slotted perforation」の詳細全文を読む スポンサード リンク
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