1. packer layered fracturing
packer layered fracturing is a fracturing technology widely used at home and abroad, but its operation is complicated and its cost is high. There are four types according to the packer and string selected.
1) Single packer layered fracturing
It is used to fracture the bottom layer, and is suitable for all types of oil and gas reservoirs, especially deep wells and large-scale fracturing.
2) Fracturing by layers with double packers
Any layer in a perforated oil and gas well can be fractured.
3) Bridge plug packer fracturing by layers.
4) Layered fracturing with sliding sleeve packer
In China, sand blaster is used to construct pipe string with sliding sleeve, and the sliding sleeve is opened by throwing ball to suppress pressure. This fracturing method can construct multiple layers at one time without moving string, killing well and blowout; Multi-layers are fractured layer by layer and production is sought.
2. flow-limiting layered fracturing
is used for oil wells that want to fracture multiple layers with different fracture pressures. By controlling the number and diameter of perforation holes in each layer, and increasing the injection displacement as much as possible, the bottom hole pressure is improved by first fracturing the perforation friction, so as to achieve the purpose of dividing the pressure into multiple layers at one time.
the key of current-limiting layered fracturing is to design a reasonable perforation scheme according to the requirements of fracturing, including perforation holes, hole density and aperture, so that completion and fracturing can form a unified whole.
1. selective fracturing with wax balls
when an oil-soluble wax ball temporary plugging agent is added to the fracturing fluid, the fracturing fluid will preferentially enter the high-permeability layer, and wax balls will deposit to plug the high-permeability layer, thus fracturing the low-permeability layer. After the oil well was put into production, crude oil gradually dissolved the wax ball to remove the blockage. If the high permeability layer is a high aquifer, plugging the ball and unsealing it will help reduce the water cut of the oil well.
2. selective fracturing with plugging ball
the interval to be fractured in the well is shot at one time, firstly, the interval with low fracturing pressure is fractured and then sand is added, and then the interval is temporarily plugged by injecting displacement fluid with plugging ball; Then increase the pump pressure to open the stratum with slightly higher fracture pressure, and finish the construction after injecting displacement fluid as required, or continue to inject displacement fluid with plugging balls to temporarily plug this interval and fracture other intervals. Thereby improving the oil production/water absorption profile.
second, crack control and high-pressure fracturing technology
The basic principle is to add floating or sinking guiding agent into the pre-fluid, and bring it into the crack through the pre-fluid. The floating guiding agent and sinking guiding agent respectively float and sink at the top and bottom of the artificial crack to form a compacted low-permeability artificial barrier to prevent the pressure in the crack from spreading upward/downward, so as to achieve the purpose of controlling the crack height. In order to make the two guiding agents float and sink, the pump is usually stopped for a short time after injecting the liquid with guiding agent, and then normal fracturing operation is carried out.
the joint height control technology of artificial interlayer is mainly used for 1) the massive homogeneous layer with the interlayer between production layer and non-production layer; 2)
There is no good barrier between the production layer and the gas and water layers; 3) The stress difference between the production layer and the shielding layer cannot effectively control the vertical extension of cracks.
iii. test fracturing technology
test fracturing, also known as small-scale test fracturing, is to conduct a small-scale fracturing and analyze the fracturing pressure to obtain fracture-related parameters. Including fracture extension pressure test, fracture closure pressure test, micro-injection test and so on.
the commonly used splitting technology in China: hydraulic pressure.
hydraulic fracturing is to use high-pressure pump on the ground to squeeze fracturing fluid with high viscosity into the reservoir through the wellbore. When the injection rate of fracturing fluid exceeds the absorption capacity of the reservoir, a high pressure will be formed on the reservoir at the bottom of the well. When this pressure exceeds the fracture pressure of the reservoir rock near the bottom of the well, the reservoir will be pressed open and cracks will occur. At this time, if fracturing fluid is continuously squeezed into the reservoir, the fracture will continue to expand into the reservoir. In order to keep the cracked fracture in an open state, sand-carrying fluid with proppant (usually quartz sand) is then squeezed into the oil layer. After the sand-carrying fluid enters the fracture, on the one hand, it can make the fracture continue to extend forward, on the other hand, it can support the cracked fracture and prevent it from closing. Then the displacement fluid is injected to displace all the sand-carrying fluid in the wellbore into the fracture, and the fracture is supported by quartz sand. Finally, the injected high-viscosity fracturing fluid will be automatically degraded and discharged out of the wellbore, leaving one or more fractures with different lengths, widths and heights in the oil layer, thus establishing a new fluid channel between the oil layer and the wellbore. After fracturing, the production of oil and gas wells will generally increase greatly.