How to realize the high pressure and large capacity demand of fracturing wellhead？
Fracturing is a kind of reservoir reconstruction technology that uses hydraulic action to form artificial fractures in oil and gas layers and improve the fluid flow capacity in oil and gas layers. Using the high-pressure pump set on the ground, inject large-displacement, high-viscosity liquid into the formation through the wellbore, and build up high pressure at the bottom of the well. When the pressure exceeds the bearing capacity of the formation, fractures will be formed in the formation near the bottom of the well. Continue to inject the liquid carrying the proppant, the fractures gradually extend forward, and the proppant plays the role of propping the fractures, forming sand-filled fractures with a certain size and high conductivity, allowing oil and gas to easily flow into the well through the fractures, achieving increased production and injection effect.
The basic principles of fracturing stimulation are mainly divided into the following three points:
- Change the fluid form
Fractures formed after fracturing extend from the bottom of the well to the depths of the formation. Oil and gas are converted from radial flow to bilinear flow, which is easier to flow into the wellbore.
- Communicate oil and gas reservoir areas
Due to the heterogeneity of the formation, the hydrocarbon accumulation zone is not necessarily connected to the bottom hole. The artificial fractures formed by fracturing can connect these isolated accumulation zones with the bottom of the well and add new oil supply areas. Communication between oil and gas reservoirs is an important reason for fracturing to increase production.
- Overcome the pollution of the formation near the bottom of the well
The permeability of fractures near the bottom hole is the key to oil and gas production. The fractures after fracturing can solve the low production consequences caused by bottom hole contamination.
Used to fix the wellhead of the drilling well, connect the wellhead casing string, seal and control the annular space between the pipes, suspend the tubing, control the pressure of the wellhead and adjust the flow rate of the oil (gas) well, and the tubing that can induce oil to the wellhead It can also be used to close oil wells when necessary, and can also be used for special operations such as acid fracturing, water injection, and testing.
- It consists of three parts: casing head, tubing head and production (gas) tree.
- Applicable to the various casing, tubing procedures and various connection methods.
Unconventional large-diameter fracturing wellhead devices are especially suitable for unconventional shale gas exploitation and ultra-low permeability oil and gas reservoir exploitation fracturing processes, and are important devices for the exploitation of unconventional oil and gas resources. Unconventional oil and gas resources have their special properties. Large-scale fracturing and reconstruction are required in the process of exploration and development. The general construction displacement of conventional fracturing is 4-6m3/min, and the construction fluid volume is generally 500-600m3. But the construction displacement of unconventional fracturing is 10-15m3/min, the single-layer fluid consumption is about 2000m3, and the pressure is above 105MPa, which determines that the fracturing wellhead must not only be able to withstand the construction pressure, but also must have a large enough bore. The current commonly used fracturing wellhead devices cannot meet the process requirements of unconventional fracturing with high pressure and large displacement.
In response to the above problems, Sanjack has developed an unconventional large-diameter fracturing wellhead device to meet the needs of high-pressure, large-displacement unconventional fracturing processes.
The fracturing wellhead structure consists of tubing headgate valve (1), tubing head (2), adapter flange (3), master manual flat gate valve (4), master hydraulic flat gate valve (5), cross (6), wing gate valve (7), fracturing head (8), union (9), check valve (11), pressure gauge (12), etc.
The upper part of the cross is equipped with a fracturing head. The fracturing head is seven-way or eight-way. It can be connected to five or six fracturing trucks to inject fracturing fluid into the well at the same time or continuously to ensure the formation’s fracturing quality and effect, and the recovery factor is improved. The fracturing head is a multi-faceted cone with 5 to 6 faces. Each face of the cone is processed with a fracturing fluid injection hole communicating with the main bore. The axis of the fracturing fluid injection hole is perpendicular to the plane and intersects the axis of the main bore. A set of screw holes are machined around each fracturing fluid injection hole. The union joint is fastened to the screw hole by screws, and the union joint is connected to the fracturing truck high-pressure pipelines, and the diameter of the manual flat gate valve on the main bore, the diameter of the hydraulic flat gate valve, the diameter of the main bore of the fracturing head, and the diameter of the fracturing fluid injection hole are all 4 1 /16in or 5 1/8in. The main bore manual gate valve opening screw is a ball screw to reduce the switching torque of the gate valve, which is convenient for operation. The hydraulic flat gate valve is equipped with a hydraulic piston and a manual screw. Under normal circumstances, the hydraulic system can be remotely controlled. Hydraulic pressure drives the hydraulic piston and, then the hydraulic piston takes the valve stem down to close the hydraulic gate valve. In the special case of hydraulic control failure, the handwheel can be manually rotated, and the valve stem is pushed down by the opening screw to close the hydraulic gate valve to ensure the operation safety.
The wellhead structure developed by Sanjack has the characteristics of large bore, high working pressure, convenient installation, and operation, and is equipped with remote control function, which greatly improves the safety and reliability of on-site operation.