Fracturing refers to the formation of high pressure in the wellbore to form the formation of cracks in the construction process. Usually refers to the hydraulic fracturing, hydraulic fracturing refers to the application of hydraulic pressure principle, from the ground pumped with a proppant carrying high-pressure working fluid, so that formation and maintain cracks, is widely used in domestic and foreign effective production, Measures to increase. As the high-conductivity capacity of the proppant filled with cracks is equivalent to expand the radius of the wellbore, increasing the discharge area, greatly reducing the seepage resistance, which can greatly improve the oil and gas production, improve oil production speed, shorten the mining cycle, cost.
1, fracturing wellhead
Fracturing wellheads can be divided into two categories:
① fracturing wellhead with oil tree.
② the use of large elbow, pitcher, wellhead ball valve and wellhead controller dedicated fracturing wellhead.
2, fracturing tube sinks
At present, many types of fracturing tube sinks, pressure and the maximum sand capacity is not the same. Commonly used fracturing pipe and dedicated ground manifold. Dedicated ground pipe with 8 connectors, the fissure can choose a connection. High-pressure pipeline diameter Ф76mm, diameter Ф60mm, the maximum pressure up to 100MPa.
3, pitching device
There are two kinds of pitching device, one is in front of the wellhead device for the stratified fracturing column in the cast ball ball throwers, the other is the election pressure or fractures fractures blocking the eyeball with the ball. US imports pitcher, the maximum working pressure of 100MPa, a loaded Ф22mm blocking ball 200, electric rotation pitch 12 laps per minute, 4 balls per lap.
Fracturing vehicle group
Fracturing equipment mainly includes fracturing vehicles, sand vehicles, instrument vehicles, pipe and other vehicles.
Fracturing is the main power of fracturing equipment, its role is to produce high pressure, large displacement into the formation of fracturing fluid, pressure from the formation, and the proppant into the cracks. It is the key equipment in the construction of fracturing, mainly by the vehicle, drive pump power, transmission, fracturing pump composed of four parts.
2, blender car
The role of the blender is the proppant, fracturing fluid and a variety of additives in a certain proportion of mixing, and mixed with the sand into the fracturing truck, into the well. At present, there are two kinds of blender car mixed sand truck, wind suction mixer and imitation of the new type of mixed sand. Blast truck mainly by the liquid, sand, transmission three systems.
3, other equipment
In addition to fracturing vehicles, sand mixer main equipment, there are instrument car, tanker, transport sand and so on. Instrument car is used for construction, record the various parameters of the fracturing process, control the other fracturing equipment, the central system, also known as fracturing command vehicles.
Fracturing column mainly by the fracturing tubing, packer, sandblasting, hydraulic anchor and other components. At present, the downhole string can be divided into general fracturing column and stratified fracturing column.
1, fracturing tubing
Fracturing should use special tubing. Compressive strength should meet the design requirements. Shallow diameter, low pressure can be used J55 steel grade, diameter Ф62mm tubing (diameter φ73mm); in the deep wells and deep wells using N80 or P105 diameter Ф62mm or Ф76mm thicker tubing, the maximum pressure is 70Mpa and 90Mpa.
At present, there are more types of packers for fracturing, and shallow or compact 50°C low temperature plastic packers are used. Deep well using expansion, compression or mechanical 90 ℃above the plastic box packer. Deep well large diameter CS-1 packer, working pressure 105Mpa, operating temperature up to 177 ℃.
3, sandblasting device
The main role of sandblasting is a throttle, resulting in fracturing pressure inside and outside the column to ensure that the packer seal; the second is leading to the formation of the mouth, so that fracturing fluid into the reservoir, the third is to avoid direct impact of fracturing sets Pipe wall damage.
4, fracturing column
Fracturing string is generally divided into general fracturing column and stratified fracturing column.
The general fracturing column structure is: tubing + hydraulic anchor + packer + nozzle. Hydraulic anchor: the pressure inside the tubing, under the action of the pressure anchor to open out on the casing wall, anchor tubing, to prevent axial displacement of downhole tools. When the tubing pressure is balanced, the anchors are retracted by the spring force to release the anchoring effect.
2) layered fracturing column
The layered fracturing column includes:
① double sealed card single layer: Ф73mm or Ф88.9mm plus thick tubing + hydraulic anchor + packer + sandblast + packer + wire block. After fracturing, the other sections can be fractured with the same method.
② three cards double: Ф73mm or Ф88.9mm tubing + hydraulic anchor + packer + sandblasting device (with sets) + packer + sandblast (no sets) + packer + dead block. Can not move the column fracturing layer.
③ four card three layers: Ф73mm or Ф88.9mm tubing + packer + sandblasting device (a set) + packer + sandblasting device (B sets) + packer + sandblasting device (C no sets) + Packer + dead block. Can not move the column fracturing three layers.
In the process of measuring and assembling the fracturing column, the tubing length change of the tubing due to the temperature effect, the piston effect, the expansion effect and the bending effect is taken into account.
The main role of fracturing fluid is to pass the energy of the ground equipment to the rock of the reservoir, the oil layer of the rock split to form cracks, the proppant transported to the cracks. Fracturing fluid in the construction according to the role of different stages can be divided into pre-liquid, carrying sand, the replacement of three kinds of liquid.
In order to carry out the smooth implementation of fracturing, the fracturing fluid is required to have low filtration capacity, high carrying capacity, reducing resistance, stability, compatibility, low residue, easy to return row and other properties. With the development of the petroleum industry, the scale of fracturing construction is getting bigger and bigger, the amount of fracturing fluid is getting bigger and bigger, so the fracturing fluid should have the characteristics of wide supply, low cost and simple preparation to meet the requirements of large fracturing and New well fracturing construction.