What sucker rod downhole pump is suitable for the production of large-angle oil wells and horizontal wells?

Inclined wells refer to wells with an inclination angle in drilling engineering. The wellhead and the design target point are not on a vertical line, but a well that deviates from the vertical line of the wellhead by a certain distance in a given direction according to the designed scheme.

In the oil and gas industry, absolute vertical wells are rare. However, if the well of a well deviates too far from the vertical, or even exceeds the maximum allowable deflection value, the well is a curved well.

In this way, the risk of mechanical equipment failure will increase, leading to high costs. In addition, excessive wear of the casing and joints may also occur at this time. In the process of well-designed deep well drilling, if the direction of the borehole changes suddenly in the shallower part of the well, the rotating drill pipe will endure excessive alternating stress. This is the main reason for the early fatigue failure of drill pipes.

Despite these potential risks, as long as the well deviation is properly controlled, deviated wells still have many advantages over vertical wells. For the development of a particular oil field, a deviated well may even be the only feasible method.

 

With the continuous improvement of oilfield development requirements, the proportion of directional wells, horizontal wells, multilateral wells, etc. in the drilling is increasing. These wells all have inclined sections with different angles.

Horizontal wells are special wells whose maximum inclination angle reaches or approaches 90° (generally not less than 86°) and maintains a certain length of horizontal section in the oil layer. Sometimes for some special needs, the well inclination angle can exceed 90°, “turning upwards”. Generally speaking, horizontal wells are suitable for thin oil and gas layers or fractured oil and gas layers, with the purpose of increasing the exposed area of oil and gas layers.

Although the cost of horizontal wells is higher than that of vertical wells, the production of non-fractured reservoirs is about 3 times that of vertical wells, and the production of reservoirs with natural fractures can reach 12 times that of vertical wells. The recovery rate is much higher than that of vertical wells.

 

At present, due to the reduction of formation pressure and the impact of surface facilities and buildings, a large number of horizontal wells or inclined wells are used in the drilling process. In the production process of horizontal oil wells or inclined wells, the most commonly used downhole pumps are inclined downhole pumps. However, the maximum allowable angle of the currently used inclined well downhole pump is 70°. When the slope of the oil well is greater than 70°, due to the action of gravity, the general inclined well downhole pump will cause the valve ball to contact and strike the inner wall of the valve cover, thereby causing the center line of the valve seat and the valve ball to be displaced. When closed, the valve ball is quickly reset by the reset pin under the push of the spring. There is a certain delay due to the non-repetition of the center line, which causes leakage. Since each impact location is the same point on the sealing surface at the lower end of the valve seat, the valve seat seal fails. Thereby shortening the life cycle of the downhole pump.

In order to solve these problems, Sanjack Group has developed a new type of downhole that is suitable for conventional production and can realize the production of large-angle oil wells and horizontal oil wells. This downhole pump is composed of downhole pump barrel assembly, plunger assembly and fixed valve assembly. The structure diagram is as follows:

1Sucker rod8Traveling valve Ball
2Barrel assembly9Lower Chamber
3Plunger assembly10Standing valve
4Traveling valve cover11Spring
5Spring12Standing valve cage cover
6Traveling valve13Standing valve
7Traveling valve Cage cover14Standing valve assembly

 

The plunger assembly of the new downhole pump is provided with traveling valves on the upper and lower ends. A cage valve cover is arranged in the traveling valve cover of the traveling valve. A fixed cage valve cover is provided in the standing valve cover of the standing valve. The contact surface of the traveling cage valve cover and the traveling valve ball is a concave surface, and the depth of the inner concave surface is greater than the radius of the traveling valve ball. A plurality of through grooves are opened around the inner concave surface. The outer circle of the floating cage valve cover is provided with multiple oil passages. The contact surface between the fixed cage valve cover and the standing valve ball is an internal concave surface. The depth of the concave surface is greater than the radius of the standing valve ball. A plurality of through grooves are opened around the inner concave surface, and the outer circle of the fixed cage valve cover is provided with a plurality of oil passages. When the downhole pump on the stroke, the sucker rod drives the plunger assembly upward, and the traveling valve is closed under the action of the spring and the oil pressure. The upward movement of the plunger assembly causes the pressure in the lower chamber of the downhole pump barrel assembly.Under the pressure of the underground crude oil, the standing valve ball is pushed into the lower cavity of the downhole pump barrel through the groove and the oil passage of the fixed cage valve cover of the standing valve.

At the same time, the crude oil in the upper cavity of the downhole pump barrel is lifted to the ground. When the sucker downhole pump strokes downward, the sucker rod pushes the plunger assembly downward, the pressure in the lower chamber of the downhole pump barrel assembly increases, and the standing valve closed under the action of the spring and oil pressure.

The traveling valve is opened under pressure, and the crude oil in the lower chamber of the downhole pump barrel assembly enters the upper chamber of the downhole pump barrel through the groove and oil passage of the cage cover of the traveling valve.

The new sucker rod downhole pump has a simple structure. The traveling ball and standing valve ball always stay in the concave surface of cage bonnet and fixed cage bonnet.

The traveling valve ball and the standing valve ball will not contact the inner wall of the traveling valve cover and the standing valve cover due to gravity, nor will they deviate from the center line of the valve seat. The valve seat sealing failure is avoided, thereby improving the service life of the downhole pump.