How to pump super heavy crude oil？
Globally, the heavy oil reserves have become more important as a future energy source. An excess of 50% of the world’s hydrocarbons have an oil gravity of <20° API. These hydrocarbon assets are normally bitumen and heavy oil, where most of these deposits are located in China, Canada, Venezuela, and Russia.
Typically, the heavy oil viscosity is varied within the range of 500 and 15,000 cP, and for bitumen, it’s about 100,000 cP. Such crudes are usually found in shallow reservoirs (300–600 m depths), and normally the average flow rate of an individual well can be from 1 to 70 m3/day. Therefore, to reach economic production rates, all oil wells need to be pumped at low bottom-hole pressures. Besides, hydrocarbons are typically produced from unconsolidated reservoirs which are susceptible to sand production that can exceed above 30% by volume.
In the process of extracting oil from the stratum, mechanical equipment is used to lift the crude oil in the well to the ground, and the sucker rod pump is the main oil extraction equipment. A sucker rod pump is a special form of reciprocating pump. The power is transmitted from the ground to the downhole through the sucker rod, so that the plunger of the sucker rod pump moves up and down to lift the crude oil in the oil well along the tubing to the ground.
At present, in the steam huff and puff heavy oil production process, the most commonly used sucker rod pump is the double plunger steam injection sucker rod pump. However, when extracting super heavy oil with a viscosity greater than 50,000 mPa • s, a hollow sucker rod is required. Cooperate with hot water on the pump or cable heating on the pump to reduce the viscosity of the crude oil on the pump. However, the double plunger steam injection pumping is in use, because there is no disconnector on the pump plunger, hollow pumping The oil rod can only be run into the well at the same time as the pump.
There is a seal between the joints of the hollow sucker rod. The temperature resistance of the sealing ring cannot reach the high temperature during steam injection. The high temperature will seriously affect the sealing and service life of the hollow sucker rod. Therefore, the original double-plunger steam injection pumping cannot use hollow sucker rods to implement hot water penetration and pump electric heating processes, so it cannot meet the needs of ultra-heavy oil production processes.
This design consists of a disconnector, a pump barrel assembly, a plunger assembly, and a fixed valve assembly. The plunger assembly is connected to the hollow sucker rod through the disconnector. The disconnector is composed of an upper body and a lower body. There are multiple pump barrel steam injection grooves and plunger steam injection grooves on the barrel and plunger. An outer barrel is installed on the outside of the pump barrel. The upper and lower ends of the outer barrel are connected to the heat-insulating oil pipe through the upper and lower joints of the outer barrel.
The lower end is connected to the lower plunger joint, the upper end of the fixed valve assembly has a fixed valve upper joint, a lock ring is installed between the lower plunger joint and the upper joint of the fixed valve, and a ring groove is opened on the cylindrical surface of the lower plunger joint , There is a protruding claw at the lower end, and a groove is opened at the upper end of the joint on the fixed valve. When injecting steam, lower the fixed valve assembly and the pump barrel assembly, the plunger assembly and the lower body of the disconnector to the design depth together with the insulated tubing.
At this time, the claws of the lower plunger joint and the groove at the upper end of the fixed valve Match, the plunger assembly is locked by the lock ring through the ring groove on the lower plunger joint, so that the plunger steam injection groove of the plunger and the pump barrel steam injection groove of the pump barrel is in the same position, and the steam passes through the upper joint of the outer barrel, The upper joint of the plunger enters the inner cavity of the plunger, and then enters the annular space between the pump barrel and the outer barrel through the plunger steam injection groove and the pump barrel steam injection groove, and then enters the oil layer through the insulated oil pipe. When the steam injection is completed, the upper body of the decoupler is connected to the hollow sucker rod, and it is lowered into the well.
After reaching the position, the hollow sucker rod is docked with the lower body of the decoupler by its own weight, and the hollow sucker rod is lifted up. Drive the plunger assembly upward, the plunger seals the steam injection groove of the pump barrel where there is no steam injection groove, and the oil well pump can pump oil normally. Since there is a disconnector between the sucker pump and the hollow sucker rod, the hollow sucker rod can be lowered after the steam injection is completed, so that the hot water penetration process and electric heating process on the pump can be realized.
When the steam injection operation is required again, the hollow sucker rod pushes the plunger assembly so that the protruding claw of the lower plunger joint matches the groove at the upper end of the fixed valve. At this time, the plunger steam injection groove of the plunger and the pump barrel of the pump barrel The steam injection groove is at the same position, and the hollow sucker rod is rotated clockwise at the same time, the disconnector separates the hollow sucker rod from the plunger assembly, and lifts the hollow sucker rod out of the wellhead, and then performs steam injection.
This design has a simple structure and can realize the process of mixing hot water on the pump or cable heating on the pump, and can inject steam into the formation in any well section.
