With the acceleration of offshore water injection work, the start of offshore liquid extraction production and the requirements of “energy saving and consumption reduction” in oil production plants, due to the high pump efficiency of the screw pump, it is better able to adapt to production conditions with high gas and sand content, and the ground equipment occupies a small area. , with outstanding features of simple management and moderate displacement adjustment. Therefore, testing large-displacement screw pumps in oil wells with sufficient fluid supply in the formation and well-bore trajectories well suited to screw pump oil production will have a positive effect on reducing the cost of offshore crude oil production.
1. Application of large-displacement screw pump lifting process
After the Shengtuo Oilfield of the Shengli Oil Production Plant entered a period of extremely high water content, sand production and polymer injection worsened the oil well conditions, and the electric pump wells had high fluid production unit consumption. To meet the requirements of development and production and improve the oil well conditions, they expanded and improved The adaptability and adaptability of conventional lifting process screw pumps to enable optimized production of oil wells.
1.1 Problems faced by lifting technology
The expansion of the application scale of screw pump lifting technology in the Shengli Oil Production Plant is mainly based on the following two reasons: the need to improve the working conditions of oil well-lifting technology and save energy and reduce consumption. The Shengli Oil Production Plant has entered the third stage of oil production development. Due to the accumulation of polymer in some wells, the phenomenon of glue production occurred during the subsequent water flooding process, causing the electric pump to be blocked by glue. Since 2002, many oil wells have therefore resorted to pumping replacement or replacement. Layering measures.
The key measures for saving electricity are “liquid reduction and power consumption”, measures to raise the water content of inefficient electric pump wells and control the liquid production of wells with high water content and high energy consumption. In recent years, due to the increasing efforts to adjust the liquid production structure, the proportion of liquid production at different water content levels has changed significantly, which has gradually exposed the limitations and negative impacts of the “liquid reduction and power control” measures.
1.2 Research on supporting technologies carried out
Shengli Oil Production Plant realizes that the large-displacement screw pump mechanical lifting technology has the advantages of solving the problems of heavy oil cold recovery, high sand content, high gas content wells and low energy consumption. Based on the characteristics of large-displacement screw pumps, combined with Shengli Oil Production Plant Wellbore, well conditions and production conditions, research work has been carried out to improve the reliability of large-displacement screw pump operation.
1.2.1 Improve the displacement and lift range of the screw pump
They added 10 new large-displacement pump models to the original 7 small-displacement screw pump models, and the displacement and lift were serialized. The maximum displacement reaches 288m3 at 100r/min speed, and the maximum lift reaches 1350m at large displacement.
1.2.2 Supporting pipe string structure
The main factors affecting the maintenance-free period of screw pumps are rod breakage and pipe leakage. They seized on the weak links in the production of screw pumps and developed new anchoring devices, pressure testing devices, reverse buckling of oil pipes, pipe string straightening and other technologies to effectively solve problems such as oil pipe tripping, deflection and pressure testing.
They use steel continuous sucker rods that do not have couplings. Compared with ordinary rods and hollow rods when rotating and transmitting torque, they can greatly reduce the friction per unit area between the oil pipe and the sucker rod in inclined wells, and reduce the friction caused by eccentric wear. It has the advantage of causing rod breakage, and at the same time, adding lining pipes to the oil pipes in highly inclined wells extends the oil well pump inspection cycle.
It is equipped with a lined pipe + continuous rod matching mode to solve the problem of serious eccentric wear of the rod and tube and frequent operations and is suitable for the production of oil wells with a liquid production volume of more than 100m3. The wear amount (0.38) of the lined oil pipe is only 61.2% of the wear amount (0.62) of the N80 oil pipe, and the lined pipe has outstanding protection performance for the sucker rod. For oil wells with less liquid volume, they are equipped with a trapezoidal buckle rod + centring matching mode to reduce the wear of the rod string and extend the oil well pump inspection cycle.
1.2.3 Research on diagnostic technology of screw pump
The research on screw pump diagnostic technology enables the monitoring of the operating status of the screw pump. Through test data, it can conduct qualitative and quantitative analysis and diagnosis of 9 types of faults such as screw pump rods, pipes, and pumps, allowing oil well managers to adjust the rotation speed and optimize The operating conditions of the screw pump provide the basis.
1.3 Application effect of large-displacement screw pump
In the Shengtuo Oilfield of Shengli Oil Production Plant, given the extremely high water cut period, the polymer injection wells produced glue and blocked the electric pumps during the subsequent water flooding process, and adopted measures such as “liquid reduction and power control” to expand the use of large-displacement screw pumps under ideal circumstances. Research and application have enabled large-displacement screw pumps to achieve great improvements in the lift, pump inspection cycles, and control of eccentric wear, enriching the plant’s oil well-lifting technology. Through the promotion and application of large-displacement screw pumps, the advantages of energy saving and consumption reduction of screw pumps can be fully utilized.
2. The necessity of applying large-displacement screw pumps in Chengdao Oilfield
As the oil field develops in the middle and later stages, it is required to meet the “energy saving and consumption reduction” requirements of Tiye and oil production plants. The large-displacement screw pump mechanical oil production process is an ideal choice, which can effectively solve the cold recovery of heavy oil and high sand content. , high gas content wells and other problems encountered in the mining process.
2.1 Problems faced by lifting technology
2.1.1 Water injection is relatively delayed, formation energy is insufficient, and oil-gas ratio increases
After years of rolling development in the Guantao Formation, the main strata of the Chengdao Oilfield, the pre-production block has now entered the mid-stage of development. Due to years of unpaid bills for water injection work and an imperfect injection and production well network, the formation pressure of the main oil layer in the Chengdao Oilfield is close to the saturation pressure and the formation is seriously deficient, increasing the oil-gas ratio and crude oil viscosity, which poses challenges to electric pump production.
2.1.2 Special oil and gas reservoirs such as heavy oil and high gas-oil ratio require liquid extraction production methods
The current production methods at sea are mainly electric submersible pumps and screw pumps. Although the main application in Chengdao is mature and reliable, and the pump inspection cycle is long, there is still a possibility of trace sand production and new production during the middle and late stages of liquid extraction in the Guantao Formation. Heavy oil blocks and high gas-to-oil ratio blocks have poor adaptability. It is necessary to further improve the performance of lifting equipment or to select other feasible lifting methods in a targeted manner.
2.1.3 Electric pump production consumes high energy
The electric submersible pump has a high lifting head and a wide range of displacement adjustments. It is very useful for lowering the dynamic fluid level of the oil well, reducing the back pressure on the oil layer, amplifying the production pressure difference, strengthening the medium and medium permeability formations, liberating the low permeability formations, and increasing the oil production rate. efficient. However, this oil production method consumes a lot of power; the pump efficiency and life will be greatly reduced when used in wells with high gas and sand content and well fluid scaling.
2.2 Requirements for energy saving and consumption reduction
According to statistics from PetroChina, electricity costs account for 46% of the entire oil field production costs. The screw pump adjusts the speed to adapt to the liquid production capacity of the oil well in different periods. It has the outstanding advantages of high system efficiency and low energy consumption.
A 22kW screw pump can achieve a liquid extraction requirement of 150m3/d and consumes 528kW·h per day. A 43kW electric pump can achieve a liquid extraction requirement of 150m3/d and consumes 1032kW·h per day. It operates for 3000 days a year, using Compared with electric pumps, screw pumps can save 15×104kW·h per year, and the economic benefits are very considerable.