Using low-friction plunger pump to increase pump efficiency and application of anti-offset grinding technology

Application of Low-friction Plunger Pump to Improve Pump Efficiency and Prevention of Offset Abrasive Technology HAN Xiu-ting1, WANG De-xi2, WANG Yan3, ZHOU Lu-fang1, WANG Xiu-ling1 (1.Technology Development Department, Daqing Oilfield Co., Ltd., Daqing 163453, Heilongjiang, China;2. Limited by Daqing Oilfield 6th Responsible Company Oil Production Plant, Daqing, Heilongjiang 163114, China; 3 Daqing Oilfield Co., Ltd. Oil Production Plant, Daqing, Heilongjiang 163114, China) Analysis of grinding mechanism, development and application of low-friction piston pumps with polymer flooding to solve small friction loss and small amount of leakage Puzzles. The anti-biasing grinding matching technology was implemented, and three kinds of string in-line testers were developed to solve the problem of eccentric wear of the rods, extending the working life of the rods and improving the pump efficiency.

Fund Project: Supported by Key Scientific and Technological Research Project (GB03A502) of Heilongjiang Province.

Engineer, research direction is oil production and mechanical oil recovery. E-mail:hanxiutpetrochina 1 Partial Abrasive Mechanism of Pumping Unit 11 Mechanical friction of sucker rod The axial and ellipticity of the plunger and the pump cylinder of the pump are small, especially the gap between the plunger and the pump cylinder. When the pumping polymer fluid contains more solid particles, the frictional resistance of the pump is even greater. Laboratory tests have found that the number of pumping units and the polymer concentration increase, and the measured axial pressure also increases. For high-concentration polymer flooding wells, the pump gap is small so that the plunger's down-flow resistance is 6kN or more. A large number of experiments have proved that the smaller the pump gap, the larger the pump diameter, the higher the pump speed, and the greater the polymer concentration, the greater the mechanical friction resistance of the pump.

2 Sucker rod buckling and wear The length and diameter ratio of the sucker rod string can reach 40 000, so its axial pressure is very large, and the rod string is prone to destabilization or sinusoidal and spiral bending. The critical length and critical load of the sinusoidal buckling and helical buckling of the pole are calculated as the distance from the neutral point to the pump end under the critical load of the two-rotation buckling, m; q is the effective weight of the pole, N/m;/zx and Flx is the critical load of sinusoidal and helical buckling, respectively. N. When the axial pressure of the sucker rod is greater than the sinusoidal buckling critical load, the sucker rod generates a positive pressure on the tube wall. Suction Rod Coupling and Tubing Han Xiting etc.: The lateral force between the application of low-friction plunger pump to improve pump efficiency and anti-offset grinding technology is lateral force, N/m; Fa is axial pressure, N; for the distance between the sucker rod coupling and the inner wall of the tubing, m. The positive pressure is different, and the rod tube wear amount is also different. The distribution resistance fh caused by the buckling is calculated by the following equation: The wear amount of the sucker rod and the tubing at different axial pressures is calculated using equations (5) and (6). When the axial pressure reaches 6kN, the wear amount of the fe2mm sucker rod coupling is 1mm/a. During the reciprocating motion of the sucker rod, the 1m long elastic rod generates vibration when the load periodically changes. . The test study found that the vibration force of the downhole pole is large, with a maximum value of 259 kN. The partial pressure state of the pole below the force neutral point also changes with the vibration, and the maximum pressure value also increases, forming an instantaneous lateral force. From formula (5), it can be seen that the degree of eccentric wear increases and the frictional force of the rod increases.

The downward resistance between the plunger and the pump cylinder gap and the over flow channel acts on the sucker rod, the bottom is the largest and gradually decreases upwards, and the neutralization point is zero load.

This force destabilizes the pole and generates lateral forces. The vibration force of the rod string influences the pressure conditions below the neutral point, which increases the maximum pressure value. The polymer flooding well sucker rod is subjected to a normal force in a relatively flowing viscoelastic fluid and distributed throughout the rod 121. So the polymer flooding well sucker rod withstands the above three forces; polymer well-free The sucker rod is mainly influenced by the lateral force caused by the axial force.

2 High efficiency and low friction plunger pump 1 Structure and principle of low friction plunger pump Low friction piston pump consists of plunger, pump cylinder, and movable and fixed Verr 131 composition, plunger and pump cylinder clearance With the cooperation, the Verre is connected to the plunger through a screw thread, which is characterized in that a plurality of ring grooves are processed on the outer circle of the plunger, which increases the clearance between the plunger and the pump barrel to achieve the purpose of reducing the friction resistance. The fluid passes through the wide and narrow grooves, increasing the local resistance and reducing leakage. In particular, when polymer viscoelastic fluids are produced, long molecular chains shrink and expand in the gaps of the low friction pump, creating tensile stress, increasing hydraulic friction and slowing down the flow of polymer fluid in the gaps. Reduce leakage.

The fluid flows in the normal pump gap, and the unit length of the pressure loss hw can be calculated using the following formula: 4: Ring Groove Low friction pump Unit length The pressure loss is the increased resistance due to the viscoelastic fluid.

A large number of annular grooves are added on the surface of the plunger, and one groove generates 2 partial losses. When the total number of grooves is n, 2n partial losses will occur. The test data shows that the local frictional resistance is much greater than the frictional resistance along the unit length, especially the local frictional resistance of the polymer-containing viscoelastic fluid. Thus, it can be concluded that formula (7) and formula (8) can be used to derive the calculation of the leakage loss of 2 low-friction pumps. The formula for the loss of conventional pumps is 151. The formula for the leakage loss of low-frictional pumps is 161 lengths of pressure loss. , MPa/mm; f is the viscosity of the polymer-containing medium Contrast type (9) and formula (10) due to the friction resistance of the pump is inversely proportional to the amount of leakage, the ring groove low friction low friction resistance plunger pump structure profile pump Large pressure loss, so q, in the same gap, because the conventional pump hydraulic loss is less than the ring groove low friction pump, the same hydraulic loss, the low friction pump gap leakage q' is less than the loss of the conventional pump The quantity q ~ formula (11) shows that assuming that the lifting head and the leakage amount are the same, considering that the low friction pump is affected by the local hydraulic loss of a large number of slots, the clearance S is larger than the gap of the conventional pump. From equation (1), it can be seen that the friction resistance between the plunger and the pump barrel is lower than that of the conventional pump when the low friction resistance pump maintains the conventional pump leakage amount.

Therefore, the ring groove low friction pump can reduce the friction loss while reducing the friction resistance, which can reduce the eccentric wear, improve pump efficiency and reduce energy consumption.

4 Low Friction Pump Parameters Optimal Design Low Friction Pump Piston Groove Spacing a Groove width b Groove depth The gap between the plunger and the pump cylinder, Di, is a variable, and the test data is returned. The friction resistance and leakage of the low-friction pump when the pressure regulator is 10MPa is the Qf776 pump barrel inner diameter, mm; n is the mass concentration of the polymer solution, mg/L; Fi is the friction resistance of the low friction pump, N. Measured are, are, 16, and substituting values ​​into equations (12) and (13), QuFuQ and F can be found, the relative error between the calculated value and the measured value is less than 10% to the piston annular gap and groove geometric parameters As a variable, with the objective of minimizing the amount of leakage and friction, the optimization of the orthogonal method was performed.

Calculate the optimized structure size of the polymer concentration of 300mg/L and the pump diameter of 83mm low-frictional pump: the groove width b is 29mm; the groove spacing a is 8mm; the groove depth d is 15mm; the gap between the plunger and the pump cylinder is 0139mm.2 5 Low Friction Resistance Pump Loss and Friction Resistance Indoor Test The comparison of the leakage loss and friction resistance between the low friction resistance pump and the conventional piston pump shows that under the same test conditions, with the increase of the pump clearance, both The difference in the amount of leakage of the pump gradually increased, and the loss of the low friction pump was significantly lower than that of the conventional pump and the API standard. When the gap is the same, the friction of a conventional pump is much greater than that of a low friction pump. The test results also confirmed that the low friction pump reduces the amount of leakage and also reduces the mechanical friction. This phenomenon is particularly noticeable when lifting polymer-containing fluids.

3 Axial Force Test of Pumping Unit Well In order to test the stress condition of the downhole sucker rod, an in situ on-line measurement of tension, pressure and lateral force at any position of the sucker rod string was invented to solve the downhole online pull. Pressure, lateral force test problems.

1 Test principle Test principle of tension and lateral force test instrument w: The two ends of the test instrument are connected with the sucker rod and record the change of force when the rod is in motion. After the test is completed, remove the instrument for ground data playback. Connect the tester to different positions for testing, and measure the force of the sucker rod at different positions.

32 Field Test Analysis of Axial Force of Pumping Wells The wells with severe partial wear, polymer concentration exceeding 400mg/L, and pump inspection period of approximately six months were tested. The test results show that the downhole friction resistance of the pumping unit in the well is relatively high. Big. In the pumping wells of Daqing, Jilin, Shengli and Zhongyuan oilfields, 100 wells were tested for their strength.

The North 1-3 well uses a three-cylinder plunger pump with a polymer concentration of 600 mg/L and a secondary pump gap. Tests have found that the polished rod of the well pumping unit is sometimes difficult to descend. Four pressure testers were installed near the plunger, 600m, 400m and the wellhead, respectively. Tests have found that the axial pressure reaches 5kN or more. The North 2-P27 well uses conventional pumps and low friction pumps. I, Han Xiuting, etc.: Use of low-friction plunger pump to improve pump efficiency and anti-offset grinding technology. Application of bookmark17 close to the plunger end, stress test results show that the application of low-friction pump's pole and force to move down 150m Pole force conditions.

4 Field application effects and prospects A low-frictional pump has been applied to a large area of ​​polymer flooding wells, and anti-deviation grinding measures such as sucker bar centralizers have been used. The statistics of 217 wells of 570 low-friction pump wells indicate that The maximum load is reduced by 9.7kN The minimum load is increased by 23kN, the pump efficiency is increased from 53.6% to 63.5%, and the system efficiency is increased from 247% to 312%. The main application is above 300mg/L polymer concentration and affected by polymer cement. Wells, pumping period increased from 300d to 790d pump efficiency has been maintained at more than 60%. This technology can be used in most pumping wells to reduce the effects of eccentric wear, improve pump efficiency, increase the amount of crude oil, and save energy and reduce consumption.