At present, the number of rod pumps in China's oil field accounts for a large proportion, most of which are plunger type oil well pumps, and conventional plunger pump has become one of the main oil recovery methods.
Because most of the domestic oil field has entered the high water cut development period, coupled with the impact of high sand, high temperature steam heavy oil exploitation, medium mining and strong polymer corrosion and poor well conditions and other factors, the plunger pump of the pump barrel and plunger wear, corrosion, scratches more and more serious, the average pump detection period and the shorter, some even less than 30 days are needed for the pump, seriously affect and improve the overall economic efficiency of oilfield development. Many institutions at home and abroad have invested a great deal of strength to study the failure causes and protection measures of the pump. One of the effective methods is to optimize the material and surface treatment process of the pump cylinder and plunger.
The tribology system is composed of pump barrel and plunger friction pair and surrounding working conditions and conditions. The corrosion wear volume of the system is determined by the total amount of corrosion and wear of piston pump and the amount of corrosion wear of plunger. The corrosion and wear volume of pump barrel and plunger is determined by the physicochemical properties, mutual movement relations, working environment and conditions. Finally, judging from the angle of the oil pump, the choice of material and surface treatment process of the pump barrel and plunger is the decisive factor to determine the corrosion wear amount of the tribology system.
The purpose of selecting and optimizing the pump and plunger material and the surface treatment process is to minimize the corrosion wear of the tribological system. Due to many factors, so the pump barrel and plunger of the material selection, is still not a theoretical guidance, R & D personnel currently do most of the work is the selection of materials and surface treatment processes all kinds of pump barrel and plunger, and indoor wear test in corrosive wear conditions. The results from tests to determine in in this experimental condition, should choose what kind of pump cylinder plunger material. Here are two experimental results:
Results: the first pump tube material and surface treatment process of 45 steel electroless Ni-P plating, chrome plating, the surface of 303 steel 4% - 6% chromium nitride pressure 3; plunger materials and surface treatment technology for carbon steel, carbon steel, laser processing, naval brass electroless nickel phosphorus alloy, Monel alloy chrome 4. The above materials are paired to wear resistance test. The friction pairs used in the test are made up of ring and block. The medium is clear water, the temperature is 60 C, and the viscosity is 0.000653Pa/s. Test machine for friction and wear testing machine MG200 high temperature. The total friction stroke of the loaded 1kN is 20km. Through the experimental research on the wear resistance of different pump barrel and plunger material and surface treatment process, and according to the principle of first failure of plunger, the best matching materials for pump barrel and plunger friction pair can be selected as carbon steel, electroless Ni-P alloy and carbon steel chrome plating respectively.
Results: second kinds of pump tube material and surface treatment for the carbon steel chrome plated, carbon steel electroless nickel phosphorus alloy and 38CrMoAl nitride; plunger materials and surface treatment process, the surface of carbon steel chrome plated carbon steel electroless nickel phosphorus alloy, carbon steel surface spray welding of nickel based alloys and 38CrMoAl nitride, were matched into 9 pairs of friction. The experimental friction pair is made up of a ring and a column. Test medium for oily wastewater, of which 5% of oil content in water; mineral: 11000mg/1 chloride, carbon dioxide 25mg/1, calcium 25mg/1, magnesium bicarbonate ions 30mg/1, 13mg/1, 8mg/1, total iron sand; 0.4%; temperature is 60 DEG C. The domestic MG-200 high speed high temperature friction and wear testing machine is also used. The test load is 100N, and the total friction course is about 6km. The results of the test are considered to be the best matching between the carbon steel spray welding plunger and the chromium plated steel pump tube, and the 38CrMoAI nitrogen plunger is paired with the chromium plated steel pump tube.
It can be seen that the laboratory test results are obtained under the set conditions. If the test conditions vary, the workload will be huge. Even if the conditions are different, it is not necessarily consistent with the downhole conditions of the oil field, so the experimental results are limited. Because of the different test conditions and the shape of the friction pair, there is no comparability between the experimental results.
It can be seen that the matching of the pump cylinder and the plunger material has its shortcomings through the test, and there is no theoretical guidance for the test, so the test work is very heavy. The material used in the test is only known as the existing material, and it is difficult to make other materials that have not been used on the pump but may have better performance.
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