Electric submersible screw pump (ESPCP) for use in Kulin horizontal wells

Electric submersible screw pump (ESPCP) is a combination of screw pump (PCP) and electric submersible pump (ESP), which is a downhole fluid lifting system that is very suitable for horizontal wells. It belongs to a rodless pump system and avoids tube and rod friction loss . Screw pump can withstand the formation of sand. The Kulin horizontal well project started in early 2002 and completed in December 2003. The first horizontal well was Kulin082 (KL082) and the second one was Kulin083 (KL083). After the completion of the project, the electric submersible screw pump was used for artificial lift. KL082 initial Nissan liquid 708bbl, Nissan oil 531bbl, moisture content 25%; KL083 daily production 518bbl, Nissan oil 394bbl, moisture content of 24%. In view of the unconsolidated sand in the adjacent Duri field, serious sand production greatly reduces the pumping efficiency of the rod pump, whereas the horizontal well is difficult to control with the naked eye prefabricated screen pipe production. Therefore, the Kulin horizontal well is sand-tolerant Rodless pump for artificial lift. Because the screw pump can not be used for horizontal wells, ESP can not deal with sand, so the final selection of ESP pumps. Electric submerged screw pumps used in Kulin horizontal wells were installed in 95 / 8in production bays with straight-well sections with well slopes below 2 ° / 100ft. Screw in the stator rubber working temperature range of 135 ~ 150oF, lower than the temperature limit of rubber. Flow and pump efficiency are controlled by ground-based variable speed drives (VSDs). The output of these two horizontal wells is 2.5-3.5 times higher than the average output of vertical wells in the same area. 1. The design of electric submersible screw pump Electric submersible screw pump using electric submersible pump as a downhole drive system. Screw pump is the rotor in the center of the stator rotation, as the rotor rotates to pump fluid. Rotor made of stainless steel, chrome-plated surface corrosion. Manufacturers can provide different temperature limits according to bottomhole temperature stator rubber. Existing products are capable of withstanding temperatures up to 95 ° C (203 ° F), 105 ° C (221 ° F), 135 ° C (275 ° F), and 150 ° C (302 ° F). As the bottom hole temperature is about 65.6 ℃, so choose the temperature of 95 ℃ (203 ℉) of the product. In addition, consider whether the rubber is compatible with the aromatic hydrocarbons in the fluid. At the same time, the power required to start the operation of the screw pump, casing size, bottom hole temperature determines the size of the electric submersible pump motor. The main function of the gear reducer is to provide the required speed and torque of the screw pump. The seal prevents underflow fluid from entering the gear unit and motor. The flexible shaft converts the rotation of the seal shaft into the torque required for the screw pump. 2. The installation of electric submersible screw pump The design and installation of electric submersible screw pump is the limit of the vertical well section with a maximum well slope of 15 ° / 100ft. The electric submersible screw pump from the well KL082 was installed at a depth of 1440 ft with a true vertical depth of 1267 ft and an inclination of 64 ° with a well slope of 1.6 ° / 100 ft. The KL083 well was installed at a depth of 1014 ft with a true vertical depth of 891 ft and an inclination of 58 ° with a well slope of 1.5 ° / 100 ft using a 31/2 in. Tubing. At the same time, install a 31 / 2in control valve and a mixing valve at 90ft above the pump and install a cable protector to prevent friction between the cable and the bushing. Installed two electric submersible pump motor actual speed of 2333rpm, gear reducer transmission ratio 9: 1, pump speed 259rpm, screw pump flow 881bbl / d. 3. Field application KL082 well electric submersible screw pump for 800 days, the average pump efficiency of 66%, no signs of failure, but found some problems during the initial run, the reason may be blocked into the liquid inlet, reverse reversal through the motor smoothly ruled out, Turn into normal production. KL083 well electric submersible screw pump work for 450 days, the average pump efficiency of 56%, there is no pump failure caused the problem of downtime. 4. CONCLUSIONS (1) Electric submersible screw pumps are a combination of electric submersible pumps and screw pumps and have many features that are suitable for horizontal wells: a. High production efficiency even for viscous fluids with high solids content; b. Rodless pump system to eliminate the friction loss; c. There is no packing box, to avoid the surface oil spill; d. High torque; e. Can be reversed by the motor backwash. (2) The average pump efficiency of Kulin horizontal well electric submersible screw pump is 56% ~ 66%. In stark contrast, the pumping efficiency of rod pump with Duri horizontal well is less than 30%. (3) The working life of electric submersible screw pump is long, which is fully demonstrated in the production of well KL082 and well KL083. As of June 2004, the well of the well KL082 has been stable for more than 800 days and the well of the well KL083 has survived for more than 450 days.