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ESP With Backup Oil Heating System

IP.com Disclosure Number: IPCOM000237690D
Publication Date: 2014-Jul-02
Document File: 2 page(s) / 91K

Publishing Venue

The IP.com Prior Art Database

Abstract

Well fluid contamination is one of the primary causes of ESP failure, especially in motors. Well fluid enters and exits the ESP seal section as required to maintain a pressure equilibrium between the motor oil and well fluid. While the motor is at operating temperature, very little flow occurs between the seal and wellbore. However, during ESP shutdown, the motor and seal may cool down to the bottom hole temperature, which can be up to 100F or more below the motor operating temperature. This cooling can cause significant volume reduction of the motor oil, resulting in the ingress of well fluid into seal section. Given sufficient startup/shutdown cycles, the well fluid may eventually penetrate through barriers such as bags, chambers, check valves or face seals, resulting in motor contamination. A means to prevent cooling of the motor and seal section during shutdown would reduce this failure mode. This invention is for providing a backup heat source to prevent motor oil shrinkage in the ESP motor and seal during ESP shutdown. During ESP shutdown, the motor and seal may cool down to the bottom hole temperature, which can be up to 100F or more below the motor operating temperature. This cooling can cause significant volume reduction of the motor oil, approximately 5 per 100F, amounting to a quart or more for a large motor and seal that must be replaced by well fluid. While most of the well fluid is routed as intended to the outside of the top bag or the bottom of the top chamber, some inevitably penetrates through barriers such as bags, chambers, check valves or face seals, resulting in motor contamination, and builds up during subsequent shutdowns. Sometimes, especially after the motor gets very hot, an abnormally high amount of oil is released through the check valve(s) and into the wellbore. After shutdown, the elastomer bags must collapse an additional amount to make up for this lost oil. This cycle can result in a completely collapsed bag, which is susceptible to puncture and tearing resulting in severe leakage of well fluid. Even if there are only labyrinth chambers and no bags, the specific gravity of the well fluid may not be sufficiently large enough to allow for the gravity separation in the lab chambers to work properly. A means to prevent cooling of the motor and seal section during shutdown would reduce ingress of well fluid into the seal section, thus reducing these failure modes. This invention is for providing a backup heat source to prevent motor oil shrinkage in the ESP motor and seal during ESP shutdown. See Figure 1 for a process diagram of an ESP with backup oil heater vs. a standard ESP. Different embodiments for heating the oil include: flange heaters, strip heaters, and energizing the motor coils with a battery. Also, an impeller or other agitation device may be used in conjunction with a torsional spring to generate heat.

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ESP With Backup Oil Heating System

Well fluid contamination is one of the primary causes of ESP failure, especially in motors. Well fluid enters and exits the ESP seal section as required to maintain a pressure equilibrium between the motor oil and well fluid. While the motor is at operating temperature, very little flow occurs between the seal and wellbore. However, during ESP shutdown, the motor and seal may cool down to the bottom hole temperature, which can be up to 100F or more below the motor operating temperature. This cooling can cause significant volume reduction of the motor oil, resulting in the ingress of well fluid into seal section. Given sufficient startup/shutdown cycles, the well fluid may eventually penetrate through barriers such as bags, chambers, check valves or face seals, resulting in motor contamination. A means to prevent cooling of the motor and seal section during shutdown would reduce this failure mode. This invention is for providing a backup heat source to prevent motor oil shrinkage in the ESP motor and seal during ESP shutdown.

During ESP shutdown, the motor and seal may cool down to the bottom hole temperature, which can be up to 100F or more below the motor operating temperature. This cooling can cause significant volume reduction of the motor oil, approximately 5 per 100F, amounting to a quart or more for a large motor and seal that must be replaced by well fluid. While most of the well fluid is routed as intended to the outside of the top bag or the bottom of the top chamber, some inevitably penetrates through barriers such as ba...