A deep Granite Wash well was tested on an Electrical Submersible Pump (ESP) after being shut-in for 11 months due to uneconomic and unsatisfactory rod lift operations. The three main objectives of the test were: (1) to determine if an ESP system can be successfully utilized on a gas well; (2) to implement a downhole recirculation system; and, (3) to monitor the economic impact of the installation of the ESP unit. The challenges for the ESP system for this specific test included: (i) motor cooling restriction due to absence of adequate rathole; (ii) production from multiple perforations over 600 ft spread; (iii) low liquid flow (<400 BPD); (iv) high gas-liquid ratio (>1600 CF/BBL); (v) deep well depth (10,000 ft); (vi) small ID production casing (5.5" 17lb/ft); and, (vii) high potential wellbore scaling/corrosion issues. Due to these challenges, using a traditional motor shroud jacket was considered a disadvantage. As a result, a downhole recirculation system was used as an alternative method to (a) prevent potential gas locking; (b) circulate fluid to keep the motor cool; and, (c) enhance capillary deployment of scale and corrosion chemical treatment. This paper presents basic principles of the application of ESP systems in a gas well, principles of implementing a downhole recirculation system, and uncommon techniques to effectively operate an ESP unit in dewatering gas wells. It also includes the historical design challenges, system specific design/operation, and production results of the tested well. The test concludes that it is possible to successfully and economically de-water a deep non-conventional gas well utilizing a properly designed ESP with a downhole recirculation system. In addition, the test had demonstrated the benefits of web-based monitoring of the variable speed controller and downhole sensor information.
Technology Update Electrical submersible pump (ESP) systems are critical to achieving the maximum production rates and reservoir pressure drawdown that improve ultimate recovery. But when gas pockets enter the wellbore and cause system interruptions, the effectiveness of a traditional ESP can be undermined. Gas-handling capability is one of the most complex and challenging issues in artificial lift. Production in unconventional wells varies significantly, depending on the evolution of the reservoir. In a typical scenario, the well begins producing with high liquid rates and some gas. Over a period of a few months, oil production rates fall and gas production rises. While many wells can produce with small quantities of gas, the presence of large gas volumes precludes the use of conventional pumping equipment. The gas-handling challenges are exacerbated by the long horizontals and multiphase flow of oil and gas that are common in unconventional oil plays. Most horizontal wells are not perfectly horizontal. The wells’ lateral portions have undulations that cause the accumulation of water in the low spots and gas in the high spots. During the production phase in unconventional plays, higher levels of natural gas are usually released from the pay zone as reservoir pressure depletes. This gas typically enters the horizontal wellbore and accumulates in the high side of the lateral, creating large gas slugs that cause low-flow or no-flow conditions in an ESP system as they move up the wellbore. The resulting cycling and gas-lock conditions affect system reliability, which can interrupt production and limit ultimate reserves recovery. In challenging downhole conditions, operators often choose to install an ESP system below the perforations. This scenario is particularly useful in wells with high gas content in the fluid stream and in highly productive wells, where operators want to maximize the pressure drawdown to release additional reserves from the reservoir. Placing the ESP below the perforations separates the gas from the fluid, eliminating issues associated with gas entering the ESP. However, reliability becomes a concern because fluid does not flow past the motor at the appropriate velocity to ensure motor cooling. To overcome this issue, the ESP motor can be encased in a shroud, but using a shroud can limit the size of the ESP system and, therefore, production rates.
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