1 Gubkin Russian State University of Oil and Gas (National Research University), Moscow, Russian Federation 2 LLC OKB-GAMMA, Moscow region, Ivanteevka, Russian Federation
Keywords: downhole heating cable, ways to combat ARPD, well electric heating systems, waxing, controlled temperature regime of fluid
According to manufacturers, a downhole heating cable is a simple, technologically advanced and cost-effective way to prevent the formation of asphalt-resinous and paraffin deposits (ARPD). Indeed, the controlled temperature regime of the extracted fluid in the interval of intensive paraffin deposition makes it possible to prevent waxing processes and avoid of such methods of combating ARPD, such as scraping, hot washing, and the use of inhibitors. In addition to preventing ARPD, downhole heating cables are able to handle high viscosity of oil and gas hydrates. The technology itself implies the use of special heating cables of a specific length with a flat or round cross-section. Basically, round shaped cables are installed in wells with electric submersible pump (ESP) for fountain, gaslift methods of production, while flat-shaped cables in wells with sucker rod pump (SRP). However, a downhole heating cable is to be chosen for each case with respect for the total number of terms of its applicability: the desired temperature of the fluid; depth of formation ARPD; cable heat resistance; energy efficiency; the mode and method of operating the well. The main difference between such heating cables is the way they are installed. Round cables are installed in the tubing, while flat cables are installed in the annular space, which leads to a significant difference in energy consumption. The market is now dominated by downhole heating cables with one and two heat zones. Such cables are able to successfully combat ARPD. The authors of this article believe that to reduce the cost of heating wells, a heating cable with a large number of heat release zones of different power is needed. The operation of wells with such a heating cable will not only be more cost-effective compared to its analogues, but also more stable, since there will be zones with lower power at the depth, which reduces the likelihood of its local overheating. This article provides an overview of typical borehole heating cables. Also, the authors of the article proposed an optimized design of a borehole heating cable, which significantly differs from existing analogues in terms of safety and energy efficiency.
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