Active Cooling method for Downhole Systems in High Temperature Environment

DOI: 10.18462/iir.compr.2017.0230

Stav prijatia: Abstrakt odmietnutý

Autori

Abstrakt

In the search for new oil and gas reservoirs, increasing amounts of hydrocarbon resources are being found in fields which are considered to be high-pressure/high-temperature (HP/HT) wells. Also, an increasing number of ultra-HP/HT (high-pressure, high-temperature) wells with reservoir temperature above 205°C are likely to be drilled, completed and produced. But the downhole electronics experiences high failure rates at these conditions. Active and passive cooling are options for extending the operability and reliability of electronics in downhole systems in HP/HT and ultra-HP/HT environments. Passive methods provide cooling for a short duration because they are designed to provide a fixed capacity for heat absorption from the system. If the tool is likely to be exposed to HP/HT or ultra-HP/HT conditions for a long duration, then the use of active cooling methods may become necessary. Active cooling methods use electric power to reject heat at relatively lower temperatures to the higher-temperature wellbore fluid (or the formation) by using a suitable heat pump or a thermodynamic cycle. Thermoacoustic coolers, stirling cryocoolers, and pulse tube refrigerators can all be described using the reverse-Brayton cycle because each of these processes includes adiabatic compression, isobaric heat transfer, adiabatic expansion, and isobaric heat transfer. It is important to choose the optimal thermodynamic cycle and working fluid so that the power consumption is minimized. In this paper we present a process analysis of various thermodynamic cycles, and a combination of numerical computation and experimental approach has been undertaken for this study to develop efficient cooling solutions for downhole tools. The theoretical and experimental thermodynamic analysis leads to the conclusion that a reverse-Brayton cycle, by virtue of being completely reversible, is ideal for this application. In addition, we present an analytical methodology to improve the system efficiency for this cycle. The study from this work demonstrates the active cooling method for downhole systems using in high-temperature environment, and provides a baseline framework for design methods that should be considered for developing optimized thermal management solutions. The preliminary test and system analysis show that the common MWD/LWD tools with this kind of active cooling device can reliably operate above 200°C. This paper will highlight the technical development and present helpful case histories and recommendations.

Kľúčové slová

Downhole Tools While Drilling;
High Temperature;
Active Cooling;
New Technical Development