Effects of Packer Locations on Downhole Electric Heater Performance: Experimental Test and Economic Analysis

Abstract

A downhole electric heater, which reduces heat loss along a heat insulation pipe, is a key apparatus used to ignite oil shale underground. Downhole heaters working together with packers can improve the heating efficiency of high-temperature gases, while different packer locations will directly affect the external air temperature of the heater shell and, subsequently, the performance and total cost of the downhole heaters. A device was developed to simulate the external conditions of heater shells at different packer locations. Then, the effects of external air temperature on the performance of a downhole heater with pitches of 50, 160, and 210 mm were experimentally studied. In the test, results indicated that the heater with a packer at its outlet had an accelerated heating rate in the initial stage and decreased temperature in the final stage. Additionally, the lowest heating rod surface temperature and highest comprehensive performance were achieved with minimal irreversible loss and lower total cost when using a downhole electric heater with a packer set at its outlet. In addition, the downhole electric heater with a helical pitch of 50 mm and a packer at its outlet was more effective than other schemes in the high Reynolds number region. These findings are beneficial for shortening the oil production time in oil shale in situ pyrolysis and heavy oil thermal recovery.

Investigations on the Performance of a Downhole Electric Heater with Different Parameters Used in Oil Shale In Situ Conversion

“…If a high-temperature fluid forms a thermal short circuit in the oil shale layer, the combustion reaction will quickly stop, and secondary ignition is difficult, which affects the stability of the downhole in situ conversion process. 13,14 Therefore, the downhole combustion heaters are not suitable for in situ conversion of unconventional reservoirs.…”

“…They claim that the angle of the elliptical tube arrangement has a significant impact on the performance of the heat exchanger. Guo et al 4,14 studied downhole electric heaters with continuous helical baffles and explored the effect of the packer position on the performance of downhole heaters. They pointed out that a downhole electric heater with a helical pitch of 50 mm and a packer installed at its outlet is the best solution to achieve optimal comprehensive performance and lower total cost.…”

Evaluation of bedding effect on the bursting liability of coal and coal-rock combination under different bedding dip angles

“…During the in-situ conversion of oil shale, temperature (heat) is an instrumental factor (Sun et al, 2021a). In the actual process, the high-temperature gas enters the oil shale, and part of the gas is lost through the wellbore annulus (Guo et al, 2020;Wang et al, 2020), which not only wastes energy but also causes thermal damage to the casing and wellhead (Liu et al, 2020). The loss of high temperature gas affects the conversion process.…”

Evaluation on the Seal Performance of SMP-Based Packers in Oil Wells

“…Recently, a packer made of thermo-responsive shape memory polymers with a smaller size has been proposed as a potential seal component [ 15 , 16 ]. Packers are an important downhole tool for sealing the annulus and isolating the oil and gas layers to implement production operations [ 17 ]. However, conventional mechanical packers have poor reliability, large size, difficult downhole access in complex wells, and high construction risks [ 18 , 19 ].…”