Electrical heaters are being used in numerous down-hole applications including flow assurance, viscosity reduction, steam replacement (Cyclic Steam Stimulation and Steam Assisted Gravity Drainage) and a process called Insitu Conversion Process (ICP). These applications are described in SPE-165323-MS and SPE-170146-MS. Historically the heater has been attached to a pipe string with clamps. This has proven the technology works on short lengths but is labor intensive at the well site and not suitable for commercial application. This paper will describe an alternative method using coiled tubing for electrical heater deployment.
Historically, long high power, high temperature, Mineral Insulated (MI) Cable heaters (over 300 feet) had to be fabricated with splices that increased the diameter about three times at the location of the splice. Recently an improved ceramic material technology has allowed the heaters to operate at higher voltages. This allows an increase in total heater length and the ability to insert into coiled tubing. Along with the increase in voltage, a new fabrication technique allows "spliceless heaters" to be manufactured in continuous lengths to over 10,000 feet. Given this new manufacturing technology, trials have been performed to place the heater and instrumentation in coiled tubing and deployed with conventional coiled tubing technology.
This paper reviews the improvements in the heater technology that allows spliceless fabrication and medium voltage operation. A review of initial deployment pilots is presented including a 2000 foot heated section installation by Shell in the Grosmont reservoir in Alberta Canada. The initial insertion of the heater in coiled tubing was done on an airstrip in Texas and then the coiled tubing was transported to Alberta Canada for deployment. Numerous pictures and installation caveats are included in the paper.
This system of using coiled tubing for deployment has taken much of the labor from the well site to an off-site manufacturing location, reducing cost and streamlining the deployment at the well site. This process moves deployment of electrical heaters in downhole applications from a one-off pilot installation system to a commercially viable system with greatly improved economics and reliability. While the Grosmont installation used 4.5 inch coiled tubing, new heater designs make it possible to use 2.875 inch coiled tubing with the power and temperature characteristics necessary for technically functional application.