Downhole electric heating has historically been unreliable or limited to short, often vertical, well sections. Technology improvements over the past several years now allow for reliable, long length, relatively high powered, downhole electric heating suitable for extended-reach horizontal wells. The application of this downhole electric heating technology in two different horizontal cold-producing heavy oil wells in Alberta is presented. The first field case study discusses the application of electric heating in a mature, depleted field as a secondary recovery method while the second case study examines a virgin heavy oil reservoir, where cold production by artificial lift was economically challenged. The completion, installation, expected and actual results of both cases studies are compared and contrasted. Both field deployments demonstrate the benefits and efficacy of applying downhole electric heating. In the case of the mature depleted field, electric heating resulted in a 4X-5X increase in oil rate, sustained over a period of close to two years. The energy ratio of the heating value of the incremental produced oil to the injected heat was slightly over 7.0. In the virgin heavy oil field, electric heating reduced the viscosity of the oil in the wellbore from time zero, which allows for higher rates of oil production along the complete length of the long horizontal lateral at higher, if desired, bottomhole pressures than in a cold-producing well. This degree of freedom may ultimately allow for an operating policy that suppresses excessive production of dissolved gas, thereby helping conserve reservoir energy. Early production data in this field show 4X-6X higher oil rates form the heated well than from the cold-producing benchmark well in the same reservoir. Numerical simulation models, which include reactions that account for the foamy nature of the produced oil and the downhole injection of heat, have been developed and calibrated against field data. The models can be used to prescribe the range of optimal reservoir and fluid properties to select the most promising targets (fields, wells) for downhole electric heating as a production optimization method, which is crucially important in the current low oil price scenario. The same models can also be used during the execution of the project to explore optimal operating conditions and operating procedures. Downhole electric heating in long horizontal wells is now a commercially available technology that can be reliably applied as a production optimization recovery scheme in heavy oil reservoirs. Understanding the optimum reservoir conditions where the application of downhole electric heating maximizes economic benefits will assist in identifying areas of opportunity to meaningfully increase reserves and production in heavy oil reservoirs in Alberta as well as around the world.
Downhole electric heating has historically been unreliable or limited to short, often vertical, well sections. Technology improvements over the past several years now allow for reliable, long length, relatively high-powered, downhole electric heating suitable for extended-reach horizontal wells. The application of this downhole electric heating technology in a horizontal cold-producing heavy oil well in Alberta, Canada is presented in this paper. The field case demonstrates the benefits and efficacy of applying downhole electric heating, especially if it is applied early in the production life of the well. Early production data showed 4X-6X higher oil rates from the heated well than from a cold-producing benchmark well in the same reservoir. In fact, after a few weeks of operation, it was no longer possible to operate the benchmark well in pure cold-production mode as it watered out, whereas the heated well has been producing for twenty (20) months without any increase in water rate. The energy ratio, defined as the heating value of the incremental produced oil to the injected heat, is over 20.0, resulting in a carbon-dioxide footprint of less than 40 kgCO2/bbl, which is lower than the greenhouse gas intensity of the average crude oil consumed in the US. A numerical simulation model that includes reactions that account for the foamy nature of the produced oil and the downhole injection of heat, has been developed and calibrated against field data. The model can be used to prescribe the range of optimal reservoir and fluid properties to select the most promising targets (fields, wells) for downhole electric heating as a production optimization method. The same model can also be used during the execution of the project to explore optimal operating conditions and operating procedures. Downhole electric heating in long horizontal wells is now a commercially available technology that can be reliably applied as a production optimization recovery scheme in heavy oil reservoirs. Understanding the optimum reservoir conditions where the application of downhole electric heating maximizes economic benefits will assist in identifying areas of opportunity to meaningfully increase reserves and production in heavy oil reservoirs around the world.
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 Љspliceless heatersЉ 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.
Thermal recovery schemes are becoming increasingly common as many processes transition from trials and piloting to fully commercialized technologies. These processes often rely on high quality temperature and pressure data that are accurate and reliable over an extended period of time and at reservoir temperatures in excess of 180°C, potentially up to 300°C. Ideally, the number of discrete temperature measurement points in a well is maximized to decrease the possibility that temperature related events go undetected. This new approach is based on a thin, advanced, high temperature index polymeric insulation material which enables reliable Type-K thermocouples to be used.The development of the thermocouple pairs was based on fundamental material characterization, followed by lab and simulated-use testing. A customized two dimensional stationary thermal simulation tool was utilized to optimize efficiency in temperature response behavior of the cable design. It allowed for the modeling of a multipoint thermocouple bundle temperature profile under the influence of longitudinal and axial heat conduction. The combination of experimental testing and theoretical simulation created an architecture which offers the highest density of thermocouple points possible in standard stainless steel tubing sizes.Mechanical testing in combination with temperature exposure shows high temperature performance within cut-through and thermoplastic flow tests. The most critical potential failure modes relate back to these properties and could yield false temperature measurements at wrong locations. In addition, accelerated aging testing demonstrates insulation integrity with a temperature index of 300°C. Comparison measurement with standard available polymeric insulation shows a significant increase in reliability, achievable number of measurement points, and higher operating temperatures. Temperature simulation data show a high level of agreement to measured laboratory testing.A prototype cable has been installed in an observation well at Statoil's SAGD Leismer Demonstration Project by suspending the cable inside of the casing. This observation well intersects the active steam chamber; thus, the cable is exposed to high and ambient temperatures with an abrupt transition between the two zones. Standard mineral insulated (MI) Type-K thermocouples were previously clamped to the exterior of the casing and cemented in place. Field trial data will be presented demonstrating a high degree of correlation between the prototype cable thermocouples and the standard thermocouples over a significant period of time.Novel/Additive Information: The innovative, durable, thin, polymeric insulation material capable of operating up to 300°C, enables the use of thermocouples. A cable design utilizing this material is presented, which allows for a high density of temperature points. Well-operators can now rely on established Type-K thermocouples to provide high resolution data over the length of the well. For instance, over 60 points encapsulated in ½Љ tubing c...
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