Harvesting Geothermal Energy from Produced Reservoir Fluids Eliminates CO2 Emission from Production Facility Operations
Authors: Muhammad Moin , Al Balushi Saja , Murtland Carrie 
Published: February 2022

Objective

ICE thermal Harvesting has developed a patented technology to convert neglected thermal energy existing in producing oil and gas wells to 100% emissions free electrical power to fulfil in-field power needs and improve operators’ emissions profile. By leveraging advanced process design and automation, heat is harvested and converted to electricity which is then safely delivered to local equipment, the grid, or energy storage fields.

During production of oil and gas from high-temperature, high-pressure formations, reservoir fluids are sent through a surface choke reducing the pressure prior to flowing to surface production equipment and pipelines. Flowing pressures before a choke can be as high as 10,000 psi and will most commonly be reduced to pressures below 1,400 psi. This pressure regulation is critical to both limit unmitigated flow from the well, optimizing the ultimate recovery from the reservoir, as well as to protect surface assets from potentially damaging flowing pressures. However, as the flowing pressure is reduced, the temperature as a result also drops significantly and the thermal energy is lost.

Additionally, due to the depth of many of these producer wells, the fluid being produced from the subterranean reservoirs contain large amounts of thermal energy. Currently, this thermal energy is unutilized because there is no existing methodology or technology to effectively capture this thermal energy or convert it to electrical power.

Based on the EIA estimates, there are roughly 900,000 producing wells across US lands and waters. From conservative initial ICE estimates, at least 7,500 of these well sites have the potential to be utilized for this application. With electric power rates of ICE packages varying from 125kW to 210kW, this would equate to 937,500 MW to 1,575,000 MW of emissions free power production for consumption within the United States.

Contrary to previous past projects exploring similar technologies aiming to utilize oil and gas wells as geothermal reserviors, the requirement of continuously pumping large volumes of fresh water downhole is eliminated by utilizing producing wells instead of reconditioning de-commissioned wells. Because the wells are already producing, the ICE system relies on the reservoir pressure or others production lift mechnism to push the oil and gas stream back to surface, rather than pumping large volumes of fluid downhole to recover the geothermal energy. The benefit of this is reducing the parasitic loads imposed by pumping fluid downhole, ultimately improving net power output by over 50%.

ICE's innovations to date have been primarily centered around the harvesting of one or more heat sources, aggregating those heat sources in an optimal manner through a patented process loop, and modulating heat transfer through automated control methods. This controlled thermal product is then transferred to the Organic Rankine Cycle generator portion of the system for conversion to electricity. Building upon decades of experience in the electrification of oilfield services, ICE engineers designed the system to be highly mobile, modular, and scalable to comply with the demands of remote oilfield operations. Contrary to other heat-to-power systems, the ICE system does not necessitate civil infrastructure work or the employment of EPC firms to install.

ICE systems are planned to be installed in processes spanning several industrial spaces including cement manufacturing, power production, and industrial manufacturing; anywhere large industrial cooling is required, there exists opportunity to implement ICE technology. The initial strong interest from oil and gas operators has caused the initial deployments to focus on the energy sector. These applications are found across the oil and gas value chain, ranging from upstream, midstream, and downstream processes.

For this overview, two ICE system applications will be described. For the first application, thermal energy will be harvested from aggregated oil production from 11 conventional wells. As liquid production is aggregated in-field and routed toward initial processing, the production stream will flow though ICE Thermal Harvesting's system, where heat will be extracted from the stream.

The second application will harvest thermal energy from natural gas wells. In this application, hot, high- pressure gas from two wells will flow through the ICE system in the vicinity of the wellhead where flowing pressures are still high. Wellhead temperatures of these wells are greater than 230 degrees Fahrenheit. The ICE system is expected to have a cooling impact of over 40 degrees Fahrenheit on the gas stream during the power production process, which will greatly reduce the cooling duty required on location.

Both projects will be executed in three phases: Phase 1: Assessing the feasibility of power production from subject assets by evaluating production dataPhase 2: Utilizing the measured heat within the subject assets, ICE will finalize engineering design on heat exchange equipment best suited to harvest the maximum amount of thermal energy from production streams.Phase 3: Critical parameters will be continuously monitored remotely. Optimization engineering to be performed to maximize power production from the system to achieve as close to 125kW nameplate output as possible.