Utilization of waste heat from produced liquids in oil and gas fields

In the process of crude oil production, a large amount of thermal energy needs to be consumed to achieve gathering, transportation, dehydration and temperature maintenance. Produced liquid stores a huge amount of waste heat energy, which is a very valuable thermal energy resource. In order to make effective use of waste heat resources, oil and gas field enterprises take the waste heat in the produced liquid as an important starting point for energy saving, emission reduction, quality improvement and efficiency, and promote the application of heat pump and other technologies to convert waste heat into heat energy that can be used for production, and have achieved good economic and environmental benefits.

With the large-scale development of oil and gas fields, the waste heat in the produced fluid increases, which cannot be effectively utilized. Sinopec oil and gas field enterprises have adopted heat pumps and other technologies to replace oil-fired and gas-fired heating furnaces, so that the waste heat of the produced liquid can be used for heating the production and living systems of oil and gas fields, which has promoted carbon reduction and efficiency improvement in the production process of oil and gas fields.

The utilization of waste heat from produced liquid is an effective measure to implement the "dual carbon" strategy.In recent years, China has built a new development pattern, promoted high-quality development, incorporated carbon peak and carbon neutrality into the overall layout of ecological civilization construction and overall economic and social development, and successively issued many policies and documents to support the development of geothermal energy. In February this year, the National Energy Administration issued the "Action Plan for Accelerating the Integrated Development of Oil and Gas Exploration and Development and New Energy (2023~2025)", proposing to accelerate the development and utilization of geothermal energy, wind energy and solar energy resources. In April, the "2023 Energy Work Guidance" was issued, proposing to actively promote the non-electric use of renewable energy such as geothermal energy and solar heating. These policies have brought rare opportunities for domestic upstream enterprises to develop geothermal energy.

Heating is an important part of the oil and gas field gathering and transportation system, which ensures the completion of the crude oil moisture content index and the normal transportation of crude oil. In the past, the heating furnaces and steam injection boilers used for heating were fueled by crude oil, which was carbon emission intensive. With the in-depth promotion of the "dual carbon" strategy by oil and gas field enterprises and the adjustment of the energy consumption structure of the heating link, the fuel oil has been gradually changed to natural gas. However, "oil-to-gas" only realizes the shift from high-carbon to low-carbon energy consumption, and cannot meet the requirements of energy saving, low-carbon, clean and environmental protection in oil and gas fields. In the continuous exploration and practice, the technology of waste heat utilization of produced liquid has been emphasized.

As the development of oil and gas fields enters the middle and late stages, the water content of crude oil pumped from underground to the surface increases year by year, forming a large number of low-grade waste heat resources, which will be wasted if these resources are reinjected into the ground. For example, if the water content of the produced liquid in the development process of an oilfield is more than 90%, at 800,000~900,000 cubic meters, and the temperature is 32~65 degrees Celsius, if the waste heat with a temperature difference of 10 degrees Celsius can be extracted from it, 350,000 tons of standard coal can be saved every year.

Oil and gas field enterprises adopt advanced, environmentally friendly and energy-saving waste heat utilization technology of produced liquid, and implement the "waste heat instead of gas" model, that is, replace natural gas with waste heat from produced liquid in the process of oil and gas gathering and transportation, which can accelerate the realization of the goal from low-carbon to zero-carbon.Experts said that the development and utilization of waste heat in the produced fluid should focus on cost reduction and efficiency increase, carbon asset management and collaborative innovation.

Focus on reducing costs and increasing efficiency. Strengthen the analysis of the potential of produced liquid waste heat resources, optimize screening, and implement it steadily; It is necessary to revitalize the existing resource assets of the oilfield, such as combining the recharge of geothermal waste heat sewage with the development of crude oil, making full use of the existing distribution and transportation pipeline network and production sewage treatment facilities, and striving to reduce the investment in sewage recharge. At the same time, the on-site application and testing should be strengthened, and factors such as associated gas, purchased natural gas, purchased electricity costs, and increased sales revenue of natural gas commodities should be comprehensively considered under the condition that the produced liquid source heat pump is basically running at full capacity, so as to improve the economic benefits of the project.

Focus on carbon asset management. Once carbon tax and carbon tariff are levied, it will be directly related to the survival and development of enterprises. Therefore, oil and gas fields should accelerate the research on carbon footprint and carbon labeling of new energy projects, and use carbon finance to achieve more carbon benefits. The development and utilization of produced liquid waste heat should be combined with carbon asset management, and it is necessary to pay attention to the restart process of the CCER (China Certified Voluntary Emission Reduction) trading market, pay close attention to the research progress of geothermal methodology, and do a good job in the calculation of carbon emissions, carbon emission economic analysis, carbon emission reduction measures and effect analysis of produced liquid waste heat projects, and actively apply for CCER projects after the resumption of the CCER trading market.