Application of Renewable Energy in the Oil and Gas Industry
The oil and gas industry is a major contributor to greenhouse gas (GHG) emissions, a concern it has been seeking to address for some time. The complete paper reviews the types of renewable energy used in oil and gas fields that have appeared in the literature. Use of renewables offers many advantages, including saving hydrocarbon resources, minimizing the oil industry’s GHG emissions, and enhancing its public image.
Technologies used to capture the sun’s energy can be classified into two categories, photovoltaic (PV) cells and concentration of solar power (CSP). Both technologies have been used in the field successfully to support oil and gas production.
Solar PV devices, or solar cells, change sunlight directly into electricity. PV panels have been used for decades in the oil fields and have been used in offshore platforms and remote locations to provide power to various applications, including:
Providing power for wellhead control panels
Use in cathodic protection stations along cross-country pipelines
Providing power to supervisory control and data-acquisition systems in remote locations
Providing power for chemical-injection pumps
Concentration of Solar Power (CSP)
CSP plants concentrate solar rays to heat a fluid, which then directly or indirectly powers a turbine and an electricity generator. The most widely used CSP technology is that of parabolic troughs. A single-axis system is used to move the parabolic trough, tracking the sun movement during the day. This focuses the solar radiation to a stationary network of pipes carrying water to generate steam.
Heavy-oil production by thermal recovery is characterized by high-energy intensity, creating opportunities for using renewable energy. The traditional method to generate steam for thermal-recovery projects is the use of once-through steam generators (OTSGs). They bear this name because water is heated to superheated steam in a single-pass loop.
Two primary drawbacks exist in using OTSGs for thermal recovery: the large amount of hydrocarbon fuel required to generate steam and the amount of carbon dioxide (CO2) generated from burning the hydrocarbon fuel. Solar energy offers the solution to these two problems. CSP plants generate steam without using hydrocarbon fuel and without GHG emission. Solar steam admittedly faces its own challenges, including the large upfront investment, seasonal and daily variations in solar radiation, and adverse weather effects (e.g., sand and dust storms).
California and the Arabian Gulf countries are within the latitude of 15° and 35° north, an ideal latitude for capturing solar radiation. The first three solar steam plants in oil fields for heavy-oil production were the 21Z in California in 2011, the Amal field in Oman in 2012, and the Coalinga project in California in 2014. More recently, Petroleum Development Oman, in conjunction with GlassPoint Solar, is building the Miraah project in South Oman, the largest solar plant in the world in terms of peak energy production. The solar plant is shown below.
[Editor’s Note: As of May 2020, the Omani government—GlassPoint’s largest investor—liquidated its 31% stake in the company because of the steep fall in oil and gas prices caused by the global economic slowdown in the wake of the coronavirus pandemic The move effectively shuttered the Silicon Valley company that had received an estimated $130 million in funding since it was founded in 2008. The first and only major project to use the approach is PDO’s Miraah facility which cost around $600 million to build in 2017. The facility, which will continue to operate, generates more than 1 MW of electricity and 6,000 tons of steam per day. PDO estimates the 2-km2 solar field saves the company 5.6 trillion BTUs of natural gas and 300,000 tons of CO2 emissions each year.]
Another promising development involves the use of solar energy for thermal-enhanced oil recovery for small onshore heavy-oil fields. Such an application is attractive for isolated small fields where steamflooding is not economical or practical. The literature has presented a technical-economic feasibility study on the integration of CSP technology in this role. Parabolic-trough solar panels are used to heat a heat transfer fluid (synthetic oil), which is circulated through coiled tubing. The reservoir is gradually warmed in the vicinity of the drain and decreases the pressure drop in the reservoir and the well drain. This technology requires high-performance insulation material for the coiled tubing to minimize thermal losses between the surface heat source and the production zone.
The petroleum and wind-energy sectors have coexisted independently in marine environments without significant interaction. One study in the literature calculated offshore wind energy in assessing its potential use on the more than 4,000 offshore platforms in the Gulf of Mexico. The research indicated that connecting offshore oil and gas platforms to offshore wind turbines, and to the onshore electrical grid in the Gulf of Mexico, was feasible
On the other side of the globe, engineers proposed a hybrid solar/wind system for power generation to suit the enviromental conditions offshore Malaysia. The monsoon season there can last 3 or 4 months every year, inevitably affecting the performance of PV solar panels. This problem can be alleviated by combining a wind turbine and solar panels in one power system suitable for wellhead platforms located far from a power source. The hybrid system offers advantages such as elimination of the requirements for fuel gas, increased relaibility of the power supply (particularly during the monsoon season in Malaysian waters), and reduction in the size of the battery bank.
Ocean currents are generated from forces such as the Earth's rotation, wind, differences in water density caused by variations in temperature and salinity, and the gravitation forces of the moon. A novel autonomous subsea power hub was developed that uses ocean currents to generate electricity. In 2017, the subsea power hub was tested successfully for 8 months offshore the UK in the Orkney Islands. The subsea power hub is an intelligent energy-management system comprising a turbine, a generator, a battery pack, and an electrical conditioning system.
Ocean Thermal Energy Conversion (OTEC)
The temperature of ocean water drops with depth. The OTEC technology concept is based on the use of seawater temperatures at different depths to generate electricity for a secondary power use on an oil platform or on a floating production, storage, and offloading (FPSO) vessel. This technology is particularly applicable to deep water. Because energy transfer takes place at a lower temperature level than in a conventional Rankine cycle, the system is modeled using an organic Rankine cycle (ORC).
The Rankine cycle is used as the standard thermodynamic cycle in steam-power plants. The fluid used in an ORC is an organic high-molecular-mass fluid with a liquid/vapor phase change or boiling point occurring at a lower temperature than at the water/steam phase change. The cold deep water is the heat sink for the ORC, while the shallow warm water acts as the heat source for the ORC. Cold water is pumped through a riser to the condenser (heat sink) on the topside and then discharged overboard. Similarly, the shallow warm water is pumped to the evaporator (heat source) and then discharged into the sea. The working fluid of the ORC is vaporized in the evaporator and then expanded through the turbine, which is coupled to an alternator to generate electricity. The exhaust vapors from the turbine are condensed into liquid in the condenser and then pumped to the evaporator.
The OTEC process can be closed-loop, open-loop, or a hybrid thereof. The process has a better efficiency when the difference between the hot and cold temperature is approximately 20°C. Therefore, it is recommended mainly for tropical areas where the depth for cold water (5°C) is between 600 and 1000 m and the hot temperature at the surface is 25°C.
The oil industry is not only a major producer of energy but also a major consumer.
Several renewable energy technologies have been applied or have the potential for use in oil fields. Each, naturally, has advantages and limitations.
Using renewables offers many advantages, including saving hydrocarbon resources, minimizing industry GHG emissions, and enhancing the industry’s public image.
The industry continues to research and develop new technologies to use renewable energy in oil and gas fields.
The continuous growth in the application of renewables in the industry will help move the world along a sustainable energy path.
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30 July 2020
03 August 2020