Sour Crude – A Strategic Energy Resource
Crude oil having high concentration of sulfur, otherwise known as “sour” crude, poses significant safety and logistics issues along the entire oil and gas value chain. Very sour crude presents a threat to both infrastructure and human health, requiring specialized equipment for sour service, safety procedures, frequent maintenance, and PPE and specialized training for workers.
In general, sulfur content and API gravity are the two major properties that impact the value of crude oil, because of the expense in handling sour crude as compared to the relative ease of working with lighter, “sweet” crude oil. Sour crude, however, is common throughout the world and represents an important energy source. In fact, of the 373.1 million barrels of oil in the U.S. Strategic Petroleum Reserve (APR) on July 5, 2024, approximately 61% is sour crude, which is the type of oil that most U.S. refineries are configured to process.
How Sour Is It?
Sour crude typically has sulfur content greater than 0.5%, or 5000 parts per million (ppm) and requires treatment to process it into end products, such as gasoline, diesel, jet fuel, etc. Sulfur, however, is not typically found by itself in sour oil, it is usually part of another substance, such as thiophene, pyridine, mercaptans, and other substances.
In this article, we cover the trends driving the development of sour crude assets in the United States, the traditional methods for treating it, and technological advancements promising to unlock the value of sour oil reserves having very high sulfur concentrations.
Sour Production Trending Higher
The shale revolution that began in 2010 in the United States was made possible by technological advancements in horizontal drilling and hydraulic fracture stimulation. These innovations created a resurgence in American oil production and helped the U.S. become a net crude exporter after being a significant net importer for decades. These new drilling and completion techniques led to a renewed focus on the development of unconventional sources, namely oil shale.
E&P operators quickly delineated the primary shale resource plays, determined their “fairways,” and tapped into the most productive areas first, gradually moving towards less favorable areas. In the Permian Basin, as development drilling expanded westward into the Delaware basin region of West Texas and eastern New Mexico, the quality of crude oil declined, marked notably by increased sulfur content.
In West Texas, particularly, oil produced from these newer fields often contains very high levels of hydrogen sulfide (H2S), ranging from 17,000 to 30,000 ppm, far above the 5000 ppm that generally defines “sour” crude. This concentration is not only highly toxic but also exceeds the capabilities of traditional sour takeaway infrastructure and refining processes.
The very high sulfur levels of crude oil produced in the newer unconventional oil fields presents the industry with a completely different problem – there just isn’t local treating capacity to sweeten the sour crude, let alone the sour takeaway infrastructure to move it to market. Without a solution, these sour crude assets will remain undeveloped.
As development increasingly focuses on high sulfur assets (over 10,000 ppm), technological innovations for desulfurization will become more important.
Technology and Treatment Solutions
Traditional Oil Desulfurization Methods
There are several traditional oil desulfurization methods, including:
Hydrodesulfurization (HDS). HDS is a common method in the petroleum industry to reduce the sulfur content of crude oil. Typically, HDS works by co-feeding oil and H2 to a fixed-bed reactor packed with an appropriate HDS catalyst. HDS, however, requires a significant capital investment, limiting its use to large volume applications at refineries to desulfurize finished liquid fuel products, such as gasoline, diesel, jet fuel, and others.
Extractive Desulfurization. Extractive desulfurization is a liquid–liquid extraction process and the two liquid phases must be immiscible. Extractive processes require a mixing vessel to bring the sulfur compounds into contact with a solvent, then the hydrocarbons are separated from the sulfur via distillation. This process, however, is typically not cost-effective for heavy oil.
Adsorptive Desulfurization. Adsorption methods use a solid sorbent to selectively adsorb sulfur compounds from the oil. The efficiency of this method is a function of several factors, including the choice of the sorbent material, its selectivity to organosulfur compounds relative to hydrocarbons, adsorption capacity, durability, and regenerability. Also, as the sorbent is used up, the media must be changed. Adsorbent methods are generally ineffective at industrial scale because of sorbent limitations.
Oxidative Desulfurization (ODS). Oxidative desulfurization works by contacting the sulfur compounds with an oxidant, which creates a chemical reaction that breaks down sulfur compounds and removes them from the oil. ODS has been successfully employed for sweetening sour gas and is an alternative to HDS for creating ultra-low sulfur diesel fuel in refineries. Like HDS, ODS requires specialized equipment. The primary drawbacks with ODS include the high cost of the favored oxidant (t-butyl-hydroperoxide or “TBHP”) and the need to treat the waste byproducts.
Biodesulfurization. Biologic methods use microorganisms that “eat” the sulfur compounds, making these methods “green” in the sense that there are no harmful byproducts. Biodesulfurization processes, however, are highly sensitive to changes in temperature, flow rate, and sulfur content and are typically unsuitable for large-scale oil production.
Innovations in Crude Oil Desulfurization – Turn Up the Heat!
Thermal processes have the potential to provide cost-effective crude oil desulfurization at scale. The Emission Control Treater (ECT) from Pioneer Energy can play a crucial role by cost-effectively unlocking the value of very sour crude oil resources. As previously mentioned, very sour crude oil having sulfur content of 15,000 ppm or greater exceeds the operational capabilities of most sour takeaway infrastructure and treating capacity.
Features of the ECT system include:
Heats crude up to point where the H2S comes out of solution.
Wide operating envelope from 500 to 2500 barrels of oil per day (BOPD), with larger scale also possible.
Closed-loop system.
No open flame.
Electric powered.
Thermal process, not a chemical reaction.
READ MORE: Pioneer Emissions Control Treater (ECT)
How it Works
The ECT leverages the application of heat instead of relying on a chemical reaction. The ECT process heats the crude oil to a temperature where the H2S is driven out of the liquid and put into the gas stream. Once in the gas, it is in concentrations suitable for sour service infrastructure; it can be treated cost-effectively downstream at a natural gas processing plant.
Additionally, the ECT thermal process drives CO2 out of the crude and into the gas stream, and this CO2 is routinely accommodated at the natural gas processing plant.
Benefits of the ECT for Crude Oil Desulfurization
The ECT system delivers several benefits:
Better stabilization. As the H2S is driven out, all liquids remain in the crude providing for better separation and ability to recapture the valuable oil.
No Byproducts. The ECT uses heat to drive the H2S out of crude instead of using a chemical reaction, so there are no harmful byproducts or special waste disposal requirements.
Emissions Mitigation. The process is hermetically sealed for no venting or flaring.
Enhanced Safety Profile. Elimination of venting, flaring, and fugitive emissions enhances the operational safety profile.
Life of Well Solution. The ECT lineup includes a variety of sizes so operators can right-size the equipment as a well naturally declines. As production moves down the decline curve, larger units can be swapped out with smaller ones that use less power for lower LOE, while the larger unit gets refurbished for service on newer wells.
Environmental and Regulatory Implications
Beyond safety concerns, managing sulfur in crude oil aligns with broader environmental goals. By reducing emissions and ensuring compliance with stringent regulations, technology-based solutions like the Pioneer Energy ECT enable the development of otherwise inaccessible oil resources. This is crucial as the industry moves towards minimizing its environmental footprint and meeting zero-emission targets.
Summary
In conclusion, while sour crude oil resources with very high sulfur content (above 10,000 ppm) pose significant challenges to operators, advancements in technology offer promising solutions. Thermal oil desulfurization using the ECT from Pioneer Energy offers operators a safe, effective, and efficient method for developing very sour crude oil assets.
Contact us today to learn how Pioneer Energy technology can help you unlock the value of your very sour crude assets.
About Pioneer Energy
Pioneer Energy is the leading provider of field equipment for processing hydrocarbons at well sites and facilities. We are pioneering technology for decarbonizing oil & gas production with innovative technologies that offer operators the most reliable, rugged and easy-to-use solutions for reducing emissions and converting inefficiencies into profits.
Based in Colorado, our technologies are operating successfully in multiple oil and gas regions. Pioneer Energy’s engineering, field service, and remote operations teams provide best-in-class support for our domestic and international customers, and we offer custom engineering design and fabrication services in our state-of-the-art manufacturing facility.