Having successfully used microbial biotechnology for site remediation and gold recovery projects, a team of Australian and U.S. geoscientists and engineers are on a mission to apply the technology to in-situ oil and gas recovery – in perhaps its most promising way.
While microbial enhanced oil recovery has been around as a tertiary recovery method for decades, it hasn’t yielded substantial results, said Jim Dirstein, a geophysicist with Auric BioRecovery.
“Historically, the industry has favored the application of lab-designed superbugs or adding nutrient-rich material to a target and hoping for the best,” he explained. “Unfortunately, this approach has been largely unsuccessful, and a more sophisticated approach is needed.”
Dirstein and his colleagues presented a novel approach to in-situ MEOR for hydrocarbons at the International Meeting for Applied Geoscience and Energy last month in Houston.
They emphasized that by using specific types of microbes and a tailored in-situ recovery process, not only could yields be increased, but the need for hydraulic fracturing could be substantially reduced or eliminated.
Going Extreme
The objective of MEOR is to fully extract the hydrocarbon reserves from a well. Even after primary and secondary oil recovery methods are performed, a widely estimated 30-60 percent of oil reserves remain in wells, leaving this organic matter trapped in the reservoir.
For shale gas and heavy oil plays, a key factor in in-situ enhanced recovery is permeability. When natural fractures do not suffice, hydraulic fracturing has typically been the go-to method. Yet, in many cases, microbes can perform the same job by breaking down organic matter in a rock and creating migration pathways that behave like natural fractures.
For example, kerogens are organic matter in shale that, when intact, can inhibit the movement of gas, Dirstein explained. The breakdown of kerogens by microbes can improve permeability. Yet, one of the keys to success is selecting the right microbes for the job.
Ideal microbes come from extreme environments, in terms of temperature or salinity, and have developed mechanisms to survive in such conditions. These microbes can perform mineralogical and organic modifications for commercial resource recovery, said Leslie Thompson, founder and principal scientist at Auric. In essence, they can create “bio-permeability” as an alternative to hydraulic fracturing in tight formations for oil and gas production.
Having worked with more than 6,000 types of “extremophilic” microbes, the team can identify and isolate naturally occurring microbes along with their associated nutritional needs, creating a site-specific solution for recovery projects. The microbes are introduced to a reservoir through an injection well in large enough quantities to perform their task on a commercial timeframe, Thompson said. Monitoring wells measure the viability of the microbial community to ensure effective concentrations and their nutritional needs are maintained.
This approach is what Auric believes sets microbial biotechnology apart from past applications.
Road to Recovery
In terms of MEOR, unconventional gas reserves (primarily methane) and heavy oils are ideal targets, particularly the significant amount of unconventional gas reserves in North America, Thompson said.
The right microbes can alter the minerology of conventional reservoirs and tight formations, resulting in the development of significant new pathways.
“The increased permeability is accomplished without the use of toxic materials and high pressures and is a green alternative to conventional frac’ing,” she said.
Hydrocarbon production can be further enhanced by microbes that generate additional methane – through a process called methanogenesis – from readily available organic matter in shale.
For example, when a kerogen-rich shale core with a 94-percent composition of methane was introduced to a tailored microbial consortia, the bacteria yielded more than just methane, Dirstein said. As the kerogens broke down, the percentage of methane decreased and was replaced by higher caloric gases including ethane, ethylene, propane and butane, and liquids including pentane, hexane, heptane and octane.
In terms of heavy oils, “bio-cracking” microbes can transform high molecular weight petroleum products into lighter products by breaking down paraffins and asphaltenes in a reservoir.
“Heavy oil projects often have a very low recovery factor,” Thompson said. “Implementing technologies that permanently reduce the viscosity of the oil would enable the recovery of additional oil from the reservoir, resulting in higher recovery factors (and) extending field commerciality.”
Lab data shows that it takes roughly three to five days for microbes to break down organic matter and for migration pathways to be created, and 30-90 days for large-scale applications, Thompson said, emphasizing that the technology has the potential to perform at a commercial scale.
Microbial biotechnology also can be used for in-situ refining of sub-surface coal. Certain microbial consortia have the ability to refine coal to yield additional methane, hydrogen and hydrocarbons with higher caloric values.
Dirstein quoted a former colleague, A. R. Scott, who once worked on coal seam gas projects in Australia: “If only one-hundredth of 1 percent of U.S. coal resources were converted into methane through microbial processes, coal gas reserves would increase by 23 TCF, or approximately 10 percent of current reserves.”
Dirstein added: “We believe our microbial solution has the potential to achieve this with respect to revitalizing aging coalbed methane projects, with bonus yields of high caloric value hydrocarbons as well as about 10 percent hydrogen.”
Microbial Recipes
Microbial technologies are effectively used in a wide range of industries, including the food industry, bio-remediation, bioplastics, industrial enzymes, agriculture and sewage treatment, to name a few. However, their success in hydrocarbon recovery has been largely ineffective, MacCulloch said. He added that brewing up a generic batch of microbes and pumping them down a well has yielded results with a success rate of less than 10 percent.
The “brew” pumped down the well must consist of a subset of the native microbial population, containing only the types of microbes best suited for the desired task, he explained. Furthermore, the food-grade nutrients included in the brew must promote the growth of the right populations. This process is continuously monitored to ensure the concentration and makeup of the microbial population and their nutrients are sustained for the life of the project. In some cases, improving the permeability and yield of a reservoir can be accomplished with a single microbial consortium or require a multi-stage approach, MacCulloch said.
Eventually, the microbes will revert to their original population distribution unless the microbial subpopulation is regularly replenished.
“This is why it is safe to put microbes down a well,” MacCulloch said. “The microbial brew pumped down a well consists of the same types of microbes that are initially present, only the population demographics have changed. Once the modified microbial population ceases to be injected, the population demographics will revert to the status quo.”
Applications of microbial technology require a good understanding of minerology and pore fluid composition. Cores, samples of formation fluids and details of the reservoir conditions, such as temperature and pressure, are therefore needed.
While some microbial recovery projects might need to be paired with hydraulic fracturing, microbial pathway creation might replace hydraulic fracturing completely in some projects, said Art Fisher, a chemical engineer with Auric.
Pathway to the Future
The oil and gas industry has typically been slow to accept and adopt new ideas, however the use of MEOR appears to be growing.
For example, a January 2024 report by Precision Business Insights valued the global MEOR market at $1.3 billion in 2023 and projected its growth at a significant compound annual growth rate of 12.1 percent from 2024-2030.
Some of its key players include: Weatherford International, Occidental Petroleum, Halliburton, Titan Oil, Chevron, BP, Shell and Schlumberger, according to various online market reports.
Aside from oil and gas, other areas in the resource sector where microbes can play a key role are the remediation of cyanide and nitrates from spent leach heap mine sites. Not only would the microbial treatment mitigate heap toxicity, the simultaneous recovery of remaining gold and silver offers a very commercial bonus, MacCulloch said. Flooded underground mine sites would be another logical application.
Auric, which once operated as Pintail Technologies, is currently working on its fifth gold recovery project from spent leach heaps. Yet, microbial biotechnology is transforming these liabilities into profitable assets. MacCulloch believes it can do the same for “black gold” and gas moving forward.