Biogenic Methane Generation in Coal Seams
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Solution Overview
Problem
The existing coal bed natural gas (CBNG) extraction methods are inefficient and costly, with a short operational life of wells and significant infrastructure abandonment due to coal bed depletion, and they do not effectively utilize existing infrastructure for sustainable natural gas production.
Innovation Solution
A method involving the selection of coal seams with microbial presence, injection of tracers to determine permeability, and introduction of biodegradable materials for fermentation by anaerobic bacteria to generate methane gas, which is then extracted using existing CBNG infrastructure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional CBNG extraction methods are used, then natural gas can be produced from coal seams, but the operational life of wells is short (less than 8 years) and infrastructure must be decommissioned due to coal bed depletion
Solution Approach 1:
The patent changes the chemical composition parameters of the coal seam by injecting biodegradable materials that serve as substrates for microbial metabolism. This transforms the physical-chemical state of the coal bed, enabling sustained methane generation through biogenic processes rather than relying solely on the depletion of original coal bed methane, thereby extending the operational life of the infrastructure.
Solution Approach 2:
The system utilizes indigenous microbial populations already present in the coal seam to perform the function of methane generation. By providing biodegradable substrates, the system enables the microbial community to self-generate methane continuously, eliminating the need for external methane sources and allowing sustained production throughout the infrastructure's operational life.
2Productivity
If CBNG extraction infrastructure is built, then natural gas production is achieved, but significant capital investment is lost when coal beds become depleted and infrastructure is decommissioned
Solution Approach 1:
The patent establishes a continuous methane generation process by periodically injecting biodegradable materials into the coal seam. This ensures that the infrastructure remains productive throughout its operational life rather than becoming depleted, allowing the system to continuously generate methane from the biodegradable substrates through microbial action, thereby avoiding capital loss from premature decommissioning.
Solution Approach 2:
The system recovers value from biodegradable materials that would otherwise be discarded or have limited utility. By injecting these materials into the coal seam, the system transforms waste biomass into a valuable methane production substrate, creating an additional revenue stream that offsets infrastructure costs and extends the economic life of the investment.
3Adaptability or versatility
If existing CBNG infrastructure is utilized for sustainable gas production, then resource efficiency improves, but the infrastructure was originally designed for conventional CBM extraction, not biogenic gas generation
Solution Approach 1:
The patent makes the CBNG infrastructure multi-functional by enabling it to perform both its original function of extracting coal bed methane and a new function of generating biogenic methane through microbial action. The same injection wells, production wells, and surface facilities can handle both conventional CBM and biogenically produced methane, maximizing infrastructure utilization and avoiding the need for separate dedicated facilities.
Solution Approach 2:
The patent introduces biodegradable materials as an intermediary substance that bridges the gap between the existing infrastructure and the new biogenic methane generation function. These materials serve as a medium that, when metabolized by indigenous microbes, produce methane that can be collected through the existing infrastructure, thereby enabling infrastructure adaptation without major modifications.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This method enhances the production of secondary biogenic natural gas by increasing microbial populations and activity in coal seams, allowing for sustainable natural gas generation and recycling of biomass, thereby extending the life of existing infrastructure and reducing resource waste.
Implementation Method 1
permitting a chosen quantity of the biodegradable materials to be digested or fermented by microbial action in the coal seam, whereby methane gas is generated
Implementation Method 2
permitting a chosen quantity of the biodegradable materials to be digested or fermented by anaerobic bacteria in the coal bed, whereby methane gas is generated
Implementation Method 3
permitting a chosen quantity of the biodegradable materials to be digested or fermented by microbial action in the coal seam, whereby methane gas is generated
Data Source
AI summary
The use of coal fields as subsurface bioreactors for producing sustainable methane gas from terrestrial sources of biomass is described. Microbial presence is determined for a target coal formation, and tracers are injected to determine permeability, porosity, volume, and minimum and a maximum material injection rates. At least one injection well and at least one circulation well effective for generating an injection rate between the minimum and maximum injection rates are provided for injecting a solution of biodegradable materials into the coal seam. A chosen quantity of biodegradable materials is allowed to be digested, fermented and converted by microbial action within the coal seam. Methane gas is extracted through producing and injecting wells, although pumping will enhance gas recovery.