Appendix J: Enhanced coal bed methane recovery

Overview

Coal bed methane (or coal seam methane) is a mixture of mainly methane, and trace quantities of light hydrocarbons, nitrogen, and CO2, which are generated during the geological transformation from peat to anthracite coal in underground coal seams. The gas is adsorbed onto micro-pores on the surface of the coal, and exists in a near-liquid form at high pressures. The amount of gas which is generated and trapped within the coal depends on the quality and permeability of the coal, and the pressure and depth of the coal seam, but it can be generated in excess of 100m3 per tonne of coal formed.

Conventional coal bed methane extraction is achieved by dewatering and reducing the pressure in the coal bed, such that adsorbed methane is released from the porous coal surface. Conventional coal bed methane extraction may leave up to 50 per cent of the methane in the seam. In CO2-ECBM, CO2 is preferentially adsorbed on the porous coal surfaces, releasing additional methane in the process.

This adsorptive storage mechanism is considered verifiable. Further confidence in storage permanence may be attributed to the cap rock formation having already been verified as an effective trapping mechanism throughout the methane production process, which takes place over millions of years.

Technology status

Commercial production of coal bed methane is currently limited to conventional extraction e.g. without the use of CO2.

ECBM technology is still in the development phase, though this is in large part due to current lack of commercial incentive for the process, as opposed to any insurmountable technical hurdles. The most high-profile ECBM pilot was located in Alberta, Canada, which commenced in 1997 and was focussed on research and development into single and multi-pilot wells, optimising working fluid properties, matching CO2 sources with suitable sinks in the region, and environmental and verification monitoring.

Research status

There are several research projects currently underway to further develop ECBM;

Research is being carried out in the US by the Department of Energy, in Canada by the former Alberta Research Council (now Alberta Innovates), in Australia by the CSIRO, in Switzerland by ETH and, in the UK, The Netherlands and China. Research is aimed at discovering the many unknown variables in the ECBM process and to understand the modelling characterization of a single and multi-component adsorption/desorption behaviour of different coal types.

In the US, a US DOE sponsored pilot project in Marshall County, West Virginia, and being undertaken by Consol Energy will inject up to 18000t CO2 over an approximately two-years into horizontal wells, with useful data to be gathered on gas production and composition, and monitoring of the site to continue for two-years after injection ceases. Injection commenced in 2009.

Earlier in 2010, CSIRO announced a CO2-ECBM demonstration project in China partnering with China United Coal Bed Methane Corporation Ltd (CUCBMC) and supported by JCOAL, Japan. The project plans to inject 2000t CO2 into the Liulin Gas Block, Shanxi Province at a depth of approximately 500m, and investigate the effect of horizontal drilling through the coal seams, with increased CO2 flow rates predicted.

The former Alberta Research Council (now part of Alberta Innovates – Technology Futures) is involved in a joint project with CUCBMC in the south Qinshui Basin of Shanxi Province in North China, this pilot project is testing the viability of storing CO2 in deep, unmineable coalbeds, and of enhancing coalbed methane recovery by CO2 injection. In the initial (completed) phase of the project, 192 tonnes of liquid CO2 were injected into a single coal seam in 13 injection cycles, soaked, and produced back. Future phases of the project involve the design and implementation of a multi-well pilot and evaluation of the commercial prospects of the ECBM technology.

Another project development has been in place in Alberta, Canada since 1997 and is ongoing in an area where there are abundant coal-bed methane sources, but little commercial activity in the industry as a result of low permeability. The area covered is 20 – 40 acres in which 5 injection wells are installed, testing the adsorption of CO2 from a coal seam situated at a depth of 500 meters. This project has many major participants including; Air Liquide Canada, BP, Environment Canada, Japan Coal Energy Centre, Netherlands Institute of Applied Geoscience, Sproule Industry, Suncor Energy Inc., Tesseract Corporation (USA), UK Department of trade & Industry and the US Department of Energy. The research was undertaken with initial pilot studies and the feasibility of CO2 and N2 injection ratios to improve ECBM recovery rates. The project learning’s suggest that even in tight reservoirs, continuous CO2 injection is possible and that in effect, The injected CO2 remains in the reservoir while increasing sweep efficiency.

Further research into ECBM is currently being encouraged by western governments and is expected to grow and develop greatly in the coming years. This could subsequently lead to the creation of projects focused mainly in the developed world where coal beds, carbon point source locations, energy demand and storage regulations are favourable to ECBM application.

Project development

Project development is limited. Most projects underway would be considered research, pilot or small scale demonstration projects. No commercial projects are presently being developed.

The most referenced prior commercial scale CO2-ECBM demonstration/project was the Allison Unit ECBM Pilot, located in San Juan County in southern New Mexico. The Allison Pilot was part of the US DOE funded Coal-Seq project, operated by Advanced Resources International and Burlington resources and consisted of 4 injection wells and 16 producer wells, injecting approximately 335,000 tonnes of CO2 between 1995 and 2001, with incremental methane recovery of approximately 30,000 tonnes. Burlington has not rolled out ECBM across the remainder of their coal seams in the San Juan Basin.

CO2 utilisation

CO2 utilisation rates will depend on the nature of the coal seam, in particular the storage ratio (the ratio of CO2 adsorbed to CBM desorbed) and the pressure of the seam. For high volatile bituminous coals at low to medium pressures, The storage ratio is approximately 2:1. For lower quality coals at the same pressure, The storage ratio increases to approximately 8:1, and can be as high as 13:1 for lignite.

It has been estimated that there is the potential to increase worldwide CBM production, utilising ECBM, by 18 trillion cubic metres, while simultaneously sequestering 345Gt of CO2 (Massarotto et al, 2005).

Results from research held in 29 sites for potential CBM and ECBM in China have determined that CO2 storage potential is about 143Gt in the countries coal bed. This could sequester CO2 emissions for an estimated 50 years based on China’s CO2 emission levels in 2000. Simultaneously, The production of methane from ECBM has been estimated to reach 3.4 and 3.8 Tm3 respectively, which equates to 218 years of production at China’s 2002 production rates (Hongguan et al., 2006).

In the Netherlands, 3.4 Mt of CO2 from chemical installations could be sequestered, as well as 55Mt from power plants. Four potential ECBM areas were assessed, where it was estimated that between 54Mt – 9Gt of CO2 could be sequestered between all four – depending on the technological advances for coal seam access (Hamelinck et al., 2002).

Studies have carried out evaluations of CO2 and flue gas injection scenarios, showed that an injection of 100 per cent CO2 in an 80-acre five-spot pattern indicate that low-rank coal can store 1.27 – 2.25 Bcf of CO2, whilst ECBM recovery reached levels of 0.62 – 1.10 Bcf. Simulation results of flue gas injection composed of 87 per cent N2 and 13 per cent CO2 indicated that these same coals can absorb CO2 levels of 0.34–0.59 Bcf at depths of 6,200 ft, whilst ECBM recovery reached levels of 0.68 – 1.20 Bcf (Hernandez et al., 2006).

Potential markets

ECBM as a technology is region specific, requiring proximity of point source emitters of CO2 and suitable coal seams. Market opportunities exist within the US, Europe, New Zealand, Canada, Australia and most of the developed world with high coal levels. The technology could progress to developing countries with large coal reverses, although this is expected to happen once research is more advanced and projects in the developed world have proved successful. Favourable conditions such as coal bed and carbon point source proximity, energy demand and storage regulations will help market drive.

The Chinese are currently very interested in this technology as a result of their high dependence on coal power plants. The potential for this technology to spread in China is massive, considering storage through ECBM could store 50 years of China’s CO2 emission, based on 2000 levels, once the technology has been developed more widely.

US market

The abundance of deep coal beds in the US presents strong market opportunities for ECBM. In 2009, more than 1,170 million tonnes of coal was mined, more than at any other time in US history. Last year the US Energy Information Administration estimated that the remaining US recoverable coal reserves at just less than 263 billion tonnes.

The US currently has projects researching the ECBM process in Alabama (Black Warrior). The US Department of Energy has committed itself to this research, which strengthens the view that there is a good opportunity in the US for this market.

European market

Coal is mined in significant amounts in various European states. Research that has taken place into ECBM, for example projects in the Upper Silesian Basin of Poland (RECOPOL project funded by the EC) and the Sulcis Coal Province in Italy, and prospects in the UK continental shelf and in Russia and Ukraine, amongst others, suggest real market opportunities in Europe.

Development countries

There are large coal basins in various other countries that have significant ECBM potential, for example China, India, and Indonesia. However there is not much detailed information available on ECBM development so far in these, and other, developing countries.

Market drivers

The main market drivers for this technology are natural gas prices and a potential carbon emissions trading scheme, with higher pricing for each providing a greater driver for deployment of CO2-ECBM.

Level of investment required (to advance the technology)

Little information is available regarding the level of investment that would be required to advance ECBM technology. Although the technology has operated at a commercial demonstration scale from 1995, The technology is still in the development phase and research is continuing. The total amount required is likely to be significant.

Potential revenue generation

The revenue generation of ECBM will be dependent on a number of factors and will largely be affected by the individual locations and quality of the individual sites. The main drivers affecting the profit potential include cost of CO2, value of methane, cost of processing, cost of implementation and transportation.

Price sensitivity

The pricing of the projects, including the technology and the potential revenues, will be affected by the same factors as mentioned above.

Commercial benefit

The commercial benefit of ECBM is potentially very strong, tapping into the energy market to meet high energy demands with methane. The coal-bed methane industry represents a substantial market for CO2, especially if the CO2 is readily available from local coal-fired power plants to produce CO2 in enough quantity to facilitate enhanced coal-bed methane recovery at a large scale.

As has been discussed, ECBM technology would have to improve to ensure economical recovery.

Benefits

ECBM could deliver many potential benefits, including;

  • Significant increase in natural gas production through ECBM for both feedstock and product considering an approximate 2:1 injection ratio is required. In China, as an example of a country with large coal reserves, ECBM could generate 3.8Tm3 of natural gas, equalising 218 years of production based on China’s 2002 levels.
  • Environmental benefits through burning methane (the cleanest of the fossil fuels) to meet energy demands instead of through burning carbon rich fuels, such as coal.
  • Employment opportunities in regions and countries where ECBM is applied.

Barriers

The barriers to widespread ECBM development include:

  • research is still at a development level, with further studies and research required to understand the fundamental issues related to ECBM, particularly around the modelling of a single and multi-component adsorption/desorption behaviour of different coal types;
  • ECBM is location specific, while preparation of a potential ECBM sites requires extensive study and development. This presents high costs barriers and currently limits expansion of the technology into green field sites; and
  • higher natural gas prices are likely to be required.