DE-FE0000888

Goal
The primary goal of this project is to analyze and develop strategies for water resource management within the coalbed methane (CBM) reservoirs of the Black Warrior Basin. The objective is to develop a large, high-quality database and geographic information system (GIS) to provide a basis for the development of efficient regulatory guidance by quantifying the environmental impacts of CBM produced waters and potentially optimize production operations and regulatory frameworks. Such regulatory guidance will provide environmental protection while simultaneously ensuring CBM delivery to the marketplace.

Performer
Geological Survey of Alabama, Tuscaloosa, AL, 35486-6999

Collaborators
Black Warrior Methane
Coalbed Methane Association of Alabama
El Paso Exploration and Production
Energen Resources
Geomet
HighMount Exploration and Production
U.S. Geological Survey

Background
Produced water management is a subject of increasing environmental scrutiny. Produced water is a valuable commodity usable over a broad range of municipal, industrial, and agricultural applications. Some applications, such as using produced water for hydraulic fracturing, can increase efficiency while simultaneously reducing the costs of basic CBM operations. Use of produced water outside the CBM industry adds value to CBM production operations by facilitating industry, enhancing agriculture, and providing vital public services to communities affected by distressed water supplies. The CBM resource base in the Black Warrior Basin is estimated to be between 10 and 20 trillion cubic feet (Tcf). Cumulative CBM production stands at 2.1 Tcf and the most recent USGS assessment indicates that an additional 4.6 to 6.9 Tcf may be recoverable. Water management issues affect all CBM producers in the Black Warrior Basin. These issues need to be critically analyzed and addressed so that full CBM recovery potential can be realized.

Impact
The Black Warrior Basin has a long and rich history of CBM development. The wealth of data and the geologic diversity of the basin provide an unparalleled opportunity to evaluate water management strategies across a spectrum of reservoir conditions. Accordingly, this study will help natural gas producers develop basic geologic, hydrologic, and water management concepts that can be applied to CBM plays throughout the world. The study will apply a spectrum of geologic, hydrologic, geochemical, petrologic, GIS, and other computational techniques to characterize the Black Warior Basin reservoir geology and basin hydrology. Study results should permit development of new water management strategies that will ensure environmental protection, foster beneficial use of produced waters, and improve reservoir performance.

Accomplishments (most recent listed first)
Researchers completed characterizing the Black Warrior Basin geologic framework and basin hydrology including construction of cross sections and contour maps that enabled a new understanding of the fundamental relationship between water chemistry and geologic framework. Gas analyses from the Robinson’s Bend Field indicated that bacterial methanogenesis has consumed nearly all available CO₂ in the coalbed gas, minimizing the need for gas processing and reducing gas field infrastructure corrosion.

Preliminary water management results indicated that produced water instream disposal is safe and effective in most of the coalbed methane plays, particularly where total dissolved solids (TDS) content is lower than 20,000 mg/L. Artificial wetlands can be used to effectively process water with higher TDS concentrations—even those approaching that of seawater. Geochemical analysis of 47 water samples in 2011 indicated the concentrations of nearly all major nonmetallic and metallic constituents correlated positively with TDS content.

Twenty-four gas samples were analyzed for bulk composition and stable isotopic composition. Stable isotopic data indicated mixing of biogenic and thermogenic gas. Carbon isotopes showed a strong relationship to the thermal maturity of the host coal. Organic compounds analysis data collected to date will be used to determine dissolved organics, bacterial methanogenesis, and potential health issues associated with the utilization of produced water.

Initial efforts were directed toward characterizing coalbed methane reservoirs and deeper strata that can be used for subsurface disposal of produced water. Databases on well completions, peak, cumulative, and annual gas production are now complete. A project web site has been posted at the following URL: http://www.gsa.state.al.us/gsa/cbm/Coalbed%20Methane%20Research.htm [external site]

Reservoir pressure data indicated that the hydrologic system within the coal-bearing section is strongly stratified and compartmentalized, with underpressure being most widespread in the Mary Lee coal zone. Isotopic data from coalbed gases further indicate mixing of thermogenic and late-stage biogenic methane. Isotopic composition is strongly related to coal rank and, as rank decreases, produced gases become strongly depleted in ¹³C1. Isotopic analysis of calcite cement in joint and cleat systems showed strong linkage with water chemistry, gas chemistry, and reservoir temperature and confirmed that coal seams were the main sites of late-stage bacterial methanogenesis.

A presentation entitled “Four Decades of Coalbed Methane Development in the Black Warrior Basin” was delivered at the SPE Applied Technology Workshop in West Bengal, India.

Surface geology of the Black Warrior Basin

Current Status (November 2012)
A presentation was given to the Alabama Mining Institute in October highlighting the project progress. Going forward, researchers will continue the mapping and field life-cycle analysis, as well as the evaluation of various water management strategies used in the basin. Researchers are revising a manuscript being submitted for publication in Applied Geochemistry. This manuscript focuses on the organic compounds in produced water from the Black Warrior coalbed methane reservoirs and was composed in cooperation with USGS researchers. Project researchers will continue their efforts on tasks related to reservoir performance analysis and water management strategies including decline curve analysis and the mapping of cumulative, peak, and annual water and gas production.

Project Start: October 1, 2009
Project End: September 30, 2013

DOE Contribution: $725,647
Performer Contribution: $ 314,316

Contact Information:
NETL –Skip Pratt (skip.pratt@netl.doe.gov or 304-285-4396)
GSA – Jack Pashin (jpashin@gsa.state.al.us or 205-247-3558)
If you are unable to reach the above personnel, please contact the content manager.

Publications

For a listing of project publications please visit the project website at http://www.gsa.state.al.us/gsa/cbm/Coalbed%20Methane%20Research.htm [external site].

OGIP for the Black Warrior Basin