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Overview of Unconventional Gas Resources
and Development
Vello A. Kuuskraa, Advanced Resources International, vkuuskraa@adv-res.com
In a span of 20 years, the outlook for unconventional gas resources has grown from modest expectations to a major source of domestic natural gas supply, now exceeding natural gas production from the offshore Gulf of Mexico. During this time, coalbed methane, one of the three primary unconventional gas sources, has changed from a scientific curiosity to providing, last year, over 1.6 Tcf (4.4 billion cubic feet per day) of pipeline quality natural gas. Looking forward to the next 20 years, unconventional gas is expected to become the largest single source of domestic natural gas supply, with growth in all three resources - - tight gas, gas shales and coalbed methane.
Unconventional Drilling Methods for Unconventional Reservoirs
Doug Wight, VP Corporate Development, CDX Gas, LLC
For a number of years, drilling technologies like gob wells, vertical drill and frac wells and basic horizontal wells have been employed to produce methane gas trapped in low-permeability reservoirs like coal and shale. While these conventional drilling methods are well suited for very porous coal deposits, they haven’t proven economically viable in low-permeability reservoirs because they don’t drain uniformly and typically have low production and recovery rates. In addition, these conventional wells usher in numerous environmental concerns with regard to surface disturbance and water disposal.
Without efficient, effective technologies, many operators deemed coal and shale reservoirs unviable prospects. However, recent advances in drilling technologies and demands for natural gas have given operators reason to re-evaluate the feasibility of developing unconventional gas reserves.
Surface Automated Directional Drilling
Systems for CBM
Dr. Eric Maidla, Slider LLC, Eric.Maidla@Slidercorp.com
CBM & ECBM Reservoir Simulation
Jim Erdle, Computer Modelling Group Inc.
Coalbed Methane Potential in Osage
County, Oklahoma
John F. Sinclair, AMVEST Gas Resources
Cherokee and Marmaton age host rocks contain numerous thin coal seams which are present within Osage County Oklahoma. Primary seams for exploration and development are the Rowe, Bluejacket, Weir-Pitt and Dawson seams. These seams are extremely thin as aggregate and as individual seams when compared to other CBM plays outside of the Mid-continent area. When present these seams range in thickness from a few inches up to 5 feet thick. The average individual seam thickness is less than 2 feet and rarely is there more than 12 feet of coal located within a single well bore. These coals are high-volatile A coals and in some instances grade into medium-volatile coals. Vitrinite reflectance values range from .85 to 1.1 and generally increase with depth.
Structurally, Osage County is located within the Northeast Shelf of Oklahoma. General dip is to the west, but there are numerous domes and NE-SW trending anticlines located in Osage County. Basement faulting is the primary mechanism for creating structural disturbance and many of these faults appear to be compressional features derived from movement originating in the Arkoma Basin.
Coal Gas Orgins and Exploration Strategies
Andrew R. Scott, Altuda Energy Corporation, andrews@altuda.com
Natural gas prices are expected to remain relatively high over the next two to five years and these higher gas prices have turned coalbed into one of the most active gas plays in the United States. Coalbed methane is an important part of the natural gas supply for the U.S. and now represents more than 8 percent of total gas production and 9 percent of dry gas proved reserves and these values are expected to increase. Exploration for coalbed methane in remote or frontier regions is often hampered by the absence of an adequate data base which inhibits detailed evaluation of coalbed methane exploration potential. However, exploration strategies can be developed or refined based upon, coal gas and formation water compositional and isotopic data collected during early exploration.
Any combination of four basic types of coal gases (or any combination of these types of coal gases) may be present in a coal bed: (1) thermogenic, that include early thermogenic and main-stage thermogenic, (2) secondary biogenic, (3) migrated thermogenic or secondary biogenic, and (4) indigenous thermogenic or biogenic. Areas of highest gas content are often associated with upward flow potential and the most effective conventional and hydrodynamic traps are perpendicular to migration pathways. Therefore, exploration strategies can be based upon gas chemistry and inferred coal gas origins, and inferred migration pathways using a hydrologic approach to coalbed methane exploration. For example, if the formation waters are saline, then the types of coal gases will probably be early thermogenic or thermogenic (depending on coal rank). . Thermogenic gas contents are highly variable, but may have very high values exceeding 600 scf/ton. If the coal gases migrated updip, then exploration targets should be on the downdip side of potential permeability barriers or on structural highs and even synclinal axes where higher permeability might exist.
Coalbed Methane Production and Completion
Optimization
Mike
Miller, Marshall Miller and Associates
Many companies have become involved in coalbed methane (CBM) exploration and production in recent years. Although the majority of these companies are established oil and gas operators, many have jumped into the play without CBM experience or input from those with it. They usually have reviewed publications that discuss CBM and seen presentations of increasing CBM production and numbers of wells, concluding that the opportunity is great. However, by failing to properly support development efforts with geologists, engineers and operations personnel that possess adequate CBM experience, returns on invested capital are often much less than could have been achieved.
The primary purpose of this presentation is to review some key factors that should be considered in CBM prospect selection and evaluation, and in optimizing well completions and production. Attention to the items discussed here should enable startup CBM operators to climb the learning curve more rapidly and perhaps delineate some techniques that will help established CBM operators improve project performance.
Cementing Strategies
Mike Stephens, Drilling Specialites
Regulatory Trends in Coalbed Methane - Kansas | Oklahoma
Overview of Coal Gas Reservoir Properties of the Western Interior
Research Coreholes
Simon Testa, TICORA Geoscience
TICORA Geosciences, Inc. collaborated with El Paso Production Company and Colt Energy, Inc. to collect detailed core datasets from samples collected in seven core holes located in the Western Interior Coal Region (WIC Region) of the North American Mid-continent. The cooperative research project, funded by the Gas Research Institute, included analysis of 197 canister desorption experiments collected from Middle Pennsylvanian coal and carbonaceous shale intervals in the Forest City, Cherokee, and Arkoma basins. Desorbed gas content, gas composition, gas storage capacity, and coal characterization data were measured. Analysis of these data resulted in three regional relationships between sorption properties and coal rank (i.e., thermal maturity):
Coalbed Methane Pipeline Interconnects
Phillip Rullman, Southern Star Pipeline
http://www.nmcpttc.org/Case_Studies/CBMconf/index.html
Last Modified January 2005