Mining or in situ disintegration of hard material – Tunnel recovery of fluid material
Reexamination Certificate
2003-06-19
2004-11-30
Kreck, John (Department: 3673)
Mining or in situ disintegration of hard material
Tunnel recovery of fluid material
C299S008000
Reexamination Certificate
active
06824224
ABSTRACT:
BACKGROUND
This invention relates to a method of extracting methane dissolved in water which saturates certain coal beds. More particularly, it relates to a method which may not require the drilling of wells, the upgrading of existing roads, the construction of new roads on currently undisturbed lands, or the construction of a network of new pipelines across public and/or private lands. It may proceed without generating offensive noise or raising dust clouds. It may not cause disturbance to surface lands or require their restoration. It may not bring about a decrease in local property values. It may not lead to increased erosion or sedimentation in the areas where the resource is located or downstream from these areas. It may not result in the extraction of salt or salt water from the coal beds. It may not cause contamination of surface or ground water, and may therefore not affect either the quality or the quantity of currently used water resources. It may result in the extraction of a greater fraction of the methane from the same resources, and thus produce a much greater amount of energy from them, when compared to currently used methods. It may also require a much smaller amount of outside energy for the development of these resources. It may provide long-term, steady, and year-round employment of a highly technical nature. It may add to the income of the region where it is applied without adversely affecting the existing economy or way of life. It may operate in harmony with the natural landscape and with the physical characteristics of the resource and the area in which it is found, and may cause no harm to that area. In short, this invention offers an alternative method of extracting coalbed methane which may be superior to that currently employed.
Coalbed methane is a form of natural gas which is found at various sites in the western United States and elsewhere. It differs from conventional natural gas, which is confined to the interstices of porous rock formations which are overlain by an impermeable geologic stratum which keeps the gas from escaping into the atmosphere. Coalbed methane consists instead of various hydrocarbons which belong to the paraffin series of compounds, and which are dissolved in water which permeates certain coal beds found deep underground. It has been given the name coalbed methane because this gas is essentially the only one which can be readily extracted from the deposit by using the current method of drilling wells down into the coal beds from above.
This selective production results from the differing thermodynamic properties of the gaseous paraffins. Methane is only slightly soluble in water at atmospheric pressure, but its solubility increases rapidly as the pressure increases. Ethane is only marginally soluble in water at all pressures, and is therefore rare in saturated coal beds. Propane and butane are quite soluble in water at all pressures, including atmospheric. When a well is drilled into a water- and gas-saturated coal bed, the pressure of that water is almost instantaneously reduced to values near atmospheric. This drastically reduces the solubility of the methane in the water and causes it to bubble out rapidly, forming a lightweight froth which is forced upward through the well by the much higher pressure found in the coal bed surrounding the well. This pressure is so high that such wells are often artesian in nature, and tend to spew both gas and water into the air unless the well is quickly capped.
When this froth reaches the surface and is captured in a suitable container, it can easily be separated by gravity into methane and water. The methane is then pumped into pipelines for delivery to the market. But this superfluity of methane discharge lasts only a short time. The tiny portion of the coal bed punctured by each well quickly becomes exhausted of its limited supply of both water and methane, and the diffusion of both fluids through the coal from as yet untapped regions nearby proceeds very slowly. To keep the well producing, therefore, a pump must then be installed to force more methane-containing water to the surface. In order to speed up the supply, another process called hydraulic fracturing is often added. Water is pumped down the well into the coal bed at high pressures in order to break the coal into smaller fragments and thus expand the network of microscopic cracks through which diffusion normally takes place. Since the latter two named processes—pumping water upward and then pumping other water downward—counteract each other, each process must be conducted for a limited time and then reversed for a comparable period. In between, long periods of inaction must be endured.
This method of extraction inevitably brings with it certain social, environmental, and economic side effects which at times can be quite severe. Since the wells must often penetrate thousands of feet of overburden before encountering the coal beds, very tall drilling rigs and very long sections of both drilling pipe and casing must be used in order to minimize the frequency of adding new sections. Thus the trucks transporting these materials to the drilling site must also be of great length. In order to accommodate this length, the roads leading to all sites must be made wide enough to allow these trucks to negotiate curves. Both these roads and the well sites themselves must be cleared of vegetation and flattened over extremely large expanses in order that the trucks and rigs can be maneuvered easily. This means that an open space covering dozens of acres must be cleared for each site surrounding a drill hole which may be only a foot or so in diameter. In places where the terrain is not flat, or where the soil is fragile, this disturbed land can be restored to its original condition only with great difficulty and at great expense.
In areas where coalbed methane wells have been drilled near homes supplied by water wells tapping into aquifers which lie above the coal beds, severe contamination of the water from these wells has occurred subsequent to the drilling of the methane wells. This contamination consists of hydrocarbons dissolved in the water, and has led to incidents such as water taps whose output can be ignited when opened, as well as gas-filled well houses which have exploded due to a spark of some kind. This situation, which definitely did not exist prior to the gas well drilling, was undoubtedly caused by propane, butane, and/or residual methane forced upward to the higher aquifers around the outside of the unsealed methane well casings.
The drilling of large and deep wells for methane, as well as other related processes, leads to loud persistent noise which often continues day and night. And the movement of energy company vehicles along the almost always unpaved roads serving the wells generates large and persistent dust clouds which cannot be confined to the well sites. Both of these aspects of the process cause severe annoyance to other residents of the vicinity. Moreover, the production of gas from each well is of limited duration, since the portion of the coal bed near it quickly becomes depressurized and dewatered. Thus the long-term exploitation of such a deposit requires repeated moving of the drilling and pumping equipment from one site to another. All of this disturbance is expected to continue for many years and to affect vast tracts of land, thus making it very difficult, if not impossible, for others to dwell in the same areas or to use the same land for other purposes without undergoing major unfavorable changes in their life styles.
Each well must be served by its own pipeline, and each of these must be connected to a network of larger pipelines leading to market areas. For safety purposes, all of these lines must be buried underground. In order to minimize the total length of the pipelines, they must be laid in lines as straight as possible, thus crossing numerous parcels of both public lands, which dominate the regions where coalbed methane is found, as well as many private parcels which have been owned and occupi
Cimarron Technology Ltd.
Kreck John
LandOfFree
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