Patent Application
20140318805
None
1. Technical Field
Well configurations and methods used in gas production from coal bed formations which once depleted allow conventional mining of the coal bed.
2. Background Art
Gas production from coal bed formations once depleted is commonly followed by conventional mining of the coal itself. Wells with horizontal segments extending through the formation are an effective well configuration for gas recovery when completed with stimulation and production enhancing treatments.
Effective completion techniques commonly involve incorporating multiple drop ball actuated sleeve valves in metallic production string. These valves are also metallic and once installed in the well are opened in a sequence starting with the lowest valve and progressing up the well to the valve located nearest the surface.
Typically, the lowest valve is opened by pumping an actuator ball down to the lowest valve to engage a seat on the valve sleeve and, thereafter, pressure is increased causing the metal pin to shear and the sleeve to move, opening the production tubing to the formation. Treatment fluids and solids are pumped through the open valve into the surrounding formation. Once the first treatment is complete, a ball is dropped to open the next valve and isolate the well from the first valve, and treatment procedures are repeated though the second valve.
This treatment process is repeated up the well and then gas production is initiated. In the sense of wells the relative directional terms, such as, upper are used to refer to the positions closer to the well head along the wellbore and not necessarily higher in elevation. In that regard, the lower is used to refer to position further away from the well head along the wellbore.
It is typical to mine the coal using conventional equipment once the gas has been depleted. It is practically impossible to recover the horizontal production tubing. To avoid explosions and damage to mining equipment large areas of the coal bed must be abandoned. The risk of an explosion ignited by sparks generated from contact between the cutting heads of mining equipment and the subsurface metallic production tubing and valves cannot be tolerated.
There is a need for a well configuration that provides for safe mining of the coal bed once the gas well's usefulness ends.
A horizontal well configuration for coal bed gas recovery is disclosed which eliminates the risks of explosion during coal mining. The production subsurface gas production configuration is designed so that it may be constructed from “non-sparking” materials. This allows mining equipment to be operated near and even in contact with the gas recovery wellbore equipment. Indeed, the mining equipment can cut through and break up the gas recovery wellbore equipment during the coal mining operation without interrupting the mining process.
In one embodiment the production tubing and well treatment valves are constructed entirely from non-sparking materials. The term “non-sparking” materials is used to refer to those materials which when struck do not readily produce high heat sparks. Other terms that have been used to describe these materials, include, “spark reduced”, “spark-resistant” and “spark proof.” Spark testing can be performed by applying a material to a spinning grinding wheel of aluminum oxide or carborundum and comparing the color, volume, amount, nature of any sparks to a known sample.
In an additional, embodiment the production tubing and well treatment valves are constructed from non-sparking materials that can only produce cold sparks. Cold sparks have a low heat level and do not ignite carbon disulfide.
In a further embodiment, the production tubing and well treatment valves are constructed entirely from brass, bronze, monel metal, copper-aluminum alloys, and copper-beryllium allows.
In another embodiment, the production tubing and well treatment valves are constructed without including ferrous materials.
In an additional embodiment, the production tubing and well treatment valves are constructed from non-metallic composite materials. Non-metallic composite material is used herein to refer to material composed of reinforcement (fibers, particles, flakes, and/or fillers) embedded in a matrix (polymers or ceramics).
In a further embodiment, the production tubing and well treatment valves are minable using coal mining equipment.
The drawing is incorporated into and forms a part of the specification to illustrate at least one embodiment and example of the present invention. Together with the written description, the drawing serves to explain the principles of the invention. The drawing is only for the purpose of illustrating at least one preferred example of at least one embodiment of the invention and is not to be construed as limiting the invention to only the illustrated and described example or examples. The various advantages and features of the various embodiments of the present invention will be apparent from a consideration of the drawing in which:
The present invention provides an improved well configuration for use in coal gas production.
Referring more particularly to the drawings, wherein like reference characters are used throughout the various figures to refer to like or corresponding parts, there is shown in
The horizontal extending portion 14 comprises a plurality of sleeve valves 20 spaced along lengths of production tubing 22. The sleeve valves are installed in the closed position and are opened by engaging a seat on the sleeve of the valve with an object such as a ball or dart and raising pressure in the well to shift the sleeve to the open position. In the open position ports in the outer wall of the valve body connect the tubing string with the surrounding formation. Frac and other formation treatments can be pumped through the valve ports and into the formation.
Once the well treatments are completed, production of gas from the coal formation is commenced using methods well known in the industry. When it is desirable to commence mining of the coal itself, gas production is discontinued and mining commenced. According to the present inventions, all of the vertically extending portion 12, horizontally extending portion 14 and valves 20 that are located in the coal bed are made from materials that are minable, i.e., material that can be safely mined with the coal bed materials using conventional mining equipment without damaging the mining equipment.
In the preferred embodiment all of the vertically extending portion 12, production tubing 22 in the horizontally extending portion 14 and valves 20 located in the coal bed is made from composite material (resin material formed with a fiber reinforcement wrapped or helically wound around a mandrel). Non-metallic composite material is used herein to refer to material composed of reinforcement (fibers, particles, flakes, and/or fillers) embedded in a matrix (polymers or ceramics). The matrix holds the reinforcement to form the desired shape while the reinforcement improves the overall mechanical properties of the matrix. A common plastic composite used in forming cylindrical components, such as, includes fiber reinforced polymers of plastic matrix reinforced by fine fibers of glass or carbon fiber. The plastic matrix may be epoxy, a thermosetting plastic or thermoplastic. Examples include polymerized synthetics or chemically modified natural resins including thermoplastic materials such as polyvinyl, polystyrene, and polyethylene and thermosetting materials such as polyesters, epoxies, and silicones that are used with fillers, stabilizers, pigments, and other components to form plastics. Typical manufacturing methods include wrapping resin soaked fiber around a waxed mold.
The production tubing 22 has means for connecting the tubing sections together on its ends. In the illustrated embodiment external pipe threads machined on the ends connected together by an internally threaded collar. Alternatively the tubing sections can be made with threaded pin and box ends. In
The well components formed from reinforced resin located in the coal bed are minable, in that, they will when engaged by cutting heads on conventional mining equipment break up into pieces with the coal bed materials without damage to the mining equipment and without causing an explosion from sparks.
Turning first to
Sleeve valve 120 comprises a cylindrical body 124 which has internal threads 126 at its upper end and internal threads 128 at its lower end. Body 124 has an axially extending bore 130. Threads 126 connect the valve body 124 to tubing section 122 with the bore 130 in fluid communication with the interior of the tubing 122.
An annular stop collar 132 is connected to lower end internal threads 128. The lower end of collar 132 is connected to a tubing section 122. Collar 132 has a bore 134 which is smaller than bore 130. An upward facing annular shoulder 136 is formed at the interface between the bores 130 and 136.
One or more radially extending ports 138 are formed in the wall of the body 124. These ports 138 form a pathway for treatment fluids and materials to be pumped from the production tubing and into the surrounding coal bed formation 18.
An axially movable internal sleeve shaped valve element assembly 140 is mounted in the bore 130. The valve element 140 comprises separate upper section 144 and lower section 146. Mating frusto conical surfaces 146 on the sections 142 and 144 hold the sections in axial alignment when in the closed position. The valve element assembly is illustrated in the closed position blocking flow through ports 138. When the valve is move axially down in the direction of arrow D to uncover ports 138, a flow pathway for treatment fluids and materials is opened through ports 138.
The valve element 140 is held in the closed position by two C-rings 150 mounted in grooves formed in the valve element 140 exterior and wall of bore 130. These C-rings are made from frangible material such as fiber reinforced resin or the like. C-rings 150 hold the sections 142 and 144 together. Seal rings 152 are mounted in grooves formed on the exterior surface of the sleeve valve element 140. These seal rings 152 engage the interior wall of bore 130 to seal the annular space between the valve element and the body.
To move the valve element 140 to the open position a ball 154 (shown in dotted lines) of the appropriate size is pumped down the well until it engages and seats on the upper end 156 of the valve element 140. Pressure is raised until the downward force on the valve element 140 causes the C-rings to shear. With the C-rings sheared, valve element 140 moved down in the direction of arrow D until it strikes shoulder 136 where the valve element says in the open position.
An alternative embodiment of the valve element is illustrated in
In the above embodiment frangible C-rings are used to hold the valve element in the closed position. It is envisioned that as an alternative, the C-rings could be replaced with frangible pins extending between the wall of body 122 and each of the portions 142 and 144 or valve element 140. Other examples of pins could be constructed from minable non-sparking materials, such as, plastics, resins, lead, monel metal (copper-nickel alloy), copper-aluminum alloys (aluminum bronze), or copper-beryllium alloys (beryllium bronze).
In additional examples, the valve components could be constructed from resin, or other minable non-sparking materials, such as, plastics, lead, monel metal (copper-nickel alloy), copper-aluminum alloys (aluminum bronze), or copper-beryllium alloys (beryllium bronze).
While compositions and methods are described in terms of “comprising,” “containing,” or “including” various components or steps, the compositions and methods also can “consist essentially of” or “consist of” the various components and steps. As used herein, the words “comprise,” “have,” “include,” and all grammatical variations thereof are each intended to have an open, non-limiting meaning that does not exclude additional elements or steps.
Therefore, the present inventions are well adapted to carry out the objects and attain the ends and advantages mentioned as well as those which are inherent therein. While the invention has been depicted, described, and is defined by reference to exemplary embodiments of the inventions, such a reference does not imply a limitation on the inventions, and no such limitation is to be inferred. The inventions are capable of considerable modification, alteration, and equivalents in form and function, as will occur to those ordinarily skilled in the pertinent arts and having the benefit of this disclosure. The depicted and described embodiments of the inventions are exemplary only, and are not exhaustive of the scope of the inventions. Consequently, the inventions are intended to be limited only by the spirit and scope of the appended claims, giving full cognizance to equivalents in all respects.
Also, the terms in the claims have their plain, ordinary meaning unless otherwise explicitly and clearly defined by the patentee. Moreover, the indefinite articles “a” or “an”, as used in the claims, are defined herein to mean one or more than one of the element that it introduces. If there is any conflict in the usages of a word or term in this specification and one or more patent(s) or other documents that may be incorporated herein by reference, the definitions that are consistent with this specification should be adopted.
