WO2005077051A2

WO2005077051A2 - Horizontal bore cryogenic drilling method

Info

Publication number: WO2005077051A2
Application number: PCT/US2005/004086
Authority: WO
Inventors: Thomas J. Miller; John R. Jansen
Original assignee: Ch2M Hill, Inc.; Ruekert & Mielke, Inc.
Priority date: 2004-02-09
Filing date: 2005-02-09
Publication date: 2005-08-25
Also published as: WO2005077051A3

Abstract

An apparatus for drilling a horizontal bore in an earth formation includes in a first embodiment a vertical caisson installed in or near the earth formation. A horizontal casing extends radially externally and internally of the caisson. A grindable pipe extends radially externally from the horizontal casing into the earth formation. A method of forming a horizontal bore in an earth formation includes providing the vertical caisson, horizontal casing and grindable pipe of the first embodiment of the apparatus. The method includes creating a first freeze zone of frozen moisture about the grindable casing by flowing a cryogenic fluid through the grindable casing and then forming a pilot bore in the earth formation extending from the caisson through the freeze zone.

Description

HORIZONTAL BORE CRYOGENIC DRILLING METHOD

TECHNICAL FIELD The present invention is directed toward drilling bores in earth formations, and more particularly to horizontal bore cryogenic drilling methods and apparatus.

BACKGROUND ART In many aquifers, the ability to produce water by traditional vertical wells is limited by several factors. In the case of thin aquifers, vertical wells do not allow a long enough section of screen to be installed across the productive formation. This limits the area of the seepage base that can transmit water into the well and reduces the amount of available drawdown that can be created to induce flow toward the well. Both of these factors prevent vertical wells from producing as much water as could be potentially extracted. In other cases, the most productive portion of the aquifer is located under a physical obstruction where a vertical well cannot be installed. These obstructions typically include rivers, lakes, wetlands, structures or other areas where a wellhead is not permitted or access for a vertical drilling rig is impractical. Horizontal wells are often constructed near or under sources of groundwater recharge, such as rivers, lakes or wetlands. As used herein, "horizontal" well or bore means a well or bore that is not exclusively vertical, but has a substantially horizontal or sub-horizontal portion substantially parallel to the ground surface that allows the horizontal bore to access aquifers of limited depth or to access aquifers blocked from vertical access by obstructions as discussed above. Installing a screen under a source of recharge has the effect of inducing additional recharge to the aquifer. This can substantially increase the sustained yield of a horizontal well by capturing surface water. Horizontal water supply wells have been traditionally constructed using radial horizontal collector wells, also known as Ranney® type wells. Radial horizontal collector wells are constructed with large vertical caissons, several feet to tens of feet in diameter, installed to the depth of interest. Well screens or casings are jacked or otherwise advanced horizontally from the caisson to the geologic formation. The well screens or casings form horizontal laterals that conduct water from the formation into the caisson where it is pumped to the surface. Building a radial horizontal collector well using this conventional construction technique is a difficult and lengthy undertaking. For this reason, radial horizontal collector wells are often several times the cost of a traditional vertical well, hi addition, the laterals cannot generally be steered or directed other than by simple linear protection from the caisson. The method has limited ability to project laterals through boulders, cobbles or other obstruction or difficult drilling conditions. An additional problem with this conventional construction technique is fluid invasion into the open face of the lateral cannot be controlled during construction. This creates a need to pump significant volumes of water to keep the caissons from flooding during construction.

The lateral jacking process usually requires workers to be at the bottom of the caisson. This forces workers to endure wet conditions in a confined space below the water table with all the inherent risks and safety hazards that can occur under such conditions. Horizontal directional drilling has been used to install utilities such as pipelines and cables, to extract geologic samples, and for various other purposes. These methods involve mud rotary drilling in which the bit enters the ground from a trench or shallow angle from the surface. The bit is directed horizontally as it is pushed from the surface via the drill string, hi some recent manifestations, the drill bit can be steered down hole using several cutting heads on a down hole drilling motor. The bit can be steered to direct the bore hole vertically or horizontally. Directionally drilled horizontal holes can be drilled to a point of underground termination. The bit and drill string may then be removed and the well is completed from the opening of the bore hole at the surface. This type of horizontal hole is called a blind hole as the end of the hole is never seen. Horizontal bore holes can also be steered to the surface and terminated above ground. These two sided completions are commonly called continuous bores and allow materials to be introduced into the hole from either side in order to complete construction of , for example, a water supply well. One known maker of horizontal directional drills is Nermeer Manufacturing Company of Pella, Iowa. Examples of their horizontal directional drills can be seen on their website. All known existing horizontal directionally drilled bore holes use drilling mud to keep the hole from collapsing, prevent the invasion of large volumes of formation water, remove the cuttings from the bore hole as the drill string advances and provide power and cooling for the down hole drilling motor. The drill muds fall into two major categories, muds based on inorganic clay minerals, such as bentonite, or organic polymers known as biosolid muds. While the use of drilling mud is necessary for the construction of the bore hole, either type of mud produces undesirable effects on the formation around the bore hole. The drilling mud is kept under positive hydraulic head in the bore hole to keep the formation from collapsing. The hydraulic head causes the mud to exfiltrate from the bore hole into the adjacent formation. As it penetrates the formation, the mud creates a zone of invasion which reduces the permeability of the formation adjacent to the bore hole. This has the desirable effect of reducing infiltration of formation water into the bore hole during well construction, but also creates a zone of low permeability that limits the ability of water to flow into the bore hole after construction is completed. Horizontally directionally drilled bore holes are most commonly used to install cables and pipelines. In these applications, mud invasion of the formation is not a significant concern. However, recently horizontally directionally drilled bore holes have been used to install well screens for environmental remediation wells and for high capacity water supply wells. In these applications, the zone of low permeability created by mud invasion significantly reduces the production capacity of the well. To date, efforts to remove the drilling mud from the invaded zone have proven to be expensive and of only limited effectiveness. Additional limitations of horizontal directionally drilled borings using drilling muds are commonly encountered. The method has limited ability to prevent collapse of the bore hole in formations containing cobbles and loose gravel. This can cause the formation to collapse on the drilling string. In addition, there is a tendency for cuttings to settle out of the mud forming an obstruction on the bottom of the horizontal portion of the hole. This can also trap the drill string in the hole. Finally, a curved radius of the bore hole is used as a fulcrum to bend the drill string from sub-horizontal to horizontal. In many applications, the formations lack the structural integrity to withstand the stress as the drill rod is forced into the formation at the top of the bore hole. This results in an irregularly shaped bore hole known as a key seat. Key seats can trap the bit in the hole for blind well installations. As a result, grouted casings must be installed across the curved radius of the sub-horizontal portion of the bore hole for longer blind well completions or when dealing with soft formations. This increases the cost and complexity of the drilling operation. In the drilling of vertical wells, problems of contamination of the area adjacent the well bore by drilling muds has been recognized. Also, where vertical wells have been drilled in earth formations having a high water content, problems have been experienced in extracting water fast enough to effectively advance the drill. In addition, particularly in places where certain shales swell or hydrate in the presence of an influx of water into the well bore, problems have been encountered with the shale becoming loosened and sloughing into the hole necessitating large quantities of shale and cuttings to be lifted out of the well bore. Indeed, if enough shale is loosened, the drill string may even become stuck. One solution to these problems that has been proposed is using cryogenic gas or liquids as a drilling mud to form a frozen boundary around the vertical bore as it is drilled.

Vertical cryogenic drilling methods are described in Maguire, U.S. Patent No. 3,612,192 and

Weaver, U.S. Patent No. 3,774,701. However, there is no suggestion in these references of the desirability of using vertical cryogenic well drilling techniques for the construction of horizontal bores. Rebhan, U.S. Patent No. 4,516,876, describes a tunnel construction technique wherein a pair of vertical caissons are installed at opposite ends of a horizontal tunnel segment. A pilot hole is then drilled between the caissons. A freezing pipe is inserted into the hole and a cooling agent is supplied to the hole to freeze soil adjacent the freeze pipe. Upon creating a freeze zone of sufficient diameter a rotary excavating device rotates around the freezer work pipe to excavate the tunnel. Upon completing excavation of the lengthwise segment of the tunnel, the freezer work pipe is advanced to create a further length of freeze zone and casings can be installed in the newly excavated tunnel. The technique of Rebhan does not contemplate the use of directionally controlled drilling equipment. Further, the Rebhan reference fails to teach an effective way to limit infusion of water into the caisson as the horizontal bore is drilled. The present invention is directed toward overcoming one or more of the problems discussed above.

SUMMARY OF THE INVENTION One aspect of the invention is a diverter apparatus comprising a housing defining a diverter chamber. The housing extends along a housing axis having at one end along the axis a connector for connecting the housing in fluid communication to a casing and having at a second end along the axis an aperture configured to axially receive a drill rod. The housing further includes a diverter outlet in communication with the diverter chamber between the connector and the aperture, hi one embodiment, a packing gland may be provided in operative association with the aperture to form a seal with a drill rod axially received in the aperture, hi this embodiment, the housing may include a plate removably attached to the second end of the housing with the plate defining the aperture. The plate is configured to retain the packing gland in operative association with the aperture. Another aspect of the invention is an apparatus for drilling a horizontal bore in an earth formation. The apparatus includes a vertical caisson installed in or near the earth formation. A horizontal casing extends radially internally and externally of the caisson. A grindable pipe extends radially externally from the horizontal casing into the earth formation.

In one embodiment, a diverter as described above may be connected to the internally extending portion of the horizontal casing, h this embodiment a riser pipe is preferably provided in communication with the diverter outlet. An airlift pipe may be provided in fluid communication with the riser pipe with the airlift pipe communicating with the source of pressurized air to provide the pressurized air to the riser pipe. Yet another aspect of the invention is a method of forming a horizontal bore in the earth formation. The method includes providing a vertical caisson in or near the earth formation and installing in a caisson wall a casing extending radially externally and internally of the caisson. A first freeze zone of frozen moisture is created about a portion of the casing extending radially externally of the caisson. A pilot bore of a first select diameter is formed along a desired path of a horizontal bore in the earth formation extending from the casing through the first freeze zone. A cryogenic fluid is flowed through the pilot bore to form a second freeze zone of frozen moisture adjacent the pilot bore having a second select diameter. A primary bore having a third select diameter greater than the first select diameter and less than the second select diameter is formed within the freeze zone along the desired path of the horizontal bore. The flowing of cryogenic fluid through the pilot bore may be accomplished by first inserting a grindable casing into the pilot bore and flowing the cryogenic fluid through the grindable casing, hi this embodiment the primary bore is formed with the grindable casing in place. A further aspect of the invention is a method of forming a horizontal bore in an earth formation from a vertical caisson in or near the earth formation. A casing is installed in a wall of the caisson extending radially internally and externally of the caisson. A first freeze zone of frozen moisture is formed about the portion of the casing extending radially externally of the caisson. A drill string having a drill rod communicating with a cutting tool is provided for engaging the earth formation. A cryogenic fluid is flowed through the drill rod and the cutting tool to drive the cutting tool and remove cuttings from a bore formed by the cutting tool. The cutting tool is directed into the earth formation through the casing and the first freeze zone and a bore freeze zone is formed in the earth formation in advance of the cutting tool with the cryogenic fluid flowing through the cutting tool. The cutting tool is advanced into the earth formation to form the bore at a rate enabling continuous formation of the bore freeze zone in advance of the cutting tool, i one embodiment, following formation of the primary bore, the drill string is removed and a screen or gravel pack and screen is installed within a portion of the primary bore while the bore freeze zone remains frozen. In this embodiment a valve may then be attached in fluid communication with the extending portion of the casing and a conduit may be attached in fluid communication with the valve. Another apect of the invention is a method of forming a horizontal bore in an earth formation. A pilot hole is formed of a first select diameter along a desired path of the horizontal bore. A grindable casing, preferably a high-density polyethylene casing, is inserted into the pilot hole. A cryogenic fluid is flowed through the grindable casing to form a freeze zone of frozen moisture adjacent to the grindable casing having a second selected diameter. A primary bore is formed having a third select diameter greater than the first select diameter and less than the second select diameter within the freeze zone along the desired path of the horizontal bore with the grindable casing in place. The second diameter is selected to be sufficiently greater than the third select diameter to prevent collapse of the freeze zone. Yet a further aspect of the present invention is a method of forming a horizontal bore in an earth formation which includes providing a drill string having a conduit communicating with a cutting tool for engaging the earth formation. A cryogenic fluid is flowed through the conduit and the cutting tool to drive the cutting tool and remove cuttings from a bore formed by the cutting tool. The cutting tool is directed into an earth formation at a ground surface above the earth formation and a freeze zone is formed in the earth formation in advance of the cutting tool by the cryogenic fluid flowing through the cutting tool. The cutting tool is then advanced into the earth formation to form the horizontal bore at a rate enabling continued formation of a freeze zone in advance of the cutting tool. A transverse portion of the horizontal bore transverse the ground surface and a substantially horizontal portion of the horizontal bore substantially parallel to the ground surface are formed with the transition between the transverse and horizontal portions having sufficient structural integrity to withstand mechanical forces of the drill string. The horizontal bore cryogenic drilling method in accordance with the present invention eliminates the need to use conventional drilling muds which can both pollute the earth formations around a well screen and plug the formation to prevent the efficient flow of water into a horizontal well bore. The cryogenic fluid further allows freezing of an earth formation around the bore hole which allows the earth formation to take on the character of hard rock. This not only improves the structural integrity in the vicinity of the bore, but it eliminates infiltration of formation fluid and eliminates exfiltration of drilling fluids. The cryogenic technique further provides a solid formation which enables the use of drilling hammers as an alternative to rotary drills which can speed construction of the bore, h addition, the frozen cuttings act like dry powdered rock, which can be more efficiently removed from a bore by a cryogenic drilling fluid. The cryogenic technique also renders irrelevant encountering cohesive soils such as clay which might otherwise form problematic clay balls. Furthermore, physical changes to the formation around the bore hole created by the cryogenic method are temporary. The formation will revert to its natural conditions shortly after circulation of the cryogenic fluid is stopped. By way of contrast, mud rotary methods require elaborate well development processes to remove the mud invasion from the formation and these processes have proven unsatisfactory. Particularly with respect to the vertical caisson embodiments, when used with a directional drill, the horizontal bore hole can be drilled directionally, either laterally or vertically, to provide both curved and linear sections of borehole in any direction. The vertical caisson embodiments also minimize formation friction and lessen the jacking strength of equipment and strength of screens and casings required in jacking processes, creating the potential for longer horizontal bore holes. The vertical caisson embodiments further decrease or eliminate water flow into the vertical caissons, reducing or eliminating the need to dewater the caisson during drilling and creating a safer work environment within the casing.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a schematic cross-section of a pilot bore for a cryogenic horizontal bore in accordance with the present invention; Fig. 2 is a schematic cross-section of a pilot bore of Fig. 1 illustrating a freeze zone formed around the pilot bore; Fig. 3 is a schematic cross-section illustrating a horizontal directional drill reaming the pilot bore of Fig. 2; Fig. 4 is a schematic cross-section of a horizontal well including a gravel pack and screen in a horizontal portion and a casing, grouted or ungrouted, between the ground surface and the gravel pack and screen; Fig. 5 is a schematic cross-section of Fig. 4 including a submersible pump in a horizontal portion of the well; Fig. 6 is a schematic cross-section of the horizontal well of Fig. 4 including a vertical shaft including a submersible pump in communication with the horizontal well; Fig. 7 is a schematic cross-section of a completed continuous bore made in accordance with the horizontal bore cryogenic drilling method of the present invention; Fig. 8 is a horizontal cross-section of a bore illustrating a second embodiment of a horizontal bore cryogenic drilling method in accordance with the present invention; Fig. 9 is a schematic view of an apparatus and method for drilling a cryogenic horizontal bore using a vertical caisson in accordance with the present invention; Fig. 10 is a side elevation view of a diverter in accordance with the present invention; Fig. 11 is a rear elevation view of the diverter of Fig. 10; Fig. 12 is a cross-section of the diverter of Fig. 10 taken along line 12-12 of Fig. 11; and Fig. 13 is a schematic view of a test pumping configuration of the vertical caisson horizontal well in accordance with the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT The present is invention contemplates the use of standard horizontal directional drilling equipment with only minor modifications to accommodate a cryogenic fluid. One representative manufacturer of horizontal directional drills is the Vermeer Manufacturing Company of Pella, Iowa. These horizontal directional drills allow the formation of bores having an initial portion transverse a surface of the earth which then transitions to a horizontal portion of a horizontal bore. The horizontal directional drills may also be used with the vertical caisson apparatus and methods disclosed herein and allow for vertical or lateral curves to avoid objects to follow formations. Alternatively, the vertical caisson apparatus and methods can be practiced with known conventional non-directional drilling techniques. As mentioned above, use of cryogenic fluids may require modifications to standard horizontal directional rigs or other rigs used with the vertical caissons. For example, it will likely be necessary to provide a substitute material for low carbon steel used in conventional drill strings because the low carbon steel may become too brittle at cryogenic temperatures. For vertical drill strings, use of aluminum drill pipe or steel pipe containing 9% or more nickel has been suggested. Weaver, U.S. Patent No. 3,774, 701, at column 2, line 68-73. Use of cryogenics may also require modification of conductor pipe, casing head, bits, rotary hose and circulating head gaskets used in conventional flow horizontal drilling systems. As used herein, cryogenic fluid means chilled gas, liquefied gasses or cryogenic brine solutions. Representative chilled gasses may include nitrogen, natural gas, carbon dioxide, methane, propane, neon and the like. Liquefied gases may include liquefied nitrogen, propane, carbon dioxide, methane, natural gas and the like. Obviously, modifications to conventional horizontal directional drill equipment will be a function of a particular cryogenic fluid selected. Weaver, U.S. Patent No. 3,774,701, the contents of which are expressly incorporated herein by reference, discloses use of compressed air as a cryogenic gas, steps to remove moisture from the air and modification of a vertical drill bit for use with chilled compressed air. Maguire, U.S. Patent No. 3,612,192, which is also expressly incorporated by reference herein, similarly teaches a vertical cryogenic drill system using chilled gas such as air. A first horizontal cryogenic drilling method is disclosed with reference to Figs. 1-7.

Fig. 1 illustrates a pilot horizontal bore 10 within an earth formation 12. The pilot bore 10 includes a transverse portion 14 transverse to a ground surface 16 and a horizontal portion 18 substantially parallel to the ground surface 16, each having a first diameter Dl. The pilot bore 10 may be formed either through the use of a horizontal directional drill using a cryogenic fluid or by conventional drilling muds. Following formation of the horizontal pilot bore 10, a grindable casing or freeze pipe 20 is inserted into the pilot bore. The grindable casing or freeze tube may be made of any material having sufficient structural integrity to be axially inserted into pilot bore, sufficient structural integrity at cryogenic temperatures to reliably flow cryogenic fluid to the pilot bore and yet be soft enough to be drilled up with conventional drilling equipment. A plastic casing such as one made of high density polyethylene (HDPE) or other suitable plastics may be preferred.. For blind bore construction, the grindable casing may consist of an outer pipe and an inner pipe having an annular space between the two pipes to conduct the cryogenic fluid to or from the drill bit. For continuous well construction, the grindable casing may consist of a single pipe. Referring next to Fig. 2, a cryogenic fluid is injected into the mouth 22 of an inner pipe of grindable casing 20 and the cryogenic fluid flows through the inner pipe, through the annular space between the inner pipe and an outer pipe and out a mouth of the pilot bore 14. The cryogenic fluid could be directed to flow down the outer annulus and return up the inner pipe as a variation of this method. For a continuous bore, the cryogenic fluid flows through the grindable casing 20 from one side of the bore to the other. Two piece freeze pipes may be used for continuous bore construction as a variation of the method. The cryogenic fluid forms a freeze zone 26 having a second diameter D2 in the vicinity of the grindable casing 20. Referring to Fig. 3, after formation of a freeze zone of a select diameter D2, a horizontal direction drill string 30 having a cutting tool 32 sized to form a primary bore 34 of a third select diameter D3 reams the primary bore 34 with the grindable casing left in place.

The diameter D2 of the freeze zone 26 is selected to be sufficiently greater than the diameter D3 of the primary bore 34 that collapse of the primary bore 34 is prevented. In addition, the freeze zone 26 is of sufficient diameter to withstand forces applied to the earth formation as the primary bore 34 transitions from a transverse portion to a horizontal portion without collapse of the primary bore or formation of a key seat large enough to trap the cutting tool 32.

In this manner, the need to install support casings in this transition zone is eliminated. In the embodiment illustrated in Figs. 1-3, the horizontal directional drill string may either use cryogenic fluids in place of drilling mud or conventional drilling mud for the pilot bore. Use of cryogenic fluids is preferred so as to maintain the integrity of the freeze zone during the second boring operation and to minimize the introduction of contaminates into the vicinity of the bore. Referring to Fig. A, following completion of the primary bore 34, a gravel pack 36 and screen 38 are preferably installed in the horizontal portion of the primary bore to facilitate flow of water into the primary bore, particularly where the primary bore is to be used as a well. Screens or slotted casings may be used with or without gravel packs. In addition, a casing 40 is installed in the well bore between the ground surface and the gravel pack and screen. The casing may be grouted or ungrouted. The gravel pack and screen and casing are preferably installed before thawing of the freeze zone to maintain the structural integrity of the bore during construction. As illustrated in Fig. 5, for a water supply well a submersible pump 42 can be installed in the horizontal portion of the bore, preferably using a spacer to keep the pump off the screen or casing. Alternatively, the submersible pump may be installed in the transverse portion of the well bore. In an alternative design illustrated in Fig. 6, a vertical interceptor well 46 is installed between the ground surface and the horizontal portion of the bore. A pump 48 is provided in the proximity of the intersection between the vertical interceptor well 46 and the horizontal portion of the well bore at sufficient depth below the water column in the interceptor well 46 and a pipe 50 extends between the pump 48 and the ground surface for the extraction of water from the horizontal bore. While Figs. 1-6 are directed to a blind bore construction, Fig. 7 illustrates that the method may be used to construct a continuous bore configuration 52. For a continuous bore, a single piece freeze pipe may be used to pass cryogenic fluids through the bore. Another aspect of the present invention is a single pass horizontal bore cryogenic drilling method. This method can be illustrated with reference to Fig. 8. A drill string 60 having a conduit in communication with a cutting tool or drill head 62 is provided. The cutting tool 62 is intended for engaging and cutting through an earth formation. The cutting tool 62 may be a rotary drill bit, drilling motor, or a hammer bit modified as discussed above for use with a cryogenic fluid. A cryogenic fluid is flowed through the conduit and the cutting tool and performs several functions. The cryogenic fluid first drives the cutting tool and then functions to remove cuttings from a bore formed by the cutting tool. As an alternate manifestation of the method, the drill rod may be rotated to provide power to the cutting tool or drill bit. The cryogenic fluid further forms a temporary freeze wall 64 in advance of the cutting tool 62. hi constructing the horizontal bore, the cutting tool is directed into an earth formation and the cryogenic fluid begins forming the freeze zone. A freeze zone of sufficient structural integrity to prevent collapse of the bore is formed. The cutting tool is then advanced along a select path into the earth formation to form the bore at a rate which enables continued formation of the freeze zone in advance of the cutting tool as illustrated in Fig. 8. As with the two pass teclmique described above, the single pass cryogenic drilling method may be used to either to form a blind bore as illustrated in Fig. 8 or a continuous bore of the type illustrated in Fig. 7. Following completion of the drilling of the bore, a well can be completed by adding the screen, gravel pack and screen and grouted or ungrouted casing as illustrated in Fig. 4. In addition, the submersible pump 42 illustrated in Fig. 5 or the vertical interceptor well 46 illustrated in Fig. 6 may be provided to complete formation of the well. Fig. 9 illustrates a vertical caisson horizontal bore cryogenic drilling apparatus 102. The apparatus 102 includes a vertical caisson defined by a caisson wall 104 which is shown cut away in Fig. 9 for the purpose of clarity. The vertical caisson is constructed using standard industry construction techniques. A horizontal casing 106 extends radially externally and internally of the caisson through a hole in the caisson wall 104. For the purpose of this specification, "horizontal" means substantially horizontal with respect to the vertical caisson wall. The horizontal casing is set into the caisson wall using a gasket and bolts, a threaded coupling or some other fastening device enabling a water tight fit. The horizontal casing is permanently formed through the caisson wall and is of suitable diameter and design to accept a drill string, production string, casing and valves. When installed, a temporary freeze pipe 108 which may include a distal end plate 110 extends from the horizontal casing 106. The temporary freeze pipe 108 and end plate 110 are preferably grindable as described with respect to the grindable casing for freeze pipe 20 above. In addition, the temporary freeze pipe may include the inner and outer pipe structure as described above with respect to the grinding casing or freezing pipe

20 to allow for the circulation of cryogenic fluid therein. Alternatively, the temporary freeze pipe 108 and end plate 110 maybe made of steel, although this will require removal of the temporary freeze pipe prior to utilizing the drilling methods discussed below. A diverter 112 is attached in fluid communication to the internally extending portion of the horizontal casing 106. Referring to Fig. 10, the diverter 112 comprises a housing 114 defining an inner diverter chamber 116 (see Fig. 12). The diverter housing extends generally along an axis 118 and has at one end along the axis an internally threaded collar 120 configured to threadably engage complimentary external threads on the horizontal casing 106 to attach the diverter thereto in fluid tight communication. The housing further has a second end along the axis 118 having an aperture 122 configured to axially receive a drill rod 124. The diverter further includes a diverter outlet 126 in communication with the diverter chamber 116. Preferably, the diverter further includes a packing gland 128 operatively associated with the aperture 122 to form a seal with the drill rod 124 axially received in the aperture 122, as best seen in Figs. 11 and 12. A removable plate 130 is attached and is part of the second end of the housing and acts to retain the packing gland in place. The removable plate 130 further allows for both removal and maintenance of the packing gland and for axial insertion of the drill string, casing, screening material and the like through the diverter and into a horizontal bore. The removable plate 130 is preferably held in place by a number of fasteners such as bolts 132. The packing gland is made of a temperature resistant elastomer or other material that forms a durable seal with the drill rod 124. The seal preferably is sufficiently tight to prevent flow of water or cryogenic fluid into the caisson during the drilling of a cryogenic horizontal bore. Referring to Fig. 12, in one embodiment, complimentary annular grooves 134, 136 around the aperture 122 at the second end of the housing and an inner portion of the plate 130 are configured to receive the annular packing gland 128. Of course, other structures for retaining the packing gland in contact with the drill rod 124 are considered to be within the scope of the invention. A cutting bin 140 may be provided in communication with the diverter chamber 116, preferably at the bottom of the diverter chamber 116 to receive larger cuttings which settle out of the flow path of the fluids. The cutting bin 140 includes a clean out door 142 that seals when closed. As an alternative to the threaded collar 120 on the front end of the housing 114, the connection to the horizontal casing may be by abutting complimentary annular flanges on the housing and horizontal casing 106 having a gasket sandwiched therebetween. The flanges are held together with fasteners such as bolts, in a similar manner that the plate 130 is attached to the second end of the housing as illustrated in Fig. 12. Returning to Fig. 9, a riser pipe 144 is connected to the diverter outlet 126 for conveying cuttings and spent cryogenic fluid to the surface. An airlift pipe 146 in fluid communication with a source of pressurized air 148 may be provided in communication with the riser pipe. The volume of the diverter chamber 116 and the diameter of the riser pipe are designed to maintain sufficient fluid velocity to lift drill cuttings up the riser pipe and out the caisson. However, the airlift pipe 146 provides additional pressurized air to maintain sufficient up-hole velocity to lift the cuttings out of the caisson. A ventilation pipe 150 may be provided for providing air within the vertical caisson for exhausting cryogenic gasses for the benefit of workers within the vertical caisson. The vertical caisson horizontal bore cryogenic drilling apparatus 102 is, as described above, installed in a conventional vertical caisson located in or near an earth formation within which a horizontal bore is to be placed. The horizontal casing 106 is first installed in a caisson wall 104 with the temporary freeze pipe 108 extending into the formation. Cryogenic fluid is then flowed into the temporary freeze pipe 108 in the manner described above to form a first freeze zone 154 of frozen moisture about the portion of the casing extending radially externally of the caisson. Next, the diverter 112 is attached to the internally extending portion of the casing, preferably using the internally threaded collar 120. Thereafter the riser pipe 144 is attached to the diverter outlet 126. The removable plate 130 is removed from the second end of the housing and a drill string including a drill head is axially inserted into the diverter and casing as represented by the drill rod 124 shown extending from the diverter in Fig. 9. The packing gland 128 axially receives drill rod 124 and the removable plate 130 is fastened to the second end of the housing. Preferably the drill train is then advanced by a directional horizontal drilling machine in a similar manner described in the preceding embodiments.

Alternatively, a conventional non-directional drilling machine may be used. The drill head grinds trie temporary freeze pipe 150 and extends into the formation. Up to this point, the first freeze zone 154 prevents intrusion of moisture into the vertical caisson. In one embodiment, a cryogenic fluid is flowed through the drill rod 124 and into the cutting tool to drive the cutting tool and remove cuttings from a bore formed by the cutting tool, with the cuttings flowing into the diverter and out the riser pipe. The cutting tool is directed into the earth formation with a bore (or second) freeze zone being formed in the earth formation in advance of the cutting tool by the cryogenic fluid flowing through the cutting tool. The cutting tool is advanced into the earth formation to form the bore at a rate enabling continuous formation of the bore freeze zone in advance of the cutting tool. Such a process is described in greater detail with reference to Fig. 8 above. Following completion of the horizontal bore, the removable plate 130 is removed from the second end of the diverter to allow access to the horizontal bore and the drill train is removed. At this point a screen or gravel pack and screen may be installed within the primary bore while the bore freeze zone remains frozen. In an alternate embodiment, once the drill string is installed within the diverter 112 as described above with respect to the previous embodiment, a pilot bore of a first select diameter is formed along a desired path of the horizontal bore in the earth formation extending from the casing through the first freeze zone. A cryogenic fluid is then flowed through the pilot bore to form a second (or bore) freeze zone of frozen moisture adjacent the pilot bore having a second select diameter. Thereafter a primary bore having a third select diameter greater than the first select diameter and less than the second select diameter is formed within the freeze zone along the desired path of the horizontal bore. The second freeze zone may be formed by flowing cryogenic fluid through the drill rod operatively associated with the drill head which forms the pilot bore. Thereafter the drill rod is removed and the primary bore is drilled. Alternatively, the drill string can be removed as described above and a grindable casing can be installed in the pilot bore with cryogenic fluid flowing through the grindable casing to form the second freeze zone. Thereafter the primary bore can be formed by drilling the primary bore in the second freeze zone with the grindable casing in place. This process is described in greater detail with reference to Figs. 1-7 above. In the same manner described above, a screen or gravel pack and screen can be installed within the primary bore while the second freeze zone remains frozen. Fig. 13 illustrates a structure for testing the horizontal well while preventing water from infiltrating the caisson. After the horizontal bore is installed in one of the manners as described above and a screen or production casing 158 is installed in communication with the horizontal casing 106, the diverter 112 is removed and replaced with a valve 156 and a stand pipe 158 which enable test pumping without flooding the caisson. After the screen has been adequately developed, it can be temporarily sealed off using the valve 156 to allow removal of the stand pipe 158 and the construction of additional horizontal bore holes from the caisson in one of the manners described above without flooding the caisson. The horizontal bore cryogenic drilling methods described above allow for expedient and economic drilling of water supply wells where horizontal wells are of particular advantage. The cryogenic techniques eliminate the need for drilling muds which cannot only contaminate water formations, but lead to plugging of the well bore/earth formation interface wall and thus inhibiting of efficient operation of the horizontal well. The freeze wall formed during the cryogenic horizontal well drilling method prevents collapse of the drilling hole during drilling and further allows for installation of gravel packs, screens and casings without collapse of the bore hole. These many advantages can be provided by relatively simple modifications of preexisting directional horizontal drilling equipment. While the particular embodiments herein are primarily described for use in forming horizontal water supply wells, the methods may also be employed in any application where preventing invasion of drilling muds into earth formations is desired. For example, in the construction of environmental horizontal wells for remediation or construction of groundwater basin recharge wells, geotechnical borings, dewatering wells, borings above the zone of saturation, or injection wells of various types. This invention specifically contemplates horizontal to sub-horizontal borings used to install instrumentation and equipment for a variety of geotechnical purposes, to temporarily stabilize ground for a variety of purposes, or to collect samples of soil or in-situ formation fluids in a stabilized solid form.

Claims

What is claimed is: 1. An apparatus for drilling a horizontal bore in an earth formation comprising: a vertical caisson installed in or near the earth formation; a horizontal casing extending radially externally and internally of the caisson; and a grindable pipe extending radially externally from the horizontal casing into the earth fonnation.

2. The apparatus of claim 1 further comprising: a diverter, the diverter comprising a housing defining a diverter chamber, the housing extending along a housing axis having at one end along the axis connecting means for connecting the housing in fluid communication to the internally extending horizontal casing and having at a second end along the axis an aperture configured to axially receive a drill rod, the housing further having a diverter outlet in communication with the diverter chamber between the connecting means and the aperture.

3. The apparatus of claim 1 further comprising a riser pipe in communication with the diverter outlet. 4. The apparatus of claim 1 further comprising an air lift pipe in fluid communication with the riser pipe, the air lift pipe communicating a source of pressurized air with the riser pipe.

5. The apparatus of claim 1 further comprising a source of cryogenic fluid in fluid communication with the grindable pipe.

6. An apparatus comprising a housing defining a diverter chamber, the housing extending along a housing axis having at one end along the axis connecting means for connecting the housing in fluid communication to a casing and having at a second end along the axis an aperture configured to axially receive a drill rod, the housing further having a diverter outlet in communication with the diverter chamber between the connecting means and the aperture.

7. The apparatus of claim 6 further comprising a riser pipe in communication with the diverter outlet.

8. The apparatus of claim 6 further comprising a packing gland operatively associated with the aperture to fonn a seal with a drill rod axially received in the aperture.

9. The apparatus of claim 6 wherein the housing further comprises a plate removably attached to the second end of the housing, the plate defining the aperture. 1O. The apparatus of claim 9 further comprising a packing gland operatively associated with the aperture to form a seal with a drill rod axially received in the aperture, the packing gland being retained in operative association with the aperture by the plate.

11. The apparatus of claim 10 further comprising an annular slot defined between the second end of the housing and the plate for receiving the packing gland.

12. The apparatus of claim 6 wherein the connecting means is configured for releasable connection to a casing. 13. The apparatus of claim 6 wherein the connecting means comprises threads configured to theadably engage complimentary threads on a casing.

14. The apparatus of claim 6 wherein the connecting means comprises an annular flange on the housing configured to mate with an annular flange on the casing and a gasket sandwiched between the annular flanges.

15. A method of forming a horizontal bore in an earth formation comprising: a) providing a vertical caisson in or near the earth formation; b) installing a casing extending radially externally and internally of the caisson; c) creating a first freeze zone of frozen moisture about the portion of the casing extending radially externally of the caisson; d) forming a pilot bore of a first select diameter along a desired path of a horizontal bore in the earth formation extending from the casing through the first freeze zone; e) flowing a cryogenic fluid through the pilot bore to form a second freeze zone of frozen moisture adjacent the pilot bore having a second select diameter; and f) forming a primary bore having a third select diameter greater than the first select diameter and less that the second select diameter within the freeze zone along the desired path of the horizontal bore.

16. The method of claim 15 further comprising: following step d), inserting a grindable casing into the pilot bore; perfonning step e) by flowing the cryogenic fluid through the grindable casing; and performing step f) with the grindable casing in place.

17. The method of claim 15 further comprising: following step c), installing a diverter in communication with the internally extending portion of the casing, the diverter being configured to axially receive a drill rod in an aperture axially aligned with the casing and to direct cuttings received from the casing to a diverter outlet for removal from the diverter.

18. The method of claim 15 further comprising following step f): g) installing a screen or gravel pack and screen with a portion of the primary bore while the second freeze zone remains frozen.

19. The method of claim 18 further comprising following step g): h) attaching a valve in fluid communication with the internally extending portion of the casing and attaching a conduit in fluid communication with the valve.

20. The method of claim 15 wherein step e) is perfonned by flowing the cryogenic fluid through a drill rod operatively associated with a drill head fonning the pilot bore.

21. A method of forming a horizontal bore in an earth formation comprising: a) providing a vertical caisson in or near the earth formation; b) installing a casing extending radially externally and internally of the caisson; c) creating a first freeze zone of frozen moisture about the portion of the casing extending radially externally of the caisson; d) providing a drill string having a drill rod communicating with a cutting tool for engaging the earth formation; e) flowing a cryogenic fluid through the drill rod and the cutting tool to drive the cutting tool and remove cuttings from a bore formed by the cutting tool; f) directing the cutting tool into the earth formation through the casing and the first freeze zone to form a primary bore; g) forming a bore freeze zone in the earth formation in advance of the cutting tool with the cryogenic fluid flowing through the cutting tool; and h) advancing the cutting tool into the earth formation to form the primary bore at a rate enabling continuous formation of the bore freeze zone in advance of the cutting tool.

22. The method of claim 21 further comprising: following step c), installing a diverter in communication with the internally extending portion of the casing, the diverter being configured to axially receive a drill train in an aperture axially aligned with the casing and to direct cuttings received from the casing to a diverter outlet for removal from the diverter.

23. The method of claim 21 further comprising following step h): i) removing the drill string; and j) installing a screen or gravel pack and screen within a portion of the primary bore while the bore freeze zone remains frozen.

24. The method of claim 23 further comprising following step j): k) attaching a valve in fluid communication with the internally extending portion of the casing and attaching a conduit in fluid communication with the valve.

25. A method of fonning a horizontal bore in an earth formation comprising: a) forming a pilot bore of a first select diameter along a desired path of a horizontal bore; b) inserting a grindable casing into the pilot bore; c) flowing a cryogenic fluid through the grindable casing to form a freeze zone of frozen moisture adjacent to the grindable casing having a second select diameter; and d) forming a primary bore having a third select diameter greater than the first select diameter and less than the second select diameter within the freeze zone along the desired path of the horizontal bore with the grindable casing in place, the second select diameter being sufficiently greater than the third select diameter to prevent collapse of the primary bore.

26. The method of claim 25 wherein step a) is performed using a directionally controlled drill string driven by a cryogenic fluid.

27. The method of claim 25 further comprising: e) installing a screen or gravel pack and screen within a portion of the primary bore while the freeze zone remains sufficiently frozen to prevent collapse of the portion of the primary bore.

28. The method of claim 25 wherein steps a)-d) are perfonned from a ground surface overlying the earth fonnation and the horizontal bore includes a transverse portion transverse to the ground surface and a substantially horizontal portion substantially parallel to the ground surface.

29. The method of claim 28 further comprising: e) installing a screen or gravel pack and screen in the substantially horizontal portion of the primary bore while the freeze zone remains sufficiently frozen to prevent collapse of the primary bore.

30. The method of claim 29 further comprising: f) installing a casing between the ground surface and the screen.

31. The method of claim 30 further comprising: g) installing a submersible pump in one of the transverse portion or the substantially horizontal portion.

32. The method of claim 29 further comprising: f) providing a vertical shaft between the ground surface and the substantially horizontal portion of the primary bore; and g) providing a pump proximate an intersection between the vertical shaft and the substantially horizontal portion of the primary bore.

33. The method of claim 28 wherein in step c) the second select diameter defines a freeze zone of sufficient structural integrity to withstand mechanical forces of a directional drill string used in step d) as the primary bore transitions from the transverse portion to the substantially horizontal portion without collapse of the primary bore.

34. The method of claim 25 further comprising: e. installing geotechnical instrumentation in the primary bore.

35. The method of claim 25 further comprising: e. collecting soil or stabilized fluid samples in solid form from the earth formation.

36. A method of fonning a horizontal bore in an earth formation comprising: a) providing a drill string having a conduit communicating with a cutting tool for engaging the earth formation; b) flowing a cryogenic fluid through the conduit and the cutting tool to drive the cutting tool and remove cuttings from a bore formed by the cutting tool; c) directing the cutting tool into an earth formation at a ground surface above the earth formation; d) forming a freeze zone in the earth formation in advance of the cutting tool with the cryogenic fluid flowing through the cutting tool; e) advancing the cutting tool into the earth formation to form the bore at a rate enabling continuous formation of a freeze zone in advance of the cutting tool; and f) forming a transverse portion of the horizontal bore transverse to the ground surface and a substantially horizontal portion of the horizontal bore substantially parallel to the ground surface, the freeze zone having sufficient structural integrity to withstand mechanical forces of the drill string as the bore transitions from the transverse portion to the substantially horizontal portion without collapse of the bore.

37. The method of claim 36 further comprising installing a screen or gravel pack and screen within the substantially horizontal portion of the bore while the freeze zone remains sufficiently frozen to prevent collapse of the substantially horizontal portion of the bore. 38. The method of claim 37 further comprising installing a submersible pump in either the transverse portion or the substantially horizontal portion of the bore.

39. The method of claim 37 further comprising providing a vertical shaft between the ground surface and the substantially horizontal portion of the bore and providing a pump proximate an intersection between the vertical shaft and the substantially horizontal portion of the bore.

40. The method of claim 37 further comprising: f) installing casing between the ground surface and the screen.