Deeply buried transmission line

Abstract

A deeply buried transmission line and a method for installing same wherein the majority of the line is buried at depth (e.g. up to 5000 feet or more) well below conventionally buried lines. This provide much greater security from either accidental or intentional damage to the line. The line is initiated by drilling a wellbore in a downward vertical direction to a first depth (e.g. about 500 feet) from spaced surface points before the respective wellbores are curved into in a horizontal direction towards each other at a second depth (e.g. about 5000 feet) where they ultimately intersect. By drilling a wellbore downward from small, spaced surface plots at either end of the line, only a small surface area is affected during the installation of the line.

Description

DESCRIPTION

[0001] 1. Technical Field

[0002] The present invention relates to a transmission line buried deep in the earth and in one of its aspects relates to a transmission line (e.g. liquid pipeline, electrical power line, communication line, etc.) and a method for installing the line deep within the earth or beneath bodies of waters in order to protect the line and reduce the disturbance to the surface during installation and maintenance.

[0003] 2. Background of the Invention

[0004] In laying transmission lines across long distances, it is common to bury the line in a trench which is only a few feet deep (e.g. 20 feet or less) below the surface). For example, pipelines for transporting hydrocarbons (i.e. crude oil, refined products, etc.) are typically constructed by welding joints of pipe together as they lay on the ground and then lowering the welded line into a prepared trench. The trench is then filled with soil to bury the line. However, since a trench must be dug along most of the length of the pipeline, a large contiguous right-of-way on the surface is required to install the line. Further, major environmental disturbances and disruptions may occur during the ditching operation and the installation of the line. This is also true for buried electrical power or communication transmission lines where long lengths of cable or the like are likewise buried just below the ground in relative shallow trenches.

[0005] Since these transmission lines are buried relatively close to the surface, they are susceptible to damage and/or destruction from causes either unintentional and intentional. For example, it is not uncommon for buried transmission lines to be unintentionally severed while the surface is being excavated for roads, buildings, other transmission lines, or the like. The accidental severance of these lines can result in a major disaster in both property and lives and can substantially paralyze a community or industry until the lines are repaired. Likewise, in the modern political climate, the relatively-shallow buried lines may also become targets for espionage or sabotage by protesters or terrorists seeking to disrupt the normal operations in a community.

[0006] Due to the long distances traversed by such lines, it is extremely difficult and expensive to provide the necessary security along their entire lengths, especially where the lines pass through remote and/or rugged terrain. Accordingly, a need exists for a transmission lie which is protected from damage by surface excavations and which is secure from vandalism and/or sabotage over most of its length.

SUMMARY OF THE INVENTION

[0007] The present invention provides a deeply buried transmission line and a method for installing the line wherein the majority of the line is buried at depth (e.g. up to 5000 feet or more) which is significantly deeper than more conventionally buried transmission lines (e.g. about 20 feet). This provide much greater security for the transmission line from either accidental or intentional damage during its operational life. Further, the transmission line of the present invention is initiated in a substantially straight down direction at both ends so that the line is well below surface obstructions and other buried objects before it is kicked off in a horizontal direction. This greatly reduces, if not eliminates, the danger of the line striking or otherwise damaging other structures, i.e. other buried transmission lines).

[0008] Still further, the present transmission line only affects a relatively small surface area during installation, operation, and maintenance. That is, the present transmission line is initiated at either ends from small surface area plots (e.g. ±2 acres) which are spaced from each other by long distances (e.g. up to 7000 feet or more). By requiring only widely-spaced, small areas on the surface to install and maintain the transmission line, the amount of disruption, etc. to the surface is minimized. Also, these small plots can easily be secured which, in turn, can substantially reduce damage due to vandalism and/or sabotage.

[0009] More particularly, the present invention provides a deeply buried transmission line and a method for installing the line between a first point and a second point which are spaced on the surface of the earth. Basically, a first wellbore (i.e. target well) is drilled downward in a substantially vertical direction from the first point to a first depth (e.g. about at least 500 feet) and is then diverted through a curved section into a substantially horizontal section which extends towards said second point at a second depth (e.g. about 5000 feet).

[0010] Subsequent to or concurrent therewith, a second wellbore (i.e. capture well) is drilled downward in a substantially vertical direction from the second point to a first depth (e.g. about at least 500 feet) and then is diverted towards the first wellbore at a second depth (e.g. about 5000 feet) until the second wellbore intersects the first wellbore. The intersected or interconnected wellbores now form a deeply buried transmission line between said first and said second points on the surface which, in turn, can be spaced from about 3000 feet to about 7000 feet from each other.

[0011] Both the first wellbore and the second wellbore is typically cased throughout substantially at least their respective vertical sections with at least string of casing (e.g. conductor casing, surface casing, intermediate casing, etc.) which, in turn, can be connected with a liner to provide a continuous cased and sealed passage between the first point and said second point. The strings of casing and the liner can be cemented within the wellbores as will be understood in the art. The completed line can be used as a pipeline for fluids or can be used as a buried passage for a transmission cable (e.g. power, communication, etc.) between the first and second points on the surface.

[0012] If more than one span of the deeply buried transmission line is needed to cover a prescribed distance, additional spans can be completed in the same way as described above. The next span is installed by drilling another first wellbore (i.e. target well) from the same surface plot as that used in drilling the second wellbore (i.e. target well) of the previous span of the transmission line. The next span is then completed and the second wellbore of the previous span of transmission line is connected or manifolded to the next first wellbore of the next span of transmission line. This procedure is repeated until enough spans have been installed to complete the transmission line over the desired distance. Since the manifolded wellbores of adjacent spans lie in close proximity to each other (e.g. about 20 feet apart) and since the upper ends of the wellbore are the only exposed portions of the line at the surface, security for the entire line can be maintained by merely patrolling and/or monitoring the spaced, surface plots.

BRIEF DESCRIPTION OF THE DRAWINGS

[0013] The actual construction, operation, and apparent advantages of the present invention will be better understood by referring to the drawings which are not necessarily to scale and in which like numerals identify like parts and in which:

[0014] FIG. 1 is a perspective elevational view, partly in section, of one span of the deeply buried transmission line in accordance with the present invention;

[0015] FIGS. 2A-2C are perspective elevational views, partly in section, of the sequence of steps followed in constructing and installing the transmission line of the present invention;

[0016] FIG. 3 is a perspective elevational view, partly in section, of the surface manifold which connects two adjacent spans of the transmission line of FIGS. 2A-2C together; and

[0017] FIG. 4 is a detailed, sectional view of one span of the transmission line of the present invention.

BEST KNOWN MODE FOR CARRYING OUT THE INVENTION

[0018] Referring more particularly to the drawings, FIG. 1 illustrates a typical span of a deeply-buried, transmission line 10 in accordance with the present invention. As used herein, “transmission line” is intended to cover both fluid-conveying lines (e.g. pipelines) and power or data lines (e.g. electrical, telephone, etc.). As illustrated in FIG. 1, one span of line 10 extends over a significant distance or length “L” between a first surface point A and a second surface point B which, in turn, may lie on opposite sides of major surface obstructions (e.g. buildings 11, body of water 12, and/or a wooded area 13). Deeply buried line 10 will typically lie at a maximum depth “D” of up to about 5000 feet over the majority of its length “L”.

[0019] Since the distance “L” between points A and B is normally substantial (e.g. up to about 7 miles or more), only a relatively small number of relatively small, surface-area plots 14 (e.g. about ±2 acres) will be required for installing and maintaining line 10 over long distances. Further, since plots 14 are small in surface area and are spaced at long intervals (e.g. up to 7 miles or more), only a small portion of the surface along line 10 will be disturbed (i.e. only at each plot 14) during installation of line 10. Still further, since line 10 can only be reasonably accessed from the surface at each of plots 14, line 10 can be secured against vandalism and/or sabotage by merely securing or patrolling the plots 14 spaced along line 10.

[0020] As will be more fully explained below, line 10 has a substantially vertical section V (FIG. 4) at either end which extends downward from the surface 15 at points A and B, respectively, to a significant depth before line 10 curves through a “sail angle” zone S and into a substantially horizontal section H which, in turn, extends between and connects the two vertical sections together. By initiating the line 10 in a downward vertical direction for a significant depth (e.g. about ±500 feet), the line 10 will be below any object buried near the surface at most conventional depths (e.g. other transmission lines, foundations for buildings, most bodies of water, etc.) before the line is directed into its horizontal direction, thereby substantially eliminating any chance that line 10 will contact, damage or be impeded by any such near-surface objects. The actual depth of vertical section V in a particular application will depend on a variety of factors, e.g. the ultimate length of span 10, geological strata in the area, fresh water zones to be protected, the required size of line 10, governmental regulations, etc.).

[0021] Referring now to FIGS. 2A-2C and 4, the preferred method for installing transmission line 10 is illustrated. First, a target well T is drilled from surface plot 14 at point A by using conventional, known directional drilling techniques. Target well T is initiated in substantial downward, vertical direction for a significant depth (e.g. ±500 feet). As will be fully understood in this art, the vertical section Va of well T is cased and cemented with conventional conductor string 20A and surface casing 21A (FIG. 4). Again, using conventional and well known directional drilling techniques, target well T is then diverted through a “sail angle” section S into the desired horizontal direction towards point B.

[0022] By using known and commercially-available techniques (e.g. measurements-while-drilling, gyroscopic surveying, etc.), the wellbore of well T can be accurately “steered” from the surface through the “sail angle” zone Sa and horizontal section H to its final destination (i.e. point X). While the distance from point A will vary with a particular application, typically, point X will lie approximately ⅔rds of the distance to point B. Of course, wellbore T can be cased and cemented with one or more intermediate strings (e.g. 22A, 22B) during the drilling of well T as is typically done in the drilling of directional wells.

[0023] Once target well T has been drilled or concurrent therewith, a capture well C is initiated on plot 14 at point B (FIG. 2A). Capture well C is drilled downward through vertical section Vb and is cased with conductor string 20B and surface casing string 21B at the appropriate times. Again, using known and available technology, capture well C is then steered through “sail angle” zone Sb and horizontal section H until it intersects target well T. There are several systems available for the accurate drilling and positioning one well bore in relation to a second wellbore; i.e. methods for drilling (a) substantially parallel wellbores for steam-assisted gravity drainage wells, (b) offset wells to intersect and kill blowouts or fires in adjacent wells; (c) etc..

[0024] Such technology and services are commercially available from a variety of contractors; e.g. Vector Magnetics Inc., Ithaca N.Y.; Gyrodata Corp., Houston, Tex.. For example, a sonde(s) 25 (FIG. 2A), e.g. magnetic, acoustic, etc., may be lowered into target well T which can be sensed when properly directing the drilling of capture well C into intersection with target well T. Again, capture well C can be cased with one or more intermediate strings 22B, 23B, as needed during the drilling of well C.

[0025] Once wells T and C intersect, sonde(s) 25 are removed and the capture well C is cleaned out all the way to casing shoe 24A at the end of intermediate casing string 23A. The wellbore is now complete between points A and B. The wellbore, including horizontal section and ghost hole G, is then preferably filled with a completion fluid, e.g. gel-type drilling mud, to aid in running a liner 30 between intermediate casing strings 23A and 23B. Liner 30 is installed through capture well C using known techniques which are routinely used for casing horizontal wellbores.

[0026] The liner 30 is lowered through intermediate casing string 23B in capture well C, across horizontal section H and into intermediate casing string 23A in target well T. Casing 30 is of sufficient length to span between casing shoes 24A and 24B and extend for a short distance into both of the respective intermediate casing strings. Depending on the particular application, liner 30 may range from about 3000 feet or less to about 7000 feet or more. Preferably, liner 30 is then cemented in place by using standard well cementing procedures.

[0027] If line 10 is to be used to transport fluids (e.g. gas or liquid) between points A and B, it is now ready for operation. The fluids will flow through in either direction through the completed, sealed pipeline comprised of intermediate casing string 23A, liner 30, and intermediate casing string 23B. If line 10 is comprised of more than one span, the upper ends of adjacent capture wells C and target well T will be manifolded together at the surface with an appropriate connection 40 (FIG. 3).

[0028] That is, both a target well T of one span of line 10 and a capture well C for an adjacent span of line 10 are drilled on the same plot 14. This can be done by separate drilling rigs or it can be done merely moving the same drilling rig over on plot 14 after a first span is completed. The surface ends of wells T and C will be spaced a short distance Z (e.g. about 20 feet or so) from each other within the small plot 14 (e.g. ±2 acres). Also, plots 14 may also include pump or compressor stations, treatment stations, etc., which are normally associated with fluid pipelines.

[0029] If transmission line 10 is to be used for power, data, or communication lines, a power or data transmission cable (not shown) would be extended through the completed wellbore (i.e. intermediate casing 23A, liner 30, and intermediate casing 23B) between points A and B. This could be done by attaching the cable or a pull line to a “pig” (i.e. piston) and then forcing the pig from point A to point B by pumping fluid behind the pig such as is done in “pigging” operations used in cleaning the pipelines. Once the pig arrived at point B, the cable can then be “spliced” to a span of cable in an adjacent wellbore similarly explained above in relation to FIG. 3.

[0030] It can be seen that since the majority of transmission line 10 is “buried” at a significant depth (e.g. about 500 feet or greater), the only effective surface exposure of transmission line 10 is within the spaced plots 14. Since each plot 14 is of small surface area (e.g. ±2 acres) and since each plot is spaced from the other by a significant distance (e.g. up to 7000 feet or more), security enclosures can easily be provided for each plot and each plot can be monitored and/or patrolled which greatly increases the safety and security of the overall transmission line 10.

Claims

1. A method for installing a deeply buried transmission line between a first point and a second point which are spaced on the surface of the earth, said method comprising:

drilling a first wellbore downward in a substantially vertical direction from said first point to a first depth and then diverting said first wellbore through a curved section and into a substantially horizontal section which extends towards said second point at a second depth;

ceasing the drilling of said first wellbore before it reaches said second point;

drilling a second wellbore downward in a substantially vertical direction from said second point to a first depth and then diverting said second wellbore through a curved section and into a substantially horizontal section which extends towards said first wellbore at a second depth; and

ceasing the drilling of said second wellbore after it intersects said first wellbore whereby the interconnected said first and said second wellbores form said transmission line between said first and said second points.

2. The method of claim 1 wherein said first depth of said first wellbore is at least about 500 feet and said first depth of said second wellbore is at least about 500 feet.

3. The method of claim 2 wherein said second depth of said first wellbore is at least about 5000 feet and said second depth of said second wellbore is at least about 5000 feet.

4. The method of claim 2 wherein said first point on the surface is spaced from about 3000 feet to about 7000 feet from said second point.

5. The method of claim 4 wherein said first point is located within a first plot having a surface area of ±2 acres and said second point is located within a second plot having a surface area of ±2 acres.

6. The method of claim 1 including:

casing said first wellbore and said second wellbores with conduit to provide a continuous cased passage between said first point and said second point.

7. The method of claim 6 wherein casing said first wellbore and said second wellbores comprises:

casing said first wellbore throughout said substantially vertical direction with one or more strings of casing;

casing said second wellbore throughout its said substantially vertical direction with one or more strings of casing; and

running a liner between said casing in said first wellbore and said casing in said second wellbore.

8. The method of claim 7 including:

cementing said casing in said first and said second wellbores; and

cementing said liner to thereby provided a sealed passage between said first point and said second point.

9. The method of claim 8 wherein said sealed passage provides a flowpath for fluids.

10. The method of claim 8 including:

extending a transmission cable between said first point and said second point through said sealed passage.

11. The method of claim 5 including:

drilling a second first wellbore for a second deeply buried transmission line downward within said second plot from which said second wellbore of said deeply buried transmission line is drilled; and

connecting said second wellbore to said second first wellbore within said second plot.

12. The method of claim 11 wherein said second wellbore and said second first wellbore are spaced on the surface from each other at a distance of about 20 feet.

13. A deeply buried transmission line extending between a first point and a second point space on the surface of the earth, said transmission line comprising:

a first wellbore extending downward from said first point in a substantially vertical direction to a first depth and then in a substantially horizontal direction towards said second point at a second depth; and

a second wellbore extending downward from said second point in a substantially vertical direction to a first depth and then in a substantially horizontal direction towards said first wellbore at a second depth until said second wellbore intersects said first wellbore whereby the intersected said first and second wellbores form said deeply buried transmission line.

14. The deeply buried transmission line of claim 13 wherein said first depth of said first wellbore is at least about 500 feet and said first depth of said second wellbore is at least about 500 feet.

15. The deeply buried transmission line of claim 14 wherein said second depth of said first wellbore is at least about 5000 feet and said second depth of said second wellbore is at least about 5000 feet.

16. The deeply buried transmission line of claim 15 wherein said first point on said surface is spaced from about 3000 feet to about 7000 feet from said second point on said surface.

17. The deeply buried transmission line of claim 16 wherein said first point is located within a plot having a surface area of ±2 acres and said second point is located within a plot having a surface area of ±2 acres.

18. The deeply buried transmission line of claim 13 including:

at least one string of casing in said first wellbore and extending substantially throughout said vertical direction of said first wellbore;

at least one string of casing in said second wellbore and extending substantially throughout said vertical direction of said second wellbore; and

a liner connecting said at least one string of casing in said first wellbore and said at least one string of casing in said second wellbore.

19. The deeply buried transmission line of claim 18 wherein said transmission line is used to transport fluids.

20. The deeply buried transmission line of claim 18 including:

a transmission cable extending from said first point to said second point through said at least one string of casing in said first wellbore, said liner, and said at least one string of casing in said second wellbore.