Pressure activated injection probe

Information

  • Patent Grant
  • 6604579
  • Patent Number
    6,604,579
  • Date Filed
    Thursday, January 3, 2002
    23 years ago
  • Date Issued
    Tuesday, August 12, 2003
    22 years ago
  • Inventors
  • Original Assignees
  • Examiners
    • Schoeppel; Roger
    Agents
    • Thompson; Jeffrey L.
    • Thompson & Thompson, P.A.
Abstract
An injection probe assembly is disclosed for injecting material into subsurface formations for making geotechnical improvements. The probe assembly includes a sheath having an upper end for attaching to a mating tool string and a lower end for receiving a solid drive point. The sheath has a reduced diameter injection area which includes an interior space enclosed by a tubular sidewall, a valve seat, and a plurality of injection ports extending through the sidewall through which materials can be injected laterally. A check valve spool is arranged for sliding movement within the interior space for preventing back-flow of material into the interior space. The spool is seated on the valve seat and covers the injection ports in a first position, and is unseated from the valve seat with the injection ports uncovered in a second position. The spool is responsive to pressure changes of the injected materials.
Description




BACKGROUND OF THE INVENTION




1. Field of the Invention




The present invention relates generally to devices for injecting materials into the earth's subsurface. In particular, the present invention relates to drivable probes used for injecting materials into the subsurface for remediating soil and ground water contamination, stabilizing soil, and making other geotechnical improvements.




2. Description of the Related Art




The use of direct push techniques to inject chemicals into the subsurface for the remediation or clean up of contaminated ground water and soil gained notoriety in the mid to late 1990s. The use of small diameter tools as a conduit to deliver remediation materials into contaminated, subsurface zones can be an efficient method to remediate contaminated soils.




To date, the bulk of injection work is being done with equipment and techniques designed for hole abandonment grouting. As shown in

FIG. 1

, this particular technique uses a probe assembly


10


having a point


11


that closes off the leading end


12


of the tool string


13


. After the initial investigation (e.g., soil sampling, ground water sampling, etc.) the open probe hole


14


must be properly sealed with a suitable grout mix


15


to prevent migration of contaminated soils throughout the probe hole


14


.




The conventional tool string


13


is first advanced to the bottom of the open probe hole


14


. The tool string


13


is then retracted allowing the point


11


(often referred to as the “expendable point”) to fall off leaving the inside diameter (“ID”) of the tool string


13


open to the soil. A grout mix


15


is then pumped through the ID of the tool string


13


as the tool string


13


is retracted out of the probe hole


14


. The probe hole


14


is filled to the top as the tool string


13


is retracted. This particular approach is commonly referred to as “bottom up grouting.”




Remediation materials are often delivered in this same manner. The problem with injecting remediation materials with this technique is ensuring that the material is evenly injected into the soil throughout the entire injection interval. As the tool string


13


is retracted and material is being injected, the resistance to material flow into the soil will change as the geological characteristics change. This can lead to more material being injected into zones.


16


,


18


with less resistance to flow and less material going into zones


17


with a higher resistance to flow. For this reason, the use of a “top down injection” approach is more advantageous.





FIG. 2

illustrates an injection probe assembly


20


for use in a top down injection technique. The top down injection approach uses a reduced diameter injection area


21


along the sheath


22


of the probe assembly


20


to define an injection interval. The defined injection area


21


on the sheath


22


eliminates the open hole below the tool string where the injected material would be exposed to differing soil with varying resistances to flow, as in the bottom up grouting and injection techniques shown in FIG.


1


. The top down injection approach ensures that the material is being injected evenly over the entire injection interval.




A difficulty in top down injection techniques is the lack of tooling available for such an approach. Since the injection takes place during several advancements of the tool string


24


, clogging of the sheath


22


or the tool string


24


is often a problem. In addition to clogging, the soil around the injection point


25


can resist flow, causing pressure to build up in the soil formation and inside the tool string


24


. This excess formation pressure causes the material


23


being injected to flow back up through the tool string


24


where it is displaced through the top of the tool string


24


and spills onto the ground at the top of the probe hole.




Thus, there is a need in the industry for an improved tool string for use in top down injection techniques which eliminates clogging and prevents back-flow of injection material.




SUMMARY OF THE INVENTION




It is an object of the present invention to provide an injection probe that solves the above-described problems with existing top down injection techniques.




It is a further object of the present invention to provide an injection probe that ensures material is injected evenly over the desired interval, that prevents the tool string from clogging during normal string advancement, and that prevents back-flow of the injection material up the tool string when pressure develops within the soil formation.




It is a further object of the present invention to provide an improved pressure activated injection probe that can be used effectively to provide uniform top down injection into the subsoil without clogging, and that is economical to manufacture, capable of a long operating life, and particularly well suited for use in remediating contaminated soils and ground water.




In order to solve the problems with the prior art described above, the applicant has developed an improved pressure activated injection probe assembly for injecting materials into subsurface formations to remediate contaminated soils and ground water, to inject grout materials for soil stabilization, and for making other geotechnical improvements. The probe assembly includes a sheath having an upper end for attaching to a mating tool string and a lower end for receiving a solid drive point. The sheath has a reduced diameter injection area which includes an interior space enclosed by a tubular sidewall, a valve seat, and at least one and preferably a plurality of injection ports extending through the sidewall through which materials can be injected laterally. A check valve spool is arranged for sliding movement within the interior space of the sheath for preventing clogging and back-flow of material into the interior space. The valve spool has a first closed position in which an upper end thereof is seated on the valve seat and an outer cylindrical surface covers the inner sides of the injection ports. The valve spool has a second open position in which the upper end is unseated from the valve seat and the injection ports are open to the interior space. The valve spool is biased toward its closed position by a compression spring, and is responsive to pressure changes within the sheath for movement between the closed and open positions.




According to a broad aspect of the present invention, an injection probe is provided, comprising: a tubular assembly having an upper end for attaching to a mating tool string, a lower end for receiving a solid drive point, an upper seal portion adjacent to the upper end, a lower seal portion adjacent to the lower end, and an injection area between the upper and lower seal portions. The injection area has a smaller outer diameter than the upper and lower seal portions, an interior space enclosed by a tubular sidewall, a valve seat, and at least one and preferably a plurality of injection ports extending through the sidewall through which materials can be injected laterally into a subsurface formation. A check valve spool is arranged for sliding movement within the interior space of the injection area for preventing back-flow of material into the interior space. The check valve spool has a first position in which an end portion of the check valve spool is seated on the valve seat and an outer surface of the check valve spool covers the injection ports and prevents material from flowing back into the interior space through the injection ports. The valve spool has a second position in which the end portion of the check valve spool is unseated from the valve seat and the injection ports are open to the interior space.




Numerous other objects of the present invention will be apparent to those skilled in this art from the following description wherein there is shown and described a preferred embodiment of the present invention, simply by way of illustration of one of the modes best suited to carry out the invention. As will be realized, the invention is capable of other different embodiments, and its several details are capable of modification in various obvious aspects without departing from the invention. Accordingly, the drawings and description should be regarded as illustrative in nature and not restrictive.











BRIEF DESCRIPTION OF THE DRAWINGS




The present invention will become more clearly appreciated as the disclosure of the invention is made with reference to the accompanying drawings. In the drawings:





FIG. 1

is a cross section view providing an overview of conventional “bottom up” grouting and injection techniques.





FIG. 2

is a cross section view providing an overview of a “top down” injection technique.





FIG. 3

is an exploded front view of a pressure activated injection probe assembly of the present invention.





FIG. 4

is a partially cutaway front view of the pressure activated injection probe of the present invention with a check valve closed to prevent soil and other material from entering the probe.





FIG. 5

is a partially cutaway front view of the pressure activated injection probe of the present invention with the check valve open to allow material to flow out of the injection ports.











DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT




A pressure activated injection probe assembly


20


according to a preferred embodiment of the present invention will now be described with reference to

FIGS. 2

to


5


of the accompanying drawings.




The injection probe assembly


20


includes a tool string


24


, an injection probe sheath


22


, and a solid drive point


25


. The solid drive point


25


includes a conical-shaped tip


26


that tapers to a point, and a male-threaded mating portion


27


adapted to be received in a female-threaded opening


28


at the lower end of the sheath


22


. The tool string


24


is attached to an upper end of the sheath


22


using a suitable mating connection. For example, the sheath


22


can be provided with male threads


29


at its upper end, and the tool string


24


can be provided with corresponding female threads at its lower end to make raw the mating connection.




The tool string


24


comprises a plurality of probe rods which are attachable together to form different working lengths. For example, the probe rods forming the tool string


24


may be provided in several short lengths which are attachable together end-to-end in a series to form a variable working length. As the probe sheath


22


and drive point


25


are driven vertically into the ground during use, additional probe rods can be added to the top of the tool string


24


. When the sheath


22


and drive point


25


are at the desired depth, a manifold


30


is attached to an upper end of the tool string


24


. The manifold


30


includes a port


31


for introducing materials to be injected into a longitudinal bore of the tool string


24


. Materials to be injected can thus be pumped through the tool string


24


to a longitudinal inner passage


32


of the sheath


22


.




The sheath


22


includes an upper seal portion


33


adjacent to the upper end, a lower seal portion


34


adjacent to the lower end, and a reduced diameter injection area


21


between the upper and lower seal portions


33


,


34


. The injection area


21


has at least one and preferably a plurality of injection ports


35


extending from a hollow interior space


36


of the sheath


22


through a tubular sidewall


37


thereof through which materials can be injected laterally. In a preferred embodiment, four injection ports


35


of approximately 0.25 inch diameter each are spaced evenly around the injection area


21


approximately 90 degrees apart from each other.




The injection area


21


has a smaller outer diameter than the upper and lower seal portions


33


,


34


. The outer diameters of the upper and lower seal portions


33


,


34


of the sheath


22


corresponds with the size of the bore


38


through the subsurface formation


39


created by the drive point


25


and the tapered lower edge


40


of the sheath


22


. As a result, the upper and lower seal portions


33


,


34


fit snugly against the subsurface formation


39


in which the probe assembly


20


is placed, and containment seals are created above and below the injection area


21


. The containment seals created by the upper and lower seal portions


33


,


34


enhance the precision and uniformity of the injection at each injection interval.




A valve seat


41


is machined within the sheath


22


above the injection ports


35


. The valve seat


41


is located between the hollow interior space


36


of the injection area


21


and the inner passage


32


of the upper portion of the sheath


22


.




A check valve spool


42


is arranged for sliding movement within the interior space


36


of the injection area


21


. The check valve spool


42


is a generally cylindrical member formed of a polyethylene material having an upper end


43


with a tapered edge


44


adapted to engage and seal against the valve seat


41


. The cylindrical outer surface


45


of the check valve spool


42


is slidably received within the cylindrical inner surface


46


of the tubular sidewall


37


of the sheath


22


with a close tolerance fit (e.g., 0.005″ inch).




The check valve spool


42


has a first “closed” position (

FIG. 4

) in which the tapered edge


44


of the upper end


43


of the check valve spool


42


is seated on the valve seat


41


. The seal created between the check valve spool


42


and the valve seat


41


prevents fluid from flowing back up through the inner passage


32


of the sheath


22


and the bore of the tool string


24


when positive pressure is encountered within the soil formation


39


. The outer surface


45


of the check valve spool


42


also covers the inner sides of the injection ports


35


in this first position and prevents soil and other foreign material from flowing back into the interior space


36


through the injection ports


35


. Since soil can only enter the injection ports


35


, and not the interior space


36


of the sheath


22


, the system will not plug during nonpumping periods.




The check valve spool


42


has a second “open” position (

FIG. 5

) in which the upper end


43


of the check valve spool


42


is unseated from the valve seat


41


and the injection ports


35


are open to the interior space


36


. The valve spool


42


is movable from the first position to the second position when a sufficient positive fluid pressure exists within the inner passage


32


of the sheath as material is pumped through the tool string


24


.




A compression spring


47


is arranged within the sheath


22


near a lower end thereof to engage and bias the check valve spool


42


toward the check valve seat


41


. The spring


47


operates to move the check valve spool


42


from the second open position back to the first closed position when a positive pressure ceases to exist within the inner passage


32


of the sheath


22


. The spring constant of the spring


47


is sufficient to maintain the check valve spool


42


in the first position until a predetermined positive pressure is introduced into the sheath


22


, and also to overcome frictional forces in returning the valve spool


42


from the second open position to the first closed position. A lower end of the spring


47


is seated against an inner surface


48


of the solid drive point


25


. In a preferred embodiment, the spring


47


is made of stainless steel.




The check valve spool


42


has an annular groove


49


formed in the cylindrical portion near a lower end thereof. An O-ring


50


is positioned in the annular groove


49


to create a seal between the valve spool


42


and the inner surface


46


of the sheath


22


. The O-ring


50


prevents soil and other foreign material from flowing around the check valve spool


42


into the lower portion of the sheath


22


, where it would interfere with the operation of the spring


47


.




The injection probe


20


is assembled by placing the O-ring


50


on the check valve spool


42


, sliding the valve spool


42


through the lower end of the sheath


22


and into the interior space


36


of the injection area


21


, inserting the compression spring


47


through the lower end of the sheath


22


into engagement with the check valve spool


42


, and threading the drive point


25


into the mating female threads


28


at the lower end of the sheath


22


. The assembly process can therefore be accomplished quickly and easily.




In operation, the injection probe assembly


20


is driven vertically into the ground to a desired depth in a subsurface formation


39


. The injection area


21


of the sheath


22


is aligned with the subsurface formation


39


to be treated. Material is then pumped through the tool string


24


into the sheath


22


. When the positive pressure of the material in the inner passage


32


above the valve spool


42


overcomes the spring force of the compression spring


47


, the valve spool


42


shifts off of the valve seat


41


and the injection ports


35


are exposed. This allows material to flow laterally out of the injection ports


35


of the sheath


22


and into the subsurface formation


39


. When positive pressure is decreased or eliminated from the inner passage


32


of the sheath


22


, the spring


47


moves the valve spool


42


back against the valve seat


41


, thus eliminating back flow through the injection ports


35


. The cylindrical outer surface


45


of the valve spool


42


blocks the injection ports


35


in this position. The injection probe assembly


20


can then be advanced to the next injection interval with the injection ports


35


closed to prevent clogging of the assembly.




It will be appreciated that certain features of the present invention described above can be changed without departing from the scope of the invention. For example, the valve spool


42


can be formed of a material other than polyethylene to maintain chemical compatibility with different injection materials. In conditions where driving the tool string will be very difficult and.require extensive percussion on the tool string, a hardened steel check valve spool


42


may be used. Also, the size and number of the injection ports


35


can be increased or decreased to accommodate different material viscosity and flow rates.




While the invention has been specifically described in connection with specific embodiments thereof, it is to be understood that this is by way of illustration and not of limitation, and the scope of the appended claims should be construed as broadly as the prior art will permit.



Claims
  • 1. An injection probe assembly, comprising:a tubular sheath having upper and lower ends and an injection area between the upper and lower ends, the injection area having a hollow interior space enclosed by a tubular sidewall and at least one injection port extending through the sidewall for allowing materials to be injected laterally through the injection port into a subsurface formation; and a check valve spool located within the hollow interior space of the injection area for preventing back-flow of material into the interior space, the check valve spool having a first position in which the injection port is closed to the hollow interior space, and a second position in which the injection port is open to the hollow interior space.
  • 2. The injection probe assembly according to claim 1, further comprising an upper seal portion between the injection area and the upper end, and a lower seal portion between the injection area and the lower end, the upper and lower seal portions each having a larger outer diameter than an outer diameter of the injection area to create respective seals above and below the injection port during operation.
  • 3. The injection probe assembly according to claim 1, further comprising a spring arranged within the sheath to engage and bias the check valve spool toward a check valve seat located within the sheath above the injection port.
  • 4. The injection probe assembly according to claim 1, wherein said check valve spool is slidably received within the interior space of the injection area with a close tolerance fit between an outer surface of the check valve spool and an inner surface of the tubular sidewall of the sheath.
  • 5. The injection probe assembly according to claim 1, wherein said check valve spool has a generally cylindrical portion having a cylindrical outer surface that corresponds in size to a cylindrical inner surface of the sidewall of the injection area through which the injection port extends.
  • 6. The injection probe assembly according to claim 5, wherein said check valve spool has an annular groove formed in said cylindrical portion near a lower end thereof, and an O-ring positioned in said annular groove to prevent material from flowing around said check valve spool.
  • 7. The injection probe assembly according to claim 1, wherein said check valve spool is slidable from said first position to said second position against the bias of a spring.
  • 8. The injection probe assembly according to claim 1, wherein the sheath has an inner passage extending from the upper end to the injection area for delivering materials to be injected to the injection area, and a check valve seat located between the inner passage and the injection area, said check valve spool engaging the check valve seat and closing the inner passage from the injection area in its first position.
  • 9. The injection probe assembly according to claim 8, wherein said check valve spool is slidable from said first position to said second position against a spring bias when a positive pressure is introduced into the inner passage of the sheath.
  • 10. An injection probe assembly, comprising:a tool string; a drive point; and a sheath having upper and lower ends, the upper end being mated to the tool string, and the drive point being received in the lower end, the sheath further comprising: an injection area between the upper and lower ends having a hollow interior space enclosed by a tubular sidewall and at least one injection port extending through the sidewall for allowing materials to be injected laterally through the injection port into a subsurface formation; and a check valve spool located within the hollow interior space of the injection area for preventing back-flow of material into the interior space, the check valve spool having a first position in which the injection port is closed to the hollow interior space, and a second position in which the injection port is open to the hollow interior space.
  • 11. The injection probe assembly according to claim 10, wherein said drive point includes a conical-shaped tip and a male threaded mating portion which is received in a female threaded mating portion at the lower end of the sheath.
  • 12. The injection probe assembly according to claim 10, wherein the check valve spool is arranged for sliding movement within the interior space of the injection area, and the check valve spool has an end portion facing a valve seat within the sheath, said end portion of the check valve spool being seated against the valve seat with an outer surface of the check valve spool blocking the injection port in said first position, and said end portion of the check valve spool being unseated from the valve seat with the injection port open to the interior space in said second position.
  • 13. The injection probe assembly according to claim 12, wherein said check valve spool is responsive to fluid pressure within the sheath for movement between the first and second positions.
  • 14. An injection probe, comprising:a tubular assembly having an upper end for attaching to a mating tool string, a lower end for receiving a solid drive point, an upper seal portion adjacent to the upper end, a lower seal portion adjacent to the lower end, and an injection area between the upper and lower seal portions; the injection area having a smaller outer diameter than the upper and lower seal portions, an interior space enclosed by a tubular sidewall, a valve seat, and at least one injection port extending through the sidewall through which materials can be injected laterally into a subsurface formation; and a check valve spool arranged for sliding movement within the interior space of the injection area for preventing back-flow of material into the interior space, the check valve spool having a first position in which an end portion of the check valve spool is seated on the valve seat and an outer surface of the check valve spool covers the injection port and prevents material from flowing back into the interior space through the injection port, and a second position in which the end portion of the check valve spool is unseated from the valve seat and the injection port is open to the interior space.
  • 15. The injection probe according to claim 14, further comprising a compression spring positioned within the sheath and arranged to engage and bias the check valve spool toward the valve seat.
  • 16. The injection probe according to claim 15, further comprising an O-ring positioned on the check valve spool near an end thereof opposite the end portion facing the valve seat, said O-ring being arranged to create a seal between the outer surface of the check valve spool and an inner surface of the sheath to keep foreign material away from the compression spring.
  • 17. The injection probe according to claim 15, wherein said compression spring has first and second ends, the first end engages the check valve spool, and the second end is seated against an inner surface of the drive point.
  • 18. The injection probe according to claim 14, wherein said at least one injection port comprises a plurality of injection ports spaced circumferentially about the injection area.
  • 19. The injection probe according to claim 14, wherein said check valve spool is responsive to fluid pressure within the sheath for movement between the first and second positions.
  • 20. The injection probe according to claim 14, wherein said check valve spool is formed of a polyethylene material.
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4807707 Handley et al. Feb 1989 A
4814608 Dempsey et al. Mar 1989 A
5062486 McClenahan Nov 1991 A
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5319959 Cooper et al. Jun 1994 A
5358057 Peters et al. Oct 1994 A
5464059 Kristiansen Nov 1995 A
5743343 Heller et al. Apr 1998 A
5802996 Baxter Sep 1998 A
Non-Patent Literature Citations (1)
Entry
ESP Injection Check Valve information located at www.envservprod.com, an Internet site of Environmental Service Products, Laguana Hills, California (2001).