Gel hydration tank and method

Information

  • Patent Grant
  • 6817376
  • Patent Number
    6,817,376
  • Date Filed
    Friday, February 8, 2002
    23 years ago
  • Date Issued
    Tuesday, November 16, 2004
    20 years ago
Abstract
The present invention relates to a gel hydration tank and method for hydrating gels for use in oil well treatment operations according to which a mixture of water and gel is introduced into the interior of the tank and flows through the tank before being discharged from the tank, whereby specific devices are used to deflect and/or re-direct fluid flow so as to increase the distance traveled for a given fluid volume element, which consequently increases the plug flow efficiency of the tank.
Description




BACKGROUND




This invention relates to a gel hydration tank and method for hydrating gels for use in oil and gas well treatment operations.




Well treatment fluids are often used in oil or gas wells for well completion procedures, to acidify the well formation, and/or increase the recovery of hydrocarbons from the well by creating fractures in the formations, and the like. Many well treatment fluids of this type are composed of water and polymer gel agents and are usually formed by transporting an appropriate polymer gel agent to the well site and mixing it with excess water before the mixture is transferred to a hydration tank. The mixture is introduced into the hydration tank and the finished fluid is withdrawn from the tank on a continuum, yet the mixture must be maintained in the tank an optimum time to allow the polymer gel agent to become hydrated to form a high viscosity well treatment fluid. Thus, the design of the hydration tank is important to ensure the above and thus form an optimum well treatment fluid.











BRIEF DESCRIPTION OF THE DRAWINGS





FIG. 1

is a diagrammatic view of a typical oil well treatment operation incorporating a hydration tank.





FIG. 2A

is a top plan, broken-away, view of a hydration tank according to one embodiment of the present invention.





FIG. 2B

is a side elevational view of the hydration tank of FIG.


2


A.





FIGS. 3 and 4

are cross-sectional views taken along the lines


3





3


and


4





4


, respectively, of FIG.


2


B.











DETAILED DESCRIPTION





FIG. 1

illustrates a typical well treatment operation


10


, where a high viscosity well treatment fluid is processed for introduction into subterranean well formations. In the well treatment operation


10


, an appropriate polymer gel agent is transported to the well site, and placed in a mixing container


12


. The polymer gel agent can include dry polymer additives, stabilized polymer slurries, aqueous liquid gel concentrates, and hydrocarbon-based liquid gel concentrates.




In the mixing container


12


, the polymer gel agent is mixed with excess water and then transferred to a hydration tank


14


to allow time for the polymer gel agent to become hydrated to form a high viscosity well treatment fluid. Although the transformation from a polymer gel agent and water mixture to the resulting hydrated well treatment fluid is on a continuum, for the sake of simplicity the specification will refer to a fluid when it is not necessary to distinguish between the initial polymer gel agent and water mixture and the resulting hydrated well treatment fluid.




A pump


15


is used to transfer the hydrated fluid from the hydration tank


14


to a blending system


16


, whereby sand or another proppant and other liquid additives are accurately metered and mixed with the hydrated gel. Then, another pump


17


transfers the mixture to high pressure pumps


18


that pressurize and transfer the final mixture to the well bore


19


. In one embodiment, the well treatment operation


10


produces well treatment fluid substantially continuously. Thus, the hydration tank


14


must permit the flow of the well treatment fluid from the mixing container


12


to the pump


15


at a desired, substantially consistent, flow rate while allowing the fluid to remain in the hydration tank


14


for at least the hydrating period to ensure optimum viscosity for the resulting well treatment fluid. Thus, to establish an acceptable flow rate and residence time, the fluid should not “finger” ahead and enter the pump


15


before remaining in the hydration tank


14


for the hydration period.




As shown in

FIGS. 2A and 2B

, the hydration tank


14


according to one embodiment of the present invention includes a set of walls


22


,


24


,


26


, and


28


(wall


28


is removed for clarity in FIG.


2


B), extending perpendicular to a floor


30


and attached to the floor


30


in any conventional manner to define a fluid-tight interior portion


32


. A top


34


(partially shown in

FIG. 2A

) may be placed on top of the hydration tank


14


via structural members


36


,


38


to cover the interior portion


32


.




An inlet pipe


40


extends through the wall


26


and adjacent to the wall


28


for receiving the polymer gel agent and water from the mixing container


12


(

FIG. 1

) and introducing the fluid into the interior portion


32


. Fluid entry is controlled by mixing container


12


. An inlet valve


42


is provided for isolating the hydration tank


14


from the mixing container


12


. An outlet pipe


46


extends from the interior portion


32


and adjacent to the wall


24


to the exterior of the hydration tank


14


for allowing the discharge of the hydrated well treatment fluid from the hydration tank


14


. Fluid exit is controlled by the pump


15


. An exit valve


47


is provided for isolating the hydration tank


14


from the blending system


16


. Thus, there is a general fluid flow through the interior portion


32


from the inlet pipe


40


to the outlet pipe


46


.




The hydration tank


14


is mobile and includes a base


50


with an attached connector


52


at one end for coupling to a conventional motive source, such as a truck (not depicted). A wheel assembly


54


is attached to the other end of the base


50


.




A plurality of weirs


60


-


69


are disposed in the interior portion


32


of the hydration tank


14


in a spaced, parallel relation to establish a flow path of the fluid from the inlet pipe


40


to the outlet pipe


46


. As shown in

FIG. 3

, the weir


60


is a flat, plate-like structure having a top


70


, a flat side


72


, a bottom


74


, and a slanted side


76


. The top


70


is attached to the structural member


36


, which spans between wall


24


and wall


28


and is positioned adjacent to the top


34


of the hydration tank


14


. The flat side


72


is attached to the wall


28


, and the bottom


74


is attached to the floor


30


. The slanted side


76


is spaced from the wall


24


and creates a specific directional path for fluid to flow.




The weir


61


is shown in FIG.


4


and is also a flat, plate-like structure having a top


80


, a flat side


82


, a bottom


84


, and a slanted side


86


. The top


80


is attached to the structural member


38


, which spans between wall


24


and wall


28


and is positioned adjacent to the top


34


of the hydration tank


14


. The flat side


82


is attached to the wall


24


, and the bottom


84


is attached to the floor


30


. The slanted side


86


is spaced away from the wall


28


, and creates a specific directional path for fluid to flow. Thus, the weir


61


is substantially similar to the weir


60


, but is installed on the laterally opposing wall and is in an inverted orientation relative to the weir


60


.




The weirs


62


,


64


,


66


, and


68


are also connected to the wall


28


and are substantially identical to the weir


60


; and the weirs


63


,


65


,


67


, and


69


are also connected to the wall


24


and are substantially identical to the weir


61


. Therefore, the weirs


62


,


63


,


64


,


65


,


66


,


67


,


68


, and


69


will not be described in detail.




In operation, the fluid flows from the mixing container


12


(

FIG. 1

) and into the hydration tank


14


through the inlet pipe


40


(FIGS.


2


A and


2


B), before passing into and through the interior portion


32


of the hydration tank


14


and discharging from the outlet pipe


46


. During this flow through the interior portion


32


, the fluid is deflected by the weirs


60


-


69


in a manner to be described, and passes around the weirs


60


-


69


, with each of the weirs


60


-


69


establishing its own fluid volume movement.




The general vector for the fluid volume movement for each of the weirs


60


-


69


is dependent on the above-described spaces between the slanted sides of the weirs and the relevant opposing wall. More particularly, the fluid entering the interior portion


32


of the hydration tank


14


from the inlet pipe


40


initially encounters the weir


60


. The fluid volume movement around the weir


60


is shown in

FIG. 3

by the reference arrow B


1


. The fluid is blocked from passing between the weir


60


and each of the wall


28


, the floor


30


and the top


34


. Thus, the fluid must flow to the space between the wall


24


and the slanted side


76


, generally to the right in FIG.


3


. Also, since more fluid volume will pass through the relatively larger space between the wall


24


and portions of the slanted side


76


closer to the bottom


74


, the flow is generally downwardly, as also shown by B


1


.




The fluid next encounters the weir


61


described with reference to FIG.


4


. The fluid is blocked from passing between the weir


61


and each of the wall


24


, the floor


30


and the top


34


. Thus, fluid must flow to the space between the wall


28


and the slanted side


86


, generally to the left in

FIG. 4

as shown by B


2


. Also, since more fluid volume will pass through the relatively larger space between the wall


28


and portions of the slanted side


86


closer to the top


80


, the flow is generally upwardly, as also shown by B


2


.




It can be readily appreciated that each weir


60


-


69


establishes its own fluid volume movement, the even-reference numbered weirs


60


,


62


,


64


,


66


, and


68


producing fluid volume movements substantially similar to B


1


, and the odd-reference numbered weirs


61


,


63


,


65


,


67


, and


69


producing fluid volume movements substantially similar to B


2


.




Thus, the fluid flows in a direction in a horizontal plane of the hydration tank


14


as depicted in FIG.


2


A and denoted by the reference arrow H


1


; whereas the fluid then flows in another direction in a horizontal plane of the hydration tank


14


as denoted by the reference arrow H


2


. The alternate juxtaposition of odd-reference numbered weirs


61


,


63


,


65


,


67


, and


69


and even-reference numbered weirs


60


,


62


,


64


,


66


, and


68


, along the walls


24


and


28


, respectively, and the staggered spaced openings, create an alternating pattern of flows H


1


and H


2


.




Also, the fluid flows in a direction in a vertical plane of the hydration tank


14


as depicted in FIG.


2


B and denoted by the reference arrow V


1


; and in another direction in a vertical plane of the hydration tank


14


as denoted by the reference arrow V


2


. As noted above, the alternate juxtaposition of the slanted sides of the odd-reference numbered weirs


61


,


63


,


65


,


67


, and


69


and even-reference numbered weirs


60


,


62


,


64


,


66


, and


68


, create an alternating pattern of flows V


1


, and V


2


. Thus, the movement of fluid (H


1


and H


2


, V


1


and V


2


) through the hydration tank


14


in the above manner lengthens the distance traveled by the fluid, thus increasing the residence time to ensure hydration of the fluid in the hydration tank


14


, and allows the use of faster flow rates.




Variations and Equivalents




It is understood that the number of weirs disposed in the hydration tank


14


is disclosed only for illustrative purposes and that the invention contemplates the use of any number of weirs to create a desired flow rate, the number and size of the weirs being readily calculable based on the hydration tank


14


dimensions and hydrating period. Furthermore, the plug flow efficiency will increase with additional number of weirs, up to a limit.




Furthermore, it is understood that while the weirs show a slanted side for deflecting the fluid, an embodiment is also contemplated wherein the weirs have straight sides and the walls of the hydration tank


14


are slanted to deflect the fluid. Moreover, although a mobile embodiment of the hydration tank


14


is depicted in the drawings, it is understood that the hydration tank


14


may have various immobile embodiments.




It is also understood that all spatial references, such as “top”, “bottom”, “left”, “right”, “front”, “back”, “downwardly”, “upwardly”, “horizontal”, and “vertical” are for illustrative purposes only and can be varied within the scope of the invention.




Furthermore, it is understood that the essential flow patterns shown in the figures and described herein are for example only and the flow patterns may have directions other than horizontal and vertical.




Although only a few exemplary embodiments of this invention have been described in detail above, those skilled in the art will readily appreciate that many other modifications are possible in the exemplary embodiments without materially departing from the novel teachings and advantages of this invention. Accordingly, all such modifications are intended to be included within the scope of this invention as defined in the following claims. For example, small holes may be cut in the bottom of each weir (at the intersection of floor


30


and bottom


74


in FIG.


3


and floor


30


and bottom


84


in

FIG. 4

) to facilitate complete drainage during cleanup.



Claims
  • 1. A hydration method comprising:defining an internal chamber within a set of wells; introducing fluid into the chamber; providing at least one weir extending from one of the walls and partially across the chamber towards an opposite wall; spacing a surface of the weir from the opposite wall and defining, with the opposite wall, a first space for fluid flow between the weir and the opposite wall that varies along a dimension of the chamber; providing at least one additional weir extending from the opposite wall and partially across the chamber towards the one wall, spacing a surface of the additional weir from the one wall and defining, with the one wall, a second space for fluid flow between the additional weir and the one wall that varies along another dimension of the chamber; so that the fluid flow from the inlet and through the spaces; and then discharging the fluid from the chamber.
  • 2. The method of claim 1 wherein the one wall and the opposite wall form side walls of the tank and wherein there is a top wall and a bottom wall between which the weirs extend.
  • 3. The method of claim 2 further comprising attaching the weirs to the top wall and to the bottom wall.
  • 4. The method of claim 2 where the first space increases in a direction from the top well to the bottom wall and wherein the second space decreases in a direction from the top wall to the bottom wall.
  • 5. The method claim 4 wherein the fluid flows in a general direction from the one wall, downwardly towards the opposite wall, through the first space, and upwardly towards the one wall.
  • 6. The method of claim 1 wherein the one wall and the opposite wall form side walls of the tank and wherein two end walls extend parallel to the weirs.
  • 7. The method of claim 6 wherein the weirs extend generally parallel to each other and to the end walls.
  • 8. The method of claim 6 further comprising forming an inlet through one of the end walls for introducing the fluid and forming an outlet through the other end wall for discharging the fluid.
  • 9. The method of claim 1 further comprising disposing the surface of the one weir at an angle to the opposite wall, and disposing the surface of the additional weir at an angle to the one wall.
  • 10. The method of claim 1 wherein there are a plurality of weirs extending from the one wall and a plurality of weirs extending from the opposite wall, and further comprising disposing the weirs extending from the one wall in an alternating relationship with the weirs extending from the opposite wall along the length of the tank.
  • 11. A hydration tank comprising:a set of walls defining a internal chamber; an inlet in fluid communication with the chamber for introducing fluid into the chamber; an outlet in fluid communication with the chamber for discharging the fluid from the chamber; at least one weir extending from one of the walls and partially across the chamber towards an apposite wall, a surface of the weir being spaced from the opposite wall and defining, with the opposite wall, a first space for fluid flow between the weir and the opposite wall that varies along a dimension of the chamber; and at least one additional weir extending from the opposite wall and partially across the chamber towards the one wall, a surface of the additional weir being spaced from the one wall and defining, with the one wall, a second space for fluid flow between the additional weir and the one wall that varies along another dimension of the chamber.
  • 12. The tank of claim 11 wherein the one wall and the opposite wall form side walls of the tank and wherein there is a top wall and a bottom wall between which the weirs extend.
  • 13. The tank of claim 12 wherein the weirs are attached to the top wall and to the bottom wall.
  • 14. The tank of claim 12 where the first space increases in a direction from the top wall to the bottom wall and wherein the second space decreases in a direction from the top wall to the bottom wall.
  • 15. The tank of claim 14 wherein the fluid flows in a general direction from the one wall, downwardly towards the opposite wall, through the first space, and upwardly towards the one wall.
  • 16. The tank of claim 11 wherein the one wall and the opposite wall form side walls of the tank and wherein there are two end walls connected to the side walls.
  • 17. The tank of claim 11 wherein the weirs extend generally parallel to each other and to the end walls.
  • 18. The tank of claim 16 wherein the inlet is formed through one of the end walls and the outlet is formed through the other end wall.
  • 19. The tank of claim 11 wherein the surface of the one weir extends at an angle to the opposite wall, and wherein the surface of the additional weir extends at an angle to the one wall.
  • 20. The tank of claim 11 wherein there are a plurality of weirs extending from the one wall and a plurality of weirs extending from the opposite wall, the weirs extending from the one wall being disposed in an alternating relationship with the weirs extending from the opposite wall along the length of the tank.
US Referenced Citations (10)
Number Name Date Kind
18201 Hammer Sep 1857 A
1976879 Ewer Oct 1934 A
2047539 Wolf Jul 1936 A
2137300 Allen Nov 1938 A
2980131 Williams Apr 1961 A
3126906 Touzalin et al. Mar 1964 A
4518261 Sekimoto et al. May 1985 A
4828034 Constien et al. May 1989 A
5046856 McIntire Sep 1991 A
5052486 Wilson Oct 1991 A
Non-Patent Literature Citations (2)
Entry
A PowerPoint presentation, initially authored by James McGough, was given to a customer on Jan. 23, 2001. The PowerPoint presentation is entitled “Conoco Hydration Tank.”
Experimental field testing of the above reference invention occured on Jan. 25, 2001.