US 3713490 A
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United States Patent 1 1 Watson 1 1 Jan. 30, 1973 54 METHOD AND APPARATUS FOR 3,186,483 6 1965 Schwab ..l66/305 R SPQTTING FLUID DOWNHOLE [N A 2,488,819 11 1949 Larkin ..166/l94 BOREHOLE Primary Examiner-James A. Leppink Atmrney-Marcus L. Bates  ABSTRACT Method and apparatus for isolating the perforated area or production zone of a borehole, and subjecting the isolated portion to chemical treatment in a manner which enables the chemical to be placed into intimate contact with the production formation.
The apparatus includes a pre-loaded regulator type check valve assembly in combination with a by-pass means which is supported on the trail end of a tubing string. The by-pass means, when actuated, enables flow to occur in by-pass relationship to and from the tubing and borehole, and around the check valve assembly.
13 Claims, 7 Drawing Figures PATENTED JAN 30 um INVENTOR. BILLY RAY WATSON MARCUS L. BATES METHOD AND APPARATUS FOR SPOTTING FLUID DOWNHOLE IN A BOREI-IOLE BACKGROUND OF THE INVENTION In the art of producing oil and gas wells, it is often necessary to place a fluid; such as cement, acid, or a treatment chemical, at a specified location downhole in a borehole. For example, there are many formations which require treatment with one type of chemical prior to acidizing or fracturing the well so as to render the production formation closely adjacent to the perforations in the borehole in a condition which enables the treated formation to be solubilized when subsequently contacted with acid.
In chemically treating the fluid producing formation in accordance with previous methods, difficulty is often encountered for the reason that the fluid producing formation continuously flows toward the well bore, thereby diluting any treatment chemical which has been placed adjacent to the formation. This action greatly reduces the effectiveness of the entire treatment operation. It is therefore desirable to-be able to place a chemical or well treatment substance immediately adjacent to or in intimate contact with the fluid producing formation of a borehole, while increasing the downhole pressure the required amount to cause the normal production fluid flow direction to be reversed, that is, to flow towards or back into the formation. One means by which this expedient can be achieved is to load the well, that is, to fill the borehole annulus with sufficient fluid so as to produce a hydrostatic head which exceeds the downhole pressure. Such an endeavor is costly, and furthermore, there are wells which cannot be loaded in this manner because of their age and structural integrity.
Chemical treatment of a borehole is costly. It is desirable to limit the amount of chemical utilized in treating a well to the absolute minimum so as to effect a savings in both pumping and chemical cost.
SUMMARY OF THE INVENTION Generally, the present invention embraces method and apparatus for transporting a fluid to a specific location downhole within a borehole.
More specifically, the present invention is directed to both method and apparatus for transferring fluid to a predetermined location within a borehole by pumping the fluid downhole along an isolated flow path within the borehole and into close proximity of the location, releasing part of the fluid at a predeterminedpressure so as to enable the fluid to flow from the isolated flow path into the location; with the fluid pressure being increased to a value which precludes contamination of the pumped fluid with fluid which could otherwise be produced from the fluid producing formation.
The above method of this invention is attained by the provision of a tool sub which is supported by a tubing string. The tool sub includes a regulator check valve assembly which enables fluid to flow downhole when a predetermined pressure is applied to the fluid within the tubing string, and precludes uphole flow of fluid. Optionally included within the tool sub is a by-pass assembly comprised of a ball and fluid actuated valve element. The element, when actuated, enables uphole flow of fluid to occur and forms a by-pass around the check valve assembly.
A primary object of the present invention is the provision of a method of isolating a portion of a borehole with a fluid.
Another object of this invention is the provision of a method of treating the production formation of a borehole with a treatment chemical.
A further object of the present invention is a method of subjecting the fluid producing strata of a borehole to chemical treatment.
Still another object of this invention is the provision of apparatus for spotting fluid downhole in a borehole.
The above objects are attained in accordance with the method and apparatus as set forth and described in the abstract and summary of the invention.
These and other objects will become readily apparent to one skilled in the art upon reading the following detailed description and by referring to the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWING FIG. 1 diagrammatically sets forth a cross-sectional view of a portion of the earth, with the present invention being operatively disposed therein.
FIG. 2 is an enlarged longitudinal cross-sectional view of part of the apparatus disclosed in FIG. 1, with some additional parts thereof being'included so as to better illustrate the apparatus;
FIGS. 3, 4, 5, 6, and 7, respectively, are cross-sectional views taken along lines 33, 4-4, 5-5, 6-6, and 7-7 respectively, of FIG. 2.
DETAILED DESCRIPTION OF THE EMBODIMENT FIG. 1 schematically illustrates a pump truck, as indicated by the arrow at numeral 10, which is supported by the surface of the earth in the usual manner. The illustrated fluid conduit connects tubing 11 to the pumps associated with the truck. The tubing 11 is concentrically disposed within a borehole 12 which often extends several thousand feet into the earth. A well head 13, which can take on several forms, provides a closure member for the upper terminal end of the borehole. Perforations at 14 communicate a fluid producing strata 14' with the interior of the borehole. The
borehole may be cased all or part of its vertical length. A packer, schematically illustrated at numeral 15, is attached to the exterior surface of the tubing and to the interior surface of the casing, and prevents fluid flow thereacrosswhen the packer is properly set. The tubing string terminates at 16, with the lower marginal end portion of the tubing being in the form of one or more sub assemblies, hereinafter called a tool sub, which forms part of the present invention, and which is diagrammatically illustrated by the arrow at numeral 17.
The details of the apparatus used incarrying out the method of the present invention is more particularly shown in FIGS. 2-7. As illustrated in these remaining figures, tubing 11 has a lowermost pin thereof threadedly attached to the tool sub of the present invention. The tool sub is made up of an-upper sub 19 which is threadedly attached to a lower sub 20 by means of the illustrated threads at 21. Cap 22 is threadedly attached to the lower depending end of the lower sub with the cap and the sub having adjacent end portions as seen at 23.
The inside circumferential wall surface 24 of the upper sub is polished so as to slidably receive by-pass element 25 therein, with the interface between the element and the cylinder being fabricated or machined with close tolerance. The element is provided with a longitudinally extending orifice or central passage 26 which preferably is axially aligned with the remainder of the tubing string.
Spaced apart o-ring grooves, one of which is seen indicated by the numeral at 27, each receive an o-ring therein (not shown) so as to enhance the effective seal between the interface of the cylinder and the element. The lower face 28 of the element can be reciprocated into a lower position 29 when the element is forced to its lowermost extremity seen indicated in phantom at numeral 25'. Radially spaced apart stop members 30 are inwardly directed for a limited portion of the radius of the cylinder and presents a flat upper surface which abuttingly receives the before described lower surface 28 of the element.
Radially spaced apart ports 31 are normally positioned with respect to the element and the sub so as to preclude fluid flow from the ports into the cylinder, or vice versa. Therefore, the close tolerance of the outer wall surface of the element together with the presence of the before mentioned o-ring seals provide the required positive high pressure seal for the apparatus.
Shear pins 32 threadedly engage the wall of the sub and the element with sufficient force to normally prevents movement of the element until the pins are deliberately sheared, as will be explained in greater detail later on.
A valve seat member 33 forms a part of a relief valve assembly and is threadedly attached to a limited longitudinal portion of the inside wall surface of the upper sub by means of the threaded inner face 34. The seat 35 is formed on the lower side 36 of the valve seat member. Ball 37 forms a ball valve element which is normally urged into sealing engagement with the valve seat 35.
Valve piston 38 forms a part of the relief valve assembly and is provided with a centrally located concavity 39 which generally corresponds to the outer dimensions of ball 37. A circumferentially extending undercut marginal portion of the piston is seen at 40, and forms an annulus at 44' with respect to the inside circumferentially extending wall surface of the lower sub. The remaining outer wall surface of the piston at 41 is machined to provide a close fitting tolerance with respect to the inside peripheral wall surface which receives the piston. The lower face of the piston is provided with a circumferentially extending groove 42 which receives the upper terminal end of spring 43. Radially spaced apart ports 44 are always in communication with the chamber and the annulus 44.
The lower end of the sub is closed with a plug 45. The plug threadedly engages a marginal inside portion of the sub by the illustrated threads at 46; The upper face of the plug is provided with a circumferentially extending groove 47, which is similar to the groove seen at 42, for receiving the remaining end portion of the spring therein. Port 49 communicates the interior 41 with the exterior of the tool so as to prevent the occurrence of a pressure drop across the piston 38. The plug can be undercut at 49 if deemed desirable.
Numeral 50 indicates a free falling ball which can be made of steel, plastic, or hard rubber. The ball can be received in the indicated dashed-dot position seen at 50' so as to sealingly engage the contoured seat portion at 32 when it is desired to move the by-pass element from the stand-by position to the by-pass position.
OPERATION In operation, the tool sub is usually disposed on the tail end of the tubing string 11 with packer 15 lying above but in close proximity to the uppermost of the perforations 14. The pump truck motors are engaged and fluid, which can be any treatment chemical, is pumped down the tubing 11. Generally, a predetermined amount of treatment chemical will be released into the tubing, as for example, four barrels of liquid.
Prior to traveling downhole with the tool sub of the instant invention, the log of the well will have been consulted so as to determine the shut-in bottom hole pressure. The necessary force required to unseat ball 37 will have been preset at a value which will prevent fluid flow through the valve assembly until a pressure is delivered by the pumps of the truck into the tubing which exceeds the bottom hole pressure.
Assuming that ports 44 have been positioned below the lowermost casing perforations, and that packer 15 is ready to be set so as to isolate the portion of the borehole which is to be subjected to treatment, the pump motors of the truck may now be engaged so as to force the chemical from the tubing, through the ball valve assembly, and into the isolated portion of the borehole. As the four barrels of chemical are being spotted under the packer, a small quantity will flow around the packer as the well fluid is displaced from the isolated annulus. The packer is next set, and an additional two barrels of chemical are forced through ports 44 and into the annulus located below the packer the bottom hole pressure will naturally further increase during this step of operation since the treatment chemical cannot flow uphole and therefore it is forced back up into the hydrocarbon producing formation. The equipment is left dormant for several hours while the chemical reacts with the formation. Since the formation adjacent the borehole has been subjected to a pressure which exceeds its driving force, it follows that the well cannot make fluid and dilute the treatment chemical. This is so because fluid cannot flow past the interface between the casing and the packer, nor past the interface between the packer and the tubing string. The check valve assembly precludes flow of fluid back up through central passageway of the tubing string, while the spaced apart o-rings seated in groove 27 prevents flow of fluid through ports 31 and to the exterior of the sub. Accordingly, the treatment chemical is placed into intimate contact with the production formation, under pressure, all in a manner which prevents subsequent dilution thereof, whereby the formation can undergo proper treatment for any length of time desired.
Where the bottom hole pressure is lower than the hydrostatic head of the fluid contained within the tubpressure to a value which exceeds the hydrostatic head, otherwise the column of fluid contained within the tubing would be of a sufficient pressure to cause the valve element to open and fluid to flow into the location to be treated. Therefore, the preloaded ball check valve assembly precludes uphole flow of fluid at all times, and prevents downhole flow of fluid until a pump pressure of a predetermined value is effected at the ball valve element. This expedient enables a finite amount of chemical to be placed at a specific location downhole in a borehole.
Accordingly, when the pumping action stops, further fluid flow through the tool sub ceases because the regulator valve assembly assumes the closed configuration. Hence fluid flow is directly controlled by the pump pressure, and indirectly controlled by the spring tension of the biasing means, to enable an exact quantity of treatment fluid to be placed in the borehole and across the face of the fluid producing formation.
The extent of penetration of the chemical forced into the fluid producing formation can be closely controlled, so that the damaged portion of the formation can be treated immediately adjacent the perforations rather than back up in the production zone where it is desired to avoid contact of the formation with the treatment chemical.
Often a production formation will become damaged immediately adjacent the perforations, causing a large pressure drop to occur at this damaged area.
After treatment of the production formation has been completed, it is generally necessary to acidize or to fracture the well. Obviously, packer can be unseated and the acid pumped down the tubing string where it will displace the treatment chemical. It is desirable however, to remove the treatment chemical prior to acidizing. It is furthermore desirable that upon completion of the fracturing step that a dry tubing be pulled. For this reason ball 50 is dropped downhole where it becomes seated in the illustrated position 50'. Water or other liquid is pumped into the upper tubing portion thereby effecting a pressure differential across element 25, and when this force reaches a sufficient value, pins 32 will shear, thereby enabling the face 25 of the element to move a sufficient amount to uncover ports 31. Tubing 11 can now be swabbed back any desired amountprior to the acidizing and fracturing operation which is usually the next step of the well treatment.
Since element 25 has ball 50 seated thereon and has moved against stop members 30, acidizing will take place through ports 31.
After completion of the fracturing of the well, packer 15 is unseated, and the tubing string pulled in a dry condition. Stated differently, as the tubing string 11 is pulled, the liquid level in the last several uppermost joints will be below the floor surface of. the work-over rig because of the presence of port 31 which is now in communication with the tubing interior. Should the bypass valve be left out of the tool string, a wet string of tubing must be pulled, and this is always a distasteful job for the rough-necks even though the string may have been flushed with clean water.
Looking again to the details of thedrawings, it will be 6 seen that the tool, when in the stand-by configuration, operates as follows: fluid which flows through the interior of tubing 11 produces an insignificant pressure drop across element 25, dependent upon the diameter of orifice 26, and accordingly, shear pins 32 may be of any material such as brass or copper which requires several hundred pounds force in order to shear. It is unnecessary to seal the pins since the seals at 27 preclude fluid flow thereacross.
As fluid is forced to flow downhole and across stop members 30, the pressure is effected at the seated ball valve element 37. The frontal area of the ball which is wetted by the liquid determines the force which spring 43 must exert upon the ball in order to cause the ball to remain seated until a predetermined pressure is developed within tubing 1 1. Upon development of sufficient pressure to overcome the biasing force of the spring, piston 38 moves in a downward direction, thereby opening the valve so that fluid can flow out through ports 44 and into the formation. Hence for each individual well, the spring tension must be adjusted by placing a wrench at 48 and screwing the plug toward or away from the piston so as to pre-load the valve assembly the required amount.
When it is desired to bypass the check valve assembly, ball 50 is dropped into the illustrated position 50', and pressure is developed within the tubing until the pressure differential across the element is of a sufficient value to shear the pins.
Accordingly, those skilled in the art will realize that the present invention provides a means of spotting any chemical substance around the tail pipe of a tubing string; it provides a means for trapping chemical at a specified location within a borehole; and it provides a means of subjecting a fluid producing formation to pressure treatment. By utilizing the present invention, a specified amount of chemical can be spotted anywhere along a marginal longitudinal portion of a borehole.
Those skilled in the art of plugging old boreholes will realize the value of utilizing the instant invention for spotting predetermined quantities of cement at predetermined locations downhole in a borehole.
1. Method of treating a hydrocarbon producing formation of a borehole with a treatment chemical comprising the steps of:
l. supporting a packer means and a valve means on a tubing string and introducing the packer means and a regulator valve means into a well bore wherein the regulator valve means permits fluid in the tubing string to flow downhole and through an outlet downstream of the valve means when a sufficient pressure is developed within the tubing stringand prevents fluid from flowing uphole;
. presetting the regulator valve means to open at a value which exceeds the bottom hole pressure in the tubing string so as to prevent fluid flow downhole through the tubing string until the said bottom hole pressure in the tubing string is exceeded;
3. positioning the packer uphole of the hydrocarbon producing formation;
4. pumping treatment chemical down the tubing string nd through the regulator valve means so as to displace well fluid from close proximity of the hydrocarbon producing formation;
5. setting the packer so as to isolate a lower portion of the borehole which contains the hydrocarbon producing formation from an upper portion of the borehole;
6. increasing the pressure within the tubing string to a value which exceeds the formation pressure while forcing additional treatment chemical down the tubing string so as to subject the hydrocarbon producing formation to a pressure which exceeds the formation pressure; and,
7. removing the packer, valve means, and tubing string from the well bore after a sufficient time interval so as to enable the treatment chemical to act upon the formation.
2. The method of claim 1, and further including the step of:
8. forming a flow path which communicates the borehole annulus with the interior of the entire length of tubing string prior to carrying out step (7) so as to enable a dry tubing string to be removed from the well bore.
3. The method of claim 1, and further including the steps of:
8. interposing a relief valve between the regulator valve means and the packer;
9. actuating the relief valve prior to carrying out step (7) so as to equalize the difference in the downhole pressure and the tubing string pressure and enable a dry tubing string to be removed from the borehole.
4. The method of claim 3 wherein step (9) is carried out by running an obstruction downhole through the tubing string which engages and moves the relief valve to the open position.
5. The method of claim 1 and further including the step of adjusting the regulator valve means to cause flow to occur only when the pressure within the tubing string exceeds the formation pressure.
6. Method of spotting fluid adjacent to a hydrocarbon producing formation located downhole in a borehole comprising the steps of:
1. connecting a packer means and a regulator valve means in a tubing string; presetting the regulator valve means to open at a value which exceeds the bottom hole pressure; and, introducing the tubing string into the borehole so as to enable the packer means to be set at a location above the formation and at the same time place an outlet from the valve means in fluid communication with the formation;
2. pumping the spotting fluid down the tubing string so as to displace any well fluid from proximity of the formation;
3. setting the packer and forcing fluid down the tubing string so as to increase the pressure adjacent the formation being treated to a value which is equal to or exceeds the formation pressure thereby preventing fluid from the formation from diluting the spotting fluid;
4. unseating the packer means;
5. forming a fluid flow path at a location above the valve means which communicates the interior of the entire length of tubing string with the well bore;
6. removing the tubing string, packer, and regulator valve from the borehole.
7. The method of claim 6 wherein step (2) is carried out by pumping the spotting fluid through the regulator valve means by utilizing a surface pump to force the fluid to flow through the tubing string and into the borehole when the pressure within the tubing string outlet exceeds the shut-in bottom hole pressure at the outlet thereof.
8. The method of claim 6 wherein step (5) is carried out by interposing a relief valve assembly between the packer and the regulator valve means; and, actuating the relief valve means by a mass which is lowered through the tubing string and which forces the relief valve means to move into a bypass configuration.
9. The method of claim 6 wherein step (2) is carried out by pumping the spotting fluid through the regulator valve means by utilizing a surface pump to force the fluid to flow through the tubing string and into the borehole when the pressure within the tubing string outlet exceeds the shut-in bottom hole pressure at the outlet thereof; and
step (5) is carried out by interposing a relief valve means between the packer and the regulator valve means; and, actuating the relief valve means by a member which is transported through the string and into contact with the relief valve means so as to move the relief valve means into a bypass configuration.
10. The method of claim 6 wherein the displaced fluid which occurs during step (2) flows up the borehole and across the packer means prior to setting the packer in step (3).
11. Method of spotting fluid within a borehole adjacent to a hydrocarbon producing formation comprising the steps of:
l. running a tubing string into a borehole and placing the tubing string into a position which locates the fluid outlet of the tubing string below the hydrocarbon producing formation;
2. regulating the flow of fluid through the tubing string downhole towards the tubing string outlet, and, preventing the flow of fluid uphole through the tubing string outlet by placing a regulator flow valve means near the tubing string outlet;
3. pre-setting the regulator flow valve means at a value which will prevent fluid flowing through the tubing string outlet until the pressure within the tubing string exceeds the bottom hole pressure of the borehole;
. flow connecting the inlet of the tubing string to a source ofliquid spotting fluid;
5. increasing the pressure of the liquid spotting fluid within the tubing string to a value which causes spotting fluid to flow through the tubing string, through the regulator flow valve means, through the tubing outlet and into contact with the hydrocarbon producing formation; and
6. allowing sufficient lapse of time to expire so that the spotting fluid can treat the formation before removing the tubing string from the borehole.
12. The method of claim 11 wherein the portion of theborehole containing the production formation is isolated from the upper portion of the borehole by interposing a packer within the casing annulus at an elevation between the formation and the surface of the ground;
the step of:
7. forming a flow path between the tubing interior and the borehole at a location above the regulator flow valve means so as to enable dry tubing to be pulled from the well after the formation has been treated.