Abstract:
A well treatment tool is installed along the sucker rod string of a well, within the surrounding production tube string. The tool provides for the distribution of a treatment fluid (solvent, etc.) within the fluid being pumped or flowing from the well. The tool receives treatment fluid through the hollow sucker rod string, and distributes the fluid through a valve which is set at a predetermined pressure. When the treatment fluid pumped down the sucker rod string from the surface exceeds the predetermined opening pressure of the valve, the treatment fluid is distributed into the production tube string through one or more passages in the tool. The present tool may be used simultaneously with well production, with fluid (oil, etc.) rising up the production tube string, carrying the treatment fluid therewith. The treatment fluid is thus distributed throughout the local fluid processing system, including pipelines from the well, any initial treatment operations, and any storage tanks. The present tool is particularly well adapted for the treatment of paraffin buildups within the production tube string of an oil well. The present tool may be used with both pumping wells and flowing (e.g., artesian) wells.

Description:
This is a Continuation prior application Ser. No. 09/697,931 filed Oct. 26, 2000, now U.S. Pat. No. 6,520,260 for “WELL TREATMENT TOOL AND METHOD OF TREATING A WELL” which claims the benefit of U.S. Provisional Application Serial No. 60/161,859, filed Oct. 27, 1999. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates generally to tools and equipment used in the oil, gas, and water well industry, and more specifically to a treatment tool which secures in line along the pump actuation or “sucker” rod string in a completed well hole. The treatment tool provides for the distribution and pressure regulation of a solvent or other fluid, which is pumped into the hole through the sucker rod for distribution into the production tube or pipe string. The device may be used to provide a continuous supply of solvent or other fluid to the oil or other fluid being pumped or delivered from the well, while the well remains in continuous operation. 
     2. Description of the Prior Art 
     Wells drilled in the ground for the drawing of subterranean fluid substances often encounter various problems with undesirable foreign matter which at least partially blocks the production tube or pipe string of the finished well and obstructs the pumping or flow of the fluid from the well. When this occurs, additional time and expense is encountered as the foreign material is removed from the well and fluid flow resumes. 
     This is particularly true in the oil industry, where subterranean crude oil deposits generally have less desirable substances mixed therein. One of these substances is called paraffin, a hydrocarbon which hardens to form a wax-like material as it cools. While the crude oil is universally quite warm or even hot at a depth from a few thousand to several thousand feet beneath the surface, it tends to cool as it rises up the production tube string of a producing well. When the paraffin rises to a depth where the ambient temperature is around 160 degrees Fahrenheit, it begins to solidify and adhere to the walls of the production tube string. The problem becomes worse with decreasing temperatures nearer the surface. 
     The solidifying paraffin will eventually block the oil flow from below, and require treatment of the production string in order to remove the paraffin buildup. This is conventionally done by mechanical means, electrical heating, hot water, and/or solvents introduced into the well. However, the various means of removing the paraffin from the production string generally require that flow from the well (either pumped or free flowing) be stopped while the treatment means is introduced into the well, and the well is treated. For example, chemical treatment using solvents is quite commonly used to remove paraffin buildup, but the chemicals are conventionally forced down the production string, in the opposite direction of pumped or natural flow. Obviously, oil cannot be recovered from the well during the time the chemical is being introduced into the well. 
     However, even if the paraffin buildup is removed from the production string, paraffin buildup may still occur in the oil processing and storage system after it leaves the well. Anywhere the temperature drops below the critical level of about 160 degrees Fahrenheit, paraffin will begin to harden in the system. Typically, oil leaves the well head to a tank battery, or series of storage tanks. The oil is then processed to remove water and gas mixed therewith, by heating in a heater treater. Paraffin makes it difficult to separate water from the oil, thus requiring additional heat (generally in the form of gas separated from the oil) to produce the desired reaction. Moreover, even if the paraffin is heated to melting in the heater treater, it will still solidify in valves, pipelines, and storage tanks prior to reaching the heater. 
     Accordingly, a need will be seen for a means of treating a producing well to remove foreign substances therefrom on a continuous basis, without interrupting the output of the well. The foreign substance removal means is particularly needed in the case of wells for oil with paraffin mixed therewith, to dissolve the paraffin and keep it in solution in the oil from a point in the well below the temperature at which it begins to solidify, and throughout the entire pipe and tank system of the oil field. While the present invention is particularly well suited for use in the oil production industry, it may also be adapted for use with other types of subterranean wells. A discussion of the related art of which the inventor is aware, and its differences and distinctions from the present invention, is provided below. 
     U.S. Pat. No. 4,011,906 issued on Mar. 15, 1977 to Harvey C. Alexander et al. describes a Downhole Valve For Paraffin Control, comprising a non-concentric (axially offset) valve which is assembled as a “sub” or short length of the production tube string. Solvent is forced down the production string to the valve, where a ball check valve is forced from its normally closed position by the pressure of the solvent, to allow the solvent to flow outwardly from the production string to the space between the production string and casing. It will be seen that the forcing of the solvent downwardly through the production string, which is normally used to deliver oil to the surface, requires that the well be shut down during the time that the solvent is being forced into the well. The present valve tool, adapted for inclusion as a “sub” in the sucker rod of the well, allows oil (or other substance being delivered by the well) to continue to flow upwardly through the production tube string without interruption, during treatment of the well. The solvent is carried up through the production tube with the flow of fluid being delivered from the bottom of the well, to flush paraffin or other substances from the production string. 
     U.S. Pat. No. 4,224,993 issued on Sep. 30, 1980 to Leonard Huckaby describes a Dewaxing Valve For Use In Oil Wells, comprising a valve mounted externally to the production tube, between the production string and the outer casing of the downhole. While the valve mechanism is somewhat different than that of the Alexander et al. valve discussed above, the operation is similar, with the well being shut down during the treatment process. 
     U.S. Pat. No. 4,279,306 issued on Jul. 21, 1981 to Robert D. Weitz describes a Well Washing Tool And Method, comprising a plurality of resilient packings on a “sub” which secures in line with the production tube string of the well. Pressure causes the central sleeves of the device to extend, thereby compressing the packings against the inner walls of the well casing. Sealing the device against the well casing routes the washing fluid through the perforated casing to wash any loose material away which may surround the outer casing. The fluid returns to the annulus between the casing and production tubing by perforations in the casing above the tool. Again, the well cannot produce oil or other fluid during use of the Weitz tool, as fluid under pressure is being forced downwardly through the production tube string, unlike the present invention where downward fluid flow is only through the hollow sucker rod. 
     U.S. Pat. No. 4,681,167 issued on Jul. 21, 1987 to Paul B. Soderberg describes an Apparatus And Method For Automatically And Periodically Introducing A Fluid Into A Producing Oil Well. The apparatus includes a valve placed in the downhole, which valve is actuated by pressure and/or movement of the sucker rod therethrough. The valve essentially fills the inside of the production tube string, with actuation either blocking or opening the valve to prevent or allow fluid to flow through the production string. The device operates generally in the manner described above for the other systems of the related art, in that fluid must be pumped downwardly through the production string from time to time in order to flush paraffin or other substances from the production tube string. This of course requires that fluid production from the well be stopped during the time that solvents or other fluids are being forced down the production tube string. While Soderberg states that “Present methods for removing such deposits employ hot oil, water or steam which is generally forced down the annulus between the production string and borehole casing” (column 1, lines 44-47), none of the related art discussed above, including Soderberg, do so. Rather, they force the fluid down the production tube string, rather than down the annulus between the production string and casing or wall of the downhole. 
     U.S. Pat. No. 4,995,462 issued on Feb. 26, 1991 to David Sask et al. describes a Dewaxing Control Apparatus For Oil Well, comprising a housing installed in line with the production tubing, as in the case of other devices discussed above. Dewaxing solvent or the like is pumped down the annulus between the well casing or wall and the production tubing, with the device blocking further downward flow therepast. The solvent then enters the interior of the production tube string by means of passages through the device, and is flushed back to the surface by means of the upward flow of oil through the interior of the production tube string. This is the only art of that discussed above, which causes the solvent to flow upwardly through the production string, in the manner of the present invention. However, Sask et al. still do not pump the fluid downwardly through the hollow sucker rod, or provide a valve which is installed in the sucker rod rather than the production tube string, as in the present invention. If the Sask et al. valve required removal from the hole, the production tube string would have to be lifted and disassembled at least to the depth of the valve. Such production tube removal would of course also require the removal of the entire sucker rod string before removal of the production tube string could take place. In the present invention, only the sucker rod string would have to be removed from the hole, with the production tube string remaining in place in the hole. 
     U.S. Pat. No. 5,056,599 issued on Oct. 15, 1991 to Walter B. Comeaux et al. describes a Method For Treatment Of Wells, comprising a telescoping valve which is axially offset from the production tube string, in a configuration somewhat similar to the device of the patent to Huckaby described further above. Comeaux et al. provide an initial balancing pressure in their valve by means of a compressed nitrogen charge, which holds the valve in a closed position until a superior pressure in the well downhole pushes the valve open. The Comeaux valve depends upon pneumatic means and differential pressure for operation, unlike the present well treatment tool, and also requires that production flow from the well be interrupted for the treatment fluid (hot water, solvent, etc.) to be introduced down the production tube string, where the Comeaux et al. valve routes it into the well casing. The present valve routes the solvent down the hollow interior of the sucker rod, where the valve is disposed, and routes the fluid outwardly from the sucker rod into the production tube interior. 
     U.S. Pat. No. 5,282,263 issued on Jan. 25, 1994 to John E. Nenniger describes a Method Of Stimulating Oil Wells By Pumped Solvent Heated In Situ To Reduce Wax Obstructions. The apparatus used in the method is an electrical resistance heater which is lowered to the bottom of the production tube string of the well. Solvent is then introduced into the well via the production tube string, and heated by the heater. As in all but one of the prior art devices discussed above, production must be stopped when the Nenniger method and apparatus is used in order for the solvent to be pumped into the well, downwardly through the production tube string. Moreover, the Nenniger apparatus and method circulates the solvent outwardly through the conventional passages in the lower end of the production tube string and casing, and into the surrounding geological structure. The Nenniger heater element also precludes the installation of a pump in the well, as it seals against the pump seating nipple at the bottom of the production tube string and takes the position of the pump. Thus, production must be suspended in a pumping well, with the pump and sucker rod removed for installation of the Nenniger apparatus. 
     PCT Patent Publication W092/06274 published on Apr. 16, 1992 to John E. Nenniger describes a Method And Apparatus For Well Stimulation. This patent publication corresponds to the U.S. patent to the same inventor, described immediately above, with the same differences and distinctions being noted. 
     U.S. Pat. No. 5,924,490 issued on Jul. 20, 1999 to Stone is directed to a well treatment tool which includes a generally cylindrical body installed in a sucker rod string. The body includes an upper end which has an axial fluid flow entrance passage which accepts treatment fluid from the sucker rod string, but which is plugged at the opposite end. A ball and seat valve assembly is provided which checks the flow of fluid between the hollow sucker rod string and the fluid flow passage way defined between the sucker rod string and the production tubing. 
     None of the above inventions and patents, either singly or in combination, is seen to describe the instant invention as claimed. 
     SUMMARY OF THE INVENTION 
     The present invention comprises a well treatment tool for introducing a solvent fluid or the like to a subterranean well. The tool is particularly adapted for use in removing solidified paraffin buildup from the inner wall of the production tube string of an oil well, but may be used in other well types and treatments as well. The present tool installs concentrically in line in the “sucker rod,” or pump actuating rod string, of a well, and receives solvent or other treatment fluid through the hollow core of the sucker rod. A valve, is provided to preclude unwanted or excessive flow of solvent fluid through the device until a predetermined solvent pressure has been reached, which pressure is controllable from above ground. When adequate pressure is achieved to open the valve, the solvent or other fluid flows from the interior of the hollow sucker rod, outwardly through the tool, and into the interior of the surrounding production tube string, where it is carried upwardly back to the surface along with fluid being pumped or otherwise delivered from the well. 
     The present well treatment tool is capable of treating a well at any depth, from the very bottom of the well adjacent the pump, to any intermediate depth. The tool may be installed at any point desired along the sucker rod, as a “sub,” or shorter unit of the rod string. Preferably, the tool is installed a few hundred feet below the point at which paraffin begins to solidify in the production tube string of an oil well, in order to be flushed upwardly with the oil to dissolve the paraffin buildup thereabove. 
     It will be seen that the present tool is capable of treating a well from the problem area below ground, through the entire above ground pipeline, initial treatment, and on site storage system. The solvent delivered by the present tool is disseminated from the tool upwardly throughout the downhole production tube, due to the oil being pumped or otherwise delivered from the bottom of the hole. The oil, with the solvent carried therein, continues to keep paraffin in solution throughout its travel through the above ground initial processing and storage tank system. 
     It will be noted that the present tool is not limited to use with a pumping type well, but may also be used with a flowing or artesian well. The tool may be lowered down the production tube at the end of a sucker rod string, to the depth desired, without connecting the sucker rod string to other components (e. g., pump) therebelow. 
     Accordingly, it is a principal object of the invention to provide an improved well treatment tool for installing concentrically in line with the sucker rod string of a production subterranean fluid well. 
     It is another object of the invention to provide an improved well treatment tool which accepts treatment fluid from the hollow core of the sucker rod string, and distributes the fluid into the interior of the surrounding production tube string. 
     It is a further object of the invention to provide an improved well treatment tool which includes valve means precluding backflow of fluid from the well through the tool. 
     An additional object of the invention is to provide an improved well treatment tool which is adapted for simultaneous treatment of fluid being delivered from the well during the time the well is producing, without requiring shutdown of the well. 
     Yet another object of the invention is to provide an improved well treatment tool which is adapted to treat fluid being delivered from the well, from the location of the tool in the well downhole throughout the above ground initial treatment and storage system. 
     It is an object of the invention to provide improved elements and arrangements thereof in an apparatus for the purposes described which is inexpensive, dependable and fully effective in accomplishing its intended purposes. 
     These and other objects of the present invention will become apparent upon review of the following specification and drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The novel features believed characteristic of the invention are set forth in the appended claims. The invention itself however, as well as a preferred mode of use, further objectives and advantages thereof, will best be understood by reference to the following detailed description of the preferred embodiment when read in conjunction with the accompanying drawings, wherein: 
     FIG. 1 is an environmental elevation view in section of the present well treatment tool, showing its features and operation. 
     FIG. 2 is an environmental view in section of a pumping well with the present treatment tool installed therein. 
     FIG. 3 is an environmental view in section of a pressure well with the present treatment tool installed therein. 
     FIG. 4A is a view of a perforated sub-coupling device. 
    
    
     Similar reference characters denote corresponding features consistently throughout the attached drawings. 
     DETAILED DESCRIPTION OF THE INVENTION 
     The present invention comprises various embodiments of a well treatment tool, indicated by the reference numeral  10  in FIGS. 1,  2  and  3 . The tool  10  is used to deliver a well treatment fluid, such as a solvent indicated by the arrows S of FIG. 1, into the production fluid flow (e. g., oil, indicated by the arrows O of FIG. 1) into the production tube string P. 
     As discussed in the introduction to the Description of the Related Art, fluids delivered from subterranean wells of various types often have various contaminants or impurities therein, which can contaminate the well and/or above ground initial processing and storage systems in some way or another. An example of this is the oil industry, where subterranean crude oil often includes some fraction of paraffin therein. While the subterranean crude oil is generally sufficiently far beneath the surface that the temperature is relatively high, perhaps two hundred degrees Fahrenheit or more, it will cool as it travels up the production tube string P of the well. Paraffin, normally in solution in the crude oil, will begin to precipitate out of solution as it reaches an elevation at or below the melting point of the substance, approximately 160 degrees Fahrenheit (depending upon the specific molecular weight and structure of the paraffin material. As it solidifies, it condenses on the relatively cooler inner walls I of the production tube string P. This paraffin buildup results in a reduction in cross sectional area within the production tube string, which reduces the oil flow within the string and thus the production of the well. 
     The tool  10  of FIG. 1 has a generally cylindrical body  12 , with an internally threaded upper or first end  14  and an opposite internally threaded lower or second end  16 . The threads of the two ends  14  and  16  are configured to mate with the cooperating internal threads of a hollow sucker rod R 1  (shown schematically), concentrically connected to the upper end  14  of the tool  10  are coupled to sucker rod R 2 . The tool may have pin or box connections on either end or any combination of pin and box connections. 
     The sucker rod string portions R 1  and R 2  are generally hollow, with a concentric passage A formed therein. Normally, no fluid is passing through or resident in the passages A; the rods R 1  and R 2  are hollow in order to reduce the weight of the sucker rod string, which can be considerable in a sucker rod assembly having a length of several thousand feet. However, the central passage A of the hollow sucker rod R 1  provides for the delivery of a fluid, such as the solvent S, therethrough to the present well treatment tool  10 . The tool  10  includes an axial passage  18  in the upper end  14  thereof, which communicates with and accepts the fluid or solvent S from the upper sucker rod passage A. A normally closed valve, is installed within the tool body  12  to control the flow of fluid of outward into the wellbore. 
     It will be recognized that the fluid (oil O, etc.) at some great depth in the well is at an extremely high pressure, with the well fluid O naturally tending to flow from the high pressure area within the production tube string P to the lower pressure area within the interior passage A of the sucker rod R 1  (assuming no back pressure of treatment fluid S exists within the interior passage A). Accordingly, a spring  22  is provided to hold the valve  20  against seat  21  in a normally closed position. The spring  22  may be calibrated to provide a predetermined pressure to hold the valve  20  closed, depending upon the depth at which the tool  10  is to be installed. Various calibration means (not shown), such as a separate threaded screw adjustment, shims or washers beneath the spring  22 , etc., may be provided to adjust the spring  22  pressure, as desired. 
     When treatment fluid S is applied through the sucker rod passage A at sufficient pressure, it forces the valve  20  away from seat  21  to open against the spring  22  to allow flow of fluid S downwardly through the valve and out of the tool body  12 , by means of one or more radial fluid distribution passages  18  and into the production fluid passage F defined between the inner wall I of the production tube string P and the body  12  of the tool  10 . (The inner diameter D of the production tube string P is considerably more than the diameter of the tool  10 , with the difference in the tool diameter  30  and production tube internal diameter D defining the production fluid passage F therebetween.) As the lower end  16  of the tool  10  is solid, the treatment fluid S cannot flow downwardly into the lower sucker rod R 2 . 
     As is shown in the view of FIG. 1, valve  20  includes a generally cylindrical movable valve member  51  which is biased upward by spring  22  and which resides within cylindrical cavity  53  formed within the tool body  12 . A plurality of sliding interface seals  56  may be provided on the exterior surface of cylindrical body  51 . Preferably, these seals comprise O-ring seals which are located within O-ring seal grooves (not visible in the view of FIG. 1) which are formed circumferentially in the exterior surface of cylindrical valve body  51 . The uppermost end of valve body  51  is contoured to define a raised seat portion  55  which is biased by spring  22  into sealing engagement with valve seat  21  which is carried in the upper portion  14  of tool  10 . The contour of valve seat  24  and raised seat portion  55  should provide for good sealing engagement. 
     FIGS. 2 and 3 disclose two different types of wells which might use the present tool  10  or any alternative embodiment. In FIG. 2, a pumping type well W 1  is shown, with a downhole pump U installed in the bottom of the well W 1 . A sucker rod string, comprising an upper sucker rod portion R 1  and a lower sucker rod portion R 2 , is installed generally concentrically down the production tube string P to actuate the pump U. The upper end of the string is alternately lifted by a well pump walking beam apparatus B, to cycle the pump U in the bottom of the well W 1 . Fluid pumped upwardly from the well W 1  through the production tube string P exits the well at the wellhead H, where it is initially treated to separate water and gas therefrom and thence passed via delivery lines and control valves L to a battery of storage tanks T. All of the above described components are conventional. 
     However, a well treatment tool  10  is installed as a “sub,” or shorter than standard length of sucker rod, between the upper and lower sucker rod string portions R 1  and R 2 , at some predetermined depth in the well W 1 . In an oil and/or gas well, this depth is determined by the temperature in the well downhole, and is at a point where the temperature is at or slightly above the melting point of any paraffin issuing from the well. A point approximately three hundred feet below the paraffin solidification point has been found to be suitable. A treatment fluid storage tank  32  is provided at the surface, with a treatment fluid line  34  extending to a treatment fluid pump  36 . (The pump  36  is shown at the walking beam B, but may be located at any practicable position, as desired.) 
     From the pump  36  the fluid is routed through a flexible high pressure line  38  (e.g., high pressure hydraulic hose, etc.) to accommodate the movement of the head of the walking beam apparatus. The line  38  is joined to the upper end of the sucker rod string at a connector  40 . The treatment fluid or solvent is thus pumped downwardly into the downhole of the well W 1 , through the hollow core of the sucker rod R 1 , until it reaches the well treatment tool  10 . The pump  36  pressure is increased to exceed the preset opening pressure of the valve spring  22  of the tool  10 , whereupon the well treatment fluid is injected through the axial fluid entrance passage  18 , past the valve  20 , and outwardly through the radially disposed passage(s)  28  of the tool  10  into the production fluid passage F defined between the tool  10  and the production tube string P. 
     As the production fluid (oil, etc.) is carried upward through the production fluid passage F by the action of the downhole pump U, it will carry the well treatment fluid upwardly with it to flush or wash contaminants (e. g., paraffin buildup) from the internal walls of the production tube string P. Thus, the treatment fluid or solvent does not travel farther downwardly in the downhole of the well, where it might be lost between the production tube string and the outer downhole casing or sleeve, or perhaps be dissipated into the fluid or oil bearing strata at the bottom of the downhole. The present well treatment tool  10  ensures that all of the treatment fluid or solvent will be delivered only to those points and locations where it is needed. 
     Once the production fluid, with the well treatment fluid mixed therewith, leaves the wellhead H, it may be distributed to an initial treatment area, such as a heater treater (not shown), where the substance, e.g., crude oil, is heated to separate water and gas therefrom. The crude oil or other fluid is then placed in storage tanks T of a tank battery. With the solvent fluid being mixed with the crude oil throughout the initial processing and storage steps, it will be seen that any paraffin will remain dissolved in a liquid state within the oil, even when the oil cools in the storage tank battery. Thus, the present invention serves to preclude the formation of paraffin solids not only in the well downhole, but throughout the above ground treatment and storage system. 
     The tool  10  may be installed in the sucker rod string by means of the externally or internally threaded ends, and a suitable coupling C, with an exemplary coupling depicted in FIG.  4 A. Tools of the present invention may be fabricated having one internally threaded end and an opposite externally threaded end to eliminate the need for a coupling. 
     FIG. 3 discloses a tool  10  installation in a flowing or artesian well W 2 , where subterranean pressure is sufficient to deliver the production fluid from the well without need for any pump means. Such wells W 2  are generally capped, and may have a lubricator E installed at the wellhead, as shown schematically in FIG.  3 . In such flowing wells W 2 , no pump is required at the bottom of the well, but a chemical pump is required at the surface. This precludes any requirement for a sucker rod string installation in the production tube string P, but a partial sucker rod string R 3  is installed through the lubricator E in order to suspend a well treatment tool, e. g., tool  10 , at a predetermined depth within the well W 2 . As no pump is installed at the bottom of the downhole, no lower sucker rod string portion need extend below the tool  10  within the production tube string P. 
     Operation of the tool  10  is essentially the same as that described above for the tool  10  of the pumping well W 1  of FIG.  2 . Treatment fluid is delivered from a storage tank  32   a  to a treatment fluid pump  36   a  via a delivery line  34   a , and thence to the upper sucker rod string R 3  by means of a high pressure line  38   a . Treatment fluid travels downwardly through the upper sucker rod string R 3 , until it reaches the tool  10  installed at the lower end thereof. The fluid then passes through the internal valve mechanism of the tool when sufficient pressure is provided by the treatment fluid pump  36   a  at the surface, to be distributed from the tool into the production fluid. 
     The treatment fluid or solvent then mixes with the production fluid in the fluid passage F between the tool  10  and the surrounding production tube string P, as in the case of the pumped well W 1 . Delivery of the mixed production and treatment fluids to the surface for further processing and storage is essentially identical to that described above for the pumped well W 1 , with the fluid mixture being delivered to an initial treatment area (not shown) and thence to a battery of storage tanks T via delivery lines and valves L. The mixture of paraffin solvent with crude oil serves to preclude the paraffin from settling out of solution with the oil as it cools in the storage tanks, thus obviating any periodic need to clean out the paraffin buildup in the bottoms of the storage tanks T. 
     The tension of the spring is set in a predetermined amount which in-part controls the flow of treatment fluid. The tension must be large enough to maintain the valve in a closed position most of the time. Only under certain pressure conditions is the valve opened. One factor is the “back pressure” on the well, which is established by the equipment settings at the surface on the back pressure valve. One other factor is the amount of pressure supplied to the column of treating fluid by the chemical pump which is also located at the surface. 
     Ignoring these factors (back pressure and pump pressure), the spring must provide enough force to keep the valve closed during most portions of the chemical pump cycle. For example, in a situation in which the tool is going to be located at 2,200 feet, and in which the sucker rod string is ⅜ of an inch in diameter, a column of Xylene treating fluid, for example, will weigh approximately A pounds. Of course, additional force is generated due to the pumping action which move the sucker rod string a known distance, but this force is typically about 10-20% of A pounds ordinarily. Therefore, the force of the spring is set for the valve in the range of approximately A+Y pounds to A+X pounds, and will accordingly open at a pressure amount somewhere in that range. 
     In the preferred embodiment, the valve will generate a full one-half inch opening. Fluid will pass out and mix with the wellbore fluids. In the preferred embodiment a well may need about two gallons of Xylene per day, so the tool should delivering less than one-half quart per hour. 
     If the back pressure value is set to a particular value a higher force setting will be required for the spring. 
     In summary, the present well treatment tool  10  will be seen to provide a much needed means of providing simultaneous treatment for a producing well, without need to shut down well production for treatment. The present tool  10  may be operated continuously, if needed, but treatment may be provided on an intermittent basis as required or desired, merely by operating the treatment fluid pump at the surface accordingly. The present well treatment tool and system could be configured to operate automatically, if desired, by means of pressure or flow transducers in the output lines. If a drop in pressure or flow is detected, a signal could be sent to operate the treatment fluid pump to clear any paraffin or other buildup until normal well output pressure or flow is obtained, whereupon the treatment pump is stopped. 
     While the structure and function of the present invention has been described generally in connection with subterranean fluid wells of various types (water, oil, etc.), it should be noted that the present tool embodiments are of particular value in the oil industry for the elimination of paraffin buildup along the internal walls of the production tube string in such a well, as described further above. The treatment of the oil from a point before or below that at which the paraffin begins to solidify, throughout the remainder of the surface treatment and storage system at the well, ensures that well production will be maintained and that downtime for cleanout and treatment of paraffin residue in the surface system will be eliminated. Thus, the present tool  10  will be seen to pay for themselves in short order in the oil industry, and their usefulness in other subterranean fluid well treatment fields will be appreciated as well. 
     It is to be understood that the present invention is not limited to the sole embodiments described above, but encompasses any and all embodiments within the scope of the following claims. 
     Although the invention has been described with reference to a particular embodiment, this description is not meant to be construed in a limiting sense. Various modifications of the disclosed embodiments as well as alternative embodiments of the invention will become apparent to persons skilled in the art upon reference to the description of the invention. It is therefore contemplated that the appended clams will cover any such modifications or embodiments that fall within the scope of the invention.