Viscosity control and filtration of well fluids
Circulating completion, workover and drilling fluids used in hydrocarbon recovery are filtered after monitoring for viscosity, which frequently causes plugging of filters. A viscometer generates a signal representative of viscosity in the fluid; the signal is used by a programmable controller to divert viscous fluid from the filter, or to take other action to prevent damage to the filter. The viscometer can be used in various positions in the system. Fluids deemed too viscous for the filter can be sent to a viscosity-reducing device, which may be a heating, shear-thinning, or cavitation device, to reduce its viscosity, enabling the fluid to pass through a filter without fouling. After filtering and a return to a lower temperature, the fluid may be treated if necessary to become viscous again for a useful purpose. A temperature monitor can be deployed on the fluid emerging or downstream from the cavitation or other device to assist in correlating temperatures to viscosities of various fluids. The cavitation device can also be used to increase the concentration of a dilute polymer-containing fluid to a usefully viscous value.
This is a division of, and claims full benefit of, application Ser. No. 11/804,986 filed May 21, 2007, which is a continuation-in-part of application Ser. No. 11/080,838 filed Mar. 14, 2005, now U.S. Pat. No. 7,231,973, which in turn claims the full benefit of provisional application 60/553,590 filed Mar. 15, 2004, all of which are specifically incorporated herein by reference.
TECHNICAL FIELDThe filtration of well treatment fluids is improved by monitoring the fluids for viscosity, and diverting or treating the fluid when there is danger of filter clogging due to gel formation. Treatment includes heating and/or shear-thinning to reduce viscosity; certain filters may also effect shear-thinning. A useful viscosity can be restored after filtering if necessary.
BACKGROUND OF THE INVENTIONIn the production of oil and gas from the earth, drilling and completion fluids are commonly recirculated through a filter. The benefits of clean completion and drilling fluids have been well established. The most common method of filtering the completion and drill-in fluids has been the use of diatomaceous earth (sometimes briefly “DE”) filters and cartridge filters. In either case, the conventional filters are satisfactory for removing simple contamination, but frequent shutdowns are required to remove cake from the DE filters and to replace the cartridge filters. Cake or other solids buildup is detected or assumed from an increase in pressure or a decrease in flow rate. Cake and/or other solids cannot normally be removed by backflow or otherwise from cartridge filters, which utilize porous media. The expensive cartridge filters must be replaced.
Unfortunately, caking and solids loading of the filters are not the only causes of decreased flow or increased pressure. The widespread use of gelling agents, viscosifying agents and the like in brines, drilling mud, cleaning sweeps, and other well fluids greatly increases the incidence of filter fouling. They may be introduced to the fluid in the form of dissolved powder, circulation “pills,” viscosifying solutions, and by any other means or in various solutions known to the hydrocarbon production art. The gels or viscous liquids can include, most commonly, hydroxyethylcellulose (HEC), but xanthan gum, various guar gum derivatives, polyacrylamide and other synthetic water soluble polyacrylates are frequently introduced to wellbores.
When circulated gel-inducing agents reach a fluid return tank or holding tank, they can remain intact or become mixed into the completion fluids. Almost immediately as the gel-inducing agents enter a filter, they are likely to blind off a DE filter or plug cartridge filters. This blinding off requires a total shut down and cleaning of the filter as previously described. In the case of the DE filter, a minimum of one hour is required before filtration can resume, costing valuable rig time and expense. Replacing cartridge filters is likewise time consuming and expensive as some filter pods may hold as many as fifty (50) elements per housing.
In the current practice of filtration of well treatment fluids, there is no defense against the sudden introduction of fouling polymers and gels in the fluid entering the filters. Sudden and drastic reductions in flow and increases in pressure are common and the operators of the filters must be prepared almost without notice to shut down the filters and take action to return them to working order. Such interruptions in normal procedures are very expensive, especially in off-shore rigs and other remote sites.
Another difficulty in the re-use of well treatment fluids, and the preparation of fresh ones, is that polymeric additives can be present in a concentration too high or too low. In the case of recycled fluid, where several desired additives are present also but in varying concentrations too dilute for effective use, the question of how most efficiently to adjust them while also adjusting the polymer concentration is perplexing.
SUMMARY OF THE INVENTIONThe invention utilizes an in-line viscometer capable of detecting low viscosity fluids—that is, a viscosity slightly increased over the usual viscosity of the substantially gel-free fluids normally processed by the filter. A viscosity reading from the viscometer is connected to a programmable controller that is activated when a fluid exceeds the programmed threshold settings for allowable viscosities. The programmable controller can be programmed to do one or more of a) stop the pump, b) switch valves and by-pass the filter unit, diverting the contaminated fluid to a separate designated holding tank where chemical treatments will break the viscous fluid, c) provide a read-out or alarm for operating personnel, and d) re-establish filtration once fluid returns to below threshold levels.
One additional approach of our invention is to heat an unacceptably viscous fluid to reduce the viscosity prior to filtration. This is especially useful and economic where the viscosity-imparting agent is not significantly degraded by heating and where the viscosity-imparting properties are restored by cooling.
Generally, a viscous liquid will become less viscous as it is heated, although there are exceptions depending on the chemistry of the liquid. Oil and other hydrocarbon well brines commonly not only include various salts and other chemicals, but include polymers added to enhance the viscosity of the fluid for various purposes, principally to assure or enhance the suspension of solid particulates such as proppants, drill cuttings, sand or debris from the well. Polymeric compounds such as guar, xanthan, polyacrylamide, carboxymethylcellulose, and various derivatives of each are commonly used as viscosifiers in oil well fluids, and studies substantiate that the viscosities of typical such oilfield polymer-containing fluids generally decrease with increasing temperature—see, for example, Patel U.S. Pat. No. 5,134,118 and especially FIG. 2 of Morales et al U.S. Pat. No. 6,981,549. This is consistent with the viscosity/temperature relationships of non-Newtonian fluids in general. While the results may vary somewhat with the remainder of the compositions in actual practice, including the amount and type of solids in them, and with other conditions such as pH and hydrolysis, correlations of temperatures to viscosities are demonstrable in almost all cases where there are not overriding chemical reactions. The presence of significant amounts of clays such as diatomaceous earth should also be considered in some instances. But in most cases, the operator of a particular fluid processing system will know or be able to determine what is in the fluid he expects to filter, and can estimate within a useful degree of accuracy the concentration of polymer required to yield a particular viscosity at a given temperature. The relationship of temperature to viscosity in the commonly used guar and guar derivatives such as hydroxypropylguar (HPG), carboxymethylhydroxypropyl guar (CMHPG), cellulose derivatives such as hydroxyethyl cellulose (HEC), xanthan gum and various xanthan derivatives has been amply shown. See Monograph Volume 12, SPE, Henry L Doherty Series, Chapter 7, by John W. Ely, of “Recent Advances in Hydraulic Fracturing” by Gidley, Holditch, Noroda and Veath, pages 131, 133-134. See also Chapter 9 “Fracturing-Fluid Flow Behavior” by Cameron and Proudhomme in the same publication, pages 184, 186.
Oilfield fluids containing viscosity-imparting agents are almost always non-Newtonian, in that their viscosity will change as a function of shear rate. See the entire Cameron and Proudhomme chapter cited in the Gidley et al book cited above (pages 184-195. Accordingly, another aspect of our invention is that a reduction of the viscosity which had been attained due to the presence of a viscosity-imparting agent in the fluid to be treated may be achieved by shear-thinning, a well-known phenomenon and procedure which may occur when a viscous fluid is passed between two surfaces; frequently one surface is moving with respect to the other. For our purposes, shear-thinning is defined as a reduction in viscosity effected by shear on or in a polymer-containing fluid. It is immaterial for purposes of our definition whether the shearing causes a physical degradation of the polymer, or a new orientation or deployment of the polymer backbone in solution, or a disruption of crosslinking bonds, or a chemical result such as a change in hydrolysis of the polymer. While many if not most polymers used in oilfield fluids cause the fluid to be thixotropic, it is not essential in our invention for the thixotropic properties of the fluid to be related to the reduction in viscosity caused by shearing. Nor is the fact that the shear effect may be reversible, or irreversible, or only partially reversible when the shearing force is removed or, if the reduction in viscosity is time-dependent, may change in viscosity at some point in time after the shearing force is removed. We may utilize the shearing effect to our advantage by reducing the viscosity of a fluid which is too viscous to pass through a filter without premature fouling, in order to filter it, regardless of the physical or chemical mechanism which brings about the reduction in viscosity.
While we have described our invention in some instances using a cavitation device, which is defined below, we may also use various shear-thinning devices or machines which do not provide heating by cavitation. Such devices include, broadly, dynamometers (some of which have come to acquire that name in spite of the fact they may not measure anything) and water brakes. Water brakes and other types of absorbing dynamometers convert the energy of a rotor on a turning shaft into thermal energy due to the turbulence and/or shear-thinning generated in the water in which it is immersed. In the description below, shear-thinning may accompany heating in the cavitation device or it may be accomplished apart from a significant heating effect in any other context. We intend to include either shear-thinning or heating devices to reduce the viscosity of the used oilfield fluid, as well as devices which normally accomplish both shear-thinning and heating, such as a cavitation device. Electric heating devices of various known kinds can be used simply to elevate the temperature of the fluid, as can various heat exchangers acting to transfer waste heat from Diesel engines, compressors and the like which may be present at the site.
Where large volumes of fluids are to be filtered, the viscometer is preferably located in a bypass or sampler line for a more or less continuous sample of fluid. Also, a basket strainer or similar device may be inserted in the sampler line upstream of the viscometer to protect it from damaging objects in the fluid.
Our invention includes the incorporation of a screen, notably a wedge wire screen, upstream of the filter to intercept solids of a predetermined size before they meet the filter medium.
The invention will maximize filter life, maximize dirt holding capacity, save rig time & expense, reduce fluid loss due to contamination and waste, minimize disposal cost, and reduce operating costs.
The invention is particularly useful in conjunction with a filter of the type described by Asher and Hampton in U.S. Pat. No. 5,824,232 titled “Corrugated Filter Sheet Configured into a Cylindrical Filter Media having Near Circular Concentric Channels,” incorporated herein by reference in its entirety. Filters of sintered plastic particles are also useful—see U.S. Pat. Nos. 6,030,558 and 6,399,188 to Smith and Fullerton, wherein rapid water quenched polyolefin pellets are compacted into a desired filter shape and fused at their points of contact to form permeable shapes and masses. Although any filter satisfactory for filtering well fluids can be used we have found that the sintered pellet filters of Smith and Fullerton will filter and shear-thin at the same time. Thus the viscosity of the fluid need not be reduced prior to filtering. Also, such a filter may be advantageously considered where, for whatever reason, heating may permanently damage the polymer; in this case, shear-thinning without significant heating can be accomplished in filters of sintered particles. Such filters could be used also where the polymer is known to recover its viscosity-imparting properties within a few seconds after the cessation of shear-thinning. The Smith and Fullerton U.S. Pat. Nos. 6,030,558 and 6,399,188 are hereby specifically incorporated herein in their entireties.
In
In
As indicated above, clogging of the filter 5 will cause circulation of fluid to be suspended, as the filter is cleaned or replaced. Clogging is accelerated by viscous fluid reaching the filter surface. Frequent and disruptive clogging is expensive and time-consuming.
Optionally, a viscometer may be placed to monitor a slip stream on line 7 (viscometer 12b) or in line 9 directly downstream from pump 4 (viscometer 12c), in each case being equipped to generate a signal representing viscosity which may be used for one or more of the purposes (a) to (d) listed above, or to supplement the signal generated by viscometer 12a. In addition, if a reading in viscometer 12b is high, the fluid in line 7 may be directed immediately to viscous fluid tank 14 or elsewhere; by this procedure, the dirty fluids return tank will not be full of gel-producing material when the threshold reading is reached; rather, the liquid in the dirty fluids tank 3 would still be satisfactory for sending to the filter for some time after the point when undesirably viscous fluid begins coming from the well.
The viscosity signal may also be used to control the feeding of calcium hypochlorite, sodium hypochlorite, or other material from container 16 to the viscous fluid tank 14. These materials are known to be effective in reducing the molecular weight of hydroxyethylcellulose, a common viscosifying agent, but any chemical agent useful for reducing the viscosity of the viscous fluid diverted to viscous fluid tank 14 may be used. Programmable controller 15 can deliver such de-viscosifiers to viscous fluid tank 14 at a rate more or less proportional to the amount of viscous fluid diverted to it. Of course, feeding of the de-viscosifying agents to tank 14 could be accomplished manually or by mechanical means independent of the programmable controller.
Except for line 17 connecting programmable controller 15 with computer 19 and phone 18, the electrical connections in
To perform in an offshore facility or other harsh environment, the viscometer should contain no moving parts to wear or bind. It should be built out of 316 stainless steel, easy to clean and with low maintenance. The viscometer should be capable of pressures up to 200 psi and operate in temperatures up to 250° F. The viscosity range should be from 2 cP to 3000 cP or equivalent cup-seconds. The main focus should be on a meter that is designed for low viscosity fluid and operates at low hertz without fluid interference or impedance. Viscometers which operate using vibrating forks or rotating bobs but are generally not sensitive to low viscosity fluids and are therefore only applicable to high viscosity readings. The viscometer should be chosen with the desired threshold or cutoff viscosity in mind, as well as the conditions of use.
A screen such as depicted in
The viscometer may be operated continuously or intermittently, and the control signal(s) may also be generated either continuously or intermittently.
Our invention also includes the use of a viscometer in combination with a cavitation device (sometimes referred to herein as “SPR,” derived from the term “shockpower reactor”), usually together with temperature or additional viscosity monitoring. In this aspect of our invention, dirty fluid from a well is monitored first for viscosity. If the viscosity is above a predetermined value deemed too viscous for the filter, the fluid is diverted to pass through an SPR, where it is heated and/or shear-thinned as will be explained below. In a version of the invention using a cavitation device, described below and with respect to
Preferably the SPR, or cavitation device, is one manufactured and sold by Hydro Dynamics, Inc., of Rome, Ga., most preferably the device described in U.S. Pat. Nos. 5,385,298, 5,957,122 6,627,784 and particularly U.S. Pat. No. 5,188,090, all of which are incorporated herein by reference in their entireties. In recent years, Hydro Dynamics, Inc. has adopted the trademark “Shockwave Power Reactor” for its cavitation devices, and we use the term SPR herein to include the products of this company. The term “cavitation device” as used herein includes SPR's and cavitation devices of other designs or origins that can be used in our invention.
Definition: We use the term “cavitation device,” or “SPR,” to mean and include any device which will impart thermal energy to flowing liquid by causing bubbles or pockets of partial vacuum to form within the liquid it processes, the bubbles or pockets of partial vacuum being quickly imploded and filled by the flowing liquid. The bubbles or pockets of partial vacuum have also been described as areas within the liquid which have reached the vapor pressure of the liquid. The turbulence and/or impact, which may be called a shock wave, caused by the implosion imparts thermal energy to the liquid, which, in the case of water, may readily reach boiling temperatures. The bubbles or pockets of partial vacuum are typically created by flowing the liquid through narrow passages which present side depressions, cavities, pockets, apertures, or dead-end holes to the flowing liquid; hence the term “cavitation effect” is frequently applied, and devices known as “cavitation pumps” or “cavitation regenerators” are included in our definition. Steam or vapor generated in the cavitation device can be separated from the remaining, now concentrated, water and/or other liquid which frequently will include significant quantities of solids small enough to pass through the reactor. The term “cavitation device” as used herein includes not only all the devices described in the above itemized U.S. Pat. Nos. 5,385,298, 5,957,122, 6,627,784 and 5,188,090 but also any of the devices described by Sajewski in U.S. Pat. Nos. 5,183,513, 5,184,576, and 5,239,948, Wyszomirski in U.S. Pat. No. 3,198,191, Selivanov in U.S. Pat. No. 6,016,798, Thoma in U.S. Pat. Nos. 7,089,886, 6,976,486, 6,959,669, 6,910,448, and 6,823,820, Crosta et al in U.S. Pat. No. 6,595,759, Giebeler et al in U.S. Pat. Nos. 5,931,153 and 6,164,274, Huffman in U.S. Pat. No. 5,419,306, Archibald et al in U.S. Pat. No. 6,596,178 and other similar devices which employ a shearing effect between two close surfaces, at least one of which is moving, such as a rotor, and/or at least one of which has cavities of various designs in its surface as explained above.
In the context of the present invention, where the objective is to control the viscosity of the used fluid, especially for a filtration step, the shearing effect, known commonly as shear-thinning, can be at least as important as heating, depending on the type of polymer present. As indicated above, some polymers are able to withstand heating, or shear-thinning, or both with little effect on their viscosity-imparting properties. Others may be reduced in viscosity primarily or even exclusively by shear-thinning.
Referring now to
In
It should be understood that the necessary pumps, valves, and controls are not shown in
Also, in any of the methods, systems or configurations contemplated herein, it should be understood that the fluid may be recycled through the viscosity-reducing device, whether it is a heater, a shear-thinning, device, a cavitation device, or other viscosity-reducing device. For example, in
Referring again to
In the description of
As many polymer-containing oil well fluids are thixotropic, the action of a cavitation device will in some cases exhibit a shear-thinning effect as well as a heating effect. As noted in the definition of “cavitation device” above, an important effect of a cavitation device is to induce cavitation, which imparts heat to the fluid, but the flow patterns which bring about cavitation typically include flow in narrow passages and especially between closely parallel surfaces, one of which is moving, resulting in shear-thinning if the fluid is thixotropic, or if it is physically degraded by the shearing and/or turbulent flow in the cavitation device. As is known in the art, a polymer-containing fluid may be, at least to some extent, reversibly thixotropic. Return to its original viscosity may be time-dependent—that is, it may not assume its previous relatively high viscosity immediately on discontinuing shearing; accordingly, whatever shear-thinning effect there is on such a fluid in the cavitation device may be expected to last through the filtration step.
It was mentioned above that fluid may be recycled through the viscosity-reducing devices 67 of
The discerning reader may recognize that the concentration of polymer in the fluid emerging from the flash tank 85 in line 87 may be in a range such that, after passing through the filter 65 and cooling, will produce a viscosity in the range determined to be useful in an oilfield fluid, although this is not essential in our invention. Thus the SPR will restore the polymer to a desired concentration, at the same time assuring that the dirty fluid can be properly filtered. The filter handles lower volumes of fluid in cases where an original dilute dirty fluid would otherwise require passing a larger volume of fluid through the filter 65. Nevertheless, a filter 89 may be provided as an option where, for whatever reason, it is believed desirable to filter the dilute dirty fluid upstream (on line 72) to the SPR 67. Another option for fluids which are too dilute in polymer and thus not viscous enough for re-use is to add polymer. Low viscosity dilute fluids may occur either as a result of water mixing into the fluid in the formation or in the well, or, as a result of chemical of physical breakdown or degradation of the polymer. Some polymers are pH-sensitive, some are affected by the degree of hydrolysis, some have crosslinkages that are affected by the chemistry of the rest of the solution, and others are subject to breakdown or rupturing of their long molecules as a result of physical stress, sometimes complicated by high temperatures. A chemical feeder such as feeder 91 on line 59 may be installed to respond to readings from viscometer 64 or an additional feeder (not shown) similar to feeder 91 placed on line 61 or on line 83, to make desired adjustments in viscosity by pH, the addition of crosslinkers, polymers, or other chemicals, to enhance the viscosity of the fluid in line 83 if it is desirable to do so.
Some viscosity changes are permanent and others are restorable. Our invention provides that if the polymer loses its viscosity-imparting abilities, or a part of them, in a manner which cannot be restored without adding more, additional polymer can be introduced after filtering, not only in line 59 or 83, but in clean fluid tank 71 or a more topical point of use. If the reduced ability to restore viscosity is temporary, such as due to a change in pH or some other chemical effect, we can provide for appropriate additions to the fluid. Ideally, the operator will be aware of the reversibility and time-dependent thixotropic properties of the fluid, and take them into account in the calculations of the additives needed or desired for the next use in a well, and these future considerations can be programmed into the controllers and/or chemical feeders discussed above.
An original fluid determined to have a viscosity too high for filter 65 will normally bypass flash tank 85—that is, the fluid heated and/or shear-thinned in the SPR will have a reduced viscosity and accordingly will be sent directly to filter 65 from the SPR 67 by way of line 82, similar to
A housing 110 in
Operation of the SPR (cavitation device) is as follows. A shearing stress is created in the solution as it passes into the narrow clearance 112 between the rotor 111 and the housing 110. This shearing stress (shear thinning) causes an increase in temperature and/or a reduction in viscosity. The solution quickly encounters the cavities 117 in the rotor 111, and tends to fill the cavities, but the centrifugal force of the rotation tends to throw the liquid back out of the cavity, which creates a vacuum. The vacuum in the cavities 117 draws liquid back into them, and accordingly “shock waves” are formed as the cavities are constantly filled, emptied and filled again. Small bubbles, some of them microscopic, are formed and imploded. All of this stress on the liquid generates heat which increases the temperature of the liquid dramatically, contributing to the decrease in viscosity of a viscous solution, or facilitating removal of vapor or steam in the case of a dilute fluid. The design of the cavitation device ensures that, since the bubble collapse and much of the other stress takes place in the cavities, little or no erosion of the working surfaces of the rotor 111 takes place. Any solids present in the solution, having dimensions small enough to pass through the clearances 112 and 113 may pass through the SPR unchanged except in concentration where water is removed.
Thus it will be seen that our invention includes a method of treating a used well fluid containing a viscosity-enhancing agent, comprising passing the fluid through a filter capable of shear-thinning the fluid to reduce its viscosity while also removing solids from the fluid. The filter will desirably be made of sintered polyolefin particles having diameters no greater than one-eighth inch.
While our invention will operate with respect to any viscosity-enhancing agent in a used well fluid, guar and its derivatives, xanthan and its derivatives, and various cellulose derivatives known for their viscosity-imparting properties are especially contemplated.
In addition, our invention includes a method of treating a used well fluid deemed too viscous to pass through a filter without a risk of plugging the filter because of its viscosity, comprising heating or shear-thinning the used well fluid, thereby reducing its viscosity, and passing the fluid having a reduced viscosity through the filter. The heating or shear-thinning may be accomplished at least partly by passing the fluid between two surfaces, at least one of which is moving relative to the other, thereby reducing its viscosity, and then passing the fluid having a reduced viscosity through a filter. Our invention also includes a method of processing a dirty well fluid comprising measuring the viscosity of the well fluid, passing the well fluid through a cavitation device if the fluid is deemed too viscous to be filtered, thereby reducing the viscosity of the fluid, and filtering the fluid thereby obtained. The effect of the cavitation device may be either primarily to heat the fluid, or primarily to shear-thin the fluid, or it may have more or less variable effects of both heating and shear-thinning. Operation of the heater, shear-thinning device, cavitation device, or other viscosity-reducing device may be controlled intermittently or substantially continuously as a function of viscosity, temperature, or pH, of the treated fluid, or the concentration of any constituent therein from which viscosity of the treated fluid may be inferred.
Our invention also includes a method of filtering and conserving an oil well fluid containing a viscosifying agent comprising (a) monitoring the viscosity of the fluid, (b) if the viscosity of the fluid is deemed too high to pass through a filter, reducing the viscosity thereof to a value acceptable for filtering, filtering the fluid and recovering the filtered fluid for reuse of at least a portion of the fluid as a well fluid or a well fluid component, (c) if the viscosity of the fluid is deemed too low to be reused, removing water therefrom, thereby obtaining a concentrated fluid, filtering the concentrated fluid, and recovering the filtered concentrated fluid for reuse of at least a portion of the fluid as a well fluid or a well fluid component, and (d) if the viscosity of the fluid is neither deemed too high to pass through a filter nor too low for the fluid to be reused, filtering the fluid and recovering the filtered fluid thus obtained for reuse of at least a portion of the filtered fluid as a well fluid or a well fluid component.
Claims
1-20. (canceled)
21. Method of treating a used well fluid containing a viscosity-enhancing agent, comprising passing said fluid through a filter capable of shear-thinning said fluid, thereby reducing its viscosity while also removing solids from said fluid.
22. Method of claim 21 followed by reusing said fluid in a well.
23. Method of claim 21 wherein said viscosity-enhancing agent is a xanthan derivative.
24. Method of claim 23 followed by adjusting the hydrolysis of said xanthan derivative after it passes through said filter, whereby the viscosity of said fluid is enhanced.
25. Method of claim 24 followed by reusing said fluid in a well.
26. Method of claim 21 wherein said viscosity-enhancing agent is a guar or guar derivative.
27. Method of claim 26 wherein said guar or guar derivative is crosslinked.
28. Method of claim 21 including adding viscosity-enhancing agent to said fluid after said fluid passes through said filter.
29. Method of claim 21 wherein said filter comprises sintered particles.
30. Method of treating a used well fluid deemed too viscous to pass through a filter without a risk of plugging said filter because of its viscosity, comprising heating said used well fluid, thereby reducing its viscosity, and passing said fluid having a reduced viscosity through said filter.
31. Method of claim 30 wherein said heating is performed at least partly by passing said fluid between two surfaces, at least one of which is moving relative to the other.
32. Method of claim 30 followed by passing said filtered fluid through a heat exchanger to preheat said used well fluid, followed by treating said preheated used well fluid by the method of claim 30.
33. Method of treating a used well fluid deemed too viscous to pass through a filter without a risk of plugging said filter because of its viscosity, comprising shear-thinning said used well fluid, thereby reducing its viscosity, and passing said fluid having a reduced viscosity through said filter.
34. Method of claim 33 wherein said shear-thinning is performed at least partly by passing said fluid between two surfaces, at least one of which is moving relative to the other.
35. Method of claim 33 followed by adding viscosity-enhancing agent to said filtered, reduced viscosity fluid to increase its viscosity for reuse in a well.
36. Method of processing a dirty well fluid comprising optionally measuring the viscosity of said well fluid, passing said well fluid through a cavitation device if said fluid is deemed too viscous to be filtered, thereby reducing the viscosity of said fluid, and filtering the fluid thereby obtained.
37. Method of claim 36 wherein said reduced viscosity is obtained primarily by heating in said cavitation device.
38. Method of claim 36 wherein said reduced viscosity is obtained primarily by shear-thinning in said cavitation device.
39. Method of claim 36 including recycling at least a portion of said reduced viscosity fluid through said cavitation device.
40. Method of claim 36 including substantially continuously controlling the operation of said cavitation device to maintain a viscosity in said fluid emerging from said cavitation device such that said fluid is not deemed too viscous to be filtered.
41. Method of claim 40 including monitoring the temperature of said fluid emerging from said cavitation device and wherein the viscosity of said fluid is maintained by controlling the operation of said cavitation device to control the temperature of said fluid emerging from said cavitation device.
42-57. (canceled)
Type: Application
Filed: May 26, 2010
Publication Date: Nov 18, 2010
Inventors: Robert L. Sloan (Katy, TX), Kevin W. Smith (Houston, TX), Harry D. Smith, JR. (Montgomery, TX)
Application Number: 12/800,969
International Classification: B01D 17/12 (20060101); B01D 17/00 (20060101);