Abstract:
There is provided herein a system for premixing LCM with drilling mud for use in drilling. In the preferred embodiment, a hopper will contain apertures that release pressurized mud in such a way as to create a swirling vortex of drilling mud and LCM within a central hopper, with the drilling mud/LCM mixture preferably rotating between about 50 and 70 rpm. Adding the LCM to the hopper will mix it thoroughly with the drilling mud before it is introduced into a mud pit, thereby insuring that the final product will well-mixed and further improving the throughput of the overall process.

Description:
[0001]    This application is a continuation-in-part application of U.S. Ser. No. 11/687/420, filed Mar. 16, 2007 which claims priority to expired U.S. Provisional Patent Application Ser. No. 60/782,799, filed Mar. 16, 2006 and incorporates said applications by reference into this document as if fully set out at this point. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The instant invention applies generally to the field of oil and gas well drilling and, more specifically, to an apparatus for replacing lost circulation material (i.e., “LCM”) during drilling. 
       BACKGROUND OF THE INVENTION 
       [0003]    It is well known that fluid is regularly introduced down hole during the drilling process in order to lubricate the bit, cool it, wash away cuttings, etc. It is similarly well known that some rock formations (e.g., vugular or fractured formations, etc.) are porous to the extent that significant quantities of drilling mud may escape into the nearby rock formation during drilling. It is typical in such instances to continuously replace the drilling mud as it is lost by drawing from mud pits that are located at the well site proximate to the well. Additionally, in many cases, extraneous material is added to the mud before it is sent down into the well, which material is designed to help prevent further loss of drilling fluid from the well bore. The material might be of any type but is often fibrous or plate-like in nature and commonly consists of ground peanut shells, mica, cellophane, walnut shells, calcium carbonate, plant fibers, cottonseed hulls, ground rubber, and/or polymeric materials. Those of ordinary skill in the art will recognize that these materials are added to the mud in the hope that they will help staunch the flow of mud out of the well bore. Such additional materials are known as “lost circulation materials” or “LCM” in the argot of the trade. 
         [0004]    Those of ordinary skill in the art will recognize that combining the lost circulation materials with the drilling mud that is destined to go down into the hole can often be problematic. For example, in many instances, the LCM is much lighter than the mud with which it will be mixed. Still, the standard practice is to add the LCM to the mud by dumping sacks of it onto the surface of the mud in the pit and then using rakes and/or a fan-like rotary mechanism at the bottom of the pit to mix the LCM and distribute it uniformly throughout. Needless to say, it often takes some time to thoroughly mix many bags of LCM with the mud. Further, such open air mixing can prove to be a health hazard, as the materials that are added can readily become airborne (e.g., cottonseed hulls) and inhaled by the worker. 
         [0005]    Thus, what is needed is a system and method that allows LCM and drilling mud to be mixed more rapidly and effectively. Further, the mixing accessory should be configurable to protect the attendant from exposure to airborne particulate matter. 
         [0006]    Heretofore, as is well known in the well drilling industry, there has been a need for an invention to address and solve the above-described problems. Accordingly, it should be now recognized, as was recognized by the present inventor, that there exists, and has for some time, a need for a system that will address and solve the above-described problem. 
         [0007]    Before proceeding to the description of the present invention, however, it should be noted and remembered that the description of the invention which follows, together with the accompanying drawings, should not be considered as limiting the invention to the examples (or preferred embodiments) shown and described. This is so because those skilled in the art to which the invention pertains will be able to devise other forms of the invention within the ambit of the appended claims. 
       SUMMARY OF THE INVENTION 
       [0008]    There is provided herein a system for premixing LCMs before they are added to drilling mud. The instant invention comprises a mixing hopper, which might be open to the atmosphere or enclosed, that includes therein peripherally arranged a plurality of orifices that introduce mud under pressure into the interior of the invention. Further, the orifices will be arrayed in such a fashion as to create a vortex or whirlpool effect within the central hopper of the instant device. In a preferred embodiment, dry LCMs will be added to the hopper where they will be taken into the mud whirlpool that has been created therein. The LCM will then be forced to mix with the mud prior to being introduced into the mud pits. 
         [0009]    In some preferred embodiments, the opening into the mixing hopper will be open to the atmosphere. However, in other arrangements, it will be sealed or shut and the LCM will be delivered via closed conduit, thereby protecting the worker against exposure to airborne particulate matter that might otherwise be released when the LCM is added to the hopper. 
         [0010]    In another preferred embodiment, the vortex that is created within the hopper will rotating within certain preferred limits. More particularly, the mud orifices and mud pressure will be configured such that the air within the mud vortex does not reach down into the 
         [0011]    The foregoing has outlined in broad terms the more important features of the invention disclosed herein so that the detailed description that follows may be more clearly understood, and so that the contribution of the instant inventor to the art may be better appreciated. The instant invention is not to be limited in its application to the details of the construction and to the arrangements of the components set forth in the following description or illustrated in the drawings. Rather, the invention is capable of other embodiments and of being practiced and carried out in various other ways not specifically enumerated herein. Further, the disclosure that follows is intended to apply to all alternatives, modifications and equivalents as may be included within the spirit and scope of the invention as defined by the appended claims. Finally, it should be understood that the phraseology and terminology employed herein are for the purpose of description and should not be regarded as limiting, unless the specification specifically so limits the invention. 
         [0012]    While the instant invention will be described in connection with a preferred embodiment, it will be understood that it is not intended to limit the invention to that embodiment. On the contrary, it is intended to cover all alternatives, modifications and equivalents as may be included within the spirit and scope of the invention as defined by the appended claims. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0013]    Other objects and advantages of the invention will become apparent upon reading the following Detailed Description and upon reference to the drawings in which: 
           [0014]      FIG. 1  illustrates the general environment of the instant invention including a preferred embodiment thereof. 
           [0015]      FIG. 2  contains a detailed view of the preferred embodiment of the instant invention. 
           [0016]      FIG. 3  contains a top-down view of the instant invention. 
           [0017]      FIG. 4  contains a cross section of the mud conduit inside of the hopper which illustrates in greater detail how orifices have been introduced to provide a directed flow of mod into said hopper. 
           [0018]      FIG. 5  is a top down view of another preferred embodiment of the instant invention, wherein two oppositely directed nozzles spray mud onto the interior walls of the hopper in a directional manner. 
           [0019]      FIG. 6  illustrates a closed top version of the instant invention. 
           [0020]      FIG. 7  contains a schematic illustration of another preferred embodiment in which the mud conduits are largely external to the hopper. 
           [0021]      FIG. 8  illustrates a plan view of another preferred aspect of the instant invention which utilizes a domed partial cover to direct LCM to the periphery of the hopper. 
           [0022]      FIG. 9  contains a side view of the embodiment of  FIG. 8 . 
           [0023]      FIG. 10  contains a cross sectional view of the embodiment of  FIG. 8  which illustrates a preferred mud vortex configuration. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0024]    Referring now to the drawings wherein the reference numerals indicate the same parts throughout the several views, there is provided a system for automatically premixing LCM before those materials are consigned to a mud pit for subsequent withdrawal during drilling. 
         [0025]    By way of general background and information,  FIG. 1  contains a preferred embodiment of the instant invention  100  as might appear on a drill site. As can be seen, there are a number of mud pits  115  which are served by a mud distribution line  160 . In most variations, each depositing orifice  120  of the distribution line  160  will be controlled by a separate valve (not shown in this figure), thereby allowing the mud pits  115  to be individually filled. As is generally indicated, drilling mud  110  enters the distribution line at some point upstream from the instant invention  100  and is accumulated in the pits for subsequent withdrawal during drilling. The withdrawal mechanism is well known in the art and is not shown in  FIG. 1 . 
         [0026]    As is indicated in greater detail in  FIGS. 2A and 2B , the preferred embodiment of the instant invention is designed to sit in-line with mud distribution line  160 . In the preferred embodiment, the mud line will be about six inches in diameter and will carry mud that is pressurized to about 200 psi (thereby providing for a flow of about 1,000 gallons per minute through distribution line  160 ). Preferably, takeout line  130  will be controlled by a valve  135  and will serve to release pressurized mud to move upward and into the top of the hopper  150 . Assisting this process is swedge  220 , which is visible in  FIG. 2B  within the cutaway view of distribution line  160 , and which, in one preferred embodiment, narrows the pipe diameter down to about four inches at its downstream terminus. Preferably, the swedge  220  will be installed by cutting the distribution line  160  and installing it therein via six-inch flanges  230 , although other installation configurations are certainly possible and could readily be devised by those of ordinary skill in the art. 
         [0027]    When drilling mud  110  enters the hopper of the instant invention  150 , it is distributed internally by peripheral mud conduit  210  which is preferably located proximate the upper terminus of the hopper  150 . The lower portion of the hopper  150  rests atop a connecting pipe  140  which mates with the distribution line  160  to return the mud together with the newly added LCM to the main distribution line. 
         [0028]    Turning next to  FIG. 3 , wherein a top view of the instant invention  100  may be found, note that drilling mud  110  enters under pressure by way of takeout line  130  to the interior of the instant hopper  150 , where it is diverted into the peripheral mud distribution line  210 . 
         [0029]    In a preferred embodiment, the mud distribution line  210  will be generally rectangular in cross section, but obviously, other shapes are certainly possible and those of ordinary skill in the art have the capability to readily design such. 
         [0030]    In a preferred embodiment, the mud distribution channels  210  will be periodically breached by orifices  320  that allow the mud to escape in a directional pattern into the interior of the hopper. Each orifice  320  will preferably consist of a downward bending  310  and an upward bending  320  element which have been created from the floor of the mud distribution channel  210  by cutting an “H” pattern into the floor thereof. Then, in the preferred embodiment each half of the H will be separately bent down  310  or up  320  in such a manner as to oppose and catch the mud that is streaming through the channel  210 . Note that, because the orifices are situated at the periphery of the hopper  150  and each releases mud in a direction that is at least roughly parallel to its inner surface of the hopper  150  at the location of that orifice, this directional release of mud will cause it to swirl around the hopper  150  inner wall, thereby creating a vortex or directional swirling/mixing effect therein. In the preferred arrangement, the mud distribution channel  210  will be closed at its end remote from the mud input point. Of course, those of ordinary skill in the art will recognize that directed nozzles or other directed vents could be used in place of the preferred orifices  320 . All that is required is that at sufficient ones of the orifices  320  direct a mud stream in the same rotational direction along the inner wall surface of the hopper  150  so that a vortex or swirling effect is created therein. Thus, for purposes of the instant disclosure it should be understood and remembered that the terms “nozzle”, “vent”, “orifice”, “aperture”, etc., when used in connection with the mud distribution channel  210  should all be broadly interpreted to mean any sort of opening within the channel  210  that allows mud to be released therefrom and which tends to direct a substantial portion of the released mud in a predetermined direction. 
         [0031]    Finally, in operation after the distribution line  160  has been activated and pressurized, a worker would operate valve  135  to allow mud to travel upward and into the hopper  150  as has been described previously. At that point, or shortly thereafter, LCM would be added to the top of open hopper  150  by opening large bags of same and depositing their contents into the hopper  150 . The swirling whirlpool of drilling mud  110  will then wet the contents of the LCM and eventually wash it down into connecting pipe  140  and subsequently back into the distribution system (e.g., pipe  160 ) where it will travel until released into a mud pit  115  via aperture  120 . 
         [0032]    In another preferred arrangement ( FIG. 6 ), there is provided a premixing device  600  substantially as described above but wherein the top is closed and LCM is delivered into the interior of the hopper  150  via conduit  630 . Preferably, the LCM will be pressurized at least to the extent necessary to move it along within conduit  630 . As is indicated in  FIG. 6 , preferably the conduit  630  will terminate in a lid  610  which is designed to seal the interior of the hopper  150  against the atmosphere. 
         [0033]    Turning next to  FIG. 5 , according to still another preferred embodiment of the instant invention, there is provided a device substantially as described above but wherein the peripheral distribution channel  210  has been replaced by a “T” configuration wherein each arm of the T terminates in a directed nozzle  510 . In operation, this would work similarly to the embodiment discussed previously, in that pressurized mud  110  would move through the T, into its arms, and subsequently be directionally expelled via nozzle  510  in a manner that is designed to create a swirling vortex of drilling mud within the chamber  150 . Note that, as was discussed in connection with  FIG. 6 , the instant embodiment  500  could be either open to the atmosphere or closed depending on the needs of the user. Further, note that the directed nozzles  510  need not be aimed horizontally (or at any other particular angle) and in some cases it might be preferred that they would be aimed at different vertical angles, e.g., in some cases some of the nozzles  510  might be aimed “high” and others “low”. Such an arrangement is fully consistent with the operation of the instant invention so long as the net effect is to create a swirling mud and LCM vortex within the hopper  150 . Still further, the nozzles  510  need not be held in a stationary orientation, but each could be manually or automatically aimed at a greater or lesser inclination with respect to the horizontal and/or more toward the hopper  150  outer walls or its center depending on the needs of the particular situation. Once again, all that is required is that the net effect of the nozzles  510  be to create rotational vortex of mud and LCM be created within the hopper  150  when mud is released into the hopper  150  through them. Finally, although in the preferred embodiment the nozzles  510  will be situated within the hopper  150 , it should be noted that there is merely a preferred embodiment and there is no particular reason why they could not be situated outside of it, so long as the mud streams generated thereby are directed into the hopper  150  and create a vortex of mud and LCM therein. 
         [0034]    As a next preferred embodiment  800  and as is generally illustrated in  FIG. 7 , there is provided an embodiment wherein the greater part of the mud conduit  710  lies outside of the hopper  830 . In this embodiment, the mud conduit  710  divides the drilling mud that is arriving from the takeout line  130  and routes it to opposite sides of the hopper  830 . The mud conduit  710  then penetrates the hopper  830  and is terminated by one or more directed nozzles  720 . Of course, and as has been discussed previously, these nozzles  720  need to be aimed such that they create a vortex or other rotating action within the hopper  830  in the mud that is released thereby. Needless to say, it is not essential that the nozzles  720  be located on opposite sides of the hopper  830  nor that there be exactly two of them. All that is required is that the nozzles  720  be oriented to create a swirling effect inside of the hopper  830 . 
         [0035]    According to still another preferred embodiment, there is provided a mixing device  900  that is substantially similar to the embodiment  FIG. 7 , but wherein only a portion of the hopper opening is covered by a domed LCM diverter  820 . A central purpose of the domed diverter  820  is to direct LCM materials that are added to the hopper to its sides where they are more likely to be engaged in the vortex. That is, and as is illustrated more clearly in  FIG. 9 , when LCM  920  is added to this embodiment, it encounters diverter  820  and, rather than falling through the mud vortex and into the connecting pipe  140 , it will instead be directed toward the sides of the hopper  830  where it will encounter the vortex and the mud that is released from the nozzles  720 , thereby increasing the possibility that it will be thoroughly wetted. It should be noted that a single support member  810  has been shown but, in practice, two or more would likely be necessary. Finally, although the preferred embodiment for the diverter  820  is a domed shape, other shapes (including flat, pyramidal, etc.) could also be used so long as they force the LCM  920  toward the periphery of the hopper. 
         [0036]    Turning next to  FIG. 10 , in this figure is illustrated an important aspect of the instant invention. More particularly, the instant inventor has found that in order for the mixing process to be most effective, the bottom of the vortex  1010  must effectively terminate above the exit point where the mud leaves the hopper  150 . Preferably, the vortex  1010  will effectively terminate some distance above the floor of the hopper  150  (“D” in  FIG. 10 ). The instant inventor has determined that with hoppers of various sizes in order to keep the vortex  1010  from entering the connecting pipe  140  the rotation speed of the mud in the hopper  150  will need to be between about 50 and 70 rpm. More specifically, in the preferred embodiment with a drilling mud having a viscosity of about 28 poise (i.e., dyne-sec/cm 2 ) with no LCM added, the rotation speed will preferably be about 70 rpm. After LCM has been added, the preferred rotation speed will be slower, e.g., about 50 rpm with a viscosity of about 50 poise after adding 40 pounds per barrel of LCM. That being said, those of ordinary skill in the art will recognize that these values are only provided for purposes of illustration and not out of any intent to limit the practice of the invention these specific viscosities. What is important is that the viscosity and rotational speed be selected such that a vortex  1010  is created and its interior (i.e., air-filled portion) terminates above the point the mixed mud and LCM material exits at the bottom of the hopper  150 . 
         [0037]    Additionally, it should be noted that those of ordinary skill in the art will recognize that, in addition to viscosity, the rate (pressure) with which mud enters the hopper  150  and the angle at which it is directed downward will also have some effect on the rotational speed and depth of the vortex  1010 . In a preferred embodiment, where the main mud line has a flow rate of about 375-450 gallons per minute, about ten percent will be diverted into the hopper  150  for mixing, with the remaining 90% being used to carry the mixed product to the pit. This assumes that the nozzles are directed downward at an angle of about a 45°. 
         [0038]    Thus, the present invention is well adapted to carry out the objects and attain the ends and advantages mentioned above as well as those inherent therein. While presently preferred embodiments have been described for purposes of this disclosure, numerous changes and modifications will be apparent to those in the art. Such changes and modifications are encompassed within the spirit of this invention as defined by the appended claims.