Patent Publication Number: US-2015075869-A1

Title: Continuous gravity feed system for feeding additives to a drilling mud system

Description:
BACKGROUND 
     Boreholes are frequently drilled into the Earth&#39;s formation to recover deposits of hydrocarbons and other desirable materials trapped beneath the Earth&#39;s surface. Traditionally, a well is drilled using a drill bit attached to the lower end of what is known in the art as a drillstring. The drillstring is traditionally a long string of sections of drill pipe that are connected together end-to-end through rotary threaded pipe connections. The drillstring is rotated by a drilling rig at the surface thereby rotating the attached drill bit. Drilling fluid, or mud, is typically pumped down through the bore of the drillstring and exits through ports at the drill bit. The drilling fluid acts to both lubricate and cool the drill bit as well as to carry cuttings back to the surface. Typically, drilling mud is pumped from the surface to the drill bit through the bore of the drillstring, and is allowed to return with the cuttings through the annulus formed between the drillstring and the drilled borehole wall. At the surface, the drilling fluid is filtered to remove the cuttings and is often recycled. 
     Various difficulties may be encountered during the drilling operation, such as a fluid loss event. Drilling also includes numerous operations, including drilling, running casing, finishing, and many others. Additionally, during the drilling operation, various earth formations may result in torque or drag issues at the drill bit. Drilling fluid additives may be added to the drilling mud to address these specific issues or operations, and may be added over a limited time period. 
     For example, when a drill bit is experiencing torque or drag issues, it may be desirable to add spotting beads, a micro-bead used to provide lubricity at the drill bit. Addition of spotting beads to the drilling mud may frequently be required for only two or three days at a time during the drilling operation. As a result, drilling rigs are typically not permanently equipped to add spotting beads to the drilling mud, and this addition is often performed by simply dumping bags of spotting beads into the mud system. This feed method may result in periodic and inconsistent lubricity at the drill bit and is labor intensive, both of which are undesirable. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a simplified schematic diagram of a gravity assisted drilling additive feed system according to embodiments herein. 
         FIG. 2  is a side view of a gravity assisted drilling additive feed system according to embodiments herein. 
         FIG. 3  is a top view of a gravity assisted drilling additive feed system according to embodiments herein, with a hinged top in an open position. 
         FIG. 4  is a side view of an outlet assembly useful with a gravity assisted drilling additive feed system according to embodiments herein. 
         FIG. 5A  and  FIG. 5B  are side views of interchangeable nozzles useful with a gravity assisted drilling additive feed system according to embodiments herein, where a flow rate/time resulting from the nozzle is indicated on an exterior of the nozzle. 
         FIG. 6  is a simplified flow diagram of a process for feeding drilling additives to a mud system according to embodiments herein. 
     
    
    
     DETAILED DESCRIPTION 
     Embodiments disclosed herein relate to a continuous gravity feed system for feeding additives to a drilling mud system. More specifically, embodiments disclosed herein relate to a portable additive feed system that uses gravity to feed spotting beads to a mud system when needed during a drilling operation. 
       FIG. 1  illustrates one embodiment of an additive feed system  10 . In the embodiment, the additive feed system  10  may include an additive containment device  12  having a top  14 , a bottom  16  and side walls  30 . The additive containment device  12  may hold additives to be added to a drilling mud. Additionally, the additive containment device  12  may be of any shape configured to hold the additives while allowing the additives to flow out the bottom  16 . For example, the additive containment device  12  may be a cylinder or a rectangular prism. The top  14  may be removed from the additive containment device  12 . The top  14  may also be hingedly connected to the side walls  30  of the additive containment device  12  for ease of opening and closing. The top  14  may be opened when adding additives and closed when additives are not being added. The bottom  16  may be shaped to convey the additives to an exit of the additive containment device  12 . For example, the bottom  16  may be a frustoconical shape or a frusto-tetrahedral shape. 
     Three or more legs  32  may be attached to the bottom  16  of the additive containment device  12 . The legs  32  may be fixed to the bottom  16  or may be removable. Referring to  FIG. 1 , the legs  32  may be substantially straight. Referring to  FIG. 2  and  FIG. 3 , the legs  32  may flare outwardly to provide a more stable base. 
     Referring to  FIG. 1 , the additive containment device  12  may have a top flanged portion  26  and a bottom flanged portion  28 . The top flanged portion  26  may include the top  14  of the additive containment device  12 . Opposite the top  14 , the top flanged portion  26  may have a flange  26 F. The bottom flanged portion  28  may include the bottom  16  of the additive containment device  12 . Opposite the bottom  16 , the bottom flanged portion  28  may have a flange  28 F. The top flanged portion  26  may be connected to the bottom flanged portion  28  at the flange  26 F and the flange  28 F to form the additive containment device  12 . In this embodiment, the top flanged portion  26  may be connected to the bottom flanged portion  28  during operation of the additive feed system  10 . 
     The additive feed system  10  may have an outlet  18  that has a proximal end and a distal end. The outlet  18  may be tapered so that the distal end is narrower than the proximal end. The proximal end of the outlet  18  may be connected to the bottom  16  of the additive containment device  12 . The interior of the outlet  18  may be substantially smooth to limit or eliminate the additives from accumulating and impeding the flow of additive through the outlet  18 . The distal end of the outlet  18  may be connected to a valve  20 . The valve  20  may be any type of valve useful for solids flow. For example, the valve  20  may be configured so that it only has a fully on position and a fully off position with no intermediate positions. In some embodiments, the valve  20  may have no flow restrictions that may result in solids accumulation and potential for plugging of the valve or otherwise hindering solids flow when the valve is open. Such a full bore type valve may be beneficial for consistency of solids flow, especially with respect to a gravity feed system disclosed herein. 
     A screening member  24  may be disposed within additive containment device  12  intermediate the top  14  and the bottom  16 . The screening member  24  may filter or screen the additives disposed within the containment device  12 . The screening member  24  may limit or eliminate oversized solids or agglomerates from passing through the tank to the outlet  18 , avoiding plugging of the feed system or damage or other issues with downstream equipment, such as a mud pump. In some embodiments, the screening member  24  may be fixed. In other embodiments, the screening member  24  may be removable. The screening member  24  may be disposed between the top flange portion  26  and the bottom flange portion  28 . In further embodiments, the screening member  24  may be removed when the top flange portion  26  and the bottom flange portion  28  are disconnected. Alternatively, the screening member may be fixed to the top flange portion  26  coplanar with the flange  26 F. Additionally, the screening member  24  may be fixed to the bottom flange portion  28  coplanar with the flange  28 F 
     The valve  20  is also connected to a flow nozzle  22  having an outlet end  36  and a flow rate. The flow nozzle  22  reduces the additive flow area and may provide a substantially constant rate of additive flow from the outlet  18 . The flow nozzle  22  may provide a substantially constant rate of flow of a drilling fluid additive from the outlet  18 . The flow nozzle  22  may have a relatively smooth, tapered, inner surface transitioning from the outlet port side of the valve  20  to the inner diameter of the outlet end  36 . As shown in  FIG. 4 , to respond to changing needs in the drilling mud system, the flow nozzle  22  may be interchangeable. During operation of the the additive feed system  10 , the valve  20  may be closed, and the flow nozzle  22  with a first flow rate may be changed for the flow nozzle  22  with a second flow rate. 
     The additive containment device  12  may have an internal volume in the range from about 5 gallons to about 150 gallons or more, and the desired volume may depend upon the type and size of additive and the desired flow rate of additive through the outlet  18  and the nozzle  22 . The internal volume of the additive containment device  12  may affect the frequency that the additive containment device  12  must be refilled. In some embodiments, the internal volume of the additive containment device  12  may be in the range from about 10 to about 50 gallons; in the range from about 20 to 40 gallons in other embodiments, such as about 30 gallons. The volume of additives within the additive containment device  12  may be visually observed via opening of the top  14 , tapping of the sides of the additive containment device  12  to gauge the level, or via one or more sight glasses (not shown) disposed in the side walls  30 . 
     The additive containment device  12  may be made of a plastic material, resulting in a light weight, portable system. Because water may result in agglomeration of some additives, use of a plastic body, such as polypropylene or a vinyl polymer, may result in less moisture condensation within the additive containment device  12 . Additionally, plastic may also result in no static charge accumulation to provide for safe operation in hazardous environments. 
     The substantially constant rate of flow of the drilling fluid additive is provided via an inner diameter of the outlet end  36  of the nozzle  22 . The restriction of flow area of the nozzle  22  through which the solids may pass results in a relatively constant rate of solids to flow via gravity from the additive containment device  12 . For example, for spotting beads, such as ALPINE spotting beads, having an average diameter in the range from about 70 microns to 1000 microns, a nozzle having a 1/4 inch inner diameter may provide for a flow rate of about 43 lb/h; a nozzle having a 3/8 inch inner diameter may provide for a flow rate of about 130 lb/h, and a nozzle having a 1/2 inch inner diameter may provide for a flow rate of about 200 lb/h. As shown in  FIG. 4 , the flow nozzle  22  may be adjustable or interchangeable, such as via threading, quick connects, or other means known to those skilled in the art. Adjustable or interchangeable nozzles having these and other inner diameters may thus provide for a desired, consistent, flow rate of drilling fluid additive, where an operator may select the appropriate nozzle or flow area to achieve the desired additive composition in the drilling mud. Interchangeable nozzles, such as illustrated in  FIG. 5A  and  FIG. 5B , may be marked or otherwise identified to indicate the flow rate of drilling fluid additive through the nozzle or the approximate time for a (50-lb) bag of additive to dispense, thus providing a means to achieve a desired concentration of additive in the mud system and an indication of the approximate amount of time required to empty additive containment device  12 . 
     Referring now to  FIG. 6 , a simplified flow diagram of a process for feeding drilling fluid additives to a mud system according to embodiments herein is illustrated. The above described gravity feed systems may be used to continuously feed drilling fluid additives, such as spotting beads, to a drilling fluid or mud system. While such a system may be permanently located proximate a mud system, it is envisioned that systems herein may be used intermittently during drilling processes, such as during operations or times when spotting beads or other additives are required. 
     When needed for the temporary feeding of additives to a mud system, the additive feed system  10  may be delivered to a drilling site or drilling rig, assembled (if necessary) and located proximate a mud system. For example, an “open” mud tank  40  containing a drilling fluid or drilling mud  42  may have a flow conduit  44  feeding a mud pump  46 . The drilling mud  42  flows from the mud tank  40  through the conduit  44  and enters the suction of the mud pump  46 . The drilling mud  42  is then discharged to an outlet conduit  48  and fed downhole through the drill string to the drill bit to provide lubrication and drill cuttings removal. The additive feed system  10  may be located over a grating  50  or opening in the flow conduit  44  to allow gravity feed of the additive from the nozzle  22  into the mud system proximate the suction of the mud pump  46 . 
     Following proper location of the additive feed system  10 , a drilling fluid additive may be disposed within the additive containment device  12 , such as via opening and closing of the top  14 . The valve  20  may then be opened to initiate flow of the additive through the nozzle  22  into the the mud system via the grating  50 . As needed, additional additive may be added to additive containment device  12  so as to provide continuous flow of additive over an extended period of time. The frequency of such additions may depend upon the size of the additive containment device  12  and the flow rate of the nozzle  22 , as described above. Should the concentration of the additive need to be adjusted during use, the valve  20  may be closed and the nozzle  22  changed. A flow conduit, such as a pipe, tube, or hose (not illustrated), may be connected to the nozzle  22  to guide the flow of additive from the nozzle  22  to the mud system feed point, such as the grating  50 , minimizing effects of weather, wind, and other external factors as may be present at a drilling location or drilling rig. 
     When the drilling fluid additive is no longer required for drilling operations, the additive containment device  12  may be cleaned, disassembled, and, if necessary, removed from the drill site or drilling rig. 
     While described above with respect to an “open” mud system, location and operation of the additive feed system  10  may be performed in other manners as appropriate to the respective mud system. 
     As an example of using the additive system during a drilling operation, the lubricity of the drill bit may be increased using spotting beads, such as when a drill bit is experiencing drag and/or torque issues. Spotting beads may be disposed in the additive containment device  12  and fed to the suction side of the pump  46 . The flow rate of spotting beads into the drilling fluid may be selected to provide a concentration of spotting beads in the drilling mud in the range from about 2 to about 15 lb/bbl, such as in the range from about 8 to about 10 lb/bbl. The drilling beads may then travel through the conduit  48  to the drill bit, where the micron size spherical beads may lubricate the drill bit. 
     Embodiments herein may supply a consistent, uniform mixture of drilling fluid additives, such as spotting beads, in a drilling mud. The uniform mixture of beads resulting from the consistent feed rate provided by systems herein, for example, may provide for a consistent, controllable supply of spotting beads, resulting in a constant improvement in lubricity at the drill bit. In contrast, present methods, such as manual dumping of bags of beads, result in “pill” type flow of spotting beads or otherwise inconsistent concentrations of beads in the drilling fluid, resulting in inconsistent lubricity at the drill bit. As a result, embodiments herein may eliminate the human factor and significantly improve drilling performance, including rate of penetration. Additionally, as compared to manual dumping, feed systems according to embodiments disclosed herein may require less manpower and may prevent oversized materials from accidentally being introduced to the system. 
     Feed systems according to embodiments herein may be relatively small in size, especially compared to the mud tanks (that may be 2000 bbl or larger in volume), portable, lightweight, and easy to transport, install, and dismantle. Additionally, embodiments herein may provide for interchangeable nozzles to accurately and predictably control the flow rate of drilling fluid additives. The relatively simple operation of the gravity feed system may thus improve overall operations at a drilling site or drilling rig and may be extremely beneficial, especially for short duration needs, such as spotting. 
     Although only a few example embodiments have been described in detail above, those skilled in the art will readily appreciate that many modifications are possible in the example embodiments without materially departing from this invention. Accordingly, all such modifications are intended to be included within the scope of this disclosure as defined in the following claims. In the claims, means-plus-function clauses are intended to cover the structures described herein as performing the recited function and not only structural equivalents, but also equivalent structures. Thus, although a nail and a screw may not be structural equivalents in that a nail employs a cylindrical surface to secure wooden parts together, whereas a screw employs a helical surface, in the environment of fastening wooden parts, a nail and a screw may be equivalent structures. It is the express intention of the applicant not to invoke 35 U.S.C. §112, paragraph 6 for any limitations of any of the claims herein, except for those in which the claim expressly uses the words ‘means for’ together with an associated function.