METHOD AND SYSTEM FOR BLENDING WELLBORE TREATMENT FLUIDS

BACKGROUND

1. Field

[0001] The present disclosure relates to blending wellbore treatment fluid 42As. More specifically, the disclosure relates to blending the wellbore treatment fluid 42As to create an emulsion prior to injecting downhole.

2. Related Art

[0002] Subterranean formation l4s surrounding a hydrocarbon producing wellbores are sometimes treated to increase hydrocarbon production from the wellbores; where that treatment is sometimes referred to as well stimulation. Fluids, typically one of a fracturing fluid or a treatment fluid 42A, are delivered into the particular wellbore during most well stimulation techniques. As their name implies, fracturing fluids are used to fracture the formation 14 by subjecting the wellbore to a high fluid pressure. The fracturing fluid is delivered downhole at a pressure sufficient to overcome a yield strength of the formation 14, and thereby generate fractures in the formation 14 that project radially outward from the wellbore. Some well stimulation fluids, such as surfactants, alter characteristics of fluids downhole. Other types of fluid delivered downhole can treat the formation 14 itself by, for example, increasing permeability characteristics of the rock in the formation 14. Formation treatment usually dissolves material in the formation 14 that restricts or blocks fluid flow through the formation 14. Examples of other fluids include those that are used to treat the wellbore and those which clean scale, rust, or other debris in the well that hinders fluid flow in the well itself. [0003] Acids are often chosen for dissolving the formation 14, material in the formation 14, or material in the well which hinders fluid flow from the well. Acid is often dispersed in another fluid, such as diesel, to limit exposure of the acid to piping and other fluid-handling hardware. However, having the diesel as the continuous phase also has problems. Greater pumping power is required due to the friction losses resulting from the relatively large viscosity of diesel as compared to that of water.

SUMMARY OF THE INVENTION

[0004] Disclosed is a method of operating a wellbore, which includes introducing a flow of a continuous fluid to an entrance of a venturi, introducing a flow of a treatment fluid 42A to a portion of the venturi having a reduced cross-sectional flow area 62A such that droplets of the treatment fluid 42A found in and dispersed into the continuous fluid form a treatment emulsion E, and introducing the treatment emulsion E into a wellbore so that the droplets of the treatment fluid 42A contact a subterranean formation 14 adjacent to and in fluid communication with the wellbore. The method optionally includes diverting a portion of the treatment emulsion E to a container having the continuous fluid. In this example, the portion of the treatment emulsion E diverted to the container having the continuous fluid is generally within a designated radius from an axis of a flowline carrying the treatment emulsion E. As well, the concentration in the droplets of the treatment fluid 42A in the continuous fluid within the designated radius is less than the concentration of the treatment fluid 42A in the continuous fluid that is outside of the designated radius. In one embodiment, the treatment fluid 42A includes one or more of an acid, a stimulation acid, a surfactant, a viscoelastic surfactant, a salt, or a base. Examples of continuous fluid include water, diesel, kerosene, and combinations thereof. In an alternative embodiment, the treatment emulsion E is a first treatment emulsion E, the continuous fluid is a first continuous fluid, and the venturi is a first venturi. In such an embodiment, the method further includes directing a second continuous fluid to an entrance of a second venturi, and directing the first treatment emulsion E to a portion of the second venturi having a reduced cross- sectional flow area 62A so that droplets of the first treatment emulsion E are dispersed in the second continuous fluid to form a second treatment emulsion CE. The embodiment method further includes directing the second treatment emulsion CE into the wellbore so that the droplets of the treatment fluid 42A come into contact with subterranean formation 14 adjacent the wellbore. In an example, the treatment fluid 42A is an acid, the first continuous fluid is diesel, and the second continuous fluid is water. In an alternative embodiment example, a portion of a flow of the second treatment emulsion CE exiting the venturi is diverted back to a container housing the second continuous fluid. Optionally in this embodiment, the portion of the second treatment emulsion CE diverted to the second container is generally within a designated radius from an axis of a flowline carrying the second treatment emulsion CE, and where a concentration of the droplets of the treatment fluid 42A in the second continuous fluid within the designated radius is less than a concentration of the treatment fluid 42A in the second continuous fluid that is outside of the designated radius. In an alternative, the method further includes regulating a flow of the treatment emulsion E based on sensing the treatment emulsion E at a location downstream of the venturi.

[0005] Also disclosed is another example method of operating a wellbore, and which includes introducing a flow of a continuous fluid in a flow circuit, combining a flow of a treatment fluid 42A with the continuous fluid in the flow circuit, blending the continuous fluid and the treatment fluid 42A in a section of the flow circuit so that droplets of the treatment fluid 42A become dispersed in the continuous fluid to form a flow of a treatment emulsion E, diverting a portion of the flow of a treatment emulsion E to a container having the continuous fluid, and introducing a remaining portion of the flow of a treatment emulsion E into the wellbore. An example of the flow circuit includes piping and a venturi, and where the section of the flow circuit is the venturi. In an embodiment, the portion of the flow of a treatment emulsion E that is diverted to the container having the continuous fluid is a concentration of droplets of the treatment fluid 42A that is less than a concentration of droplets in the remaining portion. Embodiments exist that further include blending the treatment emulsion E with another continuous fluid to form a complex emulsion that comprises droplets of the treatment emulsion E in the continuous fluid.

[0006] An example of a system for operating in a wellbore is also described, and which includes a mixer having a dispersed flow inlet that receives a flow of a dispersed fluid that includes a wellbore treatment fluid 42A, a continuous flow inlet that receives a flow of a continuous fluid and that is oriented so that in the mixer the flow of a dispersed fluid intersects with the flow of a continuous fluid to form an emulsion comprising droplets of the dispersed fluid scattered within the continuous fluid, and an exit having the emulsion. The system of this example also includes an exit line having an end in communication with the exit and an end in communication with the wellbore, and that is for carrying the emulsion. In an embodiment the mixer includes a venturi having a body, a bore extending axially through the body, and a restriction in the bore, where the continuous flow inlet coincides with an end of the bore, and where the dispersed flow inlet intersects with the restriction. In an alternative, the exit line extends into the wellbore to define a treatment line, the system further including a return line having an inlet in a mid-section of the treatment line and that receives a portion of the treatment emulsion E flowing in the treatment line having a concentration of droplets of the dispersed fluid that is less than a portion of the treatment emulsion E that flows past the inlet of the return line. In an alternate embodiment, another mixer is included with the system and which includes another dispersed fluid inlet in communication with the exit line, another continuous fluid inlet in communication with another continuous fluid so that a complex emulsion is formed in the another mixer that has droplets of the emulsion in the another continuous fluid and which defines a treatment emulsion E, and another exit having the treatment emulsion E. In this example, the system further optionally includes a treatment line having an end in communication with the another exit and that is for delivering the treatment emulsion E into the wellbore.

BRIEF DESCRIPTION OF DRAWINGS

[0007] Some of the features and benefits of that in the present disclosure having been stated, and others will become apparent as the description proceeds when taken in conjunction with the accompanying drawings, in which:

[0008] Figure 1 is an elevational partial sectional view of a system for introducing a treatment emulsion E into a wellbore.

[0009] Figure 2A is a schematic view of an embodiment of a system for forming a downhole treatment emulsion E.

[0010] Figure 2B is a schematic view of an embodiment of a mixer in the system of Figure 2A.

[0011] Figure 2C is a side view of an alternate embodiment of a mixer in the system of Figure 2A.

[0012] Figure 3A is a schematic view of an alternate embodiment of a system for forming a downhole treatment emulsion E.

[0013] Figure 3B is a schematic view of an embodiment of mixers in the system of Figure 3A.

[0014] Figure 3C is a side view of an alternate embodiment of mixers in the system of Figure 3A.

DETAILED DESCRIPTION OF THE INVENTION

[0015] The method and system of the present disclosure will now be described more fully after with reference to the accompanying drawings in which embodiments are shown. The method and system of the present disclosure may be in many different forms and should not be construed as limited to the illustrated embodiments set forth; rather, these embodiments are provided so that this disclosure will be thorough, complete, and will fully convey its scope to those skilled in the art. Like numbers refer to like elements throughout. In an embodiment, usage of the term “about” includes +/- 5% of the cited magnitude. In an embodiment, usage of the term “substantially” includes +/- 5% of the cited magnitude.

[0016] It is to be further understood that the scope of the present disclosure is not limited to the exact details of construction, operation, materials, or embodiments shown and described. Modifications and equivalents will be apparent to one skilled in the art. Illustrative examples have been disclosed in the drawings and specification. Although specific terms are employed they are used in a generic and descriptive sense only and not for the purpose of limitation.

[0017] Depicted Figure 1 is an example of a wellbore treatment system 10 shown supplying a treatment emulsion E TE into a wellbore 12. The treatment emulsion E TE of this example includes a treatment fluid 42A for treating a formation 14 14 that surrounds wellbore 12. The treatment emulsion E TE of Figure 1 enters into perforations 16 shown projecting radially outward from wellbore 12 and into formation 14 14. Included with the illustrated embodiment of the wellbore treatment system 10 is a fluid source 18 for the treatment emulsion E TE; which is schematically represented on surface S and outside the wellbore 12. An optional pump 20, also on surface S, is shown as receiving treatment emulsion E TE from fluid source 18 via a suction line 22. Treatment emulsion TE is pressurized in pump 20, and discharged from pump 20 into discharge line 24 at a pressure of increased magnitude over that within suction line 22. In an alternative the combination of suction line 22 and discharge line 24 define a treatment line 25. In the illustrated example, an end of discharge line 24 distal from pump 20 terminates at a wing connection 26 of a production tree 28. Production tree 28 of Figure 1 mounts onto a wellhead housing 30, the combination of which define a wellhead assembly 32. A string of tubing 34, coupled with wellhead assembly 32 and projecting into the wellbore 12, is operable to deliver the treatment emulsion E TE into the wellbore 12. In embodiments where the treatment emulsion E TE includes an acid, channels and paths (not shown) are generated in the formation 14 14, which increases hydrocarbon drainage from formation 14 14 into wellbore 12. An optional packer is shown installed in an annular space between the tubing 34 and sidewalls of wellbore 12. Packer 36 defines a flow barrier in the annular space so that the treatment emulsion E TE is contained below the packer 36 and within a designated portion within wellbore 12.

[0018] An embodiment of fluid source 18A is schematically represented in Figure 2A. Fluid source 18A includes a container in which a continuous fluid is stored. Another container is included with the embodiment which treatment fluid 42A is stored. As described in more detail, embodiments exist where continuous fluid 38AA and treatment fluid 42A 42A are constituents of the treatment emulsion E TE of Figure 1. In a more specific embodiment, constituents of treatment fluid 42 A 42 A are delivered into the wellbore 12 to affect the wellbore 12 and/or surrounding formation 14 14 in a designated manner. Lines 44 A, 46 A respectively couple containers 37A, 40A to a mixer 48A.

[0019] Figure 2B represents a portion of the fluid source 18 A. Figure 2D illustrates lines 44A, 46A being generally oblique to one another when connected to mixer 48 A. Fluids 38 A, 42A in lines 44A, 46A, respectively, are introduced into and combined with each other in mixer 48A. Combining fluids 38 A, 42A forms an emulsion E having droplets 50AA of the treatment fluid 42A 42A distributed within the continuous fluid 38AA. Emulsion E passes from mixer 48A into treatment line 25A, which is coupled to an exit of the mixer 48A. In this illustrated example, treatment line 25A extends along an axis A _SOA that is generally parallel with line 44A and oblique or perpendicular with line 46A. By orienting line 46A at a perpendicular or oblique angle with that of line 44A, shear forces are created within mixer 48A due to the introduction of treatment fluid 42A 42A into continuous fluid 38AA. The slowing of one fluid against the other enhances the formation 14 of droplets 50AA with emulsion E.

[0020] Further illustrated in Figures 2A and 2B is an optional return line 52A for returning a portion of fluid within treatment line 25A back to continuous fluid container 37AA. In the embodiment shown in Figure 2B, return line 52A intersects a sidewall of treatment line 25 A, and is generally oblique with axis A _SOA when outside of treatment line 25A. Within treatment line 25A, return line 52A curves from an orientation that is oblique to treatment line 25A to an orientation that is substantially parallel with treatment line 25A. An end of return line 52A within treatment line 25A is open and facing upstream, defining an inlet 53A. Inlet 53A is selectively operable to receive a portion of fluid exiting mixer 48A. Not intending to be bound by theory, it is believed that in some instances droplets 50AA tend to congregate towards the outer radius of the treatment line 25A and spaced away from axis AXISSOA, and which is thought to be attributable to the velocity of fluid 38AA being greater than that of fluid 42AA. Accordingly, in the illustrated embodiment inlet 53A is strategically located generally coaxial with axis AXISSOA SO that the fluid entering return line 52A is substantially comprising of the continuous fluid 38AA and is substantially free of droplets 50AA. In one embodiment, adding return line 52A maximizes a quantity and/or concentration of droplets 50AA in emulsion E. Return line 52A also reduces unnecessary usage of continuous fluid 38AA by returning an amount of continuous fluid 38AA from within line 25 A in which little or no droplets 50AA are dispersed. Embodiments exist where an axis of inlet 53A is offset from axis A ₅ OA, and where return line 52A is not curved. In an example, a diameter of return line 52A ranges from about 30% to about 80% of a diameter of treatment line 25 A. In an example, a criteria for determining a size of return line 52A is to capture continuous fluid 38AA in which droplets 50AA have not formed or become entrained. In an alternate embodiment, inlet 53A to return line 52A is placed at or proximate to the downstream terminal end of restriction 62A. In an example embodiment, restriction 62A has a length that is substantially the same as a diameter of restriction 62A, alternatively, length of restriction 62A ranges from about one-half the diameter of restriction 62A to about that of the diameter of restriction 62A. In such an embodiment, inlet 53A to return line 52A within body 60A of venturi 54AA is positioned a distance downstream of the end of restriction 62A up to about a distance substantially equal to a diameter of line 44A, and all distances between. In an embodiment, axial distance between restriction 62A and inlet 53A is dependent on flowrates of fluid within lines 44A, 46A, and is within the capabilities of one skilled to identify a designated distance based on the flowrates. In an alternate embodiment, inlet to line 44A is elevated from a lowermost portion of continuous fluid container 37AA to avoid receiving any treatment fluid 42A 42A inadvertently transferred to continuous fluid container 37 A A via return line 52 A

[0021] Referring now to Figure 2C, schematically represented is an example of mixer 48A configured with a venturi 54AA. In this example, a motive fluid inlet 56A is provided on an upstream end of venturi 54AA, and coupled to line 44A. In this example, motive fluid inlet 56A couples to and receives continuous fluid 38AA from continuous fluid container 37 AA of Figure 2A. An outlet 58 A is formed on a downsteam end of venturi 54AA distal from motive fluid inlet 56A, and couples to treatment line 25A. Venturi 54A includes a body 60A having a bore that extends axially through, the length of body 60A. A restriction 62A, comprising part of the body 60A between the inlet and outlet 56A, 58A defines a reduced cross sectional area of bore. Fluid flowing through venturi 54AA experiences a localized increase in velocity, and a corresponding reduction in pressure when traversing the restriction 62A of body 60A.

[0022] A dispersed fluid inlet 64A is illustrated showing line 46A coupled to line 44A at restriction 62A Alternative embodiments exist where two or more dispersed fluid inlets 64A are provided around a circumference of body 60A and which introduce treatment fluid 42A 42A along different azimuthal locations around a flow of continuous fluid 38AA inside venturi 54AA. The reduced pressure within the restriction 62A provides a pressure differential between line 46A and restriction 62A such that treatment fluid 42A 42A is drawn into venturi 54AA from line . Not to be bound by theory, but it is believed that the increased fluid velocity within restriction 62A of continuous fluid 30A shearing against the treatment fluid 42A 42 leads to the formation 14 of more homogeneously dispersed droplets 50AA within the continuous fluid 38AA than merely a similar T-junction style system of feeding fluid into the system. Example materials for the treatment fluid 42A include acid, a stimulation acid, a surfactant, a viscoelastic surfactant, a salt, a base, and combinations thereof. Examples of continuous fluid 38AA include organic liquids, water, diesel, kerosene, and combinations thereof.

[0023] Example volumetric ratios of the droplets 50AA of treatment fluid 42A 42A to continuous fluid 38AA range from about 1:3 to about 1:6. In one embodiment, a particular quantity of treatment fluid 42A 42A is a mass or volumetric rate of treatment fluid 42A 42A to be mixed with continuous fluid 38AA in venturi 54AA so that a designated size and quantity of droplets 50AA are in the emulsion E. In certain embodiments, droplets 50AA have an average diameter that ranges from about 100 microns to about 1 millimeter. Further embodiments exist where an average diameter of droplets 50AA ranges between about 1 millimeters to about 3 millimeters. It is believed it is within the capabilities of those skilled in the art to identify a designated size and quantity of droplets 50AA and a particular quantity of treatment fluid 42A 42A. A pump (not shown) is alternatively included for driving treatment fluid 42A 42A through dispersed fluid inlet 64A, such as for example when a pressure differential between tank 40A and venturi 54AA is insufficient for a particular quantity of treatment fluid 42A 42A from tank 40A to enter venturi 54AA. In another alternative, a pump (not shown) is included for pressurizing fluid in line 52A sufficient for return to continuous fluid container 37AA.

[0024] Further shown in the example of Figure 2C, an optional swage 66A is shown formed downstream of venturi 54AA which provides a diameter transition to the treatment line 25A.

[0025] In an alternative, a valve 68A is provided in return line 52A. The valve 68A is configured to regulate or control a flow rate of the fluid flowing into and through return line 52A. An advantage of dispersing the treatment fluid 42A 42A within the continuous fluid 38AA is that the treatment fluid 42A 42A is kept separate from and out of contact with fluid handling equipment, such as pumps or pipes, when being transported into wellbore 12 (Figure 1). By emulsifying the treatment fluid 42A 42A within continuous fluid 38AA, interaction between the potentially harmful treatment fluid 42A 42A and fluids handling equipment is substantially diminished.

[0026] Referring now to Figure 3A, schematically shown is an alternate embodiment of a fluid source 18B. In this example, in additional to containers 37B, 40B, another container 70B is schematically represented containing another continuous fluid 72B, where continuous fluid 72B flows to another mixer 74B via line 76B. Similar to the embodiments of Figures 2A and 2B, continuous fluid 38AB from container 37 AB and treatment fluid 42A 42B from container 40B are combined in mixer 48B. Line 78B connects between mixer 48B and mixer 78B and provides a conduit for fluid leaving mixer 48B to enter mixer 74B. The blended result of mixing within mixer 74B is discharged into treatment line 25B. Similar to mixer 48 A of Figure 2B, an emulsion EB is formed by combining fluids 38B, 42B in mixer 48B (Figure 3B). Emulsion EB is delivered to mixer 74B from mixer 48B via line 78B, and in which it is combined with continuous fluid 72B. Further schematically illustrated in the example of Figure 3B are droplets 50AB in emulsion EB that are dispersed within the continuous fluid 38AB, and being directed towards mixer 74B through line 78B. In the example of Figure 3B, the emulsion EB within line 78B combines with and becomes dispersed within continuous fluid 72B inside mixer 74B and creates a complex emulsion CE shown exiting mixer 74B and in line 25B. Included within the example of complex emulsion CE of Figure 3B are droplets 80B; where droplets 80B include an inner portion that is made up of the treatment fluid 42A 42A of figure 2A, and an outer portion is made up of the continuous fluid 38AA of Figure 2A. A return line 82B is shown having an inlet end disposed within treatment line 25B and proximate an axis Axis _22B of treatment line 25B. Similar to return line 52A of Figure 2B, inlet end of return line 82B is strategically located in treatment line 25B so that a large portion of fluid within return line 82B is made up of continuous fluid 72B. In an example, a viscosity of continuous fluid 72B is less than a viscosity of the continuous fluid 38AB in which the treatment fluid 42A 42B is emulsified, which provides an advantage of reduced resistance to flow when directing the complex emulsion CE into a wellbore 12 (Figure 1), thereby lessening energy, and thus costs, associated with flowing or pumping the complex emulsion CE.

[0027] In Figure 3C shown in schematic form is an example of a portion of fluid source 18B, and which includes mixers 54B, 74B. In the example of Figure 3C, each of the mixers 48B, 74B is configured as a venturi 64B, 84B. A motive fluid inlet 86B is provided on venturi 84B, and which connects to an end of line 76B. In this example, continuous fluid 72B flowing into venturi 84B provides a motive source for the emulsion E _B flowing into venturi 84B via line 78B. An outlet 88B is shown disposed on an end of venturi 84B distal from motive fluid inlet 86B. Venturi 84B includes a body 90B having opposing ends at the inlet and outlet 86B, 88B and a restriction 92B shown formed along a portion of body 90B. Like venturi 54AB, venturi 84B includes an axial bore which has a reduced cross sectional area to define restriction 92B. The reduced cross sectional area of restriction 92B generates a localized velocity decrease, and thus localized drop of pressure, of fluid flowing through venturi 84B. The temporary rise in velocity of fluid flowing through venturi 84B provides enhanced mixing of fluids combined in venturi 84B. In this example, dispersed fluid inlet 94B is positioned proximate the restriction 92B and through which emulsion E _B is directed into venturi 84B. In an example, dispersed fluid inlet 94B is at a mid-point of an axial length of the restriction 92B. Valve 96B is illustrated disposed within return line 82B, and which in one example selectively controls the flow of the continuous fluid 72B back to the container 70B and through return line 82B. Swage 98B is one example of connection between outlet 88B and treatment line 25B. Examples of continuous fluid 72B include an organic liquid, water, diesel, kerosene, and, variations thereof.

[0028] Referring back to Figure 1, shown is an optional controller 100 that is in communication with fluid source 18 and pump 20 via communication means 102. Examples of communication means 102 include electrically conducting media, fiber optic material, telemetry, electromagnetic waves, and wireless. Additionally, communication means 104 is optionally shown connected to controller 100 and for providing communication between controller 100 and sensor 106 disposed within wellhead housing 30. Alternatively, another sensor 108 is depicted disposed within wellbore 12 and in optional communication with controller 100 via communication means 104. In one example of operation, conditions within wellbore 12 and/or wellhead housing 30 are sensed by sensors 106, 108 which is then relayed to controller 100. Optional commands are stored within controller 100 that are manually input in response to indications of measured conditions within wellbore 12 of wellhead housing 30, and which control the flow of fluids through the wellbore treatment system 10. Example ways of controlling the flow is the operation of pump 20, as well as selective opening and closing of valves 68B, 96B. In an alternate embodiment, one of or both sensors 106, 108 monitor characteristics of the treatment emulsion E TE and provide feedback to controller 100. In one example, feedback to controller 100 having characteristics of the treatment emulsion E TE includes information 14 about respective constituents in the treatment emulsion E TE and their relative volumetric and/or mass percentages. Further optionally, characteristics of the treatment emulsion E TE includes information 14 about droplets 80B (Figure 3B), such as their spatial location in a flow the treatment emulsion E TE. Alternatively, information 14 about the droplets 80B includes identification of compounds on their outer surface to ensure the droplets 80B have been properly formed, so that corrosive or other damaging compounds are blocked from contact with hardware susceptible to damage from those compounds. In one non-limiting embodiment, flow within fluid source 18 is adjusted based on feedback from sensors 106, 108. Examples of adjusting flow within fluid source 18 includes changing a flow to or from mixers 48B, 74B, such as in one or more of lines 25B, 44B, 46B, 52B, 76B, 78B, and 82B. In an example, emulsion E of Figure 2B is directed introduced into the wellbore 12 (Figure 1), thus in this example emulsion E is the treatment emulsion E TE. In another example, complex emulsion CE of Figure 3B is introduced into the wellbore 12 (Figure 1), thus in this example complex emulsion CE is the treatment emulsion E TE.

[0029] The present disclosure therefore is well adapted to carry out the objects and attain the ends and advantages mentioned, as well as others inherent. While embodiments of the disclosure have been given for purposes of disclosure, numerous changes exist in the details of procedures for accomplishing the desired results. These and other similar modifications will readily suggest themselves to those skilled in the art, and are intended to be encompassed within the spirit of the present disclosure and the scope of the appended claims.