Patent Application
20160230501
The present disclosure relates generally to oilfield equipment, and in particular to downhole tools. More specifically, the disclosure relates generally to methods and apparatus of control of an autonomous fluid valve using a “sticky switch” or biasing mechanism to control fluid flow, and the use of such mechanisms to control fluid flow between a hydrocarbon bearing subterranean formation and a tool string in a wellbore.
During the completion of a well that traverses a hydrocarbon bearing subterranean formation, production tubing and various equipment are installed in the well to enable safe and efficient production of the fluids. For example, to prevent the production of particulate material from an unconsolidated or loosely consolidated subterranean formation, certain completions include one or more sand control screens positioned proximate the desired production intervals. In other completions, to control the flow rate of production fluids into the production tubing, it is common practice to install one or more inflow control devices with the completion string.
Production from any given production tubing section can often have multiple fluid components, such as natural gas, oil and water, with the production fluid changing in proportional composition over time. Thereby, as the proportion of fluid components changes, the fluid flow characteristics will likewise change. For example, when the production fluid has a proportionately higher amount of natural gas, the viscosity of the fluid will be lower and density of the fluid will be lower than when the fluid has a proportionately higher amount of oil. It is often desirable to reduce or prevent the production of one constituent in favor of another. For example, in an oil-producing well, it may be desired to reduce or eliminate natural gas production and to maximize oil production. While various downhole tools have been utilized for controlling the flow of fluids based on their desirability, a need has arisen for a flow control system for controlling the inflow of fluids that is reliable in a variety of flow conditions. Further, a need has arisen for a flow control system that operates autonomously, that is, in response to changing conditions downhole and without requiring signals from the surface by the operator. Further, a need has arisen for a flow control system without moving mechanical parts which are subject to breakdown in adverse well conditions including from the erosive or clogging effects of sand in the fluid. Similar issues arise with regard to injection situations, with flow of fluids going into instead of out of the formation.
Embodiments are described in detail hereinafter with reference to the accompanying figures, in which:
It should be understood by those skilled in the art that the use of directional terms such as above, below, upper, lower, upward, downward and the like are used in relation to the illustrative embodiments as they are depicted in the figures, the upward direction being toward the top of the corresponding figure and the downward direction being toward the bottom of the corresponding figure. Where this is not the case and a term is being used to indicate a required orientation, the specification will state or make such clear. Uphole and downhole are used to indicate relative location or direction in relation to the surface of the earth, where upstream indicates relative position or movement towards the surface along the wellbore and downstream indicates relative position or movement further away from the surface along the wellbore, regardless of whether in a horizontal, deviated or vertical wellbore. The terms upstream and downstream are used to indicate relative position or movement of fluid in relation to the direction of fluid flow.
While the making and using of various embodiments are discussed in detail below, a practitioner of the art will appreciate that the present disclosure presents concepts that can be embodied in a variety of specific contexts. The specific embodiments discussed herein are illustrative and not limiting.
Positioned within wellbore 12 and extending from the surface is a tubing string 22. Tubing string 22 provides a conduit for fluids to travel from formation 20 upstream to the surface. Positioned within tubing string 22 in the various production intervals adjacent to formation 20 are a plurality of autonomous flow control systems 25 and a plurality of production tubing sections 24. At either end of each production tubing section 24 is a packer 26 that provides a fluid seal between tubing string 22 and the wall of wellbore 12. The space in-between each pair of adjacent packers 26 defines a production interval.
In the illustrated embodiment, each of the production tubing sections 24 includes sand control capability. Sand control screen elements or filter media associated with production tubing sections 24 are designed to allow fluids to flow therethrough but prevent particulate matter of sufficient size from flowing therethrough. While the system does not need to have a sand control screen associated with it, if one is used, then the exact design of the screen element associated with fluid flow control systems is not critical. There are many designs for sand control screens that are well known in the industry, and accordingly will not be discussed here in detail. Also, a protective outer shroud having a plurality of perforations therethrough may be positioned around the exterior of any such filter medium.
Through use of the flow control systems 25 in one or more production intervals, some control over the volume and composition of the produced fluids is enabled. For example, in an oil production operation if an undesired fluid component, such as water, steam, carbon dioxide, or natural gas, is entering one of the production intervals, the flow control system in that interval will autonomously restrict or resist production of fluid from that interval.
The term “natural gas” as used herein means a mixture of hydrocarbons (and varying quantities of non-hydrocarbons) that exist in a gaseous phase at room temperature and pressure. The term does not indicate that the natural gas is in a gaseous phase at the downhole location. Indeed, it is to be understood that the flow control system is for use in locations where the pressure and temperature are such that natural gas will be in a mostly liquefied state, though other components may be present and some components may be in a gaseous state. The disclosed concept will work with liquids or gases or when both are present.
The fluid flowing into the production tubing section 24 typically includes more than one fluid component. Typical components are natural gas, oil, water, steam or carbon dioxide. Steam and carbon dioxide are commonly used as injection fluids to drive the hydrocarbon towards the production tubular, whereas natural gas, oil and water are typically found in situ in the formation. The proportion of these components in the fluid flowing into each production tubing section 24 will vary over time and based on conditions within the formation and wellbore. Likewise, the composition of the fluid flowing into the various production tubing sections throughout the length of the entire production string can vary significantly from section to section. The flow control system is designed to reduce or restrict production from any particular interval when it has a higher proportion of an undesired component.
Accordingly, when a production interval corresponding to a particular one of the flow control systems produces a greater proportion of an undesired fluid component, the flow control system in that interval will restrict or resist production flow from that interval. Thus, the other production intervals which are producing a greater proportion of desired fluid component, in this case oil, will contribute more to the production stream entering tubing string 22. In particular, the flow rate from formation 20 to tubing string 22 will be less where the fluid must flow through a flow control system (rather than simply flowing into the tubing string). Stated another way, the flow control system creates a flow restriction on the fluid.
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A port 42 provides fluid communication from the screen annulus 32 to a flow control system having a fluid passageway 44, a switch assembly 46, and an autonomous, variable flow resistance assembly 50, such as a vortex assembly. If the variable flow resistance assembly is an exemplary vortex assembly, it includes a vortex chamber 52 in fluid communication with an outlet passageway 38. The outlet passageway 38 directs fluid into a passageway 36 in the tubular for production uphole, in a preferred embodiment. The passageway 36 is defined in this embodiment by the tubular wall 31.
The methods and apparatus herein are intended to control fluid flow based on changes in a fluid characteristic over time. Such characteristics include viscosity, velocity, flow rate, and density. The term “viscosity” as used herein means any of the rheological properties including kinematic viscosity, yield strength, viscoplasticity, surface tension, wettability, etc. As the proportional amounts of fluid components, for example, oil and natural gas, in the produced fluid change over time, the characteristic of the fluid flow also changes. When the fluid contains a relatively high proportion of natural gas, for example, the density and viscosity of the mixed fluid is less than for oil. The behavior of fluids is dependent on the characteristics of the fluid flow. Further, certain configurations of passageway restrict flow, or provide greater resistance to flow, depending on the characteristics of the fluid flow.
The fluid selector assembly 70 has a primary fluid passageway 72 and a control jet assembly 74. The control jet assembly 74 has a single control jet passageway 76. Other embodiments may employ additional control jets. The fluid F enters the fluid selector assembly 70 at the primary passageway 72 and flows towards the fluidic switch 90. A portion of the fluid flow splits off from the primary passageway 72 to the control jet assembly 74. The control jet assembly 74 includes a control jet passageway 76 having at least one inlet 77 providing fluid communication to the primary passageway 72, and an outlet 78 providing fluid communication to the fluidic switch assembly 90. A nozzle 71 can be provided if desired to create a “jet” of fluid upon exit, but it not required. The outlet 78 is connected to the fluidic switch assembly 90 and directs fluid (or communicates hydrostatic pressure) to the fluidic switch assembly. The control jet outlet 78 and the downstream portion 79 of the control jet passageway 72 longitudinally overlap the lower portion 92 of the fluidic switch assembly 90, as shown.
The exemplary control jet assembly further includes a plurality of inlets 77, as shown. The inlets preferably include flow control features 80, such as the chambers 82 shown, for controlling the volume of fluid F which enters the control jet assembly from the primary passageway dependent on the characteristic of the fluid. That is, the fluid selector assembly 70 “selects” for fluid of a preferred characteristic. In the embodiment shown, where the fluid is of a relatively higher viscosity, such as oil, the fluid flows through the inlets 77 and the control passageway 76 relatively freely. The fluid exiting the downstream portion 79 of the control jet passageway 72 through nozzle 78, therefore, “pushes” the fluid flowing from the primary passageway after its entry into the fluidic switch 90 at mouth 94. The control jet effectively directs the fluid flow towards a selected side of the switch assembly. In this case, where the production of oil is desired, the control jet directs the fluid flow through the switch 90 along the “on” side. That is, fluid is directed through the switch towards the switch “on” passageway 96 which, in turn, directs the fluid into the vortex assembly to produce a relatively direct flow toward the vortex outlet 102, as indicated by the solid arrow.
A relatively less viscous fluid, such as water or natural gas, will behave differently. A relatively lower volume of fluid will enter the control jet assembly 74 through the inlets 77 and control features 80. The control features 80 are designed to produce a pressure drop which is communicated, through the control jet passageway 76, outlet 78 and nozzle 71, to the mouth 94 of the sticky switch. The pressure drop “pulls” the fluid flow from the primary passageway 72 once it enters the sticky switch mouth 94. The fluid is then directed in the opposite direction from the oil, toward the “off” passageway 98 of the switch and into the vortex assembly 100. In the vortex assembly, the less viscous fluid is directed into the vortex chamber 104 by switch passageway 98 to produce a relatively tangential spiraled flow, as indicated by the dashed arrow.
The fluidic switch assembly 90 extends from the downstream end of the primary passageway 72 to the inlets into the vortex assembly 60 (and does not include the vortex assembly). The fluid enters the fluidic switch from the primary passageway at inlet port 93, the defined dividing line between the primary passageway 72 and the fluidic switch 90. The fluidic switch overlaps longitudinally with the downstream portion 79 of the control jet passageway 76, including the outlet 78 and nozzle 71. The fluid from the primary passageway flows into the mouth 94 of the fluidic switch where it is joined and directed by fluid entering the mouth 94 from the control jet passageway 76. The fluid is directed towards one of the fluidic switch outlet passageways 96 and 98 depending on the characteristic of the fluid at the time. The “on” passageway 96 directs fluid into the vortex assembly to produce a relatively radial flow towards the vortex outlet and a relatively low pressure drop across the valve assembly. The “off” passageway 98 directs the fluid into the vortex assembly to produce a relatively spiraled flow, thereby inducing a relatively high pressure drop across the autonomous valve assembly. Fluid will often flow through both outlet passageways 96 and 98, as shown. Note that a fluidic switch and a sticky switch are distinct types of switch.
The vortex assembly 100 has inlet ports 106 and 108 corresponding to outlet passageways 96 and 98 of the sticky switch. The fluid behavior within the vortex chamber 104 has already been described. The fluid exits through the vortex outlet 102. Optional vanes or directional devices 110 may be employed as desired.
The inlet passageway 130 communicates fluid from a source, such as formation fluid from a screen annulus, etc., to the biasing mechanism 140. Fluid flow and fluid velocity in the passageway is substantially symmetric. The inlet passageway extends as indicated and ends at the biasing mechanism. The inlet passageway has an upstream end 132 and a downstream end 134.
The biasing mechanism 140 is in fluid communication with the inlet passageway 130 and the sticky switch assembly 160. The biasing mechanism 140 may take various forms, as described herein.
The exemplary biasing mechanism 140 has a biasing mechanism passageway 142 which extends, as shown, from the downstream end of the inlet passageway to the upstream end of the sticky switch. In a preferred embodiment, the biasing mechanism 140 is defined by a widening passageway 142, as shown. The widening passageway 142 widens from a first cross-sectional area (for example, measured using the width and height of a rectangular cross-section where the inlet and widening passageways are rectangular tubular, or measured using a diameter where the inlet passageway and widening passageways are substantially cylindrical) at its upstream end 144, to a larger, second cross-sectional area at its downstream end 146. The discussion is in terms of rectangular cross-section passageways. The biasing mechanism widening passageway 142 can be thought of as having two longitudinally extending “sides,” a first side 148 and a second side 150 defined by a first side wall 152 and a second side wall 154. The first side wall 152 is substantially coextensive with the corresponding first side wall 136 of the inlet passageway 130. The second side wall 154, however, diverges from the corresponding second side wall 138 of the inlet passageway, thereby widening the biasing mechanism from its first to its second cross-sectional areas. The walls of the inlet passageway are substantially parallel. In a preferred embodiment, the widening angle .alpha. between the first and second side walls 152 and 154 is approximately five degrees.
The sticky switch 160 communicates fluid from the biasing mechanism to the vortex assembly. The sticky switch has an upstream end 162 and a downstream end 164. The sticky switch defines an “on” and an “off” outlet passageways 166 and 168, respectively, at its downstream end. The outlet passageways are in fluid communication with the vortex assembly 180. As its name implies, the sticky switch directs the fluid flow toward a selected outlet passageway. The sticky switch can thought of as having first and second sides 170 and 172, respectively, corresponding to the first and second sides of the biasing mechanism. The first and second side walls 174 and 176, diverge from the first and second biasing mechanism walls, creating a widening cross-sectional area in the switch chamber 178. The departure angles β and δ are defined, as shown, as the angle between the sticky switch wall and a line normal to the inlet passageway walls (and the first side wall of the biasing mechanism). The departure angle δ on the second side is shallower than the departure angle β on the first side. For example, the departure angle β can be approximately 80 degrees while the departure angle δ is approximately 75 degrees.
The vortex assembly 180 has inlet ports 186 and 188 corresponding to outlet passageways 166 and 168 of the sticky switch. The fluid behavior within a vortex chamber 184 has already been described. The fluid exits through the vortex outlet 182. Optional vanes or directional devices 190 may be employed as desired.
In use, a more viscous fluid, such as oil, “follows” the widening. Stated another way, the more viscous fluid tends to “stick” to the diverging (second) wall of the biasing mechanism in addition to sticking to the non-diverging (first) wall. That is, the fluid flow rate and/or fluid velocity distribution across the cross-section at the biasing mechanism downstream end 146 are relatively symmetrical from the first to the second sides. With the shallower departure angle δ upon exiting the biasing mechanism, the more viscous fluid follows, or sticks to, the second wall of the sticky switch. The switch, therefore, directs the fluid toward the selected switch outlet.
Conversely, a less viscous fluid, such as water or natural gas, does not tend to “follow” the diverging wall. Consequently, a relatively less symmetric flow distribution occurs at the biasing mechanism outlet. The flow distribution at a cross-section taken at the biasing mechanism downstream end is biased to guide the fluid flow towards the first side 170 of the sticky switch. As a result, the fluid flow is directed toward the first side of the sticky switch and to the “off” outlet passageway of the switch.
Note a difference between the fluidic switch (as in
The discussion above addresses viscosity as the fluid characteristic of concern, however, other characteristics may be selected such as flow rate, velocity, etc. Further, the configuration can be designed to “select” for relatively higher or lower viscosity fluid by reversing which side of the switch produces spiral flow, etc.
Additional embodiments can be employed using various biasing mechanisms to direct fluid flow toward or away from a side of the sticky switch. The use of these variations will not be discussed in detail where their use is similar to that described above. Like numbers are used throughout where appropriate and may not be called out.
Other curved, linear, or curvilinear contour elements may be used, such as triangular cuts, saw-tooth cuts, Tesla fluidic diodes, sinusoidal contours, ramps, etc.
Also shown is another type of biasing mechanism, a step-out 204, or abrupt change in passageway cross-section. The biasing mechanism passageway 141 has a first cross-section 206 along the upstream portion of the passageway. At a point downstream, the cross-section abruptly changes to a second cross-section 208. This abrupt change alters the fluid distribution at the biasing mechanism downstream end. The cross-sectional changes can be used alone or in combination with additional elements (as shown), and can be positioned before or after such elements. Further, the cross-section change can be from larger to smaller, and can change in shape, for example, from circular to square, etc.
The biasing mechanism causes the fluid to flow towards one side of the sticky switch for a more viscous fluid and toward the other side for a less viscous fluid.
The system and method can also be used with other flow control systems, such as inflow control devices, sliding sleeves, and other flow control devices that are already well known in the industry. The system can be either parallel with or in series with these other flow control systems.
The Abstract of the disclosure is solely for providing the United States Patent and Trademark Office and the public at large with a way by which to determine quickly from a cursory reading the nature and gist of technical disclosure, and it represents solely one or more embodiments.
While various embodiments have been illustrated in detail, the disclosure is not limited to the embodiments shown. Modifications and adaptations of the above embodiments may occur to those skilled in the art. Such modifications and adaptations are in the spirit and scope of the disclosure.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/US2013/057783 | 9/3/2013 | WO | 00 |
