Patent Application
20180272252
The present disclosure relates generally to gas evolution and dissolution, and more specifically to affecting the rates of gas evolution from liquid and gas dissolution into liquid.
Gas evolution is a physical or chemical process where gas is disengaged from solution, i.e., produced as free gas or bubbles or foam from a supersaturated solution. A supersaturated solution stores more gas than the “saturation level” governed by thermodynamics (e.g., system pressure, temperature, and composition). Gas dissolution is a different physical or chemical process by which a gas in the form of free gas, bubbles or foam enters into or is transferred to an undersaturated solution. An undersaturated solution stores less gas than the thermodynamic “saturation level.” Factors such as system temperature and pressure, level of agitation, and fluid properties affect gas evolution and gas dissolution. Gas evolution and dissolution are encountered in and can be used in a number of applications. Several oil and gas industry operations involve both gas evolution and dissolution, including, but not limited to, sulfur degassing, gas lift, artificial lift using electric submersible pumps (ESPs) and separations.
It would be desirable to effect gas evolution and dissolution rates in such operations in a more controlled and reliable way.
In general, in one aspect, the disclosure relates to a device for changing a state of a gas relative to a liquid. The device includes a section of conduit having at least one inner wall that forms a cavity for containing a multiphase fluid including a liquid and gas flowing therethrough. The device also includes at least one capillary within the cavity having a first capillary end open to the flowing gas for receiving gas and a second capillary end open to a flowing liquid for expelling gas into the flowing liquid. Through the use of the device, gas is passively transferred from the flowing gas to the flowing liquid and the transferred gas forms bubbles in the flowing liquid.
In another aspect, the disclosure relates to a fluid handling system including at least one section of conduit for flowing a multiphase fluid comprising a liquid and a gas therethrough and at least one system component in fluid communication with the at least one section of conduit. The multiphase fluid is subjected to at least one substantial change in pressure. The above-described device is located in the fluid handling system downstream of the substantial change in pressure.
In yet another aspect, the disclosure relates to a method of changing a state of a gas relative to a liquid. The method includes flowing a multiphase fluid including a liquid in the gas through a section of conduit having at least one inner wall forming a cavity such that a gas-liquid interface is present in the cavity. A capillary is located within the cavity having a first capillary end open to the flowing gas for receiving gas and a second capillary end open to the flowing liquid for expelling gas into the flowing liquid. A stream of the gas is passively received into the first capillary end open to the flowing gas and the stream of the gas is expelled from the second capillary end into the flowing liquid thereby forming bubbles of the gas in the flowing liquid.
These and other aspects, objects, features, and embodiments will be apparent from the following description and the appended claims.
The drawings illustrate only example embodiments of methods, systems, and devices for affecting rates of gas evolution and dissolution. Example embodiments can be applied to any of a number of applications. For instance, example embodiments can be used during a production field operation of a subterranean formation. Therefore, example embodiments described herein are not to be considered limiting of its scope, as affecting rates of gas evolution and/or dissolution may admit to other equally effective embodiments and/or applications. This is similarly applied to drawings illustrating any systems described herein. The elements and features shown in the drawings are not necessarily to scale, emphasis instead being placed upon clearly illustrating the principles of the example embodiments. Additionally, certain dimensions or positionings may be exaggerated to help visually convey such principles. In the drawings, reference numerals designate like or corresponding, but not necessarily identical, elements.
The example embodiments discussed herein are directed to systems, apparatus, and methods of affecting or enhancing the rates of gas evolution from liquid and gas dissolution into liquid. Example systems for affecting rates for evolving and dissolving gases described herein can be used in any type of container in which a gas can be evolved and/or dissolved. Example embodiments can be used in any of a number of applications, including but not limited to production field operations, industrial operations, production of plastics, volcanic activity, sulfur removal pits, diving, solutions produced through electrolysis, chemical plants, biomedical practice, separators, pumps, tanks, and production facilities.
For example, gas-liquid separation is a critical unit operation in crude oil production. In typical upstream oil and gas operations, the multiphase fluids produced from oil wells are separated and processed before being exported as sales and waste streams. These multiphase fluids present numerous challenges in processing, where any issues in design and operation of separators create bottlenecks requiring equipment adjustments. These alterations add operating costs, increase downtime, and/or reduced throughput, all of which result in lost value.
As another example, the unexpected evolution of additional gas in a pipeline or flowline can lead to concerns such as unplanned slugging, increased backpressure, and over prediction of pressure drop, particularly with more viscous liquids. This can compromise the integrity of the flowlines, risers, topsides, and other equipment. For proper design of compact systems, engineers must be able to determine the residence time required to meet the desired outlet gas volume fraction (GVF) specifications with reasonable certainty. Enhancing the rate of evolution and dissolution of gas using example embodiments can mitigate these problems.
In one embodiment, the disclosure relates to a device for changing a state of a gas relative to a liquid. A liquid as used herein can be any one or more substances that are free flowing and having constant volume. Examples of a liquid can include, but are not limited to, water, drilling mud, blood, liquid sulfur, polymers, and oil. A gas as used herein can be one or more of any air-like fluid substances that expand freely to fill any space available (e.g., head space). A gas as used herein can be a free gas, bubbles, gas that is in solution, and/or foam. Examples of a gas can include, but are not limited to, natural gas, nitrogen, methane, air, hydrogen sulfide, carbon monoxide, and carbon dioxide.
Referring to
The device 10 includes at least one capillary 6 within the cavity in the section of conduit 2 having a first capillary end 6A open to the flowing gas 12G for receiving gas and a second capillary end 6B open to a volume of flowing liquid 12L. As shown, in one embodiment, the capillary 6 can be a circumferential capillary attached so that the first capillary end 6A is near the top of the pipe above the gas-liquid interface 13 and the second capillary end 6B is below the gas-liquid interface 13. The first capillary end 6A can be oriented to face the flow of gas 12G. This arrangement essentially short circuits the flow of gas, sending some of it into the bulk liquid 12L.
In one embodiment, the capillary 6 has an inner diameter from 1 mm to 100 mm. In one nonlimiting example, the capillary 6 is physically supported by the inner wall of the conduit 2.
Through the use of the device 10, gas is transferred from the upper portion of the cavity in the conduit 2 to the flowing liquid 12L through the capillary 6. In use, a stream of the gas 12G is passively received into the first capillary end 6A and is expelled from the second capillary end 6B into the flowing liquid 12L The gas 12G can enter the capillary 6 and its kinetic energy overcomes capillary pressures in the capillary 6, pushes the liquid inside the capillary 6 out and creates bubbles 16 of the gas 12G within the liquid 12L. The introduced bubbles 16 enhance the rates of gas dissolution or evolution as dictated by the thermodynamic state of the specific system. The bubbles 16 can have an average diameter of less than 1 μm. In another embodiment, the bubbles 16 can have an average diameter of greater than 1 μm.
The liquid 12L and the gas 12G can be in solution as a result of thermodynamic conditions with each other and/or out of solution relative to each other. Separating the gas 12G from the liquid 12L is evolution of the gas, and integrating the gas 12G with the liquid 12L is dissolution of the gas. When the gas 12G is integrated with the liquid 12L, the gas is suspended in the liquid. There may or may not be bubbles of gas 12G in the liquid 12L. The gas 12G can be a foam within or on top of the liquid 12L. In other words, the gas 12G mixed in the liquid 12L can have any one or more of a number of forms.
Through the evolution process within the cavity in the conduit 2, the gas 12G evolves (separates from the liquid 12L) and accumulates in the headspace above interface 13. When the gas 12G dissolves, at least most of the gas 12G (to the extent that the liquid 12L becomes saturated and can no longer absorb additional quantities of the gas 12G) leaves the headspace and becomes suspended in the liquid 12L.
In one embodiment, shown in
In another embodiment, shown in
In one embodiment, the inner surface 6 of the capillary 6 is hydrophobic. The capillary 6 can be formed of a hydrophobic material. In one embodiment, the inner surface of the capillary 6 is oleophobic. The capillary 6 can be formed of an oleophobic material. In one embodiment, the inner surface of the capillary 6 is coated with a coating that can be a hydrophobic or oleophobic coating. The coating of the inner surface of the capillary 6 can be one or more of any of a number of materials (e.g., carbon nanotubes, nano-silica, polytetrafluoroethylene (PTFE), Gore-Tex®, fluorocarbons, perfluorocarbons (PFCs)) having one or more of any of a number of characteristics (e.g., smooth, adhesive, repellant). (Gore-Tex is a registered trademark of W. L. Gore and Associates.)
The coating can be hydrophobic, super-hydrophobic, oleophobic, have some other characteristic, or have any combination thereof. For example, the coating can be both hydrophobic and oleophobic to allow for increasing gas evolution regardless of the continuous phase liquid throughout the production life. The coating can be applied to the inner surface of the capillary 6 evenly, unevenly, randomly, in a pattern, and/or in any other fashion.
In one embodiment, the disclosure relates to a fluid handling system using the device 10 for changing a state of a gas relative to a liquid. The fluid handling system includes at least one section of conduit for flowing the multiphase fluid 12 therethrough. At least one system component is in fluid communication with the at least one section of conduit 2. The system component can be any suitable fluid handling components such as, but not limited to, pipes, pipe fittings, pipe bends, valves, pumps, venturis, reducers and combinations thereof. The multiphase fluid 12 is subjected to at least one substantial change in pressure. By “substantial change in pressure” is meant an increase or decrease in pressure of 10% or 10 psi, whichever is lower. In one embodiment, the at least one substantial change in pressure coincides with the at least one system component. The device 10 as described above can be employed at a location in the system downstream of the substantial change in pressure.
For example, as shown in
As shown in
In one embodiment, the fluid handling system can be a pump to facilitate the transfer of a liquid and/or gas from one location to another. In this embodiment, the substantial change in pressure coincides with increased pressure resulting from pumping the fluid. The pump can use any of a number of suitable technologies. For example, the pump can be a continuous flow syringe pump. As another example, the pump can be a piston cylinder pump. In a nonlimiting example, multiphase (gas/liquid) fluids 12 may enter an electric submersible pump (ESP). It is very important for proper ESP operation that the pressurized fluids downstream of a stage have reached equilibrium. If gas dissolution is kinetically impeded, however, the fluids may not equilibrate and the free gas fraction entering the next stage of the ESP may exceed design limits. This adversely affects ESP performance and thus the production rates. In one embodiment (not shown), the device 10 can be located within a pump inlet leading to the pump body. In one embodiment, shown in
As shown in
For illustrative purposes, consider a multiphase (e.g., oil, gas, and water) stream 12 reaching a production choke (a type of valve) 516 upstream of a compact subsea separator 512. After taking a substantial pressure drop at the choke 516, the solution gas 12G must disengage from the liquid 12L to reach the new thermodynamic equilibrium. This can include the time for solution gas to form bubbles, grow, rise and reach the bulk gas-liquid interface 13. This process must conclude within the liquid residence time (which for compact systems can be as low as 30 seconds) in the inlet piping 514 and the vessel 512.
While the time to approach equilibrium after a pressure drop is quick, it is not instantaneous. Quantifying the amount of time required for gas evolution is difficult at best, given the lack of comprehensive predictive models. With short residence times, the margin for error in estimating the extent of gas-liquid separation in the separator 512 is small, but the cost of miscalculations is high. Example embodiments can alter the rate of gas evolution and/or dissolution, greatly reducing this risk and associated cost.
The transience of gas evolving out of solution (e.g., liquid) can be a concern for heavy oil production. Heavy oil is notorious for having processing challenges related to gas-liquid separation with heavy oil emulsions, foams, and gassy crudes, making separation difficult. Typical methods for gas-liquid separation of heavy crude oils involve a combination of gravity separation for long periods of time, chemicals, and heat. Example embodiments can be used to improve gas-liquid separations of these mixtures.
As shown in
If a component of a figure is described but not expressly shown or labeled in that figure, the label used for a corresponding component in another figure can be inferred to that component. Conversely, if a component in a figure is labeled but not described, the description for such component can be substantially the same as the description for the corresponding component in another figure.
In addition, a statement that a particular embodiment (e.g., as shown in a figure herein) does not have a particular feature or component does not mean, unless expressly stated, that such embodiment is not capable of having such feature or component. For example, for purposes of present or future claims herein, a feature or component that is described as not being included in an example embodiment shown in one or more particular drawings is capable of being included in one or more claims that correspond to such one or more particular drawings herein.
In the foregoing figures showing example embodiments of affecting rates for gas evolution and dissolution, one or more of the components shown may be omitted, repeated, and/or substituted. Accordingly, example embodiments of affecting rates for gas evolution and dissolution should not be considered limited to the specific arrangements of components shown in any of the figures. For example, features shown in one or more figures or described with respect to one embodiment can be applied to another embodiment associated with a different figure or description.
As explained above, gas evolution is the process by which one or more gases 12G that are dissolved in one or more liquids 12L disengages from the liquid(s) due to pressure drop. Gas evolution is a composite of one or more of a number of processes, including but not limited to bubble nucleation, growth, rise, and coalescence. Both dissolution and evolution processes are critical to several oil and gas industry applications, including but not limited to liquid sulphur degassing, artificial lift using gas, boosting/pumping, and separations. There is very limited data available on controlling the rates of gas evolution and dissolution, and the resulting effects of controlling these rates.
Example embodiments of affecting rates for gas evolution and dissolution are described herein with reference to the accompanying drawings, in which example embodiments of affecting rates for gas evolution and dissolution are shown. Affecting rates for gas evolution and dissolution may, however, be embodied in many different forms and should not be construed as limited to the example embodiments set forth herein. Rather, these example embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of affecting rates for gas evolution and dissolution to those of ordinary skill in the art. Like, but not necessarily the same, elements (also sometimes called components) in the various figures are denoted by like reference numerals for consistency.
Terms such as “first,” “second,” “top,” “bottom,” “proximal”, “distal”, “inner,” “outer,” “within,” “front,” “rear,” and “side” are used merely to distinguish one component (or part of a component or state of a component) from another. Such terms are not meant to denote a preference or a particular orientation, and are not meant to limit embodiments of systems for gas evolution and dissolution. In the following detailed description of the example embodiments, numerous specific details are set forth in order to provide a more thorough understanding of the invention. However, it will be apparent to one of ordinary skill in the art that the invention may be practiced without these specific details. In other instances, well-known features have not been described in detail to avoid unnecessarily complicating the description.
Although embodiments described herein are made with reference to example embodiments, it should be appreciated by those skilled in the art that various modifications are well within the scope and spirit of this disclosure. Those skilled in the art will appreciate that the example embodiments described herein are not limited to any specifically discussed application and that the embodiments described herein are illustrative and not restrictive. From the description of the example embodiments, equivalents of the elements shown therein will suggest themselves to those skilled in the art, and ways of constructing other embodiments using the present disclosure will suggest themselves to practitioners of the art. Therefore, the scope of the example embodiments is not limited herein.
