Patent Application
20160230988
This disclosure generally relates to hydrocarbon disposal, and more particularly to apparatus and methods for combusting multi-phase fluids containing hydrocarbons.
Hydrocarbons are widely used as a primary source of energy, and have a significant impact on the world economy. Consequently, the discovery and efficient production of hydrocarbon resources is increasingly important. As relatively accessible hydrocarbon deposits are depleted, hydrocarbon prospecting and production has expanded to new regions that may be more difficult to reach and/or may pose new technological challenges. During typical operations, a borehole is drilled into the earth, whether on land or below the sea, to reach a reservoir containing hydrocarbons. Such hydrocarbons are typically in the form of oil, gas, or mixtures thereof which may then be brought to the surface through the borehole.
Well testing is often performed to help evaluate the possible production value of a reservoir. During well testing, a test well is drilled to produce a test flow of fluid from the reservoir. During the test flow, key parameters such as fluid pressure and fluid flow rate are monitored over a time period. The response of those parameters may be determined during various types of well tests, such as pressure drawdown, interference, reservoir limit tests, and other tests generally known by those skilled in the art. The data collected during well testing may be used to assess the economic viability of the reservoir. The costs associated with performing the testing operations may be significant, however, and therefore testing operations should be performed as efficiently and economically as possible.
Fluids produced from the test well are typically disposed of by burning, which raises environmental and safety concerns. For example, conventional burners may not completely combust the well fluids, thereby releasing black smoke and other pollutants into the surrounding environment. To reduce the amount of smoke produced during well test burning, many have proposed (such as at U.S. Pat. Nos. 3,565,562; 3,894,831; 4,419,071; and 5,096,124) to inject water into the flame, thereby to decrease the combustion temperature. Another approach, disclosed in British Patent No. GB 2,307,294, provides a burner that injects an air/water mixture into a combustion zone to reduce black smoke and other pollutants. These approaches require significant amounts of water, often in volumes greater than the amount of fluid produced during well testing. If sea water is used, as is typical for offshore well sites, chlorine and other deleterious compounds may be released into the environment. Additionally, because the hydrocarbon content of the well effluent may vary, these previous devices may cause incomplete combustion of the effluent, thereby releasing pollutants as well as unburned hydrocarbon effluent into the surrounding area.
Apparatus and methods are disclosed herein for combusting fluids having a hydrocarbon content. The fluids may be generated during well testing, oil spill cleanup, or other operations. According to the apparatus and methods disclosed herein, multi-phase hydrocarbon fluid is burned in an automated and environmentally-friendly manner without requiring separation of the water content from the hydrocarbon fluid. A feedback control loop is used that determines the water content of the incoming fluid and/or the quality of combustion produced by a burner and selectively adds an auxiliary fuel as needed. Emission gases may also be monitored to determine whether air supply to the burner should be increased or decreased.
In accordance with certain aspects of the disclosure, a method of burning a multi-phase hydrocarbon fluid includes determining a water content of the multi-phase hydrocarbon fluid, communicating the multi-phase hydrocarbon fluid to a fuel port of a burner in a primary fuel flow, initiating a flame at the burner to combust the multi-phase hydrocarbon fluid, communicating an auxiliary fuel source to the burner fuel port in an auxiliary fuel flow, and controlling the primary and auxiliary fuel flows based on the water content of the multi-phase hydrocarbon fluid.
In accordance with additional aspects of the disclosure, an apparatus for combusting a multi-phase hydrocarbon fluid may include a multi-phase flowmeter having a multi-phase flowmeter inlet fluidly communicating with a source of the multi-phase hydrocarbon fluid and a multi-phase flowmeter outlet, the multi-phase flowmeter being configured to determine a water content of the multi-phase hydrocarbon fluid. A burner may have a fuel port fluidly communicating with the multi-phase flowmeter outlet to receive a primary fuel flow of multi-phase hydrocarbon fluid, and an igniter configured to initiate a flame at the burner to combust the multi-phase hydrocarbon fluid. An auxiliary fuel source fluidly communicates with the burner fuel port, and an auxiliary fuel valve is disposed between the auxiliary fuel source and the burner fuel port, the auxiliary fuel valve having a first position configured to block an auxiliary fuel flow to the burner fuel port and a second position configured to permit the auxiliary fuel flow to the burner fuel port. A controller is operatively coupled to the multi-phase flowmeter and the auxiliary fuel valve, the controller being programmed to control the primary and auxiliary fuel flows based on the water content of the multi-phase hydrocarbon fluid.
The summary is provided to introduce a selection of concepts that are further described below in the detailed description. This summary is not intended to identify key or essential features of the claimed subject matter, nor is it intended to be used as an aid in limiting the scope of the claimed subject matter.
Embodiments of methods and apparatus for combusting a multi-phase hydrocarbon fluid are described with reference to the following figures. The same numbers are used throughout the figures to reference like features and components.
It should be understood that the drawings are not necessarily to scale and that the disclosed embodiments are sometimes illustrated diagrammatically and in partial views. In certain instances, details which are not necessary for an understanding of the disclosed methods and apparatuses or which render other details difficult to perceive may have been omitted. It should be understood, of course, that this disclosure is not limited to the particular embodiments illustrated herein.
So that the above features and advantages of the present disclosure can be understood in detail, a more particular description of the disclosure, briefly summarized above, may be had by reference to the embodiments thereof that are illustrated in the accompanying drawings. It is to be noted, however, that the drawings illustrate only typical embodiments of this disclosure and therefore are not to be considered limiting of its scope, for the disclosure may admit to other equally effective embodiments.
Methods and apparatus are disclosed herein for use with a multi-phase hydrocarbon fluid. The term “multi-phase hydrocarbon fluid” is intended to encompass any fluid having a water content and a hydrocarbon content (such as oil). Additionally, the multi-phase hydrocarbon fluid may have a gas content (such as methane). The multi-phase hydrocarbon fluid may be obtained from effluent from a supply line formed during well testing operations, oil-water mixtures created during an oil spill cleanup, or other sources.
The remaining fluid exiting the separator liquid outlet 110, which is the multi-phase hydrocarbon fluid with at least a portion of its gas content removed, is referred to herein as a “multi-phase hydrocarbon liquid” to distinguish it from the unprocessed, multi-phase hydrocarbon fluid entering the system 100. The multi-phase hydrocarbon liquid may be primarily an oil/water mixture, where the oil may be any flammable substance such as crude oil, oil-based mud, and the like while the water may be any inflammable substance such as sea water, water-based mud, and the like. Regardless of the specific components of the multi-phase hydrocarbon liquid, it will have a measurable production rate of hydrocarbon content (i.e., flammable content) and water content (i.e., inflammable content). Additionally, the multi-phase hydrocarbon liquid may also still include some residual gas content.
The multi-phase hydrocarbon fluid combustion system 100 may also include a multi-phase flowmeter 112 for analyzing the multi-phase hydrocarbon liquid exiting the separator liquid outlet 110. Accordingly, the flowmeter 112 includes a flowmeter inlet 114 in fluid communication with the separator liquid outlet 110 and a flowmeter outlet 116. In the exemplary embodiments, the multi-phase flowmeter 112 is configured to determine a water content and a hydrocarbon content of the multi-phase hydrocarbon liquid. Accordingly, the flowmeter 112 may be any device capable of determining water and/or hydrocarbon content of a liquid, such as devices that measure water/oil conductivity, capacity, or attenuation of gamma-rays passing through the liquid flow.
In some embodiments, the flowmeter 112 may be a “Vx-type” flowmeter as marketed by Schlumberger, Inc. The Vx-type flowmeter measures a differential pressure and gamma ray attenuation (at two or more energy levels) in a Venturi throat portion of the flowmeter. The pressure and attenuation information is then used to determine total mass flow rate, water content, and gas content of the multi-phase hydrocarbon liquid.
The exemplary system 100 also includes a burner 120 for combusting the multi-phase hydrocarbon liquid. The burner 120 includes a fuel port 122 fluidly communicating with the flowmeter outlet 116, such as through burner pipe 124, to receive a primary fuel flow of multi-phase hydrocarbon liquid. The burner 120 may also include an air port 126 fluidly communicating with an air source 128 (such as an air compressor) to provide an air flow for combusting the liquid.
A pilot port 130 and igniter 132 are provided to initiate a flame at the burner 120. The pilot port 130 fluidly communicates with a source of flammable gas. In some embodiments, the flammable gas source may be the gas reservoir 109, in which case a gas compressor 134 may be provided to deliver gas from the gas reservoir 109 to the pilot port 130.
The multi-phase hydrocarbon fluid combustion system 100 may further include an auxiliary fuel assembly for selectively delivering auxiliary fuel to the burner 120. The auxiliary fuel assembly may include an auxiliary fuel source, such as an auxiliary fuel tank 140, fluidly communicating with the burner fuel port 122. In the exemplary embodiment, an auxiliary fuel pipe 142 fluidly communicates between the auxiliary fuel tank 140 and the burner pipe 124, thereby placing the auxiliary fuel tank 140 and the burner fuel port 122 in fluid communication. An auxiliary fuel valve 144 is disposed in the auxiliary fuel pipe 142 between the auxiliary fuel source and the burner fuel port 122 to selectively control an auxiliary fuel flow to the burner 120. More specifically, the auxiliary fuel valve 144 may have an open position to permit the auxiliary fuel flow and a closed position to block the auxiliary fuel flow. Additionally or alternatively, the auxiliary fuel valve 144 may be controlled to be partially open in a “throttle position” that is between the fully open and fully closed positions. As such, the fuel valve 144 may be opened as needed to provide only the minimal or optimal amount of fuel in order to provide the proper mixture or amount or fuel to produce the needed combustion. In exemplary embodiments, the auxiliary fuel valve 144 may be a high speed, automatic, multi-switch valve.
The system 100 may also include a diverter tank 150 for receiving multi-phase liquid when combusting the liquid is not possible or desired. A diverter pipe 152 may fluidly communicate between the diverter tank 150 and the burner pipe 124. In the illustrated embodiment, the diverter pipe 152 is coupled to the auxiliary fuel valve 144, which may have a third position that permits fluid flow from the auxiliary fuel pipe 142 to the diverter tank 150.
An emission monitor 154 may be provided for determining a combustion quality of emission gases produced by the flame at the burner 120. In exemplary embodiments, the emission monitor 154 may be configured to determine one or more components of the emission gases, such as a NOx content, an O2 content, a CO content, a SO2 content, a benzpyrene content, a soot content, or other emission component indicative of combustion quality. For example, the emission monitor 154 may be a gas emission analyzer that uses a spectral radiometer for monitoring the fume emission spectrum.
A controller 160 is provided for controlling operation of various components of the multi-phase hydrocarbon fluid combustion system 100. The controller 160, which may include a processor, microprocessor, microcontroller, or other logic executing device, as well as memory, may be operatively coupled to the multi-phase flowmeter 112, the air source 128, the gas compressor 134, the auxiliary fuel valve 144, the igniter 132, and the emission monitor 154. The controller 160 may receive and interpret signals from these devices indicative of various measured parameters, and may send control signals for operating the devices, as discussed in greater detail below.
More specifically, the controller 160 may be operatively coupled to the multi-phase flowmeter and the auxiliary fuel valve 144 and programmed to control the primary and auxiliary fuel flows based on the water content of the multi-phase hydrocarbon liquid. In an exemplary embodiment, the controller 160 may be programmed to permit primary fuel flow to the burner 120 and block auxiliary fuel flow to the burner 120 (such as by placing the auxiliary fuel valve 144 in a first position) when the water content of the multi-phase hydrocarbon liquid is below a water content lower threshold. The water content lower threshold may be set at a water content value that indicates that the multi-phase hydrocarbon liquid may be efficiently combusted without addition of auxiliary fuel. In an exemplary embodiment, the water content lower threshold is approximately 20%.
Additionally, the controller 160 may be programmed to permit both primary and auxiliary fuel flows to the burner (such as by placing the auxiliary fuel valve 144 in a second position) when the water content is between the water content lower threshold and a water content upper threshold. The second position of the auxiliary fuel valve 144 may be the fully open position or a throttle position (i.e., partially open). When in a throttle position, the second position of the auxiliary fuel valve 144 may be modulated according to the water content of the effluent to optimize combustion. When the water content is within this range, the multi-phase hydrocarbon liquid is still capable being efficiently combusted, but it will require auxiliary fuel to do so. In an exemplary embodiment, the water content lower threshold may be approximately 25% and the water content upper threshold may be approximately 40%.
Still further, the controller 160 may be programmed to block both the primary and auxiliary fuel flows (such as by placing the auxiliary fuel valve 144 in a third position, where the multi-phase hydrocarbon liquid is communicated to the diverter tank 150) when the water content is above the water content upper threshold. When the water content is above the upper threshold, the multi-phase hydrocarbon liquid is incapable of efficient combustion, even with the addition of auxiliary fuel. Under these circumstances, the multi-phase hydrocarbon liquid may be directed to the diverter tank 150 for storage and/or reprocessing.
Additionally, the controller 160 may be programmed to control air flow to the burner based on the combustion quality of the emission gases. In some applications, the emission monitor 154 may be configured to determine the combustion quality of the emission gases by determining a NOx content, and the controller may be configured to increase the air flow when the NOx content is above an NOx threshold. Additionally or alternatively, the emission monitor 154 may be configured to determine the combustion quality of the emission gases by determining an O2 content, and the controller 160 may be programmed to increase the air flow rate when the O2 content is below an O2 lower threshold and decrease the air flow rate when the O2 content is above an O2 upper threshold.
In some embodiments, the controller 160 may be programmed to direct the multi-phase hydrocarbon fluid to the auxiliary fuel tank 140. When the multi-phase flowmeter 112 indicates that the multi-phase hydrocarbon fluid has a high hydrocarbon content, such as a hydrocarbon content greater than approximately 10%, the high-calorie hydrocarbon fluid may be stored in the auxiliary fuel tank 140 as a reserve.
The controller 160 may be operably coupled to the fuel preparation unit 210 and programmed to selective operate the fuel preparation unit 210 based on one or more determined characteristics of the multi-phase hydrocarbon liquid. For example, the controller 160 may be programmed to initiate operation of the fuel preparation unit 210 when the water content of the multi-phase hydrocarbon liquid is between a lower emulsion water content threshold (such as approximately 7%) and an upper emulsion water content threshold (such as approximately 40%). A viscosity sensor 212 may be provided at an inlet of the fuel preparation unit 210 and a pressure sensor 214 may be provided at an outlet of the fuel preparation unit 210 as shown in
Alternatively, the controller 160 may be programmed to control operation of the fuel preparation unit 210 based on the combustion quality of emission gases produced by the flame at the burner 120. For example, the fuel preparation unit 210 may be operated only when the emission monitor 154 indicates that an emission component, such as NOx or soot, exceeds an emission gases threshold.
In view of the foregoing, systems and methods are provided that may cleanly and efficiently combust multi-phase hydrocarbon fluid having a wide range of water contents. Auxiliary fuel may be selectively added to the fluid to improve subsequent combustion thereof. Additionally, fluid that cannot efficiently be combusted due to high water content is diverted from the burner to avoid release into the environment. Excess air supplied to the burner may be adjusted based on emission gases to further improve combustion. Each of these features reduces the amount of harmful emissions generated during combustion of multi-phase hydrocarbon fluids from well testing, oil spill cleanup, or other applications.
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 the burner assembly and methods for flaring low calorific content gases disclosed and claimed herein. 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 structure.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/RU2013/000797 | 9/13/2013 | WO | 00 |
