BACKGROUND

1. Field of Invention

[0001] The invention relates generally to a system and method for evaluating a multiphase flow of wellbore fluids in a tubular. More specifically, the system and method introduces thermal energy into the flow and monitors downstream heating of the fluid to estimate both fluid phase and flow velocity.

2. Description of Prior Art

[0002] Flowmeters are often used for measuring flow of fluid produced from hydrocarbon producing wellbores. Flowmeters may be deployed downhole within a producing wellbore, a jumper or caisson used in conjunction with a subsea wellbore, or a production transmission line used in distributing the produced fluids. Monitoring fluid produced from a wellbore is useful in wellbore evaluation and to project production life of a well. The produced fluid may include water and/or gas mixed with liquid hydrocarbon. Knowing the water fraction is desirable to ensure adequate means are available for separating the water from the produced fluid. Additionally, the amount and presence of gas is another indicator of wellbore performance, and vapor mass flow impacts transmission requirements. In wells having a network of wellbores, it is useful to estimate which bores produce different types of fluid.

[0003] Flowmeters can be employed that provide information regarding total flow, water cut amount, and gas fractions. However, these often require periodic analysis of the fluid entering the flowmeter. This may involve deploying a sample probe upstream of the flowmeter; which can produce inaccuracy, and may interrupt or temporarily halt fluid production. The types of flowmeters range from pressure differential, spinner type meters, thermal pulse, and capacitive sensors.

SUMMARY OF THE INVENTION

[0004] The present disclosure includes a method and apparatus for evaluating flow of a fluid downhole. An example of a method for evaluation downhole fluid flow includes applying thermal energy to the flow of fluid at a position in the flow of fluid, sensing a temperature of the fluid stream downstream of the position over time, and estimating a type of fluid in the flow of fluid based on the step of sensing temperature downstream. The method can further include generating a temperature profile based on the step of sensing a temperature. The steps of applying thermal energy to the flow of fluid can be performed at different radial positions in the flow of fluid, and temperatures downstream of the different radial positions can be sensed. This example can further include generating a temperature profile of fluid after application of thermal energy at each of the different radial positions, and identifying different phases of fluid within the flow of fluid at the different radial positions based on the step of generating the temperature profiles. The different phases of fluid can be water, liquid hydrocarbon, and gas. In an example, the thermal energy is applied upstream and spaced axially away from where the temperature is sensed at each radial position. The method can further include estimating a flow rate of the flow of fluid based on an elapsed time between when the thermal energy is applied and when a peak temperature is measured downstream. In an example, the position is first position, and wherein the step of sensing a temperature of the fluid stream downstream of the first position over time is performed at a second position, the method can further include sensing a temperature of the fluid stream at a third position that is downstream of the second position. Temperature profiles obtained at the second and third positions can be compared, this comparison can be used to identify a phase of the fluid being sensed at the second and third positions. [0005] Another example of a method of evaluating flow of a fluid downhole includes applying thermal energy to the flow of fluid at a position in the flow of fluid, sensing a temperature of the fluid stream downstream of the position over time at a first downstream location, sensing a temperature of the fluid stream downstream of the position over time at a second downstream location that is downstream of the first downstream location, and estimating a type of fluid in the flow of fluid based on a comparison of temperature profiles obtained by sensing temperatures at the first and second downstream locations. In one example, the method further includes estimating fluid flow based on a measurement of a time lapse between when the thermal energy is applied to the fluid, and when a peak of temperature is observed at the first downstream location. The method also optionally further involves repeating the steps of applying thermal energy and sensing temperature of the fluid stream at radial positions in the flow of fluid. The method optionally further includes identifying different phases of fluid within the flow of fluid.

[0006] Also disclosed herein is a system for evaluating fluid flow in a downhole wellbore, and which includes, a thermal source module that is selectively disposed in a flow of fluid in the wellbore and energized to apply thermal energy to the flow of fluid, a thermal sensor module disposed axially away from the thermal source module and disposed in the flow of the fluid in the wellbore downstream of the thermal source module, and that selectively monitors a temperature profile of the fluid over time, and a controller in communication with the thermal sensor module and that selectively identifies a phase of fluid in the flow of fluid based on an analysis of the temperature profile monitored by the thermal sensor module. The thermal sensor module can be a first thermal sensor module, the system further having a second thermal sensor module disposed downstream of the first thermal sensor module and that selectively monitors a temperature profile of the fluid over time. In an example, the controller is in communication with the second thermal sensor module. The system can also include an elongate frame to which the thermal source module and the sensor modules are coupled, and an arm having a length, a width, and a height, and a slot formed radially through the arm, and wherein the frame is coupled in the slot and pivotable about a line that projects along the height of the arm. In an embodiment, the arm mounts to a housing and is pivotal between an orientation substantially parallel with a length of the housing and to an orientation oblique to the length of the housing and that spans across a substantial portion of a diameter of the wellbore. The system can further include an arm having a plurality of thermal source modules each having a corresponding thermal sensor module disposed downstream and each along paths that intersect the thermal source modules and are substantially parallel with an axis of the wellbore.

BRIEF DESCRIPTION OF DRAWINGS

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

[0008] FIG. 1 is a side partial sectional view of an embodiment of a downhole tool having a fluid sensor assembly and disposed in a wellbore.

[0009] FIGS. 2 and 3 are side views of an embodiment of the fluid sensor assembly of FIG. 1 disposed in a deviated portion of production tubing.

[0010] FIG. 4 is a side view of a portion of the fluid sensor assembly of FIG. 1.

[0011] FIG. 5 is a graphical illustration of an example of a temperature profile over time of a stationary fluid after an instantaneous thermal energy pulse.

[0012] FIG. 6 is a graphical illustration of an example of a temperature profile over time of a moving fluid after an instantaneous thermal energy pulse.

[0013] FIG. 7 is a graphical illustration of an example of a temperature profile over time of a moving fluid after a prolonged thermal energy pulse.

[0014] FIG. 8 is a graphical illustration of an example of fluid temperature profiles at where thermal energy is applied to the fluid, and downstream at a temperature sensor.

[0015] While the invention will be described in connection with the preferred embodiments, it will be understood that it is not intended to limit the invention to that embodiment. On the contrary, it is intended to cover all alternatives, modifications, and equivalents, as may be included within the spirit and scope of the invention as defined by the appended claims.

DETAILED DESCRIPTION OF INVENTION

[0016] The method and system of the present disclosure will now be described more fully hereinafter 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 herein; rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey its scope to those skilled in the art. Like numbers refer to like elements throughout.

[0017] It is to be further understood that the scope of the present disclosure is not limited to the exact details of construction, operation, exact materials, or embodiments shown and described, as modifications and equivalents will be apparent to one skilled in the art. In the drawings and specification, there have been disclosed illustrative embodiments and, although specific terms are employed, they are used in a generic and descriptive sense only and not for the purpose of limitation. Accordingly, the improvements herein described are therefore to be limited only by the scope of the appended claims.

[0018] Figure 1 is a side partial sectional view of an example of a downhole tool 10 disposed in a wellbore 12. In this example, wellbore 12 intersects a formation 14 which includes hydrocarbons that are being produced through wellbore 12. Production tubing 16 is shown inserted within wellbore 12 and which may be coaxially disposed within casing (not shown) cemented within wellbore 12. Downhole tool 10 includes a housing 17 shown suspended on wireline 18, where wireline 18 is supported by a wellhead assembly 20 on its upper end. Included in housing 17 is a fluid sensor assembly 22 for monitoring and/or analyzing a flow of fluid F shown flowing within production tubing 16 towards wellhead assembly 20 and over housing 17. A controller 24 is shown above surface and which is in communication with downhole tool 10 and fluid sensor assembly 22 via a communication means 26. Examples exist wherein controller 24 is provided within an operations vehicle (not shown) on surface and above the opening of the wellbore 12. Although communication means 26 is illustrated as being hardwired, other embodiments exist for communication means 26 such as wireless, fiber optic, and any other form of transmitting and/or receiving signals.

[0019] Figure 2 shows in a side sectional view an example of a segment of downhole tool 10 disposed in a length of tubing 16 that resides in a deviated portion of wellbore 12. In this example fluid sensor assembly 22 includes an elongate arm 28 that couples to an extension 30 shown depending downward from housing 17 (Figure 1). In this embodiment, arm 28 selectively rotates with respect to extension 30 about a pin 32 that pivotingly couples arm 28 to extension 30. In this deviated portion of wellbore 12, fluid F is made up of different types of fluid that are in multiple phases. More specifically, a water layer 34 is shown in a lower portion of fluid F adjacent a lower section of tubing 16, and a liquid hydrocarbon layer 36 is shown disposed above water layer 34 in a mid-portion of tubing 16. In the space above liquid hydrocarbon layer 36 is a gas layer 38, that occupies the space between an upper border of liquid hydrocarbon layer 36 and the upper inner surface of tubing 16. A series of elongate slots 40i _-6 are shown formed laterally through the arm 28. Each of the slots 40i _-6 includes a thermal source module 42i _-6 , which in one example of operation transmits thermal energy into fluid F flowing in tubing 16 and past wellbore tool 10. Also disposed within each of the slots 40i _-6 are thermal sensor modules 44i _-6 that monitor temperature within the flow of fluid F. In an example, the thermal source modules 42i _-6 are heating elements, such as elongate wires, across which current is conducted to generate thermal energy, which is then transferred into the fluid F flowing past the thermal source modules 42 _1-6 . In an embodiment, the thermal sensor modules 44 _1-6 are thermocouples and when exposed to a flow of the fluid F, emit signals representative of temperature within the fluid F flowing past the thermal sensor modules 44 _1-6 , wherein the signals can be correlated to an actual temperature of the fluid F so the temperature of the fluid F can be monitored.

[0020] Figure 3 illustrates an example of operation wherein arm 28 is no longer substantially parallel with axis A _x of tubing 16, but instead has been rotated to an orientation that is oblique to axis Αχ. In this example, at least one of each of the slots 40i _-6 are each of the separate phase layers. More specifically, slot 40 ₁ is in the water layer 34 and slot 40 ₆ is disposed in the gas layer 38. Each of slots 40 _2- 5 are in the liquid hydrocarbon layer 36. Alternate embodiments of use exist where an equal number of slots 40i _-6 are disposed in each of the fluid layers 34, 36, 38, i.e. slots 40 _1;2 in water layer 34, slots 40 _3;4 in liquid hydrocarbon layer 36, and slots 40 _5;6 in gas layer 38. In this example, the thermal source modules 42 _1-6 are energized to create heating within the fluid F. Moreover, the corresponding thermal sensor modules 44 _1-6 are disposed directly downstream of their corresponding thermal source modules 42 _1-6 so that the fluid F heated by a one of the modules 42 _1-6 is sensed by its corresponding sensor 44i _-6 . Accordingly, heating created by the thermal source modules 42 _1-6 can be monitored by the respective thermal sensor modules 44i _-6 . As will be described in more detail below, analyzing the temperature profile over time of the fluid F can then help identify in which phase of fluid 34, 36, 38 the individual thermal sensor modules 44 _1-6 is disposed. Optionally, a proximity sensor system 45 can be included that provides for measurement of the angular displacement of arm 28 so that the location of each of the slots 40i _-6 can be estimated based on signal output from the proximity sensor 45. In an example, the location of the slots 40i _-6 can include either how far from the extension 30 is the specific one of the slots 40i _-6 , or a value of angle Θ of the arm 28 with respect to the extension 30. Thus, the ability to ascertain the phase of fluid F based on temperature readings from the sensor modules 44 _1-6 , coupled with output from proximity sensor 45, can provide information about the amount of the particular fluid phases 34, 36, 38 disposed within tubing 16.

[0021] Referring now to Figure 4, shown in a side view is one example of an alternate embodiment of sensor assembly 22A and which includes an aft thermal sensor module 46 _n disposed downstream of the thermal sensor module 44 _n . In this example, a module frame 48 _n is provided in slot 40 _n , and on which each of the thermal source module 42 _n , thermal sensor module 44 _n , and aft thermal sensor module 46 _n are coupled. Module frame 48 _n includes an elongate upper frame member 50 _n that is shown extending obliquely to a length of slot 40 _N and a lower frame member 51 _n that also extends obliquely along a length of slot 40 _n . Upper and lower frame members 50 _n , 51 _n project along paths that diverge from one another. Pins 52 _n , 53 _n respectively couple the upper and lower frame members 50 _n , 51 _n to the edge of the slot 40 _n . Forward ends of the upper and lower frame members 50 _n , 51 _n are coupled to one another via a forward frame member 54 _n , which is an elongate member and extends generally perpendicular to a length of slot 40 _n . The rearward ends of the upper and lower frame members 50 _n , 51 _n are coupled to one another by an elongate aft frame member 56 _n , which is generally parallel with forward frame member 54 _n . As the upper and lower frame members 50 _n , 51 _n diverge from one another along their respective lengths, the aft frame member 56 _n is longer than forward frame member 54 _n . Accordingly, frame 48 _n has a weather vane type look and with a height that increases along its length, and the pins 52 _n , 53 _n are closer to the forward frame member 54 _n than to the aft frame member 56 _n . As such, when placed in a flowing stream of fluid, the enlarged aft portion of frame 48 _n will direct the frame 48 _n that is in a path substantially parallel with the path of any flow of fluid F flowing past the arm 28. Pins 52 _n , 53 _n have a pivoting coupling with frame 48 _n which allows this weather vane type action in the flow of fluid F. Mounting brackets 58 _n , 60 _n , 62 _n respectively mount the thermal source module 42 _n , thermal sensor module 44 _n , and aft thermal sensor module 46 _n within frame 48 _n . Accordingly, the modules 42 _n , 44 _n , 46 _n are each aligned in a path P of any fluid F that flows across arm 28. Thus, the sensor modules 44 _n , 46 _n are strategically located in path P to detect heating of fluid F introduced by operation of the source module 42 _n . These modules 42 _n , 44 _n , 46 _n are all in communication with controller 24 via communication means 26A, that in this embodiment is illustrated as a wireless device or system.

[0022] Figures 5 through 7 graphically illustrate temperature profiles over time in fluids and depict differences between an instantaneous thermal energy pulse versus one that is prolonged. More specifically shown in Figure 5 is a coordinate system 64 where the abscissa represents axial distance in a body of fluid and the ordinate represents temperature T. Profile 66 represents temperature in the fluid and where the value of X equals zero represents the location where in the fluid a thermal energy input is applied. Temperature profiles 68, 70, 72 show how the temperature changes over time and becomes flatter with a reduced maximum value of temperature T. Each of the profiles 66, 68, 70, 72 follow a Gaussian profile. In the example of Figure 5, the fluid F in which the thermal energy impulse is applied is generally stationary.

[0023] Figure 6 illustrates one example of introducing a thermal energy impulse into a flowing body of fluid. In this example, the thermal energy input is a pulse which may last up to a few milliseconds. Shown plotted on coordinate system 64A are temperature profiles taken over time, i.e., 66 A, 68 A, 70 A, 72 A. More specifically, profiles 68 A, 70 A, 72 A, which represent temperature distribution at t = 0+, have corresponding peaks that move along the abscissa and in the direction of fluid flow. Moreover, as can be seen, the profiles 68A, 70A, 72A all have respective peaks that diminish over time and are less than the peak of profile 66A. Similarly, Figure 7 illustrates coordinate system 64B on which are plotted a series of profiles 66B, 68B, 70B, 72B, wherein the thermal energy input is applied not as a pulse, but over a period of time, such as one that may exceed a few hundred milliseconds. In this example, the Gaussian distribution resembles that of a sum of individual Gaussian profiles.

[0024] Figure 8 represents one example of a temperature profile 76, 78, 80 that may be recorded respectively at the thermal source module 42 _n , thermal sensor module 44 _n , and aft thermal sensor 46 _n . An advantage of multiple sensor modules 44 _n , 46 _n is that additional data may be recorded that illustrates the respective profiles 78, 80 and provides information about how quickly the temperature dissipates. Thus, studying either or both of temperature profile 78, 80, in comparison to temperature profile 76, not only can the velocity of the fluid flowing past the modules 42 _n , 44 _n , 46 _n be estimated, so may the type of fluid that flows past the sensor modules 44 _n , 46 _n . For example, the rate at which the thermal energy making up the temperature profiles dissipates can be estimated and used to identify the particular type of fluid. It is known that the Gaussian profile will become flatter in water over a time period less than that for liquid hydrocarbon. Thus, comparing the measured temperature profile and comparing that to a known temperature profile for either water or liquid hydrocarbon, the corresponding fluid being monitored may be identified.

Example

[0025] Table 1 below illustrates values of thermal conductivity, density, heat capacity, density*heat capacity, thermal diffusivity, and diffusivity ratio for crude oil, water, and methane over a range of temperature and pressure conditions. k 1 ( P p)

k [Wm ^' Y ¹ ] P ^' V] P ^{' 1} ] a

i Crude Oil 0.125 850 1800 1530000 8.16993E-08: 1.000 iWater 0.580 1000 4180 4180000 1.38756E-07; 1.698

: Methane (125 C, 8000 psi) 0.098 213 3293 702094 1.40010E-07; 1.714 i Methane (150 C, 8000 psi) 0.101 200 3293 659331 1.53754E-07; 1.882

; Methane (175 C, 8000 psi) 0.099 189 3306 623926 1.58477E-07: 1.940 i Methane (125 C, 5000 psi) 0.088 178 3294 586891 1.49757E-07: 1.833 i Methane (150 C, 5000 psi) 0.08 ₄ 145 3246 469050 1.78149E-07; 2.181

: Methane (175 C, 5000 psi) 0.085 135 3243 436633 1.95640E-07; 2.395 i Methane (125 C, 10000 psi) 0.108 240 3279 786721 1.37346E-07; 1.681

; Methane (150 C, 10000 psi) 0.107 227 3290 747057 1.43455E-07: 1.756 i Methane (175 C, 10000 psi) 0.107 216 3311 713622 1.50273E-07I 1.839

Table 1

[0026] Additionally, in combination with providing multiple sets of the modules 42 _1-6 , 44 _1-6 , 461. 6 at multiple radial locations within the bore hole (Figure 3), the location at the interface of multiple phase fluids can also be identified. More specifically, in a deviated wellbore, it will be known that the uppermost portion of the tubing will contain a gas, so that in situations when the temperature profile of gas is similar to that of water, the spatial location of where the temperature profile is being measured can provide an indication of whether or not the fluid is water or gas. Velocity can be obtained if the time between the thermal energy input and when that thermal energy is detected by the sensor modules 44 _n , 46 _n in combination with the respective distances between the modules 42 _n , 44 _n , 46 _n are known. It should be pointed out, that although the profiles in Figure 7 might appear to emulate a distorted Gaussian, the respective peak movement can still be used to obtain flow velocity of the fluid. An advantage of using a line source for the thermal energy input, i. e. , a thin resistively heated wire, is so that the system can be modeled as a one- dimensional problem. One reason why the temperature profile in water is flatter is that water has a higher thermal diffusivity than oil. Thermal diffusivity is typically defined as thermal conductivity divided by the product of mass density and heat capacity. Therefore, for the same flow rate, the fluid temperature profile after pulse heating becomes wider and shorter quicker for water than it does for oil. To visualize this phenomenon, imagine being in the frame of reference of the fluid (by traveling alongside it at the same speed) with a thermal imaging camera and seeing the injected thermal pulse diffusing left and right of where it had been injected much more quickly for water than it would for oil because water has approximately 1.7 times the thermal diffusivity of oil. In this example, in the frame of reference of the tool, the measured temporal thermal profile is compressed in time because of the relative motion between the moving fluid and the temperature sensors that are attached to the stationary tool. Because in many downhole conditions the natural gas is at a high pressure and temperature, it can have a thermal diffusivity comparable to that of water, which is why the actual radial locations of the sensor modules 44 _n , 46 _n in relationship to the directions of up and down may be required in order to differentiate the type of fluid being monitored by these modules 44 _n , 46 _n . That is, in laminar flow, gas will be on top, oil in the middle, and water on the bottom, providing an additional way to distinguish fluid types when thermal diffusivities are comparable.

[0027] The present invention described herein, therefore, is well adapted to carry out the objects and attain the ends and advantages mentioned, as well as others inherent therein. While a presently preferred embodiment of the invention has 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 invention disclosed herein and the scope of the appended claims.