Background

[0001] A well may produce fluids with a high percentage of oil, or other desired hydrocarbons, when it is first completed. Over time, however, the amount of undesirable fluids (for example, water or natural gas) in the produced fluids increases. In multi-zone wells, it is possible that undesirable fluids are produced from only a few of the zones and that the quality of the fluids produced from the well could be improved by limiting or eliminating the fluids produced from those zones. It is a challenge to determine the fraction of undesirable fluids (i.e., the“cut”) in fluids produced from zones in a well to determine which zones should be restricted in production to improve the quality of production from the well.

Brief Description of the Drawings

[0002] FIG. l is a schematic of a production system.

[0003] FIG. 2 is a schematic of a controllable inflow valve.

[0004] FIG. 3 is a schematic of a valve with in-line densitometers and flow meters.

[0005] FIG. 4 is a schematic of a valve with a densitometer and a flow meter in a side tube.

[0006] FIG. 5 is a schematic of a valve with a densitometer and a flow meter in a side tube with a pressure-holding shroud.

[0007] FIG. 6 is a schematic of a controllable inflow valve.

[0008] FIG. 7 is a schematic of a controllable inflow valve.

[0009] FIG. 8 is a schematic of a controllable inflow valve.

[0010] FIG. 9 is a schematic of a controllable inflow valve.

[0011] FIG. 10 is a schematic of a controllable inflow valve.

[0012] FIG. 11 is a schematic of a controllable inflow valve.

[0013] FIG. 12 is a schematic of a controllable inflow valve

[0014] FIG. 13 is a flow chart describing a method for determining a fraction of a subject fluid in a fluid.

[0015] FIG. 14 is a flow chart showing a method for controlling a fraction of a subject fluid in fluids produced from a well. [0016] FIG. 15A is a cross-sectional view of a valve or production tubing showing the use of a plurality of in-line densitometers and flow meters to determine holdup.

[0017] FIG. 15B is a cross-sectional view of a valve or production tubing showing the use of a plurality of densitometers and flow meters in side tubes to determine holdup.

[0018] FIG. 15C is a cross-sectional view of a valve or production tubing showing the use of a plurality of densitometers and flow meters in shrouded side tubes to determine holdup.

Detailed Description

[0019] The following detailed description illustrates embodiments of the present disclosure. These embodiments are described in sufficient detail to enable a person of ordinary skill in the art to practice these embodiments without undue experimentation. It should be understood, however, that the embodiments and examples described herein are given by way of illustration only, and not by way of limitation. Various substitutions, modifications, additions, and rearrangements may be made that remain potential applications of the disclosed techniques. Therefore, the description that follows is not to be taken as limiting on the scope of the appended claims. In particular, an element associated with a particular embodiment should not be limited to association with that particular embodiment but should be assumed to be capable of association with any embodiment discussed herein.

[0020] FIG. 1 is a schematic of a production system. A production system 102 includes production tubing 104 that carries hydrocarbons and/or other products from a well 106 to the surface 108. The well 106 includes a borehole 110 that penetrates zones H2a, H2b, 112c, etc. separated by packers H4a, 1 l4b, 1 l4c, 1 l4d, etc. Hydrocarbons and/or other products enter the borehole 110 through perforations 116 (only one is labeled). The hydrocarbons enter the production tubing through respective controllable inflow valves 1 l8a, 118b, 1 l8c, etc. A controller 120 is connected to the valves 1 l8a, 118b, 118c, etc. via control line 122 and controls the degree to which the valves 1 l8a, 118b, 1 l8c, etc. are open via the same control line 122. The control line 122 may be a hydraulic control line. The controller 120 may be at the surface, as shown in FIG. 1. The controller 120 may be below the surface 108 near or attached to one or more of the valves 1 l8a-c.

[0021] FIG. 2 is a schematic of a controllable inflow valve 202. The valve 202, with various combinations of components described in connection with FIG. 2 as discussed below in connection with FIGS. 6 through 12, is representative of any of the controllable inflow valves 118a, 118b, 118c, etc. The valve 202 includes a valve body 204. The valve body 204 contains a volume 206, which, for the purposes of this disclosure, is a mixing chamber and will be referred to herein by the term“mixing chamber 206.” The valve 202 includes an upstream fluid input 208 to the mixing chamber 206, an inflow fluid input 210 to the mixing chamber 206, and a fluid output 212 from the mixing chamber 206. The upstream fluid input 208 may be coupled to the production tubing 104 to receive fluid from upstream components (not shown), the inflow fluid input 210 receives fluid from the borehole 110 around the valve 202, and the fluid output 212 delivers fluid into the production tubing 104 for transportation to downstream components (not shown) and eventually to the surface 108. Fluid 216 entering the valve 202 through the upstream fluid input 208 mixes in the mixing chamber 206 with fluid 213 entering the valve through the inflow fluid input 210, to produce output fluid 226.

[0022] The valve 202 may include an inflow flow meter 214 to measure a volumetric flow rate of the fluid 213 flowing into the inflow fluid input 210 and to produce an inflow flow meter output 218 representing the measured volumetric flow rate of the fluid 213 flowing into the inflow fluid input 210. In this context,“to measure” or“measuring” is defined to receiving raw input from sensors, such as the inflow flow meter 214 and other similar devices described herein, converting the raw input from analog to a digital format, if necessary, and processing the resulting digital data as necessary to produce the specified output.

[0023] The valve 202 may include an inflow densitometer 220 to measure a density of the fluid 213 flowing into the inflow fluid input 210 and to produce an inflow densitometer output 222 representing the measured density of the fluid 213 flowing into in the inflow fluid input 210.

[0024] Note that, for clarity and ease of reference, the symbol for a flow meter, such as the inflow flow meter 214, includes a stylized representation of a flow meter at the bottom of a rectangular box and the symbol for a densitometer, such as inflow densitometer 220 includes a stylized representation of a densitometer at the bottom of a rectangular box.

[0025] The valve 202 may include an output densitometer 230 to measure a density of the fluid 226 flowing out of the fluid output 212 and to produce an output densitometer output 232 representing the measured density of the fluid 226 flowing out of the fluid output 212.

[0026] The valve 202 may include an output flow meter 224 to measure a volumetric flow rate of a fluid 226 flowing from the mixing chamber 206 out of the fluid output 212 and to produce an output flow meter output 228 representing the measured volumetric flow rate of the fluid 226 flowing out of the fluid output 212. [0027] The valve 202 may include an upstream densitometer 234 to measure a density of the fluid 216 flowing into the upstream fluid input 208 and to produce an upstream densitometer output 236 representing the measured density of the fluid 216 flowing into the upstream fluid input 208.

[0028] The valve 202 may include an upstream flow meter 238 to measure a volumetric flow rate of the fluid 216 flowing into the upstream fluid input 208 and to produce an upstream flow meter output 240 representing the measured volumetric flow rate of the fluid 216 flowing into the upstream fluid input 208.

[0029] The valve 202 includes a processor 242, which, may be coupled to the inflow flow meter output 218, the inflow densitometer output 222, the output flow meter output 228, the output densitometer output 232, the upstream densitometer output 236, and the upstream flow meter output 240. The processor 242 is programmed to use a subset of those outputs along with a density of oil and a density of a subject fluid to determine a fraction of the subject fluid in a fluid flowing in one or more of the inflow fluid input 210, upstream fluid input 208, or the fluid output 212.

[0030] The inflow flow meter 214, the inflow densitometer 220, the output flow meter 224, the output densitometer 230, the upstream flow meter 238, and the upstream densitometer 234 may be attached to the valve body 204.

[0031] The subject fluid could be water, could be gas, and/or could be oil. The subject fluid may be a mixture of two or more of water, gas, and oil.

[0032] The fluid 216 in the upstream fluid input 208 and a fluid 213 in the inflow fluid input 210 are mixed in the mixing chamber 206 to produce in the fluid output 212 a well-mixed combination of the fluid 216 in the upstream fluid input 208 and the fluid 213 in the inflow fluid input 210. The term“well- mixed” is defined to mean that different phases in the fluid described as“well-mixed” are homogenously distributed in the fluid and move through the production tubing 104 at the same velocity For example, a well-mixed combination of oil and water would have the oil and water homogenously mixed.

[0033] Returning to FIG. 1, an output tubular, such as the production tubing 104, is coupled to the fluid output 212. The output flow meter 224 and the output densitometer 230, are positioned within a well- mixed range l24a, l24b, l24c, etc. of the mixing chamber 206 such that the output flow meter 224 measures the volumetric flow rate of the fluid 226 flowing out of the fluid output 212 and the output densitometer 230 measures the density of the fluid 226 flowing out of the fluid output 212 in the output tubular (i.e., production tubing 104) within a well-mixed range l24a, l24b, l24c, etc. of the mixing chamber 206 in the respective valve 1 l8a, 118b, 118c, etc. The term“well-mixed range” is defined to mean the distance over which flowing fluid remains well-mixed and is typically in a range of 0 to 10 times the internal bore diameter of the fluid output 212. The well-mixed range 124a, l24b, l24c, etc. may be outside the respective valve 118a, 118b, 118c, etc., as shown in FIG. 1. The well-mixed range 124a, l24b, l24c, etc. may be inside the respective valve H8a, H8b, H8c, etc. The well-mixed range 124a, 124b, l24c, etc. may be partially outside the respective valve 1 l8a, 118b, 1 l8c, etc. and partially inside the respective valve 118a, 118b, 118c. The well-mixed range may be three feet (0.91 meters). The well-mixed range may 1 foot (0.30 meters). The well-mixed range may be three inches (7.62 centimeters).

[0034] The valve 202 includes a controllable inflow valve 244, shown in FIG. 2, to control the amount of fluid 213 entering the mixing chamber 206 through the inflow fluid input 210. The controllable inflow valve 244 may be similar to the Interval Control Valve (“ICV”) available from Halliburton. The controllable inflow valve 244 is controlled by the processor 242 by way of control line 246. The controllable inflow valve 244 can be commanded to be open, closed, or open by a controllable amount between open and closed. The controllable inflow valve 244 can be opened in 10 increments (i.e., 10 percent open, 20 percent open, 30 percent open, 40 percent open, 50 percent open, 60 percent open, 70 percent open, 80 percent open, 90 percent open, and 100 percent open).

[0035] The inflow flow meter 214, the output flow meter 224, and the upstream flow meter 238 may include Venturi devices, such as the FLOSTREAM™ Venturi flow meters available from Halliburton, that measure flow using the Venturi effect. Other types of flow meters, such as those that determine flow rate from the pressure on either side of an orifice, may be used.

[0036] The inflow densitometer 220, the output densitometer 230, and the upstream densitometer 234 may include a vibrating tube densitometer, such as those described in United States Patent No. 9,008,977, entitled Determining Fluid Density.” which is assigned to the assignee of the instant application. Such vibrating tube densitometers use measured vibration frequencies of a tubular sample cavity filled with a liquid to determine properties, including density, of the fluid. More specifically, by using an excitation source, and measuring the resulting resonant frequency of the combined fluid and tube assembly, the total mass, consisting of the mass of the tube and the fluid flowing through it, can be calculated as the mass density of the fluid changes. Therefore, by monitoring the resonant frequencies of the vibrating tube, it is possible to measure the density of the fluid mass. [0037] FIG. 3 is a schematic of a valve with in-line densitometers and flow meters. The upstream densitometer 234, the upstream flow meter 238, the output densitometer 230, and the output flow meter 224 may be in-line with the production tubing 104. The inflow flow meter 214, the inflow densitometer 220, the output flow meter 224, the output densitometer 230, the upstream flow meter 238, and the upstream densitometer 234 may be permanently installed in a zone, or inserted as needed within a zone using a wireline, Slickline, or tubing tool, depending on requirements from the operator, cost considerations, and specific conditions of the field.

[0038] The production tubing 104 may act as the tube in a vibrating-tube densitometer with the packers H4a, H4b, H4c, etc. forming the anchor points for the tube. Such embodiments may not have flow meters. A magnet may be attached to the vibrating tube and generates a time-dependent electromagnetic force (EMF) from the magnetic flux change experienced by a magnetic coil interacting with the moving magnet. Other emitters may include piezoelectric sources, mechanical hammers/tappers, micro explosions, or the flow of the fluid itself. Other detectors or sensors may include accelerometers, optical sensors (fiber Bragg grating point sensors, reflectometers, Sagnac coils, distributed acoustic, or distributed stain), piezoelectric or flexoelectric sensors, and electric strain gauges (resistive or capacitive).

[0039] The temperature and pressure within the densitometer may be measured in-situ in order to provide more accurate calculation of the fluid density, and hence water cut. Additional methods to improve the calculation are using pressure, volume, temperature (PVT) data provided by the operator or by optimizing the excitation signal and sensing signal pick-up.

[0040] Phases that have experienced separation can still be estimated by measuring multiphase flow rates using cross-correlation methods. For example, by using two densitometers at differing locations and monitoring their time series of changing density data, the speed at which a change in material density occurs can be calculated. By knowing the density of pure fluid phases, the measured change in density can be correlated to a change in water cut; by knowing the speed this change propagated, the flow rate of the changing phase can be estimated as well.

[0041] FIG. 4 is a schematic of a densitometer and a flow meter in a side tube. The valve body 204 may include a main channel 402, which may be part of or connected to the upstream fluid input 208, the inflow fluid input 210, or the fluid output 212. The valve body 204 may include a side tube 404 into which a portion 406 of the fluid 408 in the main channel 402 is diverted. A densitometer 410 may measure a density of the fluid 408 in the side tube 404. A flow meter 412 may measure a rate of flow of the fluid 406 flowing through the side tube 404 and that rate of flow is used to extrapolate the rate of flow of fluid 408 through the main channel 402.

[0042] The valve 202 may have a plurality of side tubes 404, each with a flow meter 412 and densitometer 410, placed at different azimuthal positions around the main channel 402 (see e.g., FIGS. 14A-14C discussed below).

[0043] FIG. 5 is a schematic of a densitometer and a flow meter in a side tube with a pressure-holding shroud. The arrangement shown in FIG. 4 may augmented by adding a pressure-holding shroud 502 around the densitometer 410 and the flow meter 412 to keep constant the pressure around the densitometer 410. The pressure-holding shroud 502 may contain a fluid at a pre-determined pressure. The pressure-holding shroud 502 may keep constant an acoustic impedance around the input densitometer.

[0044] The valve 202 may have a plurality of side tubes 404, each with a flow meter 412 and a densitometer 410, placed at different azimuthal positions around the main channel 402 and with all of the side tubes covered by pressure holding shroud 502 (see e.g., FIG. 14C discussed below)

[0045] Referring to FIGS. 1 and 2, a system may include the production tubing 104 penetrating an upper zone, e.g. 1 l2a, and a lower zone, e.g. 1 l2b, in the well 106. A lower zone valve 118b has a lower zone inflow fluid input 210 coupled to the lower zone 112b by which fluids from the lower zone 112b enter the lower zone valve 118b. The lower zone valve 118b has a lower zone fluid output 212 by which fluid 226 from the lower zone valve 118b enters the production tubing 104. The lower zone valve 118b has a lower zone control (i.e., controllable inflow valve 244) to control the amount of fluid 213 from the lower zone H2b that enters the production tubing 104. The lower zone valve 118b includes a lower zone cut computer 242 to measure a fraction of a subject fluid in a fluid 213 flowing into the lower zone inflow fluid input 210.

[0046] The system includes an upper zone valve 1 l8a having a first upper zone input 208 (the features shown in FIG. 2 are common to the lower zone valve 118b, described above, and the upper zone valve 1 l8a) coupled to the lower zone fluid output 212 of the lower zone valve 118b through the production tubing 104. The upper zone valve 118a includes an upper zone inflow fluid input 210 coupled to the upper zone 112a by which fluids from the upper zone 1 l2a enter the upper zone valve 118a The upper zone valve 1 l8a has an upper zone fluid output 212 by which fluid from the upper zone valve 1 l8a enters the production tubing 104. The upper zone valve H8a has an upper zone control (i.e., controllable inflow valve 244) to control the amount of fluid 213 from the upper zone 112a that enters the production tubing 104. The upper zone valve 118a has an upper zone cut computer 242 to measure a fraction of the subject fluid in a fluid 213 flowing into the upper zone inflow fluid input 210.

[0047] The system includes a subject fluid controller 120 (see FIG. 1) coupled to the lower zone control

(the controllable inflow valve 244 associated with the lower zone valve 118b) and the upper zone control (the controllable inflow valve 244 associated with the upper zone valve 1 l8a) to control the amount of fluid from the lower zone 112b that enters the production tubing 104 and amount of fluid from the upper zone 112a that enters the production tubing 104 based on the fraction of the subject fluid in a fluid flowing into the lower zone inflow fluid input 210 associated with lower zone valve 118b and the fraction of the subject fluid in a fluid flowing into the upper zone inflow fluid input 210 associated with the upper zone valve H8a.

[0048] The subject fluid controller 120 may be distributed among the upper zone cut computer 242 associated with the upper zone valve 118a and the lower zone cut computer 242 associated with the lower zone valve H8b. That is, the decision making regarding the amount offluid to enter the production tubing 104 from the upper zone 112a and the lower zone 112b may be performed partly by software in the upper zone cut computer 242 associated with the upper zone valve 118a and partly by the lower zone cut computer 242 associated with the lower zone valve 118b. All the decision making regarding the amount of fluid entering the production tubing 104 from the upper zone H2a and from the lower zone 1 l2b may be performed by software in the upper zone cut computer 242 associated with the upper zone valve 118a or by the lower zone cut computer 242 associated with the lower zone valve 118b.

[0049] FIG. 6 is a schematic of a controllable inflow valve. The valve 202 may be a version of the valve 202 shown in FIG. 2 without the output flow meter 224, the upstream densitometer 234 and the upstream flow meter 238. Further, the output densitometer 230 is in a side tube, such as densitometer 410 in side tube 404. Herein, elements in side tubes are indicated by bars across the top edge of the rectangular box representing the element.

[0050] In the embodiment shown in FIG. 6, the fraction of the subject fluid 213 flowing into the inflow fluid input 210 is computed using equation (1) below:

. PA— Po

FL = -

Ps— Po where fA is the calculated fraction of the subject fluid in the fluid 213 flowing into the inflow fluid input 210; pA is the inflow densitometer 220 output 222 representing the measured density of the fluid 213 flowing into the inflow fluid input 210; p ₀ is the density of oil, and p _s is the density of the subject fluid.

[0051] Similarly, the fraction of the subject fluid flowing out of the fluid output 212 is computed using equation (2) below:

Poutput Rq

F Output —

Ps— Po

where foirr^ is the calculated fraction of the subject fluid in the fluid 226 flowing out of the fluid output 212; poutput is the measured density 232 of the fluid 226 flowing out of the fluid output 212; p ₀ is defined above in connection with equation (1), and p _s is defined above in connection with equation (1). [0052] FA from each controllable intake valve H8a-c can be used, along with the inflow flow meter output 218 representing the measured volumetric flow rate of the fluid 213 flowing into the inflow fluid input 210 from each zone 118a-c to determine the contribution of each zone to the fraction of the subject fluid produced from the well 106 at the surface 108.

[0053] FIG. 7 is a schematic of a controllable inflow valve The valve 202 may be a version of the valve 202 shown in FIG. 2 without the upstream densitometer 234 and the upstream flow meter 238. Further, the output flow meter 224 and the output densitometer 230 are in a side tube either together, as shown in FIGS. 3, 4, and 5, or separately. fA may be calculated using equation (1) and fqiaria may be calculated using equation (2).

[0054] FIG. 8 is a schematic of a controllable inflow valve. The valve 202 may be a version of the valve 202 shown in FIG. 2 without the inflow densitometer 220 and the inflow flow meter 214. The output flow meter 224 and the output densitometer 230 are in a side tube either together, as shown in FIGS. 3, 4, and 5, or separately. The upstream flow meter 238 and the upstream densitometer 234 are in a side tube either together, as shown in FIGS. 3, 4, and 5, or separately fqpyii _ΐ may be calculated using equation (2) and FA may be calculated using equation (3) below: where fA is defined above in connection with equation (1); Qoutput is the output flow meter 224 output

228 representing the measured volumetric flow rate of the fluid 226 flowing out of the fluid output 212; pomput is defined above in connection with equation (2); Qup is the upstream flow meter 238 output 240 representing the measured volumetric flow rate of the fluid 216 flowing into the upstream fluid input 208; pup is the upstream densitometer 234 output 236 representing the measured density of the fluid 216 flowing into the upstream fluid input 208; p ₀ is defined above in connection with equation (1); and p _s is defined above in connection with equation (1).

[0055] FIG. 9 is a schematic of a controllable inflow valve. The valve 202 may be a version of the valve 202 shown in F1G. 2 without the output flow meter 224, the output densitometer, the upstream densitometer 234, and the upstream flow meter 238. f.A may be calculated using equation (1).

[0056] FIG. 10 is a schematic of a controllable inflow valve. The valve 202 may be a version of the valve 202 shown in F1G. 2 without the upstream densitometer 234 and the upstream flow meter 238. The output flow meter 224 may be a removable venturi device and the output densitometer 230 is in a side tube. FA may be calculated using equation (1) and foiiΐ ik may be calculated using equation (2).

[0057] FIG. 11 is a schematic of a controllable inflow valve. The valve 202 may be a version of the valve 202 shown in FIG. 2 without the output densitometer 230 and the output flow meter 224. The output flow meter 224 may be a removable venturi device and the output densitometer 230 is in a side tube. FA may be calculated using equation (1).

[0058] FIG. 12 is a schematic of a controllable inflow valve. The valve 202 may be a version of the valve 202 shown in FIG. 2 without the upstream densitometer 234, the upstream flow meter 238, the inflow densitometer 220, and the inflow flow meter 214. The output flow meter 224 and the output densitometer 230 may be in a side tube either together, as shown in FIGS. 3, 4, and 5, or separately fqi^ir may be calculated using equation (2).

[0059] FA from each controllable intake valve 118a-c in any of the configurations shown in FIGS. 6-11 can be used, along with the inflow flow meter output 218 representing the measured volumetric flow rate of the fluid 213 flowing into the inflow fluid input 210 from each zone H8a-c to determine the contribution of each zone to the fraction of the subject fluid produced from the well 106 at the surface 108.

[0060] foiLriiΐ from each controllable intake valve 118a-c in any of the configurations shown in FIGS. 6- 8, 10 and 12 can be used, along with the output flow meter output 228 representing the measured volumetric flow rate of the fluid 226 flowing out of the fluid output 212 from each zone H8a-c to determine the contribution of each zone to the fraction of the subject fluid produced from the well 106 at the surface 108.

[0061] Note that if a zone is not producing, there is no need to measure the fraction of subject fluid produced from the non-producing zone. For example, if zone 112b in FIG. 1 is not producing the contribution of zones 112b and 112a to the fraction of the subject fluid can be determined at zone 1 l2a.

[0062] FIG. 13 is a flow chart describing a method for determining a fraction of a subject fluid in a fluid. The method includes measuring a property of a fluid flowing through one of a plurality of passages in a valve (block 1302). The method further includes determining a fraction of a subject fluid in a fluid flowing through into the one of the plurality of passages using a density of oil, a density of the subject fluid, and the measured property (block 1304).

[0063] The density of oil may be determined from oil produced from a well 106 in which the valve 202 is installed when the well 106 first begins producing oil.

[0064] The technique described herein allows the determination of the fraction of the subject fluid from 0 percent to 100 percent in both vertical and horizontal wells.

Examples of use

[0065] FIG. 14 is a flow chart showing a method for controlling a fraction of a subject fluid in fluids produced from a well. The valve 202 is useful in the following scenario. When the well 106 is first drilled and completed, a sample is taken of the product from the well 106 (block 1402). The sample is analyzed to determine the fraction of the subject fluid (e g., water cut) in the product and the density of the oil in the product (block 1404). Additional samples of the same type are taken over time and the fraction of the subject fluid is monitored (block 1406). When the fraction of subject fluid reaches a threshold (block 1408), e.g., such that producing from the well is becoming less profitable (note that if the fraction of subject fluid has not reached the threshold (“N” branch from block 1408) processing returns to block 1406), it may be desirable to reduce the amount of fluids produced from a given zone 1 l2a, 1 l2b, 1 l2c, etc. to improve the quality of production from the well 106 (“Y” branch from block

1408. To do this, the following procedure is performed.

[0066] Respective fractions of a subject fluid in respective fluids (i.e., fluid 213 for all or a subset of the valves 118a, 118b, 118c, etc.) flowing into a plurality of valves 118a, 118b, 118c, etc. are measured (block 1410). Each of the plurality of valves H8a, H8b, H8c, etc. controls an amount of respective fluid that flows into a production tubing 104 from a respective zone H2a, 112b, H2c, etc. in the well 106. The measured fraction of the subject fluid in the fluid flowing into the production tubing 104 from a one of the plurality of valves 118a, 118b, 118c, etc. is determined to be greater than a threshold (block 1412). The one of the plurality of valves H8a, 118b, H8c, etc. is adjusted to change the amount of respective fluid that flows into the production tubing 104 from the respective zone in the well 112a, 1 l2b, 112c, etc. (block 1414) and processing returns to block 1406.

[0067] In another use, the valve 202 is useful in performing the processes described in United States Patent No. 9,388,686, entitled“Maximizing Hydrocarbon Production While Controlling Phase Behavior or Precipitation of Reservoir Impairing Liquids or Solids” (the‘686 patent), which is assigned to the assignee of the instant application. The valve 202 and the processing described above can be used to detect when the gas content of the fluid 213 entering the valve 202 through the inflow fluid input 210 is reaching the bubble point or when the content of another material in the fluid 213 entering the valve 202 through the inflow fluid input 210 reaches a point where it threatens to disrupt production from the well. The controllable inflow valve 244 can then be adjusted per the procedures described in the‘686 patent.

[0068] FIG. 15A is a cross-sectional view of a valve or production tubing showing the use of a plurality of in-line densitometers and flow meters to determine holdup. FIG. 15B is a cross-sectional view of a valve or production tubing showing the use of a plurality of densitometers and flow meters in side tubes to determine holdup. FIG. 15C is a cross-sectional view of a valve or production tubing showing the use of a plurality of densitometers and flow meters in shrouded side tubes to determine holdup. In another use, the valve 202 is useful in determining“holdup,” which is the relative volume of different phases (i.e., oil, water, gas) in the production tubing 104. Holdup is useful to know because the phases may move through the production tubing 104 at different speeds which might change the cut of each of the phases at the surface 108 compared to that at the depth of the zones 112a, 112b, 112c, etc. Typically, a water holdup measurement in the well-mixed range will give the water cut at that location.

[0069] A set of in-line densitometers and flow meters 1502 (only one is labeled), similar to the output flow meter 224 and the output densitometer 230 illustrated in FIG. 3, may be distributed around the inner perimeter of the production tubing 104, as shown in FIG. 8 A. The density and flow measurements produced from the in-line densitometers and flow meters 802 can be used to determine holdup.

[0070] A set of side tubes containing densitometers and flow meters 1504 (only one is labeled), similar to the side tubes 404, densitometers 410, and flow meters 412 illustrated in FIG. 4, may be distributed around the outer perimeter of the production tubing 104, as shown in FIG. 8B. The density and flow measurements produced from the side tubes containing densitometers and flow meters 1404 can be used to determine holdup.

[0071] The set of side tubes containing densitometers and flow meters 1504 may be shielded by a shroud 1506 similar to the shroud 502 illustrated in F1G. 5. The density and flow measurements produced from the side tubes containing densitometers and flow meters 1504 can be used to determine holdup.

Theoretical Proof-of-Concept

[0072] To verify that the proposed method has a measurable resonance frequency, a preliminary calculation comparing fundamental resonance frequencies in production tubing densitometers, as shown in the graph in Fig. 16, was undertaken. The units of the vertical axis in FIG. 10 are“resonance frequency” in Hertz (Hz) and the units of the horizontal axis are density in grams per cubic centimeter (gm/cm ³ ). ln the preliminary simulation, the outside diameter of the production tubing was taken as 4.0 inches (10.16 centimeters (cm)), the inside diameter as 3.5 inches (7.62 cm), and the length as a 1 meter (3.37 feet). Two different materials, mild steel (the solid curve in FIG. 16) and titanium alloy (the dashed curve in FIG. 16), were considered. The results show that the resonance frequency using production tubing is in the several hundred Hz range.

[0073] From a sensitivity standpoint, the production line densitometer can perform with good resolution, regardless of tubing orientation. The production tubing densitometer is expected to provide an accuracy of better than +/- 0.002 gm/cm ³ over a pressure range of 0 pounds per square inch (PS1) to 20,000 PSI and a temperature range of 75°F to 350°F under controlled conditions, giving an estimated resolution of at least 0.001 g/cm ³ . Furthermore, because of the near-linear sensitivity slope in the oil and water density range (0.7-1.1 g/cm ³ ), the density sensor can be used for 0-100% water cut determination.

In one aspect, an apparatus includes a production tubing for carrying fluids from a producing zone to a surface and a resonant tube densitometer to measure the density of the fluids carried by the production tubing, the resonant tube densitometer having a tube. A longitudinal section of the production tubing is the tube of the resonant tube densitometer.

Implementations may include one or more of the following. An upper packer and a lower packer may anchor the longitudinal section of the production tubing. A pressure holding shroud may be around the longitudinal section of the production tubing A vibration emitter may be coupled to the longitudinal section of the production tubing. The vibration emitter may include one or more of a piezoelectric source, a mechanical hammer, a mechanical tapper, and a generator of micro-explosions. The resonant tube densitometer may use a flow of fluid through the production tubing as a source of vibrations. A vibration sensor may be coupled to the longitudinal section of the production tubing. The vibration sensor may include one or more of an accelerometer, an optical sensor, a piezoelectric sensor, a flexoelectric sensors, and an electric strain gauges.

In one aspect, a method includes using a production tubing to carry fluids from a producing zone to a surface and using a resonant tube densitometer to measure the density of the fluids carried by the production tubing, the resonant tube densitometer having a tube. A longitudinal section of the production tubing is the tube of the resonant tube densitometer.

Implementations may include one or more of the following. The method may include anchoring the longitudinal section of the production tubing with an upper packer and a lower packer. The method may include surrounding the longitudinal section of the production tubing with a pressure holding shroud. The method may include coupling a vibration emitter to the longitudinal section of the production tubing. The vibration emitter may include one or more of a piezoelectric source, a mechanical hammer, a mechanical tapper, and a generator of micro-explosions. The method may include using a flow of fluid through the production tubing as a source of vibration. The method may include coupling a vibration sensor to the longitudinal section of the production tubing. The vibration sensor may include one or more of an accelerometer, an optical sensor, a piezoelectric sensor, a flexoelectric sensors, and an electric strain gauge.

In one aspect, a system includes a production tubing penetrating an upper zone and a lower zone in a well. A lower zone valve has a lower zone input coupled to the lower zone by which fluids from the lower zone enter the lower zone valve, a lower zone output by which fluid from the lower zone valve enters the production tubing, a lower zone control to control the amount of fluid from the lower zone valve that enters the production tubing, and a lower zone cut computer to measure a fraction of a subject fluid in a fluid flowing into the lower zone input. An upper zone valve has a first upper zone input coupled to the lower zone output of the lower zone valve through the production tubing, a second upper zone input coupled to the upper zone by which fluids from the upper zone enter the upper zone valve, an upper zone output by which fluid from the upper zone valve enters the production tubing, an upper zone control to control the amount of fluid from the upper zone valve that enters the production tubing, and an upper zone cut computer to measure a fraction of the subject fluid in a fluid flowing into the second upper zone input. A subject fluid controller is coupled to the lower zone control and the upper zone control to control the amount of fluid from the lower zone valve that enters the production tubing and amount of fluid from the upper zone valve that enters the production tubing based on the fraction of the subject fluid in a fluid flowing into the lower zone input and the fraction of the subject fluid in a fluid flowing into the second upper zone input. One of the lower zone control or the upper zone control has a resonant tube densitometer to measure the density of the fluids carried by the production tubing, the resonant tube densitometer having a tube. A longitudinal section of the production tubing is the tube of the resonant tube densitometer.

[0074] Implementations may include one or more of the following. The system may include an upper packer and a lower packer that anchor the longitudinal section of the production tubing. The system may include a pressure holding shroud around the longitudinal section of the production tubing. The system may include a vibration emitter coupled to the longitudinal section of the production tubing and a vibration sensor coupled to the longitudinal section of the production tubing. The operations of the flow diagrams are described with references to the systems/apparatus shown in the block diagrams. However, it should be understood that the operations of the flow diagrams could be performed by embodiments of systems and apparatus other than those discussed with reference to the block diagrams, and embodiments discussed with reference to the systems/apparatus could perform operations different than those discussed with reference to the flow diagrams.

[0075] The word“coupled” herein means a direct connection or an indirect connection. [0076] The text above describes one or more specific embodiments of a broader invention. The invention also is carried out in a variety of alternate embodiments and thus is not limited to those described here. The foregoing description of an embodiment of the invention has been presented for the purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise form disclosed. Many modifications and variations are possible in light of the above teaching. It is intended that the scope of the invention be limited not by this detailed description, but rather by the claims appended hereto.