CLAIM OF PRIORITY

[0001] This application claims priority to U.S. Patent Application No. 17/644,641 filed on December 16, 2021, the entire contents of which are hereby incorporated by reference.

TECHNICAL FIELD

[0002] This disclosure relates to production fluid analysis during hydrocarbon production.

BACKGROUND

[0003] During hydrocarbon production, a single wellbore can produce from multiple production zones by passing through multiple, stacked production zones, branching out into sidetrack wellbores, or through other arrangements. In some implementations, production fluid from various production zones are directed through the wellbore by separate production tubing. In some implementations, the production fluid from various production zones are comingled and directed through a single production tubing string. Once at a topside facility, the production fluid is separated into its various components: oil, water, and gas.

SUMMARY

[0004] This disclosure describes technologies relating to determining watercuts in multiple production zones from a single production well.

[0005] An example implementation of the subject matter described within this disclosure is a method with the following features. A wellbore that supplies production fluid from a first production zone and a second production zone is produced. Production fluids from the first and second production zone are comingled within a same production tubular. A first tracer is pulsed into the first production zone. A second tracer is pulsed into the second production zone. The first tracer and the second tracer are barcoded such that the first tracer and the second tracer can be differentiated from one another. A first tracer decay is measured at a topside facility. A second tracer decay is measured at the topside facility. A water cut of the first production zone and the second production zone is determined based upon the first tracer decay and the second tracer decay.

[0006] Aspects of the example method, which can be used alone with the example method or in conjunction with other aspects of the example method, include the following. A first subsurface control valve is actuated to regulate the production fluids from the first production zone. Alternatively or in addition, a second subsurface control valve is actuated to regulate the production fluids from the second production zone.

[0007] Aspects of the example method, which can be used alone with the example method or in conjunction with other aspects of the example method, include the following. Production remains continuous while pulsing the first tracer, while pulsing the second tracer, while measuring the decay of the first tracer, and while measuring the decay of the second tracer.

[0008] Aspects of the example method, which can be used alone with the example method or in conjunction with other aspects of the example method, include the following. Pulsing the first tracer includes ceasing flow of the first tracer.

[0009] Aspects of the example method, which can be used alone with the example method or in conjunction with other aspects of the example method, include the following. Pulsing the second tracer includes a step-function pulse of a specified duration of time.

[0010] Aspects of the example method, which can be used alone with the example method or in conjunction with other aspects of the example method, include the following. Pulsing the first tracer and the second tracer include pulsing hydrophilic tracers.

[0011] Aspects of the example method, which can be used alone with the example method or in conjunction with other aspects of the example method, include the following. Determining the water cut of the first production zone or the second production zone includes using the following equation:

Toii(i) = ~ exp(-a Qi t) wherein Totifl) is the tracer concentration in oil from a specified production zone, a is a geometrical constant of an annular completion region, approximately equal to 1/F, where V is the volume of the annular region from the mouth of the dosing line up to the mouth of the inflow control valve, Q, is a total oil production flow rate from the specified production zone, and t is time.

[0012] Aspects of the example method, which can be used alone with the example method or in conjunction with other aspects of the example method, include the following. A third tracer is pulsed into the first production zone. A fourth tracer is pulsed into the second production zone.

[0013] Aspects of the example method, which can be used alone with the example method or in conjunction with other aspects of the example method, include the following. Measuring a first tracer decay and a second tracer decay includes taking production samples at the topside facility at specified intervals. The samples are tested to determine tracer concentrations at the specified time intervals. A decay slope of each tracer in each zone is determined based upon the tested samples.

[0014] An example implementation of the subject matter described within this disclosure is a system with the following features. A production well includes a first production zone and a second production zone. Production tubing is arranged to receive production fluid from the first production zone and the second production zone. A first subsurface control valve regulates flow from the first production zone into the production tubing. A second subsurface control valve regulates flow from the second production zone into the production tubing. A first actuable injection tube has a first outlet adjacent to a first inlet of the production tubing within the first production zone. A second actuable injection tube has a second outlet adjacent to a second inlet of the production tubing within the first production zone.

[0015] Aspects of the example system, which can be used alone with the example system or in conjunction with other aspects of the example system, include the following. A third injection tube has a third outlet adjacent to the first inlet of the production tubing within the first production zone. A fourth injection tube has a fourth outlet adjacent to the second inlet of the production tubing within the second production zone.

[0016] Aspects of the example system, which can be used alone with the example system or in conjunction with other aspects of the example system, include the following. A real-time sensor is at a topside facility. A controller is configured to send a control signal to a first topside pressure pump. The control signal is configured to cause the pump to pulse a first tracer into the first production zone. The controller is configured to send a control signal to a second topside pressure pump. The control signal is configured to cause the pump to pulse a second tracer into the second production zone. The first tracer and the second tracer are barcoded such that the first tracer and the second tracer can be differentiated from one another. A first tracer decay is measured at a topside facility by the real-time sensor. A second tracer decay is measured at the topside facility by the real-time sensor. A water cut of the first production zone and the second production zone is determined by the controller based upon the first tracer decay and the second tracer decay. A control signal is sent, by the controller, to the first subsurface control valve. The signal is configured to actuate a first subsurface control valve to regulate the production fluids from the first production zone. A control signal is sent, by the controller, to the second subsurface control valve. The signal is configured to actuate a second subsurface control valve to regulate the production fluids from the second production zone.

[0017] An example implementation of the subject matter described within this disclosure is a method with the following features. A wellbore that supplies production fluid from a first production zone and a second production zone produces production fluids from the first and second production zone. The production fluids from each zone are comingled within a same production tubular. A first tracer is pulsed into the first production zone. A second tracer is pulsed into the second production zone. The first tracer and the second tracer are barcoded such that the first tracer and the second tracer can be differentiated from one another. A first tracer decay is measured at a topside facility. A second tracer decay is measured at the topside facility. A water cut of the first production zone and the second production zone is determined based upon the first tracer decay and the second tracer decay, a first subsurface control valve is actuated, responsive to determining the water cut of the first production zone and the second production zone, to regulate the production fluids from the first production zone. A second subsurface control valve is actuated, responsive to determining the water cut of the first production zone and the second production zone, to regulate the production fluids from the second production zone.

[0018] Aspects of the example method, which can be used alone with the example method or in conjunction with other aspects of the example method, include the following. Pulsing the second tracer includes ceasing flow of the first tracer. [0019] Aspects of the example method, which can be used alone with the example method or in conjunction with other aspects of the example method, include the following. Pulsing the first tracer comprises a step-function pulse of a specified duration of time.

[0020] Aspects of the example method, which can be used alone with the example method or in conjunction with other aspects of the example method, include the following. Determining the water cut of the first production zone and the second production zone includes using the following equation:

Twater(i) = To exp(-Cl Qi t) / (Ql + Ch) where Tater(t) is hydrophilic tracer concentration in water from a specified production zone, To is a tracer concentration injected down the dosing line from the surface, a is a geometrical constant of an annular production zone, a being approximately equal to 1/F, where V is an annular volume of the production zone from the mouth of the dosing line up to the mouth of the inflow control valve, C is a total production flow rate from the specified production zone, Qi is a total production flowrate from the first production zone, Q2 is a total production rate from the second production zone, and t is time.

[0021] Aspects of the example method, which can be used alone with the example method or in conjunction with other aspects of the example method, include the following. A third tracer is pulsed into the first production zone. A fourth tracer is pulsed into the second production zone.

[0022] Aspects of the example method, which can be used alone with the example method or in conjunction with other aspects of the example method, include the following. Measuring a first tracer decay and a second tracer decay includes taking production samples at the topside facility at specified intervals. The samples are tested to determine tracer concentrations at the specified time intervals. A decay slope of each tracer in each zone is determined based upon the tested samples.

[0023] Aspects of the example method, which can be used alone with the example method or in conjunction with other aspects of the example method, include the following. Production remains continuous during pulsing and measuring.

[0024] Aspects of the example method, which can be used alone with the example method or in conjunction with other aspects of the example method, include the following. Pulsing the first tracer and the second tracer includes pulsing oleophilic tracers.

[0025] Particular implementations of the subject matter described in this disclosure can be implemented so as to realize one or more of the following advantages. Aspects of this disclosure allow for water-cut determinations to be made for multiple production zones being produced from a single well. Such determinations and analysis are performed without shutting in any of the production zones. Alternatively or in addition, the subject matter described herein has a lower-cost than installing downhole flow-meters in the various laterals. The subject matter described herein also involves low capital costs to install the dosing lines and may be implemented at any time thereafter in the life of the well, even decades later.

[0026] The details of one or more implementations of the subject matter described in this disclosure are set forth in the accompanying drawings and the description below. Other features, aspects, and advantages of the subject matter will become apparent from the description, the drawings, and the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

[0027] FIG. 1 is a schematic diagram of an example well production system.

[0028] FIG. 2 is a side cross-sectional view of an example downhole production system.

[0029] FIG. 3 is a block diagram of an example controller that can be used with aspects of this disclosure.

[0030] FIGS. 4A-4C are examples of tracer pulses that can be used with aspects of this disclosure.

[0031] FIG. 5 is an example method that can be used with aspects of this disclosure.

[0032] Like reference numbers and designations in the various drawings indicate like elements.

DETAILED DESCRIPTION

[0033] This disclosure relates to determining oil production rates and water cuts within multi-zone, comingled wells. Tracers are injected into multiple zones, each zone of tracers is barcoded to identify the zone. The tracers include hydrophilic and oleophilic tracers. A transient is performed on the tracer injection. The transient creates a decay profile that can be detected at the topside facility. The profiles for each individual production zone can be used to determine a water cut for each zone. The various production zones can then be throttled to optimize hydrocarbon production.

[0034] FIG. 1 is a schematic diagram of an example well production system 100. The well production system 100 includes a topside facility 102 atop a production well 104 formed within a geologic formation. The production well 104 includes a first production zone 106a and a second production zone 106b. That is, the production well 104 passes through the first production zone 106a and the second production zone 106b. The production well 104 includes production tubing 108 passing through the production well 104. The production tubing is arranged to receive production fluid from the first production zone 106a and the second production zone 106b. The production tubing 108 is also configured to direct comingled production fluid streams from the first production zone 106a and the second production zone towards the topside facility 102. Coupled to the production tubing 108 is a first subsurface control valve 110a regulating flow from the first production zone 106a into the production tubing. Similarly, a second subsurface control valve 110b is coupled to the production tubing 108 and regulates flow from the second production zone 106b into the production tubing 108. The topside facility 102 also includes chemical injection pumps 112 that can be used to pump chemicals, such as tracers, into each production zone.

[0035] While primarily illustrated and described as a single production well 104 with two production zones (106a, 106b), any number of production wells and production zones can be used without departing from this disclosure. While illustrated as a vertical wellbore passing through two horizontal production zones, other well arrangements can be used without departing from this disclosure. For example, aspects of this disclosure are applicable to horizontal, deviated, or sidetrack production wells.

[0036] In some implementations, the topside facility 102 includes a real-time sensor 114 capable of analyzing production streams for tracers. The topside facility 102 includes a controller 116, for example, a control room. Details on an example controller and capabilities of the example controller are described throughout this disclosure. Other equipment, such as separator, pumps, and compressors, can be included within the topside facility 12 without departing from this disclosure. [0037] FIG. 2 is a side cross-sectional view of an example downhole production system 200. As previously described, the first production zone 106a flows into the production tubing 108 through the first subsurface control valve 110a. Similarly, the second production zone 106b flows into the production tubular through the second subsurface control valve 110b. A first actuable injection tube 202 has a first outlet adjacent to a first inlet 204 of the production tubing 108 within the first production zone 106a. The first injection tube 202 is configured to inject a first tracer 206 into the production fluid entering the production tubing from the first production zone 106a. Similarly, a second actuable injection tube 208/ has a second outlet adjacent to a second inlet 210 of the production tubing 108 within the first production zone 106a. The second injection tube 208 is configured to inject a second tracer 212 into the production fluid entering the production tubing from the first production zone 106a. The actuating aspect of each injection tube is performed by the topside chemical injection pumps 112 (FIG. 1). The first tracer 206 and the second tracer 212 have similar properties, for example, both tracers can be hydrophilic or oleophilic; however, the first tracer 206 and the second tracer 212 are barcoded such that they can be differentiated from one another. For example, the first tracer 206 can fluoresce responsive to a different wavelength of stimulating light than the second tracer 212. Luminescent or optically active tracers detectable can be differentiated (barcoded) by spectral characteristics such as wavelength of maximum emission, wavelength of maximum absorption, and/or luminescent lifetime. In some implementations, the tracers are trace metal ions that can be sensitively and unambiguously identified with spectroscopic methods such as x-ray fluorescence, inductively coupled plasma mass spectroscopy or inductively coupled plasma optical emission spectroscopy. In some implementations, the tracers include materials that can be degraded predictably under specific conditions and the degradation products can be detected by common spectroscopic methods after chromatographic separation. For example, polymers with a ceiling temperature, such as styrenic or methacrylate type polymers undergo depolymerizatoin when heated to the ceiling temperature. In such implementations, the monomer is a major degradation product. The monomer of specific mass can be readily detected by mass spectroscopy after gas chromatographic separation.

[0038] In some implementations, a third injection tube 214 with a third outlet adjacent to the first inlet 204 of the production tubing 108 within the first production zone 106a can be included. Similarly, in some implementations a fourth injection tube 216 with a fourth outlet adjacent to the second inlet 210 of the production tubing within the second production zone can be included. In such implementations, the third injector tube 214 and the fourth injector tube 216 are configured to inject other tracers different from the first tracer and the second tracer. For example, if the first injection tube 202 and the second injection tube 208 inject an oleophilic tracer, then the third injection tube 214 and the fourth injection tube 216 could inject a hydrophilic tracer. Tracers injected by the third injection tubing 214 and the fourth injection tubing can also be barcoded such that the tracers can be differentiated during analysis.

[0039] FIG. 3 is a schematic diagram of an example controller 116 that can be used with aspects of this disclosure. The controller 116 can, among other things, monitor parameters of the system 100 and send signals to actuate and/or adjust various operating parameters of the system 100. As shown in FIG. 3, the controller 116, in certain instances, includes a processor 350 (e.g., implemented as one processor or multiple processors) and a memory 352 (e.g., implemented as one memory or multiple memories) containing instructions that cause the processors 350 to perform operations described herein. The processors 350 are coupled to an input/output (I/O) interface 354 for sending and receiving communications with components in the system, including, for example, the real-time sensor 114. In certain instances, the controller 116 can additionally communicate status with and send actuation and/or control signals to one or more of the various system components (including an actuable systems, such as the first subsurface control valve 110a or the second subsurface control valve 110b) of the system 100, as well as other sensors (e.g., pressure sensors, temperature sensors, and other types of sensors) provided in the system 100. In certain instances, the controller 116 can communicate status and send control signals to one or more of the components within the system 100, such as the chemical pumps 112. The communications can be hard-wired, wireless or a combination of wired and wireless. In some implementations, controllers similar to the controller 116 can be located elsewhere, such as in a control room, a data van, elsewhere on a site or even remote from the site. In some implementations, the controller 116 can be a distributed controller with different portions located about a site or off site. For example, in certain instances, the controller 116 can be located at the real-time sensor 114, or it can be located in a separate control room or data van. Additional controllers can be used throughout the site as stand-alone controllers or networked controllers without departing from this disclosure.

[0040] The controller 116 can operate in monitoring, commanding, and using the system 100 for measuring tracers in various production streams and determining water-cuts of each production zone in response. To make such determinations, the controller 116 is used in conjunction with the real-time sensor or a database in which a technician can input test result values. Input and output signals, including the data from the sensor, controlled and monitored by the controller 116, can be logged continuously by the controller 116 within the controller memory 352 or at another location.

[0041] The controller 116 can have varying levels of autonomy for controlling the system 100. For example, the controller 116 can initiate a tracer pulse, and an operator adjusts the subsurface control valves (110a, 110b). Alternatively, the controller 116 can initiate a tracer pulse, receive an additional input from an operator, and adjust the subsurface control valves (110a, 110b) with no other input from an operator. Alternatively, the controller 116 can a tracer pulse and actively adjust the subsurface control valves (110a, 110b) with no input from an operator.

[0042] Regardless of the autonomy of the controller operation, the controller can perform any of the following functions. The controller is configured to send a control signal to a first topside pressure pump, such as chemical pump 112. The control signal is configured to cause the pump to pulse a first tracer 206 into the first production zone 106a. The controller is configured to send a control signal to a second topside pressure pump. The control signal is configured to cause the pump to pulse a second tracer into the second production zone. As a reminder, the first tracer and the second tracer are barcoded such that the first tracer and the second tracer can be differentiated from one another. The controller 116 can also be configured to measure, or receive a signal indicative of a measurement from the real-time sensor, a first tracer decay, the second tracer decay, or both at a topside facility 102. Based on the first tracer decay and the second tracer decay, the controller is configured to determine a water cut of the first production zone 106a and the second production zone 106b. In some implementations, the controller is configured to send a control signal to the first subsurface control valve 110a, the second subsurface control valve 110b, or both. The signal is configured to actuate the first subsurface control valve 110a, the second to subsurface control valve 110b, or both, to regulate the production fluids from the first production zone, the second production zone, or both.

[0043] FIGS. 4A-4C are examples of tracer pulses that can be used with aspects of this disclosure. Tracer concentrations are measured in phase-separated wellhead fluid samples collected at appropriate times after downhole injection. While primarily described using oleophilic tracers, similar injections and measurements can be made with hydrophilic tracers on the water production rates without departing from this disclosure. FIG. 4A shows a pulse arrangement 502 where oleophilic tracers are injected into the first production zone and the second production zone as a step function pulse, for example, a pulse that approximates a square wave, saw-tooth wave, or similar pulse with a hard transient change. The time for the first tracer pulse to be detected at the topside facility 102 is determined by the following equation: ti = Li xA /(Q1+Q2) (1) where ti is the time for the first pulse to be detected, Li is the downhole length from the topside facility 102 to the inlet to the first subsurface control valve 110a, A is the cross sectional area of the production tubing 108, Qi is the oil flow rate from the first production zone 106a, and Q2 is the oil flow rate from the second production zone 106b.

[0044] The time for the second tracer pulse to be detected at the topside facility 102 is determined by the following equation: t2 = L ₂ xA/Q ₂ (2) where t2 is the time for the second pulse to be detected after the first pulse is detected, 1.2 is the downhole length within the completion from the first subsurface control valve 110a inlet to the second subsurface control valve 110b inlet. By measuring ti and t2, the influx rates Qi and Q2 can be determined by solving equations (1) and (2).

[0045] FIG. 4B illustrates a tracer injection pulse profile where pulsing the first tracer 206 and the second tracer 212 includes abruptly ceasing a flow of each tracer. That is, steadily flowing each tracer for a set amount of time, then abruptly ceasing flow of both tracers simultaneously such that a distinct transient occurs. The decay rate in this instance has an exponential decay that can be used to determine the total oil production in each zone using the following equations:

Toil 1 ~ exp(-a Qi t) (3)

Toil 2 ~ exp(-a Q2 t) (4) Where Toil i and Toil 2 are for the tracer concentrations within the oil produced from the first production zone 106a and the second production zone 106b respectively. Such an abrupt shut-off gives rise to curves with exponential decay. Qi and Q2 are the oil influx rates into the two completion zones. The quantity a is a geometrical constant of the annular production zones, here simplified to be the same in both zones. While primarily described as being the same in both zones, in some implementations, a can be different in each zone. The quantity a is approximately equal to 1/F, where V is the volume of the annular region in each completion zone, extending from the mouth of the capillary dosing line up to the inlet of the inflow control valve. For this abrupt- shutoff injection profile, comparing the exponential decays of the two zones’ oil tracers (or the ratio of their straight-line slopes when plotted on a semi-logarithmic plot as shown in FIG. 4C) will precisely give the ratio of Qi to Q2, allowing the influx rates to be measured. The surface separator gives us the sum (Qi + Q2) to normalize the absolute oil influx rates. As the decay rate can, in some implementations, follows equations (3) and (4), as little as two measurements need to be taken to determine the decay curves. While these equations are applicable to decay curves with exponential decay, other equations can be used with different decay shapes. In certain situations, such as laminar flow situations, similar equations can be used for both oleophilic tracers and hydrophilic tracers.

[0046] FIG. 5 is an example method 500 that can be used with aspects of this disclosure. In some implementations, all or some of the method steps are performed by the controller 116. At 502, production fluid is produced from the production well 104. The production well 104 supplies production fluid from the first production zone 106a and the second production zone 106b. Production fluids from the first production zone 106a and second production zone 106b are comingled within the same production tubing 108.

[0047] At 504, a first tracer 206 is pulsed into the first production zone. At 506, a second tracer 212 is pulsed into the second production zone. The first tracer 206 and the second tracer 212 are barcoded such that the first tracer 206 and the second tracer 212 can be differentiated from one another. For example, the first tracer 206 and the second tracer 212 can fluoresce at different wavelengths. In some implementations, additional tracers can be used without departing from this disclosure, for example, a third tracer can be injected into the first production zone 106a and a fourth tracer can be injected into the second production zone 106b. In such implementations, the tracers in each zone can include hydrophilic and oleophilic tracers, for example, the first and second tracers are oleophilic tracers and while the third and fourth tracers are hydrophilic tracers.

[0048] At 508, a decay of the first tracer is measured at the topside facility 102. At 510, a decay of the second tracer is measured at the topside facility 102. In some implementations, the decay of the first tracer and the second tracer can be measured substantially simultaneously. For example, production samples can be taken at the topside facility 102 at specified intervals. Each sample is then tested to determine tracer concentrations of the first tracer 206 and the second tracer 212 at the specified time intervals. From there, a decay slope of each tracer in each zone can be determined based upon the tested samples.

[0049] At 512, a water cut of the first zone and the second zone is determined based upon the first tracer decay and the second tracer decay. Such a determination can be make using the equations described throughout this disclosure. Alternatively or in addition, oil production rates of the first production zone and the second production zone are determined based upon the first tracer decay and the second implementation decay. The water cut can be determined using either hydrophilic tracers, oleophilic tracers, or both. Regardless of the tracer used, responsive to the determined watercuts, in some implementations, the first subsurface control valve 110a, the second subsurface control valve 110b, or both, are actuated to regulate the flow of production fluids from their respective zones. Throughout the entirety of the processes and methods described herein, including while pulsing the first tracer, while pulsing the second tracer, while measuring the decay of the first tracer, and while measuring the decay of the second tracer, production of each zone remains relatively continuous (within standard operation windows).

[0050] While this disclosure contains many specific implementation details, these should not be construed as limitations on the scope of any inventions or of what may be claimed, but rather as descriptions of features specific to particular implementations. Certain features that are described in this disclosure in the context of separate implementations can also be implemented in combination in a single implementation. Conversely, various features that are described in the context of a single implementation can also be implemented in multiple implementations separately or in any suitable subcombination. Moreover, although features may be described above as acting in certain combinations and even initially claimed as such, one or more features from a claimed combination can in some cases be excised from the combination, and the claimed combination may be directed to a subcombination or variation of a subcombination.

[0051] Similarly, while operations are depicted in the drawings in a particular order, this should not be understood as requiring that such operations be performed in the particular order shown or in sequential order, or that all illustrated operations be performed, to achieve desirable results. Moreover, the separation of various system components in the implementations described above should not be understood as requiring such separation in all implementations, and it should be understood that the described program components and systems can generally be integrated together in a single product or packaged into multiple products.

[0052] Thus, particular implementations of the subject matter have been described. Other implementations are within the scope of the following claims. In some cases, the actions recited in the claims can be performed in a different order and still achieve desirable results. In addition, the processes depicted in the accompanying figures do not necessarily require the particular order shown, or sequential order, to achieve desirable results.