BACKGROUND

[0001] During drilling of a wellbore into a subterranean formation, formation fluid(s) may enter the wellbore and circulate with drilling fluid from the wellbore to the surface, and back into the wellbore. Determining isotopes present in the formation fluid may indicate reservoir compartmentalization and connectivity. Typically, isotopes are only measured at a wellbore flow-out location which may lead to erroneous results.

BRIEF DESCRIPTION OF THE DRAWINGS

[0002] These drawings illustrate certain aspects of some examples of the present invention and should not be used to limit or define the invention.

[0003] Figure 1 illustrates a system with a single analytical instrument for correcting isotope ratio calculations, in accordance with particular examples of the present disclosure;

[0004] Figure 2 illustrates a system with multiple analytical instruments for correcting isotope ratio calculations, in accordance with particular examples of the present disclosure;

[0005] Figure 3 illustrates an exemplary method to determine a corrected isotope ratio during wellbore operations, in accordance with particular examples of the present disclosure; and

[0006] Figure 4 is a schematic diagram of an exemplary drilling system including the system for correcting isotope ratio calculations, in accordance with particular examples of the present disclosure.

DETAILED DESCRIPTION

[0007] Systems and methods of the present disclosure generally relate to wellbore operations and, more particularly, may relate to correcting isotope ratio calculations during wellbore operations.

[0008] In particular examples, a lag equation may be employed to account for depth at which isotopes are removed from the formation. In certain examples, a sampling device may continuously extract a fluid sample at a flow-in location for a wellbore such as at a suction line, for example. A second sampling device may continuously extract a fluid sample at a flow-out location for the wellbore such as at a flow line, for example. Each of the sampling devices may extract sample fluids from drilling fluid in the form of a gas sample and/or a liquid sample. A flow-in sample and a flow-out sample may each be sent to a sample conditioner, and pressure and flow controller. Each sample may then flow to an analytical instrument(s) that may analyze the concentration of carbon- 12 and carbon- 13.

[0009] In particular examples, the analytical instruments may include a cavity ring-down spectrometer, an isotopic ratio mass spectrometer, a laser dispersion spectrometer, or other suitable devices that are able to analyze carbon isotopes. A signal intensity (e.g., a height of the signal) or area (e.g., area underneath the curve) outputted from these instruments may be recorded. The signal intensity or the area may be assigned a depth based on a lag equation. The signal from the flow-in sample may be subtracted from the signal from the flow-out sample, with or without a correction/ calibration factor, to provide a corrected isotope ratio. For example, isotope analysis may be performed with a single instrument and the signals may be directly subtracted. In other examples, the isotope analy sis may be performed on separate instruments, and the correction factor may be used to account for instrument bias.

[0010] The same methodology may also be performed for hydrogen, nitrogen, oxygen, sulfur, and/or other isotopes. In some examples, a physical separation device may be disposed upstream to the analytical mstrument(s) to separate molecules based on species, molecular size, and/or functional groups. The samples may also be oxidized before isotope analysis to simplify the analysis.

[0011] Figure 1 illustrates a system 100 for correcting isotope ratio calculations, in accordance with examples of the present disclosure. A flow line 102 may pass fluid 103 directly from a wellbore into a mud pit 104. A first sampling device 106 may be in fluid communication with the flow line 102. The first sampling device 106 may receive a sample of the fluid 103 from the flow line 102. A second sampling device 106 may be disposed at a suction line 108 and may also receive a sample of the fluid 103 that passes through the suction line 108 from the mud pit 104.

[0012] The sampling devices 106 may each include any suitable sampling device for continuously receiving a fluid sample directly from the flow line 102 and the suction line 108, such as, for example, Quantitative Gas Measurement Extractor, Constant Volume Extractor, Constant Volume and Temperature Extractor. Each sample may pass via conduits 107 to a sample conditioner 110, a pressure and flow controller 112, and then to an analytical instrument 114. The sample conditioner 110 may include a condensate removal jar, coalescing filter, sample dryer, and/or membrane filter.

[0013] With additional reference to Figure 2, in some examples, the system 100 may further include a second analytical instrument 114. It should be noted that when using separate analytical instruments, the isotope analysis a correction factor may be used to account for instrument bias (e.g., Equation 2).

[0014] The analytical instruments 114 may include a cavity ring-down spectrometer, an isotopic ratio mass spectrometer, a laser dispersion spectrometer, or other suitable devices that analyze (e.g., determine) carbon isotopes.

[0015] The sampling devices 106, the sample conditioner 110, the pressure and flow controller 112, and the analytical instrument 114 may be in communication (e.g., wired or wireless communication paths 115) with a computer 116 that may process data from sampling devices 106, the sample conditioner 110, the pressure and flow controller 112, and the analytical instrument 114.

[0016] In some examples, a physical separation device 117 may be disposed upstream to the analytical instrument(s) to separate molecules based on molecular size or functional groups The separation device 117 may include a gas chromatography column. The samples may also be oxidized before isotope analysis to simplify the analysis. The samples may be oxidized with a flame or a furnace with a catalyst.

[0017] The computer 116 may operate the system 100 and may include any instrumentality or aggregate of instrumentalities operable to compute, estimate, classify, process, transmit, receive, retrieve, originate, switch, store, display, manifest, detect, record, reproduce, handle, or utilize any form of information, intelligence, or data for business, scientific, control, or other purposes. The computer 116 may be any processor- driven device, such as, but not limited to, a personal computer, laptop computer, smartphone, tablet, handheld computer, dedicated processing device, and/or an array of computing devices. In addition to having a processor, the computer 116 may include a server, a memory, input/output (“I/O”) interface(s), and a network interface. The memory may be any computer-readable medium, coupled to the processor, such as RAM, ROM, and/or a removable storage device for storing data and a database management system (“DBMS”) to facilitate management of data stored in memory and/or stored in separate databases. The computer 116 may also include display devices such as a monitor featuring an operating system, media browser, and the ability to run one or more software applications. Additionally, the computer 116 may include non-transitory computer- readable media. Non-transitory computer-readable media may include any instrumentality or aggregation of instrumentalities that may retain data and/or instructions for a period of time.

[0018] The computer 116 may utilize lag equations to determine a corrected isotope ratio. A signal intensity (e.g., a height of the signal) or area (e.g., area underneath the curve) outputted from the instruments 114 may be recorded by the computer 116. The signal intensity or the area may be assigned a depth based on a lag equation. The signal from the flow-in sample may be subtracted from the signal from the flow-out sample, with or without a correction/calibration factor, to provide a corrected isotope ratio. For example, isotope analysis may be performed with a single instrument and the signals may be directly subtracted. In other examples, the isotope analysis may be performed on separate instruments, and the correction factor may be used to account for instrument bias.

[0019] A first lag equation for usage of separate analytical instruments may be defined by Equation (1):

Eq. (1) where ¹³ C is carbon-13; ¹² C is a sample of carbon-12; ¹² C standard-constant is a constant value; Signal ¹³ C is a measured signal for carbon-13; Signal ¹² C is a measured signal for carbon- 12; Signal ¹² Ci _n is the measured signal for the carbon-12 at the flow line 102; Signal ¹² Cout is the measured signal for the carbon-12 at the suction line 108; Signal ¹³ Ci _n is the measured signal for carbon-13 at the flow line 102, Signal ¹³ Cout is the measured signal for the carbon-13 at the suction line 108; the Signal may be area (e.g., area under curve of signal) or intensity (e.g., height of signal); the Calibration Factor may be a constant value or an equation. For example, the isotope analysis may be performed on separate instruments (e.g., instruments 114 on Figure 2), and the Calibration Factor may be used to account for instrument bias.

[0020] A second lag equation for a single analytical instrument without the Calibration Factor may be defined by:

Eq. (2) where ¹³ C is carbon-13; ¹² C is a sample of carbon-12; ¹² C standard-constant is a constant value; Signal ¹³ C is a measured signal for carbon-13; Signal ¹² C is a measured signal for carbon- 12; Signal ¹² Ci _n is the measured signal for the carbon-12 at the flow line 102; Signal ¹² Cout is the measured signal for the carbon-12 at the suction line 108; Signal ¹³ Ci _n is the measured signal for carbon-13 at the flow line 102, Signal ¹³ Cout is the measured signal for the carbon-13 at the suction line 108; the Signal may be area (e.g., area under curve of signal) or intensity (e.g., height of signal).

[0021] Figure 3 illustrates an exemplary method to determine a corrected isotope ratio during wellbore operations, in accordance with particular examples of the present disclosure. At step 300, a flow-in fluid sample and a flow-out fluid sample may be extracted from a flow line and a suction line for a wellbore, respectively, as shown on FIGS. 1 and 2, for example. The extraction of fluid samples may occur continuously with the sampling devices. The fluid samples may include gas and/or liquid.

[0022] At step 302, each extracted sample may be extracted with a sampling device and pass through a sample conditioner, a pressure and flow controller, and analytical instrument for analysis with a computer, as shown on FIGS. 1 and 2, for example. The analytical instrument(s) may include a cavity ring-down spectrometer, an isotopic ratio mass spectrometer, a laser dispersion spectrometer, or other suitable devices that are able to analyze/determine carbon isotopes.

[0023] At step 304, the signal intensity (e.g., a height of the signal) or area (e.g., area underneath the curve) may be outputted from the analytical instrument(s) to the computer for recordation. At step 306, the signal intensity or the area may be assigned a depth. At step 308, the computer may determine a corrected isotope ratio with Equation 1 or Equation 2. For example, the signal from the flow-in sample may be subtracted from the signal from the flow-out sample, with or without a correction/ calibration factor, to pro vide a corrected isotope ratio.

[0024] Figure 4 illustrates a drilling system 400 including the system 100 and the workflow of Figure 3 in accordance with particular examples of the present disclosure. It should be noted that while Figure 4 depicts a land-based drilling system, those skilled in the art will readily recognize that the principles described herein are equally applicable to subsea drilling operations that employ floating or sea-based platforms and/or rigs, without departing from the scope of the present disclosure.

[0025] As illustrated, the drilling system 400 may include a drilling platform 402 that supports a derrick 404 having a traveling block 406 for raising and lowering a drill string 408. The drill string 408 may include, but is not limited to, drill pipe and coiled tubing, as generally known to those skilled in the art. A top drive or kelly 410 may support the drill string 408. The drill string 408 may be lowered through a rotary table 412, in some examples. A drill bit 414 may be attached to the distal end of the drill string 408 and may be driven either by a downhole motor and/or via rotation of the drill string 408 from the well surface. Without limitation, the drill bit 414 may include, roller cone bits, PDC bits, natural diamond bits, any hole openers, reamers, coring bits, and the like. As the drill bit 414 rotates, it may create a wellbore 416 that penetrates a subterranean formation 418.

[0026] The drilling system 400 may further include a fluid monitoring and handling system 420 comprising component parts such as a mud pump 422, a solids control device 423 , a mixing hopper 425 and the mud pit 104. The mud pump 422 may include any conduits, pipelines, trucks, tubulars, and/or pipes used to convey clean drilling fluid 427 downhole. The mud pump 422 may also include any pumps, compressors, or motors (e.g., surface or downhole) used to move the clean drilling fluid 427, as well as any valves or related joints used to regulate the pressure or flowrate of the clean drilling fluid 427, and any sensors (e.g., pressure, temperature, flow rate), gauges, or combinations thereof, for example. The mud pump 422 may circulate the clean drilling fluid 427 from the mud pit 104 via the suction line 108.

[0027] The mud pump 422 may circulate the clean drilling fluid 427 through a feed pipe 428 and to the top drive or kelly 410, which may convey the clean drilling fluid 427 downhole through the interior of the drill string 408 and through one or more orifices in the drill bit 414. The now circulated drilling fluid 430 may then be circulated back to the surface via an annulus 432 defined between the drill string 408 and the walls of the wellbore 416. At the surface, the circulated drilling fluid 430 may be conveyed to the solids control device 423 via the flow line 102. The solids control device 423 may include one or more of a shaker (e.g., shale shaker), a centrifuge, a hydro-cyclone, a separator (including magnetic and electrical separators), a de-silter, a de-sander, a separator, a filter (e.g., diatomaceous earth filters), a heat exchanger, and any fluid reclamation equipment. The solids control device 423 may remove and separate recovered solids from the circulated drilling fluid 430. After passing through the solids control device 423, the clean drilling fluid 427 may move into the mud pit 104.

[0028] The sampling device(s) 106 may continuously sample/receive fluid samples. The fluid samples may pass through the sample conditioner 110, the pressure and flow controller 112, and the analytical instrument 114. As noted previously, the analytical instruments 114 may include a cavity ring-down spectrometer, an isotopic ratio mass spectrometer, a laser dispersion spectrometer, or other suitable devices that analyze carbon isotopes. The computer 116 may receive isotope information from the analytical instrument(s) 114 and may utilize a lag equation (e.g., Equation 1 or Equation 2) to determine a corrected isotope ratio. For example, the signal intensity (e.g., a height of the signal) or area (e.g., area underneath the curve) outputted from the instruments 114 may be recorded by the computer 116. The signal intensity or the area may be assigned a depth based on the lag equation. The signal from the flow-in sample may be subtracted from the signal from the flow-out sample, with or without a correction/ calibration factor, to provide a corrected isotope ratio.

[0029] For example, isotope analysis may be performed with a single instrument and the signals may be directly subtracted. In other examples, the isotope analysis may be performed on separate instruments, and the correction factor may be used to account for instrument bias. The same methodology may also be performed for hydrogen, nitrogen, oxygen, sulfur, and/or other isotopes. [0030] Accordingly, the systems and methods of the present disclosure may utilize lag equations to provide a corrected isotope ratio. The systems and methods may include any of the various features disclosed herein, including one or more of the following statements.

Statement 1. A method for correcting isotope ratios during a wellbore operation, comprising: receiving a flow-in fluid sample from a wellbore; receiving a flow-out fluid sample from the wellbore; passing each sample to an analytical instrument operable to determine isotopes in each fluid sample; outputting a signal intensity or signal area; assigning a depth to the signal intensity or the signal area; and determining a corrected isotope ratio by subtracting a signal for the flow-in fluid sample from a signal for the flow- out fluid sample.

[0031] Statement 2. The method of the statement 1, further comprising passing each sample through a sample conditioner.

[0032] Statement 3. The method of the statement 2, further comprising passing each sample through a flow and pressure controller.

[0033] Statement 4. The method of any of the preceding statements, further comprising passing each sample through a separation device to separate species within each sample.

[0034] Statement 5. The method of any of the preceding statements, further comprising receiving the flow-in fluid sample from a flow line of a drilling system.

[0035] Statement 6. The method of any of the preceding statements, further comprising receiving the flow-out fluid sample from a suction line of a drilling system.

[0036] Statement 7. The method of any of the preceding statements, further comprising passing each sample to separate analytical instruments operable to determine the isotopes in each fluid sample.

[0037] Statement 8. The method of any of the preceding statements, further comprising implementing a correction factor to determine the corrected isotope ratio due to analytical instrument bias.

[0038] Statement 9. The method of any of the preceding statements, further comprising continuously sampling the flow-in fluid sample.

[0039] Statement 10. The method of any of the preceding statements, further comprising continuously sampling the flow-out fluid sample. [0040] Statement 11. A system for correcting isotope ratios during a wellbore operation, comprising: an analytical instrument operable to determine isotopes in a wellbore fluid; a first fluid sampling device disposed at a flow-in location for a wellbore; a second fluid sampling device disposed at a flow-out location for the wellbore; and a computer operable to: receive a signal intensity or signal area from the analytical instrument; assign a depth to the signal intensity or the signal area; and determine a corrected isotope ratio by subtracting a signal for a flow-in fluid sample from a signal for the flow-out fluid sample.

[0041] Statement 12. The system of any of the statements 11, further comprising a flow and pressure controller disposed upstream to the analytical instrument.

[0042] Statement 13. The system of the statement 11 or the statement 12, further comprising a sample conditioner disposed upstream to the analytical instrument.

[0043] Statement 14. The system of any of the statements 11-13, further comprising a separation device operable to separate species within each sample.

[0044] Statement 15. The system of any of the statements 11-14, further comprising a second analytical instrument operable to determine the isotopes in the wellbore fluid.

[0045] Statement 16. The system of any of the statements 11-15, wherein the computer is further operable to implement a correction factor to determine the corrected isotope ratio due to analytical instrument bias.

[0046] Statement 17. The system of any of the statements 11-16, wherein the second sampling device is disposed at a suction line of a drilling system.

[0047] Statement 18. The system of any of the statements 11-17, wherein the first sampling device is disposed at a flow line of a drilling system.

[0048] Statement 19. The system of any of the statements 11-18, wherein the first sampling device is operable to continuously sample the wellbore fluid.

[0049] Statement 20. The system of any of the statements 11-19, wherein the second sampling device is operable to continuously sample the wellbore fluid.

[0050] The preceding description provides various examples of the systems and methods of use disclosed herein which may contain different method steps and alternative combinations of components. It should be understood that, although individual examples may be discussed herein, the present disclosure covers all combinations of the disclosed examples, including, without limitation, the different component combinations, method step combinations, and properties of the system. It should be understood that the compositions and methods are described in terms of “comprising,” “containing,” or “including” various components or steps, the compositions and methods can also “consist essentially of’ or “consist of’ the various components and steps. Moreover, the indefinite articles “a” or “an,” as used in the claims, are defined herein to mean one or more than one of the element that it introduces.

[0051] For the sake of brevity, only certain ranges are explicitly disclosed herein. However, ranges from any lower limit may be combined with any upper limit to recite a range not explicitly recited, as well as, ranges from any lower limit may be combined with any other lower limit to recite a range not explicitly recited, in the same way, ranges from any upper limit may be combined with any other upper limit to recite a range not explicitly recited. Additionally, whenever a numerical range with a lower limit and an upper limit is disclosed, any number and any included range falling within the range are specifically disclosed. In particular, every range of values (of the form, “from about a to about b,” or, equivalently, “from approximately a to b,” or, equivalently, “from approximately a-b”) disclosed herein is to be understood to set forth every number and range encompassed within the broader range of values even if not explicitly recited. Thus, every point or individual value may serve as its own lower or upper limit combined with any other point or individual value or any other lower or upper limit, to recite a range not explicitly recited.

[0052] Therefore, the present examples are well adapted to attain the ends and advantages mentioned as well as those that are inherent therein. The particular examples disclosed above are illustrative only and may be modified and practiced in different but equivalent manners apparent to those skilled in the art having the benefit of the teachings herein. Although individual examples are discussed, the disclosure covers all combinations of all of the examples. Furthermore, no limitations are intended to the details of construction or design herein shown, other than as described in the claims below. Also, the terms in the claims have their plain, ordinary meaning unless otherwise explicitly and clearly defined by the patentee. It is therefore evident that the particular illustrative examples disclosed above may be altered or modified and all such variations are considered within the scope and spirit of those examples. If there is any conflict in the usages of a word or term in this specification and one or more patent(s) or other documents that may be incorporated herein by reference, the definitions that are consistent with this specification should be adopted.