CROSS REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of U.S. Provisional Application No. 62/347,661, filed June 9, 2016, which is incorporated herein by reference.

BACKGROUND

[0002] The present disclosure relates generally to subsea chemical detectors. More specifically, in certain embodiments, the present disclosure relates to subsea chemical detectors that utilize Raman spectroscopy and associated methods and systems.

[0003] Currently chemicals in sea water may be detected through the use of mass spectrometers and Raman spectrometers. Conventional mass spectrometers offer excellent sensitivity in the range of parts per billion level. However, these conventional mass spectrometers function by flowing fluid through the instrument and thus require the use of a gas permeable membrane for water removal. A typical Raman spectrometer, on the other hand, may only offer moderate sensitivity (in the range of parts per millions), but the instrument is inherently simple to implement and does not require sample preparation (e.g. water removal).

[0004] One key attribute of Raman spectroscopy is the ability for direct chemical detection of dissolved gases in water while offering low cost portable solutions. These traditional Raman techniques, however, require a larger integration interval (several minutes) thus jeopardizes the ability to monitor transient activities in real-time. Presently used chemical detectors often take minutes to acquire a single sample.

[0005] Numerous other advanced Raman techniques exist in the literature. The most notable are the coherent Raman scattering (CRS) techniques, which offer orders of magnitude more signals than spontaneous Raman scattering. This allows for separation of the C-H stretch spectrum of methane and higher hydrocarbons from the normally overwhelming auto- fluorescence background when petroleum liquids are present. Another advantage of CRS technique is the short detector dwell time (2-8 μ8), offering the capability to perform real-time analysis. These advanced techniques, however, have yet to be utilized in the exploration and monitoring of dissolved gases in the deep ocean. Currently there is a lack of laser sources that are compact, robust and rapidly tunable. Since CRS techniques depend upon the synchronization of two very short pulses, such field applications were not possible prior to the introduction of synchronized pulsed fiber-based laser sources.

[0006] Conventional Raman spectroscopy, utilizing focus collection optics, only collects Raman signals from the substances within the focal point, i.e. depth of focus. This prevents the detection of other gases dissolved in a comparatively large volume of water. Additionally, conventional Raman spectroscopes typically only utilize a single path of light through the sample. Furthermore, conventional Raman spectroscopy employ the use of spectrometers rather than other small devices.

[0007] It is desirable to develop a new type of high speed Raman spectroscopy that is more suitable for detecting dissolved gasses in seawater.

SUMMARY

[0008] The present disclosure relates generally to subsea chemical detectors. More specifically, in certain embodiments, the present disclosure relates to subsea chemical detectors that utilize Raman spectroscopy and associated methods and systems.

[0009] In one embodiment, the present disclosure provides a chemical detector comprising a light source, sampling optics, collection optics, and a detector, wherein the sampling optics comprise collimated sampling optics and/or reflective sampling optics.

[0010] In another embodiment, the present disclosure provides a chemical detector system comprising a chemical detector, wherein the chemical detector comprises a light source, sampling optics, collection optics, and a detector, wherein the sampling optics comprise collimated sampling optics and/or reflective sampling optics; a vessel; and an umbilical connecting the chemical detector to the vessel.

[0011] In another embodiment, the present disclosure provides a method of detecting a gas comprising: providing a chemical detector, wherein the chemical detector comprises a light source, sampling optics, collection optics, and a detector, wherein the sampling optics comprise collimated sampling optics and/or reflective sampling optics; providing a sample; illuminating the sample with light from the light source to generate electromagnetic radiation; and analyzing the electromagnetic radiation to determine the presence of gas in the sample.

BRIEF DESCRIPTION OF THE DRAWINGS

[0012] A more complete and thorough understanding of the present embodiments and advantages thereof may be acquired by referring to the following description taken in conjunction with the accompanying drawings.

[0013] Figure 1 is an illustration of a chemical detector in accordance with certain embodiments of the present disclosure.

[0014] Figure 2 is an illustration of a chemical detector in accordance with certain embodiments of the present disclosure.

[0015] Figure 3 is an illustration of a chemical detector system in accordance with certain embodiments of the present disclosure.

[0016] Figure 4 is an illustration of a Raman spectrum.

[0017] The features and advantages of the present disclosure will be readily apparent to those skilled in the art. While numerous changes may be made by those skilled in the art, such changes are within the spirit of the disclosure.

DETAILED DESCRIPTION

[0018] The description that follows includes exemplary apparatuses, methods, techniques, and/or instruction sequences that embody techniques of the inventive subject matter. However, it is understood that the described embodiments may be practiced without these specific details.

[0019] The present disclosure relates generally to subsea chemical detectors. More specifically, in certain embodiments, the present disclosure relates to subsea chemical detectors that utilize Raman spectroscopy and associated methods and systems.

[0020] In certain embodiments, the present disclosure describes methods and systems that utilize detectors comprising collimated sampling optics, reflective sampling optics, and/or multi-channel detectors.

[0021] There may be several advantages to the methods and systems described herein. In certain embodiments, the detectors discussed herein may have a higher throughput, shorter sampling time, and simpler system designs than conventional detectors. In certain embodiments, the detectors discussed herein do not require precision underwater positioner to align Raman detector to the samples due to the use of substantially collimated collection optics and/or sampling optics. In certain embodiments, the use of the collimated collection optics and/or sampling optics allows Raman detection of underwater samples from the sea surface. In certain embodiments, the use of the methods and systems described herein may also allow for the realtime, long-term in situ analysis in the field.

[0022] Referring now to Figure 1, Figure 1 is a schematic of chemical detector 100 in accordance with certain embodiments of the present disclosure. In certain embodiments, chemical detector 100 may comprise light source 110, sampling optics 120, collection optics 140, and detector 150.

[0023] In certain embodiments, chemical detector 100 may comprise collimated sampling optics. A used herein, the term "collimated sampling optics" refers to sampling optics that allow for the collection of a collimated beam of light. In certain embodiments, as discussed below, the collimated sampling optics may comprise a lens capable of collecting and focusing a light beam onto a slit. In certain embodiments, the collimated light beam may be capable of collecting Raman scattering from substances within the entire collimated beam of light.

[0024] In certain embodiments, light source 110 may comprise any conventional light source used for Raman spectroscopy. In certain embodiments, light source 110 may comprise lasers and/or lamps. In certain embodiments, the light source 110 may comprise laser and/or lamps with sample illuminating wavelengths range from UV to near infrared. In certain embodiments, the laser may have a wavelength of 488 nm, 514 nm, 532 nm, 632 nm, 785 nm, 835 nm, 980 nm, and 1064 nm. In certain embodiments, the laser may have a laser line width of less than 1 nm. In certain embodiments, not shown in Figure 1, light source 110 may comprise element 122.

[0025] In certain embodiments, light source 110 may be positioned such that light from light source 110 may be sent directly or indirectly to sample 160. In certain embodiments, not illustrated in Figure 1, the sample 160 may be present in a sample chamber. In other embodiments, the sample 160 may be located outside of chemical detector 100. As used herein, the term directly refers to a direct path of light with no reflective turns and indirectly refers to an indirect path of light with one or more reflective turns. In certain embodiments, light source 110 may emit light along a pathway 111.

[0026] In certain embodiment, sampling optics 120 may comprise beam splitter 121. In certain embodiments, beam splitter 121 may be capable of directing light generated from light source 110 to a sample 160. In certain embodiments, beam splitter 121 may be capable of reflecting light from light source 110 to a sample 160. In certain embodiments, beam splitter 121 may be capable of allowing of a high percentage, for example more than 60%, more than 70%, more than 80%, or more than 90%) of a Raman signal generated from an illuminated sample 160 to pass through beam splitter 121 without being reflected along a different path or absorbed.

[0027] In certain embodiments, beam splitter 121 may comprise short- wavelength, long-wavelength, or band-pass optical filters that allow the delivery of excitation laser to the sample while passing the Raman signal. [0028] In certain embodiments, beam splitter 121 may be inclined at an angle in the range of from 30 degrees to 60 degrees with respect to pathway 111. In certain embodiments, beam splitter 121 may be inclined at an angle in the range of from 40 degrees to 50 degrees with respect to pathway 111. In certain embodiments, beam splitter 121 may be inclined 45 degrees with respect to pathway 111.

[0029] In certain embodiments, beam splitter 121 may be capable of redirecting light along pathway 111 to pathway 112. In certain embodiments, pathway 112 may be perpendicular to pathway 111. In certain embodiments, pathway 112 may be inclined or declined an angle in the range of from 70 degrees to 110 degrees with respect to pathway 111. In certain embodiments, the light traveling along pathway 111, pathway 112, and/or pathway 113 may be collimated along the entire pathways. In other embodiments, the light traveling along pathway 111, pathway 112, and/or pathway 113 may be collimated for only a portion of the pathways. In other embodiments, the light traveling along pathway 111, pathway 112, and/or pathway 113 may be not collimated.

[0030] In certain embodiments, sampling optics 120 may comprise element 122. In certain embodiments, element 122 may comprise a transmission lens. In certain embodiments, element 122 may comprises a collimating lens. In other embodiments, element 122 may comprise a reflective mirror.

[0031] In certain embodiments, element 122 may be placed in between light source 110 and beam splitter 121 along pathway 111. In other embodiments, not illustrated in Figure 1, element 122 may be placed in along pathway 112. In certain embodiments, element 122 may be capable of collimating the light generated by light source 110. In certain embodiments, element 122 may be capable of substantially collimating the light generated by light source 110.

[0032] In certain embodiments, the light in pathway 112 may be capable of illuminating a sample 160. In certain embodiments, sample 160 may comprise sea water. In certain embodiments, the sea water may comprise one or more dissolved gases. Examples of the one or more dissolved gasses that may be in the fluid include methane, ethane, propane, butane, pentane, carbon dioxide, and hydrogen sulfide. In certain embodiments, sample 160 may be external of chemical detector 100. In other embodiments, not illustrated in Figure 1, sample 160 may be present in a sample chamber.

[0033] The collimated light traveling along pathway 112 may illuminate sample 160 causing the illuminated sample to emit electromagnetic radiation or Raman scatterings along pathway 113. In certain embodiments, the electromagnetic radiation traveling along pathway 113 may be collimated along the entire pathway 113. In other embodiments, the electromagnetic radiation traveling along pathway 113 may be collimated along a portion of pathway 113. Raman scatterings emitted by the illuminated sample may depend on the chemicals within the sample 160. For example, Figure 4 illustrates a Raman spectra of a sample of isopropanol.

[0034] In certain embodiments, the electromagnetic radiation from sample 160 may then be routed to detector 150 via collection optics 140 along pathway 113. In certain embodiments, the electromagnetic radiation may pass through beam splitter 121 along pathway 113 without the majority of it being reflected and/or redirected along a different path.

[0035] In certain embodiments, collection optics 140 may comprise transmissive grating 141 and/or one or more focal lenses 142. In certain embodiments, the electromagnetic radiation may pass through transmissive grating 141 before it passes through focal lens 142. In other embodiments, the electromagnetic radiation may pass through one or more focal lenses 142 before it passes through transmissive grating 141. In certain embodiments, as shown in Figure 1, the electromagnetic radiation may pass through one or more focal lenses 142 before it passes through transmissive grating 141 and another focal lens after it passes through transmissive grating 141.

[0036] In certain embodiments, focal lenses 142 may comprise any conventional lens.

In certain embodiments, the one or more focal lenses 142 may be capable of focusing the electromagnetic radiation traveling along pathway 113 and/or pathway 114. In certain embodiments, a slit 143 may be disposed between a first focal lens 142 and a second focal lens 142.

[0037] In certain embodiments, transmissive grating 141 may comprise volume phase grating. In certain embodiments, transmissive grating 141 may be capable of splitting the electromagnetic radiation traveling along pathway 113 into several beams of light and or filtering the electromagnetic radiation traveling along pathway 113. In certain embodiments, transmissive grating 141 may be capable of redirecting the electromagnetic radiation traveling along pathway 113 to pathway 114. In certain embodiments, pathway 114 may be perpendicular to pathway 113. In certain embodiments, pathway 114 may be inclined or declined an angle in the range of from 70 degrees to 110 degrees with respect to pathway 113. [0038] In certain embodiments, not illustrated in Figure 1, collection optics 140 may comprise element 122, beam splitter 121, and lens 142.

[0039] In certain embodiments, detector 150 may be positioned to detect the filtered and redirected electromagnetic radiation and/or Raman scattering emitted from sample 160. In certain embodiments, detector 150 may comprise any conventional detector used from Raman spectroscopy. In certain embodiments, detector 150 may comprise a spectrometer.

[0040] In certain embodiments, detector 150 may comprise a multi-channel detector. In certain embodiments, detector 150 may be a multi-channel detector comprising 64 or 128 channels. In certain embodiments, detector 150 may be a multi-channel detector comprising less than 1000 channels. In certain embodiments, detector 150 may be a multi-channel detector comprising less than 500 channels. In certain embodiments, detector 150 may be a multi-channel detector comprising less than 250 channels. In certain embodiments, detector 150 may be a multi-channel comprising less than 100 channels.

[0041] In certain embodiments, detector 150 may comprise a multi-anode photomultiplier tube (PMT). In certain embodiments, the multi-anode PMT may comprise a multi-anode PMT ran in a single photon counting format. In certain embodiments, the single photon counting format may allow for an enhancement in detection and signal acquisition.

[0042] In certain embodiments, detector 150 may be capable of detecting the presence of any dissolved gases within the sample by analyzing the electromagnetic radiation generated by sample 160. In certain embodiments, chemical detector 100 may be capable of detecting dissolved gas in water, standoff detection, direct bubble detection, in-situ hydrate detection, and infrastructure leaks, other upstream/downstream detection.

[0043] In certain embodiments, not illustrated in Figure 1, detector 150 may comprise transmissive grating 141, lens 142, and slit 143.

[0044] Referring now to Figure 2, Figure 2 is a schematic of chemical detector 200, in accordance with certain embodiments of the present disclosure. In certain embodiments, chemical detector 200 may comprise light source 210, sampling optics 220, sample chamber 230, collection optics 240, and detector 250.

[0045] In certain embodiments, chemical detector 200 may comprise reflective sampling optics. As used herein in, the term "reflective sampling optics" refers to sampling optics that allow for the generation of a reflective beam within a sample chamber. In certain embodiments, the reflective sampling optics may comprise a set of mirrors disposed within the sample chamber. In certain embodiments, the use of reflective sampling optics allows for an amplification of the Raman scattering in the sample chamber due to the multiple reflections of the light in the sample chamber. In certain embodiments, the reflective sampling optics may enhance the performance of Raman measurements.

[0046] In certain embodiments, light source 210 may comprise any combination of features discussed above with respect to light source 110. In certain embodiments, light source 210 may emit light along a pathway 211. In certain embodiments, light source 210 may be positioned such that light from light source 210 may be sent directly or indirectly to sample chamber 230. In certain embodiments, not shown in Figure 2, light source 210 may comprise element 222.

[0047] In certain embodiment, sampling optics 220 may comprise beam splitter 221. In certain embodiments, beam splitter 221 may comprise any combination of features discussed above with respect to beam splitter 121. In certain embodiments, beam splitter 221 may be capable of directing light generated from light source 210 to sample chamber 230. In certain embodiments, the light traveling along pathway 212 and/or pathway 213 may be collimated along the entire pathways. In other embodiments, the light traveling along pathway 212 and/or pathway 213 may be collimated for only a portion of the pathways.

[0048] In certain embodiments, beam splitter 221 may be inclined at an angle in the range of from 30 degrees to 60 degrees with respect to pathway 211. In certain embodiments, beam splitter 221 may be inclined at an angle in the range of from 40 degrees to 50 degrees with respect to pathway 211. In certain embodiments, beam splitter 221 may be inclined at an angle of 45 degrees with respect to pathway 211.

[0049] In certain embodiments, beam splitter 221 may be capable of redirecting light along pathway 211 to pathway 212. In certain embodiments, pathway 212 may be perpendicular to pathway 211. In certain embodiments, pathway 212 may be inclined or declined an angle in the range of from 70 degrees to 110 degrees with respect to pathway 211.

[0050] In certain embodiments, sampling optics 220 may comprise element 222. In certain embodiments, element 222 may comprise any combination of features discussed above with respect to element 122.

[0051] In certain embodiments, element 222 may be placed in between light source

210 and beam splitter 221 along pathway 211. In other embodiments, not illustrated in Figure 2, element 222 may be placed in along pathway 212 or 213. [0052] In certain embodiments, sampling optics 220 may further comprise an optical cavity 223. In certain embodiments, the optical cavity may be defined by first mirror 224 and a second mirror 225. In certain embodiments, the optical cavity 223 may be disposed within sample chamber 230.

[0053] In certain embodiments, first mirror 224 may comprise dichroic mirror properties. In certain embodiments, first mirror 224 may be capable of reflecting light from light source 210 while allowing Raman scatterings from an illuminated fluid to pass through first mirror 224. In certain embodiments, first mirror 224 may be capable of reflecting 50% or more of light from light source 210 and transmitting 50% or more of the Raman scatterings. In certain embodiments, first mirror 224 may be capable of reflecting 75% or more of light from light source 210 and transmitting 75% or more of the Raman scatterings. In other embodiments, first mirror 224 may be capable of reflecting 90% or more of light from light source 210 and transmitting 90% or more of the Raman scatterings.

[0054] In certain embodiments, second mirror 225 may comprise an optical element that is capable of reflecting light from light source 210 and any Raman scattering.

[0055] In certain embodiments, first mirror 224 and second mirror 225 may be oriented to define optical cavity 223. In certain embodiments, first mirror 224 and second mirror 225 may be oriented such that the pathway 212 has a multi-pass pathway through optical cavity 223. In certain embodiments, first mirror 224 and second mirror 225 may be oriented to create more than 1000 pathways of pathway 212 between first mirror 224 and second mirror 225.

[0056] In certain embodiments, first mirror 224 and second mirror 225 may both be disposed within sample chamber 230. In certain embodiments, optical cavity 223 may be disposed within sample chamber 230. In other embodiments, sample chamber 230 may be disposed within optical cavity 223.

[0057] In certain embodiments, first mirror 224 and second mirror 225 may be placed a distance between 1 cm and 10 cm from each other. In other embodiments, first mirror 224 and second mirror 225 may be placed a distance between 10 cm and 100 cm from each other. In certain embodiments, first mirror 224 and second mirror 225 may be placed a distance of less than 1 cm from each other.

[0058] Within sample chamber 230, light along pathway 212 may illuminate any fluid disposed therein. In certain embodiments the multi-pass pathway of 212 may cause the illuminated fluid to emit electromagnetic radiation and/or Raman scatterings along pathway 213. In certain embodiments, pathway 213 may be parallel with pathway 212. In other embodiments, pathway 213 may be inclined or declined with respect to pathway 212 at an angle in the range of from 0 degrees to 180 degrees. In certain embodiments, pathway 213 may be inclined or declined with respect to pathway 212 at an angle in the range of from 45 degrees to 135 degrees.

[0059] In certain embodiments, the electromagnetic radiation from the illuminated fluid may then be routed to detector 250 via collection optics 240 along pathway 213. In certain embodiments, the electromagnetic radiation traveling along pathway 213 may be able to pass through first mirror 224 without being reflected and/or redirected along a different path.

[0060] In certain embodiments, collection optics 240 may comprise transmissive grating 241 and/or one or more focal lenses 242. In certain embodiments, the electromagnetic radiation may pass through transmissive grating 241 before it passes through focal lens 242. In other embodiments, the electromagnetic radiation may pass through one or more focal lenses 242 before it passes through transmissive grating 241. In certain embodiments, as shown in Figure 2, the electromagnetic radiation may pass through one or more focal lenses 242 before it passes through transmissive grating 241 and another focal lens 242 after it passes through transmissive grating 241.

[0061] In certain embodiments, focal lenses 242 may comprise any combination of features discussed above with respect to focal lenses 142. In certain embodiments, the one or more focal lenses 242 may be capable of focusing the electromagnetic radiation traveling along pathway 213 and/or a pathway 214. In certain embodiments, a slit 243 may be disposed between a first focal lens 242 and a second focal lens 242.

[0062] In certain embodiments, focal lens 242 may be designed as a telescope capable of collecting collimated light from distances greater than 0.5 meters, 1 meter, 5 meters, 10 meters, and/or 20 meters.

[0063] In certain embodiments, transmissive grating 241 may comprise any combination of features discussed above with respect to transmissive grating 141. In certain embodiments, transmissive grating 241 may be capable of splitting the electromagnetic radiation traveling along pathway 213 into several beams of light and or filtering the electromagnetic radiation traveling along pathway 213. In certain embodiments, transmissive grating 241 may be capable of redirecting the electromagnetic radiation traveling along pathway 213 to pathway 214. In certain embodiments, pathway 214 may be perpendicular to pathway 213. In certain embodiments, pathway 214 may be inclined or declined an angle in the range of from 70 degrees to 110 degrees with respect to pathway 213. In certain embodiments, transmissive grating 241 may function as a prism.

[0064] In certain embodiments, not illustrated in Figure 2, collection optics 240 may comprise element 222, beam splitter 221, and lens 242.

[0065] In certain embodiments, detector 250 may be positioned to detect the filtered and redirected electromagnetic radiation and/or Raman scattering from the illuminated fluid. In certain embodiments, detector 250 may comprise any combination of features discussed above with respect to detector 150.

[0066] In certain embodiments, detector 250 may be capable of detecting the presence of any dissolve gases within the fluid in sample chamber 230 by analyzing the electromagnetic radiation and/or Raman scattering.

[0067] In certain embodiments, not illustrated in Figure 2, detector 250 may comprise transmissive grating 241, lens 242, and slit 243.

[0068] In certain embodiments, the present disclosure describes a chemical detector system 1000. Referring now to Figure 3, Figure 3 illustrates chemical detector system 1000. In certain embodiments, chemical detector system 1000 may comprise vessel 1100, sea surface 1200, sea floor 1300, umbilical 1400, ROV 1500, and chemical detector 1600.

[0069] In certain embodiments, vessel 1100 may comprise any conventional vessel. In certain embodiments, an umbilical 1400 may extend from vessel 1100 to ROV 1500. In certain embodiments, ROV 1500 may comprise any conventional ROV. In certain embodiments, ROV 1500 may be equipped with a chemical detector 1600. In certain embodiments, ROV 1500 may be capable of operating chemical detector 1600.

[0070] In certain embodiments, chemical detector 1600 may comprise any combination of features discussed above with respect to chemical detector 100 and/or chemical detector 200.

[0071] In certain embodiments, chemical detector 1600 may be capable of detecting the presence of a dissolved gas in a sample. In certain embodiments, the sample may be sample of seawater above the sea floor 1300 and/or near a piece of well equipment 1700.

[0072] In another embodiment, the present disclosure provides a method of detecting a gas comprising: providing a chemical detector, wherein the chemical detector comprises a light source, sampling optics, collection optics, and a detector, illuminating a sample with light from the light source to generate electromagnetic radiation and/or Raman scatterings, and analyzing the electromagnetic radiation and/or Raman scatterings with the detector to detect the presence of a chemical in the sample.

[0073] In certain embodiments, the chemical detector may comprise any combination of features discussed above with respect to chemical detectors 100, 200, and 1600. In certain embodiments, the sample may comprise any combination of features discussed above with respect to sample 160. In certain embodiments, the electromagnetic radiation may comprise Raman scattering.

[0074] In certain embodiments, chemical detector may be capable of detecting dissolved gas in water, standoff detection, direct bubble detection, in-situ hydrate detection, and infrastructure leaks, other upstream/downstream detection.

[0075] While the embodiments are described with reference to various implementations and exploitations, it will be understood that these embodiments are illustrative and that the scope of the inventive subject matter is not limited to them. Many variations, modifications, additions and improvements are possible.

[0076] Plural instances may be provided for components, operations and/or structures described herein as a single instance. In general, structures and functionality presented as separate components in the exemplary configurations may be implemented as a combined structure or component. Similarly, structures and functionality presented as a single component may be implemented as separate components. These and other variations, modifications, additions, and improvements may fall within the scope of the inventive subject matter.