# US 10,371,633 B2 · Determining a specific gravity of a sample > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 10,371,633 B2 - Document ID: US10371633B2 - Status: Granted - Kind: B2 - Application number: 15/797,938 - Filed: 2017-10-30 - Published: 2019-05-02 - Granted: 2019-08-06 - Earliest claimed: 2017-10-30 - Assignees: Saudi Arabian Oil Company - Applicants: Saudi Arabian Oil Company - Inventors: Ezzat Hegazi; Vincent Cunningham; Maha Ali N. Alsayegh - Web page: https://patentgrep.com/patent/US10371633B2 ## CPC - G01N 21/64: Fluorescence; Phosphorescence - G01N 21/6408: {with measurement of decay time, time resolved fluorescence} - G01N 33/241: {for hydrocarbon content} - G01N 33/2823: {Raw oil, drilling fluid or polyphasic mixtures} - G01N 2021/6417: {Spectrofluorimetric devices} - G01N: INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES (measuring or testing apparatus or processes other than immunoassay, involving enzymes or microorganisms C12M, C12Q) ## Abstract Methods and systems use fluorescence to determine specific gravity of samples. A first light pulse is applied to a sample at a first angle-of-incidence. A second light pulse is applied to the sample at a second angle-of-incidence. A first ratio based on the intensity of a first fluorescence emission over a first time interval and the intensity of the first fluorescence emission over a second time interval is calculated. A second ratio based on the intensity of a second fluorescence emission over a third time interval and the intensity of the second fluorescence emission over a fourth time interval is calculated. An intensity ratio based on the first ratio and the second ratio is calculated. A specific gravity of the sample based on the intensity ratio is determined. ## Claims ### Claim 1 A method comprising: applying a first light pulse to a sample at a first angle-of-incidence; detecting an intensity of a first fluorescence emission emitted from the sample over a first time interval and a second time interval; applying a second light pulse to the sample at a second angle-of-incidence; detecting an intensity of a second fluorescence emission emitted from the sample over a third time interval and a fourth time interval; calculating, by a processor, a first ratio based on the intensity of the first fluorescence emission over the first time interval and the intensity of the first fluorescence emission over the second time interval; calculating, by a processor, a second ratio based on the intensity of the second fluorescence emission over the third time interval and the intensity of the second fluorescence emission over the fourth time interval; calculating, by a processor, an intensity ratio based on the first ratio and the second ratio; and determining a specific gravity of the sample based on the intensity ratio. ### Claim 2 (depends on 1) The method of claim 1, wherein applying the first light pulse comprises producing the first light pulse using a first single-wavelength light source. ### Claim 3 (depends on 2) The method of claim 2, wherein the first single-wavelength light source comprises a laser operating at 250 to 450 nm. ### Claim 4 (depends on 2) The method of claim 2, wherein applying the second light pulse comprises producing the second light pulse using the first single-wavelength light source. ### Claim 5 (depends on 4) The method of claim 4, comprising moving the first single-wavelength light source between producing the first light pulse and producing the second light pulse. ### Claim 6 (depends on 4) The method of claim 4, comprising moving the sample between producing the first light pulse and producing the second light pulse. ### Claim 7 (depends on 1) The method of claim 1, wherein applying the second light pulse comprises producing the second light pulse using a second single-wavelength light source. ### Claim 8 (depends on 1) The method of claim 1, wherein the sample comprises hydrocarbon fluid and the specific gravity is an API gravity. ### Claim 9 (depends on 1) The method of claim 1, wherein the first angle-of-incidence is between 5 and 30 degrees. ### Claim 10 (depends on 1) The method of claim 1, wherein the second angle-of-incidence is between 40 and 65 degrees. ### Claim 11 (depends on 1) The method of claim 1, wherein the difference between the first angle-of-incidence and the second angle-of-incidence is between 25 and 65 degrees. ### Claim 12 (depends on 1) The method of claim 1, further comprising: normalizing, by a processor, the first fluorescence emission over the first time interval and the second time interval; and normalizing, by a processor, the second fluorescence emission over the third time interval and the fourth time interval. ### Claim 13 (depends on 1) The method of claim 1, wherein the first time interval and the third time interval are synchronized to a maximum of the first light pulse and the second light pulse, respectively. ### Claim 14 (depends on 1) The method according to claim 1, wherein the second time interval and the fourth time interval are synchronized to 3 ns after a maximum of the first light pulse and the second light pulse, respectively. ### Claim 15 A method comprising: applying a first light pulse to a sample at a first angle-of-incidence; detecting an intensity of a first fluorescence emission as the intensity of the first fluorescence emission fades; applying a second light pulse to the sample at a second angle-of-incidence; detecting an intensity of a second fluorescence emission as the intensity of the second fluorescence emission fades; comparing, by a processor, the fading of the first fluorescence emission with the fading of the second fluorescence emission; and determining a specific gravity of the sample based on a ratio calculated based on a comparison of the fading of the first fluorescence emission and the fading of the second fluorescence emission. ### Claim 16 (depends on 15) The method of claim 15, wherein applying the first light pulse comprises producing the first light pulse using a first single-wavelength light source. ### Claim 17 (depends on 16) The method of claim 16, wherein applying the second light pulse comprises producing the second light pulse using the first single-wavelength light source. ### Claim 18 (depends on 17) The method of claim 17, comprising moving the first single-wavelength light source between producing the first light pulse and producing the second light pulse. ### Claim 19 (depends on 17) The method of claim 17, comprising moving the sample between producing the first light pulse and producing the second light pulse. ### Claim 20 An API gravity measurement system comprising: a fluorescence-measuring apparatus, comprising: a first single-wavelength light source configured to generate a first excitation light pulse to contact a sample at a first angle-of-incidence; a second single-wavelength light source configured to generate a second excitation light pulse to contact the sample at a second-angle of incidence; a sample holder configured to hold the sample; and a detector configured to detect an intensity of a fluorescence emission from the sample; a processor; and a computer-readable storage medium storing instructions executable by the processor, the instructions comprising: applying a first light pulse to a sample at a first angle-of-incidence; detecting an intensity of a first fluorescence emission emitted from the sample over a first time interval and a second time interval; applying a second light pulse to the sample at a second angle-of-incidence; detecting an intensity of a second fluorescence emission emitted from the surface over a third time interval and a fourth time interval; calculating, by a processor, a first ratio based on the intensity of the first fluorescence emission over the first time interval and the intensity of the first fluorescence emission over the second time interval; calculating, by a processor, a second ratio based on the intensity of the second fluorescence emission over the third time interval and the intensity of the second fluorescence emission over the fourth time interval; calculating, by a processor, an intensity ratio based on the first ratio and the second ratio; and determining a specific gravity of the sample based on the intensity ratio.