# US 5,708,203 A · Neutron logging method for quantitative wellbore fluid analysis > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 5,708,203 A - Document ID: US5708203A - Status: Granted - Kind: A - Application number: 08/795,619 - Filed: 1997-02-05 - Granted: 1998-01-13 - Earliest claimed: 1997-02-05 - Assignees: Exxon Production Research Company - Inventors: Richard M. McKinley; Walter J. Lamb - Web page: https://patentgrep.com/patent/US5708203A ## CPC - E21B 47/111: {using radioactivity} - E21B 47/11: using tracers; using radioactivity - E21B: EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS ## Abstract A neutron logging tool is used to obtain information about fluids within a wellbore. The well is shut in and a neutron log count rate (M.sub.gas) is obtained in a portion of the wellbore containing primarily gaseous fluid and a neutron log count rate (M.sub.liquid) is obtained in a portion of the wellbore containing primarily liquid fluid. Then fluid flow is reestablished in the well and a neutron log count rate (M.sub.mix) is obtained over a logging interval of interest. Previously obtained calibration data relates (M.sub.gas), (M.sub.liquid), and (M.sub.mix) to relative quantities of gaseous fluid and liquid fluid within the wellbore. ## Claims ### Claim 1 A method of quantifying gaseous fluid flow relative to liquid fluid flow in a portion of a wellbore, said method comprising: (a) obtaining calibration data which relates for at least one pipe, a volume fraction occupied by a liquid to a normalized neutron log count rate; (b) while said wellbore is shut in, using a neutron logging tool to measure a neutron log count rate for gaseous fluid (M.sub.gas) in said portion of said wellbore; (c) while said wellbore is shut in, using said neutron logging tool to measure a neutron log count rate for liquid fluid (M.sub.liquid) in said portion of said wellbore; (d) while fluids are flowing in said wellbore, using said neutron logging tool to measure a neutron log count rate for flowing fluids (M.sub.mix) in said portion of said wellbore; (e) determining a neutron log count rate ratio which relates volume fraction of said portion of said wellbore occupied by a liquid to a normalized neutron log count rate; and (f) comparing said neutron log count rate ratio to said calibration data to quantify said gaseous fluid flow relative to said liquid fluid flow in said portion of said wellbore. ### Claim 2 (depends on 1) The method of claim 1 wherein the step of obtaining said calibration data comprises correlating neutron log count rate ratios to relative quantities of said gas and said liquid in said at least one pipe. ### Claim 3 (depends on 1) The method of claim 1 wherein said at least one pipe is oriented substantially horizontal and said fluids flowing in said wellbore are layered according to density. ### Claim 4 (depends on 3) The method of claim 3 wherein the step of obtaining said calibration data comprises: (a) measuring liquid count rate(C.sub.liquid) with a neutron logging tool in said pipe containing said liquid; (b) measuring gas count rate (C.sub.gas) with said neutron logging tool in said pipe containing said gas; (c) measuring a plurality of mixture count rates (C.sub.mix) with said neutron logging tool in said pipe for a plurality of known mixtures of said liquid and said gas; and (d) for each said known mixture of said liquid and said gas, determining a neutron log count rate ratio of the difference between said gas count rate and said mixture count rate to the difference between said gas count rate and said liquid count rate (C.sub.gas -C.sub.mix)/(C.sub.gas -C.sub.liquid). ### Claim 5 (depends on 3) The method of claim 3 wherein the step of determining a neutron log count rate ratio which relates volume fraction of said portion of said wellbore occupied by a liquid to a normalized neutron log count rate comprises determining a neutron log count rate ratio equal to (M.sub.gas -M.sub.mix)/(M.sub.gas -M.sub.liquid). ### Claim 6 (depends on 1) The method of claim 1 wherein said neutron logging tool comprises a chemical neutron source and neutron detector. ### Claim 7 (depends on 6) The method of claim 6 wherein said chemical neutron source and said neutron detector are spaced about 17 inches apart. ### Claim 8 (depends on 1) The method of claim 1 wherein said neutron logging tool is an uncompensated neutron logging tool. ### Claim 9 A method of quantifying gaseous fluid flow relative to liquid fluid flow in a portion of a wellbore having fluid flow layered according to density, said method comprising: (a) obtaining calibration data which relates volume fraction of pipe occupied by a liquid to a normalized neutron log count rate; (b) shutting in said wellbore; (c) measuring a neutron log count rate for gaseous fluid (M.sub.gas) in said portion of said wellbore with a neutron logging tool; (d) measuring a neutron log count rate for liquid fluid (M.sub.liquid) in said portion of said wellbore with said neutron logging tool; (e) establishing fluid flow in said wellbore; (f) measuring a neutron log count rate for flowing fluids (M.sub.mix) over a logging interval of interest in said portion of said wellbore; (g) determining a neutron log count rate ratio equal to (M.sub.gas -M.sub.mix)/(M.sub.gas - M.sub.liquid); and (h) comparing said neutron log count rate ratio to said calibration data to quantify said gaseous fluid flow relative to said liquid fluid flow in said logging interval of interest. ### Claim 10 (depends on 9) The method of claim 9 wherein the step of obtaining said calibration data comprises correlating neutron log count ratios to relative quantities of said gas and said liquid in said pipe. ### Claim 11 (depends on 9) The method of claim 9 wherein the step of obtaining said calibration data comprises: (a) measuring liquid count rate(C.sub.liquid) with a neutron logging tool in said pipe containing said liquid; (b) measuring gas count rate (C.sub.gas) with said neutron logging tool in said pipe containing said gas; (c) measuring a plurality of mixture count rates (C.sub.mix) with said neutron logging tool in said pipe for a plurality of known mixtures of said liquid and said gas; and (d) for each said known mixture of said liquid and said gas, determining a neutron log count rate ratio of the difference between said gas count rate and said mixture count rate to the difference between said gas count rate and said liquid count rate (C.sub.gas -C.sub.mix)/(C.sub.gas -C.sub.liquid). ### Claim 12 (depends on 11) The method of claim 11 wherein said gas comprises air. ### Claim 13 (depends on 11) The method of claim 11 wherein said liquid comprises water. ### Claim 14 (depends on 11) The method of claim 11 wherein said pipe is surrounded by water-saturated sand bags. ### Claim 15 A method of identifying a suitable location for performing a shut-off workover in a portion of a wellbore having fluid flow layered according to density, said method comprising: (a) obtaining calibration data which relates volume fraction of pipe occupied by a liquid to a normalized neutron log count rate; (b) while said wellbore is shut in, measuring a neutron log count rate for gaseous fluid (M.sub.gas) in said portion of said wellbore; (c) while said wellbore is shut in, measuring a neutron log count rate for liquid fluid (M.sub.liquid) in said portion of said wellbore; (d) while fluids are flowing in said wellbore, measuring a neutron log count rate for flowing fluids (M.sub.mix) over a logging interval in said portion of said wellbore; (e) determining a neutron log count rate ratio equal to (M.sub.gas -M.sub.mix)/(M.sub.gas -M.sub.liquid); (f) comparing the neutron log count rate ratio to said calibration data to obtain quantification data representative of said gaseous fluid flow relative to said liquid fluid flow in said logging interval; and (g) repeating steps (d) through (f) as necessary until said quantification data indicates that said logging interval is a suitable location for performing a shut-off workover.