# US 2013/0152665 A1 · Measuring gas content of unconventional reservoir rocks > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2013/0152665 A1 - Document ID: US20130152665A1 - Status: Published application - Kind: A1 - Application number: 13/522,201 - Filed: 2011-01-13 - Published: 2013-06-20 - Earliest claimed: 2010-01-13 - Assignees: Santos - Inventors: Erik Christopher Dunlop; Peter John Archer; Mika Olavi Porter - Web page: https://patentgrep.com/patent/US20130152665A1 ## CPC - E21B 49/005: {Testing the nature of borehole walls or the formation by using drilling mud or cutting data} - G01N 1/2294: {Sampling soil gases or the like} - E21B 41/0099: {specially adapted for drilling for or production of natural hydrate or clathrate gas reservoirs; Drilling through or monitoring of formations containing gas hydrates or clathrates} - E21B: EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS - 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 A method of measuring the in-situ Total Gas content of an unconventional reservoir rock, the method including: drilling a borehole through a measurement interval in the reservoir to generate an annular volume of drilling mud that includes cuttings and gas, the annular volume having a leading edge and a trailing edge; diverting the leading edge of the annular volume such that all of the annular volume is captured in a degassing storage system without being exposed to atmosphere; discontinuing the diversion of the annular volume when the trailing edge of the annular volume has been captured in the degassing storage system; measuring the gas volume in the degassing storage system to determine the amount of gas per annular volume; and calculating the in-situ Total Gas content of the reservoir with reference to the amount of gas and cuttings per annular volume. ## Claims ### Claim 1 A method of measuring the in-situ Total Gas content of an unconventional reservoir rock, the method including: a) drilling a borehole through a measurement interval in the reservoir to generate an annular volume of drilling mud that includes cuttings and gas, the annular volume having a leading edge and a trailing edge; b) diverting the leading edge of the annular volume such that all of the annular volume is captured in a degassing storage system without being exposed to atmosphere; c) discontinuing the diversion of the annular volume when the trailing edge of the annular volume has been captured in the degassing storage system; d) measuring the gas volume in the degassing storage system to determine the amount of gas per annular volume; and e) calculating the in-situ Total Gas content of the reservoir with reference to the amount of gas and cuttings per annular volume. ### Claim 2 (depends on 1) A method according to claim 1, wherein the method uses a drilling rig that includes a drilling mud circulation system and a blowout preventer through which drilling mud is recirculated from and to the borehole during normal drilling operations. ### Claim 3 (depends on 2) A method according to claim 2, wherein the simultaneous closing of the blowout preventer and opening of all valves downstream of the blowout preventer diverts the leading edge of the annular volume such that all of the annular volume is captured in the degassing storage system without being exposed to atmosphere. ### Claim 4 (depends on 2) A method according to claim 2, wherein, when the trailing edge of the annular volume has been captured in the degassing storage system, the simultaneously opening of the blowout preventer and the closing of valves downstream of the blowout preventer terminating at the degassing storage system, discontinues the diversion of the annular volume. ### Claim 5 (depends on 1) A method according to claim 1, wherein, once captured in the degassing storage system, the cuttings settle out of suspension, and degassing of the drilling mud occurs over a period of time. ### Claim 6 (depends on 5) A method according to claim 5, wherein the degassing storage system includes a plurality of low-positive-pressure degassing tanks used to form a combined settling and volume measurement system, the degassing tanks initially being filled with clean water before diversion of the annular volume thereto and each having a potential headspace for gas accumulation. ### Claim 7 (depends on 6) A method according to claim 6, including at least two low-positive-pressure degassing tanks in the form of a primary degasser tank combined with one or more secondary gas measurement tanks. ### Claim 8 (depends on 7) A method according to claim 7, wherein the secondary gas measurement tanks are connected in series and are in fluid communication with the primary degasser tank to collect substantially all of the gas liberated from the primary degasser tank. ### Claim 9 (depends on 7) A method according to claim 7, wherein the secondary gas measurement tanks include sight tubes to enable tracking of the liberated gas volume. ### Claim 10 (depends on 7) A method according to claim 7, wherein upon completion of the diversion of the annular volume and subsequent degassing, no significant gas remains in the primary degasser tank, the space being occupied mostly by the drilling mud and the cuttings, with only a relatively minor volume of initial water remaining at the top of the tank. ### Claim 11 (depends on 7) A method according to claim 7, wherein an outlet of the final secondary gas measurement tank is open to atmosphere via a downstream siphon-breaker to prevent gravity-drainage of the degassing storage system, providing exposure of the initial tank water to atmosphere to allow displacement of the water as gas is liberated. ### Claim 12 (depends on 7) A method according to claim 7, wherein the initial tank water is pre-saturated with dissolved gas, of representative composition, to prevent loss of liberated gas into solution. ### Claim 13 (depends on 7) A method according to claim 7, wherein the initial tank water is heated to at least 80° C. to reduce both carbon dioxide and hydrocarbon gas solubility to negligible levels, thereby forcing these gases out of solution. ### Claim 14 (depends on 1) A method according to claim 1, wherein fresh drilling mud in the form of a gas and solids-free drilling mud is used as the drilling mud. ### Claim 15 A method of measuring the in-situ Total Gas content of an unconventional reservoir rock, the method using a drilling rig that includes a drilling mud circulation system that includes a blowout preventer through which drilling mud is recirculated from and to a borehole during normal drilling operations, the method including: a) drilling a borehole through a measurement interval in the reservoir to generate an annular volume of drilling mud that includes cuttings and gas, the annular volume having a leading edge and a trailing edge; b) simultaneously closing the blowout preventer and opening all valves downstream of the blowout preventer to divert the leading edge of the annular volume such that all of the annular volume is captured in a degassing storage system without being exposed to atmosphere; c) when the trailing edge of the annular volume has been captured in the degassing storage system, simultaneously opening the blowout preventer and valves downstream of the blowout preventer terminating at the degassing storage system to discontinue the diversion of the annular volume; d) measuring the gas volume in the degassing storage system to determine the amount of gas per annular volume; and e) calculating the in-situ Total Gas content of the reservoir with reference to the amount of gas and cuttings per annular volume. ### Claim 16 Apparatus for measuring the in-situ Total Gas content of an unconventional reservoir rock, the apparatus including: a) a drilling rig capable of drilling a borehole through a measurement interval in the gas reservoir to generate an annular volume of drilling mud that includes cuttings and gas, the annular volume having a leading edge and a trailing edge; and b) a degassing storage system capable of capturing all of the annular volume, without the annular volume being exposed to atmosphere, when the leading edge of the annular volume of the drilling mud is diverted thereto, the diversion being discontinued when the trailing edge of the annular volume has been captured in the degassing storage system; whereby the gas volume in the degassing storage system can be measured to determine the amount of gas per annular volume, and the in-situ Total Gas content of the gas reservoir can be calculated with reference to the amount of gas and cuttings per annular volume. ### Claim 17 (depends on 16) Apparatus according to claim 16, wherein the apparatus includes a drilling mud circulation system that includes a blowout preventer through which drilling mud is recirculated from and to a borehole during normal drilling operations. ### Claim 18 (depends on 17) Apparatus according to claim 17, wherein the leading edge of the annular volume is diverted to the degassing storage system by simultaneously closing the blowout preventer and opening all valves downstream of the blowout preventer. ### Claim 19 (depends on 17) Apparatus according to claim 17, wherein the diversion of the annular volume to the degassing storage system is discontinued by simultaneously opening the blowout preventer and closing valves downstream of the blowout preventer terminating at the degassing storage system. ### Claim 20 (depends on 16) Apparatus according to claim 16, wherein the degassing storage system includes a plurality of low-positive-pressure degassing tanks used to form a combined settling and volume measurement system. ### Claim 21 (depends on 20) Apparatus according to claim 20, including at least two low-positive-pressure degassing tanks in the form of a primary degasser tank combined with one or more secondary gas measurement tanks. ### Claim 22 (depends on 21) Apparatus according to claim 21, wherein the secondary gas measurement tanks are connected in series and are in fluid communication with the primary degasser tank to collect all gas liberated from the primary degasser tank. ### Claim 23 (depends on 21) Apparatus according to claim 21, wherein the secondary gas measurement tanks include sight tubes to enable tracking of the liberated gas volume. ### Claim 24 (depends on 21) Apparatus according to claim 21, wherein an outlet of the final secondary gas measurement tank is open to atmosphere via a downstream siphon-breaker to prevent gravity-drainage of the degassing storage system. ### Claim at position 25 25-26. (canceled) ### Claim 27 An apparatus for measuring the in-situ Total Gas content of an unconventional reservoir rock, the apparatus including: a) a drilling rig that includes a drilling mud circulation system that includes a blowout preventer through which drilling mud is recirculated from and to a borehole during normal drilling operations, the drilling rig being capable of drilling a borehole through a measurement interval in the gas reservoir to generate an annular volume of drilling mud that includes cuttings and gas, the annular volume having a leading edge and a trailing edge; and b) a degassing storage system capable of capturing all of the annular volume, without the annular volume being exposed to atmosphere, when the leading edge of the annular volume of the drilling mud is diverted thereto by the simultaneous closing of the blowout preventer and opening of all valves downstream of the blowout preventer, the diversion being discontinued when the trailing edge off the annular volume has been captured in the degassing storage system by the simultaneous opening of the blowout preventer and closing of valves downstream of the blowout preventer terminating at the degassing storage system; whereby the gas volume in the degassing storage system can be measured to determine the amount of gas per annular volume, and the in-situ Total Gas content of the gas reservoir can be calculated with reference to the amount of gas and cuttings per annular volume.