Measuring gas content of unconventional reservoir rocks

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.

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.

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.