Apparatus and methods for detecting gases during coring operations

A coring apparatus for acquiring a core sample from a subterranean formation, the apparatus comprising:

• an outer core barrel having a longitudinal axis, first end, and a second end opposite the first end, the second end comprising an annular core bit;
• an inner core barrel coaxially disposed within the outer core barrel, wherein the inner core barrel has a first end distal the annular core bit, a second end proximal the annular core bit, and a core sample chamber extending axially from the second end of the inner core barrel, wherein the core sample chamber is configured to receive the core sample;
• an annulus radially disposed between the outer core barrel and the inner core barrel;
• a drilling fluid distributor coupled to the first end of the inner core barrel, wherein the drilling fluid distributor includes a first flow path extending axially through the drilling fluid distributor to the core sample chamber and a second flow path extending radially from the first flow path through the distributor to the annulus;
• a gas detector coupled to the inner core barrel proximal the first end of the inner core barrel, wherein the gas detector is exposed to the core sample chamber and is configured to detect the presence of an acid gas.

A method for detecting the presence of hydrogen sulfide gas in a formation fluid from a subterranean formation, the method comprising:

• (a) lowering a coring assembly into a borehole, the coring assembly including an outer core barrel and an inner core barrel disposed within the outer core barrel, wherein the outer core barrel has a lower end comprising an annular coring bit, and wherein the inner core barrel has a longitudinal axis, an upper end, a lower end opposite the upper end, and a core sample chamber extending axially from the lower end;
• (b) drilling into the subterranean formation at a bottom of the borehole with the coring bit;
• (c) capturing a core sample from the subterranean formation within the sample chamber during step (b);
• (d) raising the coring assembly to the surface after step (c);
• (e) liberating the hydrogen sulfide gas from the core sample during step (d);
• (f) allowing the liberated hydrogen sulfide gas to migrate to an upper portion of the sample chamber during step (d) axially disposed between the core sample and the upper end of the inner core barrel;
• (g) detecting the presence of the hydrogen sulfide gas within the upper portion of the sample chamber during (d).