Systems and methods for slice selective nuclear magnetic resonance testing of fractured core plugs to determine in-situ pore volume

A non-transitory computer readable storage medium comprising program instructions for slice selective nuclear magnetic resonance (NMR) testing of a fractured core plug, the program instructions executable by a computer processor to cause the following operations:

• identifying a location of a fracture within a core plug, the location including a position and orientation of the fracture, the core plug being saturated with a saturating fluid to introduce the saturating fluid into the fracture and being sealed to inhibit the saturating fluid from leaking out of the fracture;
• identifying a slice of the core plug corresponding to the location of the fracture;
• conducting initial local slice selective NMR testing of the core plug comprising:
• subjecting the core plug to baseline conditions, the baseline conditions comprising a first stress level;
• conducting an initial NMR scan of the core plug to acquire initial T2 NMR measurements, the initial NMR scan of the core plug comprising an NMR scan of the slice of the core plug corresponding to the fracture while the core plug is subjected to the baseline conditions;
• and
• determining, based on the initial T2 NMR measurements, an initial fracture pore volume of the fracture;
• conducting in-situ local slice selective NMR testing of the core plug comprising:
• determining in-situ conditions of the core plug, the in-situ conditions comprising an in-situ stress level for the core plug;
• subjecting the core plug to in-situ conditions comprising a second stress level that is greater than the first stress level and that corresponds to the in-situ stress level;
• conducting an in-situ NMR scan of the core plug to acquire in-situ T2 NMR measurements, the in-situ NMR scan of the core plug comprising an NMR scan of the slice of the core plug corresponding to the fracture while the core plug is subjected to the in-situ conditions;
• measuring a volume of water expelled from the core plug in response to subjecting the core plug to the in-situ condition;
• determining, based on the in-situ T2 NMR measurements, an in-situ fracture pore volume of the fracture;
• determining a difference between the initial fracture pore volume of the fracture and the in-situ fracture pore volume of the fracture;
• comparing the difference between the initial fracture pore volume of the fracture and the in-situ fracture pore volume of the fracture to the volume of water expelled;
• and
• verifying, based on the comparison of the difference between the initial fracture pore volume of the fracture and the in-situ fracture pore volume of the fracture to the volume of water expelled, the in-situ fracture pore volume of the fracture.

A system for slice selective nuclear magnetic resonance (NMR) testing of a fractured core plug, comprising:

• a slice selective NMR test fixture configured to subject a fractured core plug to slice selective NMR scans;
• and
• non-transitory computer readable storage medium comprising program instructions executable by a computer processor to cause the following operations:
• identifying a location of a fracture within a core plug, the location including a position and orientation of the fracture, the core plug being saturated with a saturating fluid to introduce the saturating fluid into the fracture and being sealed to inhibit the saturating fluid from leaking out of the fracture;
• identifying a slice of the core plug corresponding to the location of the fracture;
• conducting initial local slice selective NMR testing of the core plug comprising:
• subjecting the core plug to baseline conditions, the baseline conditions comprising a first stress level;
• conducting an initial NMR scan of the core plug to acquire initial T2 NMR measurements, the initial NMR scan of the core plug comprising an NMR scan of the slice of the core plug corresponding to the fracture while the core plug is subjected to the baseline conditions;
• and
• determining, based on the initial T2 NMR measurements, an initial fracture pore volume of the fracture;
• conducting in-situ local slice selective NMR testing of the core plug comprising:
• determining in-situ conditions of the core plug, the in-situ conditions comprising an in-situ stress level for the core plug;
• subjecting the core plug to in-situ conditions comprising a second stress level that is greater than the first stress level and that corresponds to the in-situ stress level;
• conducting an in-situ NMR scan of the core plug to acquire in-situ T2 NMR measurements, the in-situ NMR scan of the core plug comprising an NMR scan of the slice of the core plug corresponding to the fracture while the core plug is subjected to the in-situ conditions;
• measuring a volume of water expelled from the core plug in response to subjecting the core plug to the in-situ condition;
• determining, based on the in-situ T2 NMR measurements, an in-situ fracture pore volume of the fracture;
• determining a difference between the initial fracture pore volume of the fracture and the in-situ fracture pore volume of the fracture;
• comparing the difference between the initial fracture pore volume of the fracture and the in-situ fracture pore volume of the fracture to the volume of water expelled;
• and
• verifying, based on the comparison of the difference between the initial fracture pore volume of the fracture and the in-situ fracture pore volume of the fracture to the volume of water expelled, the in-situ fracture pore volume of the fracture.