Apparatus, system and method for mechanical testing under confined conditions

A system for measuring mechanical properties of a rock formation, the system comprising:

• an apparatus including:
• first and second fixtures each containing a force application fixture, the force application fixture configured to apply a stress to a specimen of the downhole material when located in-between the first and second fixtures;
• a confining sleeve configured to wrap around portions of the first and second fixtures that are nearest to the specimen to form a sealed specimen chamber, the sealed specimen chamber dimensions defined by an inner surface of the confining sleeve and ends of the first and second fixtures nearest the specimen;
• a confining chamber having walls configured to contain the first and second fixtures, the confining sleeve and the specimen therein, wherein the confining chamber is configured to hold a hydraulic fluid therein such that the hydraulic fluid can exert a confining pressure on the confining sleeve to maintain the seal of the sealed specimen chamber and to maintain contact between the inner surface of the confining sleeve and the specimen when the stress is applied to the specimen;
• one or more first channels passing though one or more of the walls of the confining chamber, the one or more first channels configured to add and remove the hydraulic fluid to and from the confining chamber;
• one or more second channels passing though one or more of the walls of the confining chamber and through one of the first and second fixtures, the one or more second channels configured to add and remove a pore space fluid to and from specimen chamber ports open to the specimen chamber, wherein the pore space fluid is configured to maintain a pore pressure at the specimen chamber ports that is equal to or less than the confining pressure while the stress is applied to the specimen;
• and
• a sensor device configured to measure a displacement of the specimen while the stress is applied to the specimen.

A method of measuring mechanical properties of a downhole material, comprising:

• placing a specimen of the downhole material between force application fixtures of first and second fixtures of an apparatus;
• wrapping a confining sleeve of the apparatus around portions of the first and second fixtures that are nearest to the specimen to form a sealed specimen chamber, the sealed specimen chamber dimensions defined by an inner surface of the confining sleeve and ends of the first and second fixtures nearest the specimen;
• placing the first and second fixtures, the confining sleeve and the specimen inside a confining chamber of the apparatus;
• pumping a hydraulic fluid into the confining chamber to fill the confining chamber with the hydraulic fluid such that the hydraulic fluid exerts a constant confining pressure on the confining sleeve to maintain the seal of the sealed specimen chamber and to maintain contact between the inner surface of the confining sleeve and the specimen;
• pumping a pore space fluid to fill the sealed specimen chamber with the pore space fluid including passing the pore space fluid through one or more specimen chamber ports open to the specimen chamber such that the pore space fluid maintains a constant pore pressure at the specimen chamber ports that is equal to or less than the confining pressure;
• and
• applying a stress to the specimen through the force application fixtures, while maintaining the constant confining pressure to maintain contact between the inner surface of the confining sleeve and the specimen and while maintaining the constant pore pressure, until mechanical failure of the specimen.