Non-invasive measurement of fluid-pressure diffusivity using electro-osmosis

An apparatus for determining a fluid-pressure diffusivity in a borehole (12), comprising:

• an electrode (16);
• and
• a measurement device (18) disposed a fixed distance from the electrode (16);
• wherein the electrode (16) injects an electrical current into a point on a wall of the borehole (12),
• wherein the measurement device (18) measures at least one of strain, particle velocity, and particle acceleration at the fixed distance from the point of injection of the electrical current over time;
• and
• wherein the fluid-pressure diffusivity is determined based on the measured at least one of strain, particle velocity, and particle acceleration over time.

An apparatus (5) for determining a fluid-pressure diffusivity in a borehole (12), comprising:

• means for injecting (16) an electrical current into a point on a wall of the borehole (12);
• and
• means for measuring (18) at least one of strain, particle velocity, and particle acceleration at a fixed distance from the point of injection of the electrical current over time;
• wherein the fluid-pressure diffusivity is determined based on the measured at least one of strain, particle velocity, and particle acceleration over time.

A logging tool (5) for determining a fluid-pressure diffusivity in a borehole (12), comprising:

• an electrode (16) mounted on a pad (14);
• and
• a measurement device (18) mounted on the pad (14) a fixed distance from the electrode (16);
• wherein the pad (14) is disposed against a wall of the borehole (12) so as to facilitate the electrode (16) injecting an electrical current into a point on a wall of the borehole (12) and the measurement device (18) measures at least one of strain, particle velocity, and particle acceleration at the fixed distance from the point of injection of the electrical current over time;
• wherein the electrode (16) injects an electrical current into the point on a wall of the borehole (12);
• wherein the measurement device (18) measures at least one of strain, particle velocity, and particle acceleration at the fixed distance from the point of injection of the electrical current over time;
• and
• wherein the fluid-pressure diffusivity is determined based on the measured at least one of strain, particle velocity, and particle acceleration over time;
• and
• wherein the determining of the fluid-pressure diffusivity comprises locating a point in time at which a second time derivative of the measured at least one of strain, particle velocity, and particle acceleration is zero.