Embeddable downhole probe

A method of evaluating a geologic formation surrounding a wellbore, the method comprising:

• deploying a downhole tool into the wellbore, the downhole tool comprising:
• a tool body defining a longitudinal axis;
• a radial extension mechanism mounted on the tool body at a first location on the tool body and movable between a radially retracted configuration and a radially extended configuration with respect to the tool body;
• a shaped head having a proximal end attached to the radial extension mechanism and a distal end at which a vertex is formed;
• and
• a straddle packer including a mandrel coupled to the tool body, first and second packer elements axially spaced from one another along the mandrel and a fluid port defined in the mandrel between the first and second packer elements;
• moving the radial extension mechanism from the radially retracted configuration to the radially extended configuration to thereby radially extend the shaped head and penetrate the geologic formation with the shaped head;
• sensing a characteristic of the geologic formation through the shaped head as the shaped head is radially extended to a plurality of increments of radial depth into the geologic formation;
• determining that the shaped head has reached a radial depth beyond a hoop stress regime by observing that a change in the characteristic of the geologic formation sensed is below a predetermined threshold;
• injecting a fluid into the geologic formation;
• and
• sensing a characteristic of the of the fluid injected through the shaped head.