1. . []

The space between the shaped charge and the internal surface of the perforating gun body. The standoff is generally sufficient to allow the shaped charge jet to form before exiting the gun body.

See: perforating gun

2. . []

The distance between the external surface of a logging tool and the borehole wall. This distance has an important effect on the response of some logging measurements, notably induction and neutron porosity logs. For resistivity tools, the effect of standoff is taken into account in the borehole correction. In the neutron porosity tool, it is usually corrected for separately. In a smooth, regular hole, the standoff is constant and determined by the geometry of the logging tool string and the borehole. In rugose or irregular holes, standoff varies with depth.

See: borehole correctioncave effectneutron porosity

3. . []

A piece of material designed to hold a logging tool a certain distance away from the borehole wall. It is usually made of hard rubber and consists of four to six fins of the desired length.