NOWSCO’s Inertial Geometry Inspection system (GEOPIG) measures pipeline location coordinates (x,y,h) and provides data for measuring pipeline bending strain and strain changes used for structural analysis and integrity evaluation of pipeline systems in geotechnically unstable areas. This paper reviews the results of work to prove such a system’s accuracy and repeatability against deliberately induced strain events in a 26 inch operating gas pipeline.

An inertial geometry pipeline inspection tool provides nearly continuous measurement of pipeline centerline coordinates. Over time, run to run strain comparisons can be made providing information with respect to possible failure modes and timing.

Monitoring buried pipeline movements in geotechnically unstable areas using strain gauges and/or monitoring rods can provide incomplete information with regard to true pipeline movement due to the discrete, point type measurement of these systems. If movement occurs outside of areas where such monitoring systems are deployed, information regarding important pipeline strain changes can go unmeasured.

This paper reviews work involved in detecting, locating, and determining the magnitude and type of strain and corresponding pipeline movement induced at one unknown location within a 70 km section between two inertial geometry surveys. The inertial geometry results are compared against strain gauge field measurements.

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