One of the fruits of the partnership between CMI and bp has been the development of a technique called a “Vertical Interference Test” (VIT) to assess the effective permeability of existing wells. This test appears to be a very valuable field tool to estimate in situ permeability along existing wells.


Evaluation of well integrity

Both bp (through collaboration with Walter Crow) and Schlumberger (through collaboration with Princeton alumnus Andrew Duguid) have used Vertical Interference Tests to determine, in situ, the effective permeability of materials (mostly cements) outside of well casings. In 2012, the Celia group has continued collaborations with Andrew Duguid at Schlumberger (Andrew is a PhD alumnus of the CMI program) to analyze data from Vertical Interference Tests. The three most recent tests gave permeability estimates between about 1 milliDarcy and about 200milliDarcy. These fall within the range of other earlier measurements, and are several orders of magnitude larger than permeability of cement plugs retrieved from these locations. The latter observation points to annular flows as dominant along the boreholes.

Figure 14: Examples of images from wellbore analysis: Left: Sample showing ~3 mm channel; Center: Sample showing shale fragments in the cement; Right: Side-wall core showing casing, cement, and shale. Figures from Duguid et al. (2012).