Fluid Migration Mechanisms Due To Faulty Well Design and/or Construction
By Anthony R. Ingraffea, Ph.D., P.E., October 2012.
SUMMARY. See full paper “here.”
The most recent experience with shale gas wells in the Pennsylvania Marcellus play reflects long term, world-wide industry data with respect to new wells with compromised structural integrity. Operator-wide statistics in Pennsylvania show that about 6-7% of new wells drilled in each of the past three years have compromised structural integrity.
This apparently low failure rate should be seen in the context of a full buildout in the Pennsylvania Marcellus of at least 100,000 wells, and in the entire Marcellus, including New York, of twice that number.
Therefore, based on recent statistical evidence, one could expect at least 10,000 new wells with compromised structural integrity. It is too early to discern whether the other industry experience with this technical problem, an increase in loss of integrity with well age, will also be reflected.
However, at play in modern shale gas development are many of the key factors identified by industry researchers as having a negative influence on well structural integrity: the need for deviated wells, rapid development of a field, presence of “shallow” high-pressure gas horizons, and disturbance of young cement due to adjacent drilling activities on the same pad.
Display 1: 1,609 wells drilled in 2010. 111 well failures. 6.9 % rate of failure.
Display 2: 1,979 wells drilled in 2011. 142 well failures. 7.2 % rate of failure.
Display 3. 1,040 wells drilled Jan/Aug 2012. 67 well failures. 6.6 % rate of failure.
Display 4. Consistent with previous industry data, and not improving.