Paul Southard, Scientist, Southwest Research Institute
Despite the fact that produced water disposal and management systems are often highly-engineered and designed with multiple redundancies, significant risks are posed to water resources due to: (1) lack of knowledge of abandoned legacy wells and adequately unfractured and impermeable confining rock layers, (2) inability to design for infrequent events, and (3) inability to predict material, operational or maintenance failures in the future. We developed a risk analysis framework for operations surrounding the disposal of produced water that accounts for component failures with extremely rare occurrences and determines probabilities of total system failure. We identified the five most common events leading to a release of produced water to the environment and created fault trees for each scenario composed of the sequence of redundancy failure events for a release to occur. Representative event probabilities were informed by data from the Texas Railroad Commission and groundwater conservation districts. The risk analysis framework was employed to identify likely causes of system failure for operations in La Salle, Zavala and Dimmit counties in southwest Texas. Results will be used to assess and update guidelines for construction specifications, operations and reporting requirements aimed at protecting water resources.