Comparison of Inadvertent Return Risk Analysis Methods to As-Drilled Pressure Data and Review of the Concept of a Factor of Safety
Stefan Goerz, Nic Boelhouwer
Dans les comptes rendus d’articles de la conférence: GeoCalgary 2022: 75th Canadian Geotechnical ConferenceSession: M6
ABSTRACT: Most Horizontal Directional Drilling (HDD) projects in North America that include an engineered design, complete an annular pressure analysis prior to construction in order to mitigate risk of inadvertent returns ("frac out"). Although the accepted fluid models accurately predict actual drilling fluid pressure downhole, the accurate prediction of containing/confining pressure (i.e. hydraulic fracture or shear failure) continues to be a focus of research. HDD contractors often continuously monitor annular pressure during construction to provide a basis for mitigating risk of inadvertent returns. The pressure sensor and associated guidance software automatically record "real-time" pressure data throughout the length of the HDD crossing. This "as drilled" annular pressure data, collected from a multitude of HDD crossings, is used in combination with CCI inspection reports to determine the date, time, and pressure magnitude of actual hydraulic fracture occurrences. Through careful evaluation, occurrences of inadvertent returns have been isolated within the as drilled data sets and plotted for comparison against predicted hydraulic fracture pressures calculated by both the "Delft" and "Queens" equation using site specific geotechnical parameters. Finally, performance of the models' for predicting potential inadvertent return during construction are discussed Real time annular pressure data has been collected for many HDD installations and the actual fracture pressures have been quantified. A comparison between the Delft, Queens and real time inadvertent return data is made in order to assess the performance of each method. In addition, the concept of a crossing factor of safety versus factored calculation is reviewed to provide insight in how to evaluate the safety of HDD methods for crossings.
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Citer cet article:
Goerz, Stefan, Boelhouwer, Nic (2022) Comparison of Inadvertent Return Risk Analysis Methods to As-Drilled Pressure Data and Review of the Concept of a Factor of Safety in GEO2022. Ottawa, Ontario: Canadian Geotechnical Society.
@article{Goerz_GEO2022_369,
author = Stefan Goerz, Nic Boelhouwer,
title = Comparison of Inadvertent Return Risk Analysis Methods to As-Drilled Pressure Data and Review of the Concept of a Factor of Safety ,
year = 2022
}
title = Comparison of Inadvertent Return Risk Analysis Methods to As-Drilled Pressure Data and Review of the Concept of a Factor of Safety ,
year = 2022
}