DIC Assisted FCG Testing for Materials Used in Shale Gas Mining

Abstract

Limited mineral resources amount induce research in natural gas sequestration from non-conventional reservoirs with shale rock being a prominent example. CO2 based fracturing is promising technique for both shale rock fracturing and greenhouse effect causing gas underground storage, however CO2 in the presence of water might be corrosive for traditional materials used in natural gas wells limiting their performance in static and dynamic loading conditions. The aim of this work is to develop minisamples based technique for Fatigue Crack Growth (FCG) rate testing on casing pipe material used in conventional gas mining. 3-point bending type samples of three different W dimension has been selected for testing with FCG standard based approach as well as with optical, noncontact displacement measurements made with Digital Image Correlation (DIC) near the propagating crack tip. Results of different testing techniques for P110 steel have been discussed and conclusion drawn out giving general guidelines for proposed method usage in pipeline materials investigation. Additionally scale effect on FCG results has been revealed.