Size Effects on Triaxial Testing from Sidewall Cores for Petroleum Geomechanics

摘要

Core samples obtained from sidewall coring hardly meet the specifications for strength or elastic property measurements as described in ASTM or ISRM. However, strength and elastic properties obtained from sidewall core samples during triaxial testing conditions are important in drilling, completion and reservoir modeling. Past percussion and advanced rotary coring wireline tools have been used to cut 25.4 mm (1.0-in) plug samples, but recent advances in technology have made it possible to obtain 38.1 mm (1.5-in) plug samples from openhole wellbores. Correcting for unconfined compressive strength (UCS) obtained from core plugs with length-to-diameter ratios of less than 2 is well established using the ASTM correction factor (1986). The suitable correction factor to apply for confined compressive strengths (CCS) and its associated elastic properties during triaxial loading is not well studied. This study focuses on the aforementioned challenging test consideration by investigating the effect of size during triaxial confining conditions.