Field and experimental brittleness (toughness) determination

ARIEL CHAVEZ; OTEGUI, JOSE LUIS; MARTIN SANCHEZ; WALTER MORRIS; GUSTAVO BIANCHI

San francisco

Simposio; 49th US Rock Mechanics / Geomechanics Symposium; 2015

ARMA, American Rock Mechanics Association

Rock fracability characterization is a key issue for unconventional reservoirs stimulation. This property not only controls hydraulic fracture initiating and propagating pressure, but also affects the stimulated reservoir volume (SRV) which determines well productivity. Several parameters such as brittleness, plasticity and toughness among others are frequently referred in the literature to describe rock fracability. This paper discusses the validity of some of these parameters and emphasizes the fracture mechanics approach to characterize rock fracability based on the critical stress intensity factor (KIC). An experimental study was conducted using synthetic and real Vaca Muerta (VM) shale samples. KIC was determined using two types of specimens, the notched Brazilian disc and the semicircular three point load tests. The influence of applied load rate, material composition and medium was analyzed. The implications of these parameters in the hydraulic fracture process are discussed. The experimental results were compared with KIC values calculated using information obtained from Vaca Muerta fracture jobs.