A brittleness evaluation method based on breaking energy theory for tight reservoir in Dagang Oilfield

The tight reservoirs in Dagang Oilfield are deep in burial depth and complex in lithology, and the brittleness evaluation methods commonly used at home and abroad are not accurate enough to effectively guide the design of fracturing. As a result, the fracturing in the early days was low in success rate and not ideal in effect. In this study, from the perspective of breaking energy theory, based on a large number of core experiments, the factors affecting rock failure morphology have been analysed by using the breaking energy theory, and a brittleness evaluation method more suitable for the physical properties of tight reservoirs in Dagang Oilfield has been worked out. The results show that the main parameters affecting brittleness of tight reservoirs in Dagang Oilfield are Young’s modulus, dilatancy angle and peak strain. The correlation coefficient between the brittle index from the new method based on breaking energy theory and rock failure complexity increases to 0.789 compared with 0.329 of the brittle index from Rickman’s evaluation method. The new method solves the problem that previous brittleness index models at home and abroad are not suitable for tight reservoirs in Dagang Oilfield, and provides a theoretical basis for evaluating the fracability of tight reservoirs and improving fracturing effect in Dagang Oilfield.