A new method for evaluating the effectiveness of hydraulic fracturing in tight reservoirs

The effectiveness of hydraulic fracturing in tight reservoirs is considered to be influenced by three main factors, namely, stimulated reservoir volume (SRV), fracture density, and fracture conductivity. No conclusive method is available to predict the effectiveness of hydraulic fracturing; there is often a failure to determine whether production differences among wells are caused by the effectiveness of the hydraulic fracturing or by the geological conditions, fluid properties, and other factors. Based on the principles of energy conservation and material balance, a mathematical model for calculating the average length of fractures and hypothetical number of fractures was established by the calculus of variations to obtain the key parameters for describing fracture density and conductivity. The degree of influence of the individual parameters on the effectiveness of hydraulic fracturing is obtained from Grey correlation analysis, and two calculation models for the comprehensive evaluation parameter are proposed. The comprehensive evaluation parameters produced from the two models have a preferable correlation with the well production. This paper presents a rigorous method for evaluating the effectiveness of hydraulic fracturing, which can explain the reasons for the production differences between wells.