Advantages of the Moving Reference Point (MRP) Technique over the Net Pressure (P_(net)) Derivative Method: Comparison using Case Studies

摘要

The Moving Reference Point (MRP) technique (Pirayesh et al. 2013) successfully demonstrated its viability as a pressure-time hydraulic fracture mode interpretation tool in the Fracpack and Eagle Ford shale treatments. Al-Husain et al. (2017) extended the application of the MRP by studying a data set of five hydraulic fracture treatments from Cotton Valley and Travis Peak sand formations in east Texas. By understanding the fracture propagation behavior, they offered conclusions in terms of observations and suggestions to improve future hydraulic fracture designs across those formations in the east Texas area. This paper showed an empirical method development, and compared its results with the MRP technique analyses utilizing the same data set used by Al-Husain et al. Also, this work recognized an area of improvement in terms of MRP result presentation. An empirical method, based on derivative of net pressure (P_(net)), was developed as a pressure-time diagnostic tool. It inherited the assumptions of the original power-law fracture propagation theory developed by Perkins and Kern (1961) and refined by Nordgren (1972), except that the fracture propagates continuously during pumping. Nolte and Smith (1981) accepted the hypothesis of the continuous confined-fracture extension. However, the P_(net) Derivative agreed with the MRP method that the fracture may experience alternating cycles of propagation, dilation, and height growth during pumping. The MRP technique uses the treating pressure while, similarly to the Nolte-Smith method, the P_(net) Derivative application needed the closure pressure (P_c), which is a disadvantage for the limited budget operators. The shortcoming of using a log-log type plot was eliminated and instead a Cartesian chart was utilized mimicking the MRP method style of result display. The present study shows that the results of the MRP and the P_(net) Derivative methods are practically comparable when a considerable treating pressure change occurred. Because of the innovative moving reference point process embedded in the MRP's workflow, the technique revealed its ability to handle fluctuating pressure and to recognize fracture behavior change, even if the treating pressure change is not significant, better than the P_(net) Derivative method. This study also identified the disadvantage of presenting high-point moving average line (to smooth the fracture mode) as it pushes forward the curve in time. The minimum point average line provides more details, but keeps the general fracture mode is recommended to be presented.