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Impact of Petrophysical Properties on Hydraulic Fracture Analysis


Hydraulic fracturing is the most common stimulation method used in medium- to low-permeability and unconventional reservoirs. Accurate hydraulic fracture modeling for lithologically complex reservoirs requires detailed knowledge of the reservoir rock, including permeability, porosity, and mechanical properties, and identification of water-productive zones and barriers. The objective of this work is to determine if using detailed petrophysical properties provides fracture design parameters that better represent actual fracture behavior and subsequent well performance by using an existing hydraulic fracture treatment to model fracture behavior using both detailed and averaged petrophysical properties. Fracpro© software was used for the analysis. The models were designed with both simplified and detailed input parameters and with varying layer thickness resolutions. Modeling was based on actual treatment data from the Nash Unit #23 well located in the northern Delaware Basin producing from the lower Brushy Canyon Formation (Guadalupian). The reservoir consists of multilayered sandstone reservoirs that include thin-bedded and micro-laminated siltstone. Hydrocarbon-producing layers are in close vertical proximity to water-productive zones. Single Lithology, 10-ft, 5-ft, 2-ft, and 1-ft layer thickness models were created. The Single Lithology model has low layer thickness resolution and averaged petrophysical values. The 1-ft model has high layer thickness resolution and uses detailed petrophysical values. Data was obtained from sonic logs, point load tests, core descriptions, core analysis, and other well logs. Resulting fracture behavior variables include average fracture width, fracture and propped half-length, and total fracture and propped height. Production history matching was conducted to validate the models using actual production data from Nash Unit #23. Results from fracture and production analysis indicate that using high layer resolutions and detailed petrophysical values (e.g. 1-ft Model) yields more accurate simulation results and better represent the actual hydraulic fracture behavior. Software-default petrophysical values and simplified reservoir layer models yielded significantly over- and under-estimated fracture behavior variables. Using detailed petrophysical data in hydraulic fracture treatment designs could provide a better understanding or prediction of fracture behavior and growth, and can reduce the likelihood of treating out of zone.