The objective of the study presented in this paper is to observe the influence of variation in rock petrophysical properties on fracture development. The analysis was primarily conducted using the combination of Continuum Damage Mechanics and the Perkins-Kern-Nordgren model (CDM-PKN). Essentially, the effect of porosity, water saturation, and shale contents on the two rock mechanical properties was studied using well-log data from an oil well in Central Sumatra (sandstone). Prior to the study the data was modeled using a combination of theory of elasticity, Gassmann theory of acoustic velocity propagation, and standard log interpretation. Laboratory acoustic velocity measurements were carried out to provide required data. The resulting model-relationships between sonic velocity, Poisson ratio, porosity, water saturation, and shale contents serve as input data for the study, on which the application of CDM-PKN model show that fracture length and width are mostly affected by variation in porosity. Variations in porosity between 11 % and 20 % may result in changes of up to 18 % and 100 % in fracture length and width, respectively. In contrast, variations in fluid saturation and shale contents (max. 10 %) exhibit less influence to the fracture growth. Nevertheless, depending on reservoir fluid and clay types, omission of the latter two factors in any hydraulic fracture design could complicate the mis-prediction.

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