Petrophysical fracture identification for rock physics ... - Net Brains

Table 1: Fracture response based on the conventional well-logsStep 2: Calculating fractures properties quantitatively• Porosity fracture index ( φf _ index): If a fractured formation can be considered as adual porosity system then the effective porosity consists of both matrix porosity and asecondary (fracture porosity). The effective porosity, calculated from the sonic log, issensitive to the inter-granular porosity. Meanwhile, the porosity calculated using theneutron and density logs included the fracture porosity (Yan 2008). The equationsbelow give the relationships between fracture porosity ( φ ), fracture porosity index( φf _ index), neutron- density porosity ( φND), density porosity ( φD), sonic porosity ( φs)and neutron porosity ( φN).φ = φfND−φ,sφf _ indexφ=• Resistivity fracture index (RLog name Response Description or noteCALI Calliper log Size change Sudden variations indicate a discrete featureSP Spontaneous potential log Anomalous Need to refer to other related factorsGR Gamma-Ray log Anomalous Low background readingsDT Sonic log Apparent value change Using porosity to compare with DEN/NEU porosityFDC Formation density log A sharp drop Combined with PEF for an open fracture.LLD,LLSDeep and shallow resis. log LLD> or LLS high angle, LLD