Influence of rock physics parameters on construction of rock physics template for Middle Miocene sand in Nam Con Son basin
Abstract
Rock physics template (RPT) is a relative new tool of reservoir characterisation that can aid interpretation of well log data to help reduce the risks in seismic exploration and prospect evaluation. One of the popular RPTs is the crossplot of Vp/Vs (Compressional wave velocity/Shear wave velocity) versus AI (acoustic impedance) that proved to be very successful in reservoir characterisation of shallow unconsolidated sediments in the North Sea. However, construction of a RPT is very site dependent, thus when one extends the application of this type of RPT to other sites for those reservoirs that might be located deeper or consist of more consolidated or cemented sediments an adequate attention has to be given to the parameters in the rock physics models that are at the foundation of a RPT construction. This study deals with construction of a new RPT for the Middle Miocene sand (MMS), a gas-bearing sand located around 3,500m TVDSS(True vertical depth subsea) at Hai Thach field, Nam Con Son basin. In this research an emphasis was given to study the influence of elastic bounds and rock physics parameters such as critical porosity, coordination number, mineral fraction, dry bulk and shear moduli on construction of the RPT. As results a new RPT was successfully constructed using the Voigt-Reuss-Hill elastic bound and modified Gassmann’s equation for the gas-bearing Middle Miocene Sand, which could be characterised with acoustic impedance (AI) from 9,000 to 11,000 m/s×g/cc, Vp/Vs from 1.65 to 1.8, porosity from 11 to 16%, and gas saturation from 50% up.
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