Rock physics & Interpretation

[RP-06] Application of the Adapted Stiff Sand model to discriminate the cementation types of a gas sand

*Pham Huy Giao^1,2, Pham Hong Trang^1,3, Doan Huy Hien¹, Pham Quy Ngoc¹ (1. Vietnam Petroleum Institute, VPI (Viet Nam), 2. PetroVietnam University, PVU (Viet Nam), 3. Institute of Geological Sciences, Vietnam Academy of Science and Technology (VAST) (Viet Nam))

The Adapted Stiff Sand model (ASSM) is a new rock physical modeling approach, recently proposed at the Vietnam Petroleum Institute (VPI), to aid construction of a site-adapted rock template (ARPT) for seismo-petrophysical characterization of a strongly cemented and deep gas sand. It is modified from the known Stiff Sand model by Stanford rock physics group, with a key change in determination of the dry modulus of the sand based on the in-situ well log data and a modified Gassmann’s equation. It is known that the success of a rock physics template (RPT) depends very much on the cementation type of the clastic reservoir and the rock physics model (RPM) used for its construction. This study dealt with a Middle Miocene gas sand at the Hai Thach gas field, Nam Con Son basin, Vietnam, which consists of multiple-stacked reservoirs units with a cementation type varying at different depth levels. By applying the Adapted Stiff Sand model we could discriminate two main cementation types, i.e., clayey and calcite. Consequently, a site-adapted rock physics template (ARPT) was successfully constructed, based on which a seismic inversion could be successfully carried out for a seismo-petrophysical characterization of the target gas sand.