Publications

Reservoir rock of the Sirasun Field comprises Upper Pliocene Limestone with more than 200 ft gas column. Development plan of Sirasun field requires an accurate geological model. Combination of high resolution 3D seismic data with existing wells data were obtained for building geological framework as a basic input of 3D reservoir modeling. Depositional facies can be a key factor controlling heterogeneity in porosity and permeability. Sequence stratigraphic concept and seismic attribute generation were utilized in order to predict vertical and lateral reservoir distribution.Cores and well logs in the reservoir show four sedimentary facies, foraminiferal grainstone, foraminiferal packstone, bioturbated foraminiferal wackestone and transgressive calcareous shale facies. Sedimentary facies, biostratigraphy, ichnofossils and seismic data suggest that Paciran Limestone was deposited in a ramp-type platform depositional environment. The grainstone facies shows the best reservoir properties, which were deposited in inner ramp-middle ramp territory. Seismic geobody extraction provide better image to delineate geometrically elongated shoal body. Mainly, the reservoir quality is controlled by primary properties. Bioturbation enhanced porosity and permeability especially in finer grained facies.Ramp depositional environment was effected significantly by relative sea level change. High frequency of coarsening and fining upward succession composed this reservoir. Coarsening upward trend indicates aggradation-progradation stratal packages. Meanwhile, fining upward represents backstepping package. The overall carbonate forms a single cycle of third order sequence, which indicates HST, LST and TST in ascending order.The 3D Sirasun geological was generated by applying dynamic sedimentary facies change using stratal package guidance and geometrical distribution from 3D geobody extraction. Integrated between petrophysical analysis with 3D acoustic impedance were executed to predict porosity distribution. Eventually 3D static reservoir model was achieved through integration of structural and geological framework with petrophysical evaluations result. This realistic reservoir model is essential for future development and improves the confidence levels of original in place estimation.