Thin Basal Sand Reservoir Distribution Using Elastic Properties Approach



Aryani basal sand is typical porous conglomeratic reservoir sand that interpreted draping above the basement as a part of Lower Zelda member, Talang Akar formation. The discovery of Basal sand reservoir was identified from Aryani-X exploration well, drilled on 1989 encountered around from 10 – 16 feet of net reservoir with permeability 34.4 mD. Represented by peak horizon (positive value means increase impedance) interfering with basement reflector on single horizon, it was used to define and map reservoir presence, since there is an impedance contrast between the porous conglomeratic reservoir sand with top sealing argillaceous conglomerate and also with granitic basement rock.
Previous interpretation technique that being implemented are interpreting isochrones from Lower Zelda horizon to Basement horizon, geologically interpreted as a product of early rift deposit, with alluvial fan – braided channel depositional environment. Another approach is being implemented with geophysical techniques for this cases, emphasizing on elastic properties, using Lambda-Rho relations, with the cut off value is 15-24 GPa*g/cc. This project is just a beginning for Aryani basal sand characterization that really interesting and challenging for being developed, complexity comes from thin layer distribution, low resistivity reading and also low permeability.


Authors : Pranowo Nugroho, Gustriyansyah Mishar, Heri Gunawan, Julius Sunarta, Wahyu Seno Aji