INTEGRATED THIN BASAL SAND CHARACTERIZATION IN THE ARYANI FIELD, ASRI BASIN - SOUTHEAST SUMATRA, USING GEOLOGICAL MODELLING BASED ON THE ELASTIC PROPERTIES AND THE ROCK TYPING METHOD

摘要

The unconventional Aryani basal sand reservoir is located above the basement and is interpreted as a part of the Lower Zelda member in the Talang Akar Formation. The discovery of the Aryani Basal sand reservoir was identified from the A-01 exploration well drilled in 1989 that encountered around 10-16 feet of net reservoir with a permeability of 34.4 mD. The trough amplitude above the top basement horizon was used to define and map the net sand since there is an impedance contrast between the porous conglomeratic reservoir sand and the top sealing argillaceous conglomerate. Although relatively thin and of low permeability, the cumulative production from this sand reservoir is quite good. Therefore, it is a challenge to characterize the reservoir. Core data was taken and limited analyses have been undertaken, including X-Ray Diffraction (XRD)XRD, petrography, and conventional core analysis. This reservoir is interpreted as a product of the early syn-rift deposit, with an alluvial fan-braided channel depositional environment. Reservoir characterization constraints are thin layer distribution, low resistivity readings, and low permeability. An integrated approach of elastic properties and the Rock Typing (RT) method gives a better understanding of the reservoir compared with previous works. Several geophysical techniques are being applied to characterize the sand reservoir in this field; however, the most reliable result comes from Lambda-Rho with a cut off value between 15-24GPa*g/cc. This result is used for mapping the lateral distribution of the basal sand reservoir, while the vertical distributionwas solved by RT methods. RT classification utilized the rock-quality index and the flow-zone indicator. This classification identified rock types from the relationship of permeability-porosity, capillary pressure, and relative permeability curve. Integration of both methods satisfied geological conceptual models and will be used for the next field plan development.