RESERVOIR CHARACTERIZATION AND RESERVE ESTIMATION OF UPPER RED BED FORMATION, FIELD C, CENTRAL SUMATRA BASIN.

• Main Author: Cakrabuana, Wira
• Format: Final Project
• Language: Indonesia
• Subjects: Geologi, hidrologi & meteorologi
• Online Access: https://digilib.itb.ac.id/gdl/view/70166
• Institution: Institut Teknologi Bandung

C Field is one of petroleum field in Central Sumatera Basin owned by PT. Caltex Pacific Indonesia that had been operated since 1980s. This field which has acquisited by PT. Pertamina Hulu Energi is now developing exploration at Pematang Group interval, especially Upper Red Bed (URB) Formation. The objectives of this study are to determine facies and depositional environment, geometry and distribution, petrophysical property, and reserve estimation of reservoir at URB Formation. Datas used in this study are rock description data (core, side wall core, and cutting), biostratigraphy report data, hydrocarbon test data (hydrocarbon show data and swab test data), wireline log data, and seismic data (2D and 3D). Methods used in this study are facies analysis, petrophysical analysis, subsurface mapping, and hydrocarbon reserve estimation. Based on hydrocarbon show data there are two intervals of gas reservoir that in this study coded by Sand A and Sand B. Through facies analysis concluded that two reservoirs at URB Formation was deposited at braided river environment with fluvial channel and overbank fines architectural elements with each log vertical succession blocky and serrated. The two reservoirs have lateral geometry of channel identified by elongated/curved contur pattern and north east – south west orientation on subsurface map. Petrophysical analysis shows that Sand A and Sand B have average value of petrophysical property: volume of shale 0.16-0.34, effective porosity 0.02-0.13, and effective water saturation 0.49-0.86. Cut-off values of petrophysical property determined by swab test data are 0.23 for volume of shale, 0.07 for effective porosity, and 0.70 for effective water saturation. Original Gas in Place (OGIP) at each of Sand A and Sand B is 16388.65 MMSCF and 3536.46 MMSCF.