Alluvial fan facies and their distribution in the Lower Talang Acar Formation, Northeast Betara Oilfield, Indonesia

Abstract

This paper studies the alluvial fan facies characteristics and distribution in the Lower Talang Acar Formation in the Northeast Betara Oilfield. The conglomerate sedimentary characteristics and its distribution were studied based on core data, logging interpretation and seismic property analysis. The research indicated that alluvial fan deposits of Bed F in the Lower Talang Akar Formation were characterized by coarse granularity, poor sorting and low quality. Sand-bodies accumulate longitudinally, and inter-layers are poorly developed, extending locally in the transverse orientation. Typical logging response of alluvial fan system is summarized, and conglomerate is characterized by low gamma-ray (GR) intensity, low resistance, high density and low value between DLD and LLD, which reflects poor physical reservoir properties, coarse rocks and relatively high density. Conglomerate is developed mainly in the northeast and middle-south of the studied area. The upper part of bed F is found in a small area in the middle-south, while the lower part of bed F is developed in a relatively large area in the middle-south.

Clastic Sediment Characteristics of Gumai Formation: Preliminary Study of Tertiary Rocks in South Sumatra Basin

“…The debate of the depositional environment of the Gumai Formation indicates three depositional settings of shallow marine, deep marine, and transition between marine and terrestrial [2, 8,9,10,12,26]. Gumai Formation from West Ogan Komering Block shows the different depositional environment of middleouter Neritic in JTB-1 well and outer neritic in NRM-1 well based on benthic foraminifera assemblages [9].…”

“…The interpretation is based on geochemical analysis of samples mass chromatogram, which provides a low value of diasterane (terrestrial source) and low values of oleanana (marine origin) [2]. Gumai Formation was deposited in regressive distal delta front as a result of increased sediment load from the Sunda landmass to the northeast; the regressive cycle was periodically interrupted by subtle transgressive events comprising distal delta front shale, distributary mouth bar sands, delta bar sand, channel sands, and interdistributary shale [8]. The process of Gumai Formation deposition in transition between marine and terrestrial initially caused by uplift of Sunda Shield to the east in the Middle Miocene marked the end of the early Tertiary transgression sequence and the beginning of regression sequence that continues to the present day [8].…”

“…A detailed study about Tertiary rock in Baturaja region is restricted to Baturaja Formation [18]. Gumai Formation in Simpang and Muara Dua area is an ideal location because the location has never been studied in previous studies [1,2,[8][9][10][11][12][13][14][15][16][17]. The research study was in small rivers and roads in the Simpang and Muara Dua region.…”