Geophysical Well Log Study on the Paleoenvironment of the Hydrocarbon Producing Zones in the Erchungchi Formation, Hsinyin, SW Taiwan

Abstract

Gamma ray log facies of nine wells were used to reflect the vertical profile of grain size and were combined with well sample data to deduce the paleoenvironment of the Erchungchi "A" Member in the Hsinyin and Pachanchi areas. Four log facies were recognized in the studied intervals: a thick funnel-shaped facies representing a prograding delta; a thin funnelshaped facies representing a crevasse splay; a boxcar-shaped facies representing a distributary channel; a bell-shaped facies representing a fluvial or deltaic channel. The paleoenvironment of the Erchungchi "A" Member in the Hsinyin area is mainly an imbricated delta system whose thickest lobe is located in Well S-1. The delta was first deposited in the headstreams of the submarine channels, followed by mudstones as cap rocks which seal hydrocarbons in stratigraphic traps. There are many submarine channels in southwestern Taiwan, so similar stratigraphic hydrocarbon trap conditions may occur elsewhere in southwestern Taiwan.

Subsurface lithofacies analysis of the Fluvial Early Permian Warchha Sandstone, Potwar Basin, Pakistan

“…Selley, 1985;Cant, 1992;Posamentier and Allen, 1999;Chow et al 2005). This facies occurs within floodplain deposits and probably corresponds to fine-to medium-grained sandstone facies St and Sr (Table 1).…”

“…The presence of claystone clasts or mud pebbles in a channel deposit will generate higher values on the gamma-ray log, even if the parent material is a 'clean' sandstone. Similarly, the presence of carbonaceous material will also act to increase the value of the gamma-ray log (Chow et al 2005).…”

“…Serra and Abbott, 1982;Selley, 1985;Serra, 1985;Cant, 1992;Posamentier and Allen, 1999;Martinius et al 2002;Chow et al 2005). Detailed gammaray log analysis of five wells in the Warchha Sandstone has allowed a six-fold facies scheme to be developed (Fig.…”

“…Interpretation: This gamma-ray motif, which lacks any particular vertical trend, is characteristic of a 'clean' succession and is indicative of channel deposits (Cant, 1992;Chow et al 2005). The high value spikes within this facies likely reflect the presence of a shale-clast conglomerate (cf.…”

Reconstruction of the Depositional Setting of Tortonian Sediments in the Yowi Field, Shallow Offshore Niger Delta, Using Wireline Logs

“…Studies of modern sedimentary environments (Selley 1985;Amajor and Agbaire, 1989;Chow et al, 2005) revealed that vertical profiles of grain size from a specific environment have certain characteristics. For instance, prograding deltas and barrier bars deposit display an upward-coarsening grain size profiles (Fig.…”