Geoscience Reference
In-Depth Information
7
3D Seismic Sedimentology of Nearshore
Subaqueous Fans
-
A Case Study from
Dongying Depression, Eastern China
Yang Fengli
1,
*, Zhao Wenfang
1
, Sun Zhuan
1
,
Cheng Haisheng
2
and Peng Yunxin
3
1
School of Ocean and Earth Science, Tongji University, Shanghai,
2
Jiangsu Oilfield, SINOPEC, Yangzhou, Jiangsu,
3
Chengdu University of Technology, Chengdu, Sichuan,
China
1. Introduction
The nearshore subaqueous fan, also known as the steep bank sublacustrine fan (Zhao, 2000),
or submarine fan (Catuneanu et al., 2002; Richard & Bowman, 1998; Takahiro & Makoto,
2002), is the fan-shaped sedimentary accumulation of sand-conglomerate body located in
the footwall of major fault in rift basins (Zhang, J.L & Shen, 1991; Zhang, M. & Tian, 1999),
and commonly composed by three sub- facies including a root sub-fan, a mid sub-fan and a
marginal sub-fan. Its formation and development are controlled by basin boundary
conditions, paleotopography, tectonic evolution, the nature of the provenance, paleoclimate,
paleocurrent and other factors (Lu, 2008; Xie et al., 2004; Yan et al., 2005). In the Bohai Bay
Basin, eastern China, a nearshore subaqueous fan system of Paleogene age is widely
developed in the lower Es4 Formation in Paleogene in the northern Dongying Depression
(Fig.1). Analyses found that the mid sub-fan is the main part of the fan, characterized by the
pebbly sandstones, conglomerates and block sandstones in the braided channel microfacies,
intra-channel microfacies and leafy sandbody microfacies (Gao et al., 2008; Song, 2004; Yan
et al., 2005). Oil and gas exploration in the Dongying Depression has demonstrated that the
sand-conglomerate developed in the mid sub-fan is the effective oil and gas reservoir. Due
to a deep burial (>3500m), multi staged sub-fan development, and small seismic impedance
differences, however, to describe and predict the distribution of the effective sand-
conglomerate reservoir in the nearshore subaqueous fan is difficult. Studies have also found
that conventional 3D seismic data with industry-standard and seismic acoustic impedance
inversion data from ac+den loggings could not distinguish the effective sand-conglomerate
reservoir from sand-conglomerate sedimentary body (Song, 2004).
Seismic sedimentology is the use of seismic data to study sedimentary rocks and processes
by which they form (Zeng et al., 2001, 2004). Since its first introduction in 1998 (Zeng et al.,
1998), the concept has been applied in the identification of paleorivers, the sedimentary
facies and sedimentary environment evolutions of carbonate platform and the slope fans
with many good results (Carter, 2003; Chen.& Meng, 2004; Crumeyrolle et al., 2007; Darmad
et al., 2007; Gee & Gawthorpe, 2007; Handford & Baria, 2007; Ling et al., 2005; Lin et al.,
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