25th International Meeting on Organic Geochemistry IMOG 2011

P-287
The hydrocarbon occurrence and play-forming genetic
relationships of the deep palaeocene in Jiyang Depression, East
China
Linye Zhang, Qing Liu, Xingyou Xu, Xiangxing Kong, Shouchun Zhang, Ru Wang,
Youshu Bao, Rifang Zhu, Zheng Li
Geological Scientific Research Institute, Shengli Oilfield Branch Company, SINOPEC, Dongying, 257015,
China, Dongying, China (corresponding author:liuq_1230@sina.com)
The Jiyang Depression lies in the southeastern
part of the Bohai Bai Basin (East China) as one of its
subsidiary tectonic units. Four sags (Dongying,
Huimin, Zhanhua and Chezhen) were developed in
the Jiyang Depression. Now the deep Palaeocene
(>3500m) of Jiyang Depression faces high exploration
risks for the low recognition. So sedimentary-organic
facies and its spatial distribution, hydrocarbon
generation, migration and accumulation of the deep
source rocks (including Member of E1-2k 2 and E2-3s 4 )
are studied in order to decipher the relationships
between hydrocarbon generation and accumulation,
and to propose the favorable exploration prospects.
According to the sedimentary structures,
palaeoontolgy associations and organic matter
occurrence analysis, the Paleocene lacustrine
hydrocarbon source rocks are divided into four types
of sedimentary organic facies, namely Anoxic facies,
Anaerobic facies, Dysaerobic facies and Aerobic
facies. Combinating with well logging, the
identification marker of each facies are summarized
and the deep source rocks are evaluated. The
sedimentary organic facies distribution shows great
distinguish for the upper E2-3s 4 from the east to the
west, with most of the anoxic and anaerobic facies
occurring in the Dongying and Zhanhua Sags, while
Dysaerobic facies and Aerobic facies dominating in
the Chezhen and Huimin Sags. And the source rocks
of E1-2k 2 are also dominated by aerobic and
dysaerobic facies. It suggests there is higher
exploration potential in the east than in the west for
the deep Palaeocene.
Based on the systematical analysis of the phase state
evolution of hydrocarbon products, the minerals
catagenesis and the mechanical properties changes
of the excellent source rocks of anoxic-anaerobic
facies in E2-3s 4 , the whole hydrocarbon expulsion
process can be divided into 3 stages, including free
water expulsion stage, hydrocarbon generation and
energy rising stage, and microfracture expulsion
stage (figure 1). The major hydrocarbon expulsion of
the deep Palaeocene source rocks occur during the
microfracture expulsion stage. During the
microfracture expulsion stage, 3 oil and gas migration
modes including vertical migration, lateral migration
and downward migration can occur in different
geology conditions. Oil and source correlation indicate
that the shallow and medium depth reserves sourced
from E2-3s 4 excellent hydrocarbon source rocks of
anoxic and anaerobic facies are mainly formed
through vertical migration, and there are still plenty of
reserves forming by lateral migration and downward
migration in the deep Palaeocene for the low proved
exploration efficiency. So there is still high exploration
potential in the deep Palaeocene of Jiyang
depression.
Figure1. the microscopic lithology characteristics
of different sedimentary organic facies in Jiyang
Depression
A, B: Anoxic facies; C, D, E: Anaerobic facies; F,
G: Dysaerobic facies; H: Aerobic facies
Contribution of the deep source rocks to the
proved reserves are comparison with the basin
resources of the deep source rocks. It shows that
there is still much resources provided by the source
rocks of E2-3s 4 . Combinating with the oil and gas
migration modes analysis above mentioned, it is
concluded there is still high exploration potential in the
deep Palaeocene, including every kinds of
conventional reservoirs and the source rocks
themselves in the deep Palaeocene, and the pre-
Paleogene buried hills.
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