Goldschmidt 2012 Conference Abstracts
Multi-period Petroleum
Accumulation And Adjustment In
Carbonate Reservoirs Of Sinian
Dengying Formation In Central
Sichuan Basin
WANG RUIJU *, WANG ZECHENG, JIANG HUA,LIU WEI, LI
YONGXIN
Research Institute of Petroleum Exploration and Development,
Petrochina, Beijing, China
(*correspondence:wruiju@petrochina.com.cn)
Background and methods
Sinian Dengying Formation is an important exploration domain in
the Sichuan Basin with abundant gas, especially, gas show was
found in GGS-1 well on the slope of paleo-uplift in 2011. In fact,
sinian carbonate reservoir is also the oldest reservoir in China. The
formation and distribution of those reservoirs were major controlled
by high energy sedimentary facies, dissolution and faults. Karst
weathering crust reservoir in the Dengying Formation in Upper
Sinian was distributed quasilayered. The gas was complex
accumulated in multi-layer. Those reservoirs were composed of
carbonate rocks with low porosity and low permeability, and buried
in 4500~6500m depth with intensive heterogeneity. The spatial
distribution of effective reservoirs controlled the occurrence of
hydrocarbon and accumulated in large area, which showed an
integral enrichment characters in paleo-uplift. Through the biomarker
correlation study in reservoir soluble bitumen and extracts of source
rocks, detailed gas-source rock correlation indicates that gases were
mainly originated from both Cambrian source rocks and Sinian
source rocks. However, the natural gases were major oil-crack gases
from paleo-oil-reservoirs and kerogen crack gas.
Closely associated with the evolution of paleo-uplift, the thermal
evolution of source rock organic matter, sedimentary bural history
and pale temperature, the paleo-uplift area experienced three stages
of hydrocarbon accumulation. The first stage occurred in the Late
Caledonian tectonic cycle and a small quantity of the crude oil began
to originate from lower Cambrian source rocks. The second stage
occurred in the Late Hercynian and Indosinian tectonic cycle which
was the most important hydrocarbon charging stage, the abundant
oils and gases were made and charged into paleo-traps. The third
stage occurred in the late Himalayan tectonic cycle, oil crack gases in
paleo-uplift began to generated and adjusted into new traps formed
during tectonic periods, while kerogen crack gas in depth, charged
into reservoirs along faults, then formed complex gas reservoirs
which is now occurred in Central Sichuan Basin.
Results and Conclusion
Carbonate reservoirs of Sinian Dengying Formation in Central
Sichuan Basin show very good perspective, and its formation was
very complicated.
1) The reservoir experienced three periods petroleum
accumulation and adjustment at least, which controlled by
structure action.
2) the natural gases were major oil-crack gases from paleo-oilreservoirs and kerogen crack gas.
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