25th International Meeting on Organic Geochemistry IMOG 2011

P-371
Preliminary investigations into gas-in-place and fraccability
of shales from the Sichuan Basin, China
Jingqiang Tan 1 , Dorothee Hippler 2 , Jinchuan Zhang 3 , Ger van Graas 4 , Nicolaj Mahlstedt 1 ,
Georg Dresen 1 , Brian Horsfield 1
1 German Research Center for Geosciences, Potsdam, Germany, 2 Technical University of Berlin, Berlin,
Germany, 3 China University of Geosciences, Beijing, China, 4 Statoil, Oslo, Norway (corresponding
author:jqtan@gfz-potsdam.de)
In China, black shales deposited in marine and
terrestrial settings have a large distribution area of
over 3×10 6 km 2 [1]. The great thickness, high maturity
and high TOC of many shale formations may translate
into a huge gas potential. The total shale gas
resource is estimated at 100×10 12 m 3 , and the
recoverable reserves reported range from 21.5 to 45
×10 12 m 3 [1-2]. The most promising areas are located
in south China, especially in the Sichuan Basin and its
adjacent regions. In this study, we are investigating
the gas-in-place and fraccability of shales in the
Sichuan basin by combining regional geology with a
series of experiments on organic geochemistry and
geomechanics.
In the Sichuan Basin, black shales are prominent from
the upper Sinian to lower Cambrian, from the upper
Ordovician to lower Silurian and from the upper
Triassic to lower Jurassic systems [3]. In the lower
Cambrian (Qiongzusi Fm.) and lower Silurian
(Longmaxi Fm.), kerogens are dominantly of type I
and II with an average organic carbon content of
usually higher than 2%. Brittle minerals make up
between 37.1 and 80.8% of the total inorganic
fraction. Meanwhile, the microfissures and micropores
are developed well, total porosity can reach up to
8.10% (core sample) and 24.24% (outcrop sample)
for the Qiongzusi formation and 15.72% (core
sample) and 16.85 % (outcrop sample) for the
Longmaxi formation [4-5]. These two formations are
generally buried more than 4000 m and reach
maturities greater than 2% R0.
Our preliminary results on the lower Cambrian black
and siliceous shale outcrop samples from the
Guizhou, Hunan and Yunan provinces also suggest
high shale gas potentials. More than half of the
organic matter rich samples (up to 19.0% TOC) are in
mature (Tmax >435°) or over mature (Tmax >450°)
stages and elevated S1 values indicate high amounts
of gas-in-place (Figure 1).
References
Figure 1 PI-Tmax plot
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Xuan, Zhang Peixian, Tang Ying, Jin Tieya.
Natur. Gas Ind. 2009, 29(12):109-114 (In
Chinese with English abstract).
2. Liu Honglin, Wang Hongyan, Liu Renhe,
Zhao Qun, Lin Yingji. Acta Geologica Sinica,
2010, 84(9): 1374-1379 (In Chinese with
English abstract).
3. Editorial Committee of ―Petroleum Geology
of China‖. Sichuan Oil & Gas Field.
Petroleum Industry Press, 1987, 28-80 (In
Chinese).
4. Dong Dazhong, Chen Keming, Wang Yuman,
Li Xinjing, Wang Shejiao, Huang Jinliang. Oil
& gas geology, 2010, 31(3): 288-300 (In
Chinese with English abstract).
5. Pu boling. China University of Petroleum
Master Degree Thesis, 2008, 50(In Chinese
with English abstract).
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