- Email: [email protected]
Discussion for comments of Ehrenberg and Bjørlykke on paper “Formation mechanism of deep Cambrian dolomite reservoirs in the Tarim basin, northwestern China”
Marine and Petroleum Geology xxx (2015) 1e2
Contents lists available at ScienceDirect
Marine and Petroleum Geology journal homepage: www.elsevier.com/locate/marpetgeo
Discussion
Discussion for comments of Ehrenberg and Bjørlykke on paper “Formation mechanism of deep Cambrian dolomite reservoirs in the Tarim basin, northwestern China” Dongya Zhu No. 31 Xueyuan Road, Haidian District, Beijing, 100083, China
a r t i c l e i n f o
a b s t r a c t
Article history: Received 22 December 2015 Accepted 24 December 2015 Available online xxx
In the paper “Formation mechanism of deep Cambrian dolomite reservoirs in the Tarim basin, northwestern China” (Zhu et al., 2015), we concluded that hydrothermal alteration further enhanced porosity in the deep Cambrian dolomite reservoirs in the Tarim Basin, NW China. Professor Ehrenberg and Bjørlykke made comments that the hydrothermal dolomitization and increase in porosity were not well supported and casted doubt on the exploration potential. We insist the influence of hydrothermal alteration on and large exploration potential in the deep Cambrian dolomite reservoirs due to the unique geological conditions and the recent exploration results. © 2015 Elsevier Ltd. All rights reserved.
Keywords: Tarim basin Cambrian Deep dolomite reservoir Hydrothermal dissolution
1. In the paper, we demonstrated that the hydrothermal activity in the deep Cambrian dolomite in the Tarim Basin was related to magmatism in the Permian. Even though the homogenization temperatures (80e160 C, maximum frequency 110e130 C) of the fluid inclusions in the Cambrian dolomite are not greater than the present bottom-hole temperature, they are even greater than the burial temperature in the Permian. The burial depth was around 3.0 km in the Permian and the burial temperature was around 95 C, in that most of the homogenization temperatures are greater than the burial temperature. Zhang et al. (2009) and Dong et al. (2013) presented similar fluid inclusion temperatures for the hydrothermal in the Cambrian dolomite in the Tarim Basin. The 87Sr/86Sr ratios of the porefilling dolomite are not considerably higher than the matrix dolomite, indicating that the hydrothermal fluid was originated within or heavily contaminated by the Cambrian stratum. Zhang et al. (2009) also noticed the relatively low 87Sr/86Sr ratios and attributed to hydrothermal activity within the Cambrian. 2. Due to limitation of core samples from the deep Cambrian dolomite, only six porosity data could be measured and presented. As Ehrenberg and Bjørlykke pointed out, it may be not suitable to construct the trend line of porosity increase with depth within a large depth range (7104.7e8407.56 m). However, the deep dolomite reservoir around 8000 m does have relatively
E-mail address: [email protected].
high porosity. Hydrothermal alteration may be an important factor for the development of porosity especially in the Tarim Basin. 3. According to statistical evidence presented by Nadeau et al. (2005) and Nadeau (2011), few reservoirs at temperatures greater than 120 C can contain commercial quantities of oil or gas. However, recent explorations in the Tarim Basin discovered large amount commercial oil and gas in the Paleozoic carbonate reservoirs within depth between 6000 and 7000 m, and the reservoir temperatures are about 140e170 C (Zhu et al., 2014; Wang et al., 2015). Well ZS1 and ZS1C in the central Tarim Basin discovered liquid hydrocarbons in the Cambrian dolomite reservoirs at depth 6456.50 m and 6902.50 m (Zhang et al., 2015). The reservoir temperature in ZS1C is 169 C (Wang et al., 2015), much higher than 120 C. Hence, the hydrocarbon potential in the deep Cambrian dolomite reservoirs in the Tarim Basin are undoubled.
References Dong, S., Chen, D., Qing, H., Jiang, M., Zhou, X., 2013. In situ stable isotopic constraints on dolomitizing fluids for the hydrothermally-originated saddle dolomites at Keping, Tarim Basin. Chin. Sci. Bull. 58 (23), 2877e2882. Nadeau, P.H., Bjorkum, P.A., Walderhaug, O., 2005. Petroleum system analysis: impact of shale diagenesis on reservoir fluid pressure, hydrocarbon migration, , A.G., Vining, B.A. (Eds.), Petroleum Geology: and biodegradation risks. In: Dore North-West Europe and Global PerspectivesdProceedings of the 6th Petroleum Geology Conference. The Geological Society, London, pp. 1267e1274.
http://dx.doi.org/10.1016/j.marpetgeo.2015.12.020 0264-8172/© 2015 Elsevier Ltd. All rights reserved.
Please cite this article in press as: Zhu, D., Discussion for comments of Ehrenberg and Bjørlykke on paper “Formation mechanism of deep Cambrian dolomite reservoirs in the Tarim basin, northwestern China”, Marine and Petroleum Geology (2015), http://dx.doi.org/10.1016/ j.marpetgeo.2015.12.020
2
D. Zhu / Marine and Petroleum Geology xxx (2015) 1e2
Nadeau, P.H., 2011. Earth's energy “Golden Zone”: a synthesis from mineralogical research. Clay Min. 46, 1e24. Wang, M., Zhu, G., Ren, L., Liu, X., Zhao, S., Shi, Q., 2015. Separation and characterization of sulfur compounds in ultra-deep formation crude oils from Tarim Basin. Energy Fuels 29 (8), 4842e4849. Zhang, J., Hu, W., Qian, Y., Wang, X., Cao, J., Zhu, J., Li, Q., Xie, X., 2009. Formation of saddle dolomites in Upper Cambrian carbonates, western Tarim Basin (northwest China): implications for fault-related fluid flow. Mar. Pet. Geol. 26 (8), 1428e1440.
Zhu, D., Meng, Q., Jin, Z., Liu, Q., Hu, W., 2015. Formation mechanism of deep Cambrian dolomite reservoirs in the Tarim basin, northwestern China. Mar. Petrol. Geol. 59, 232e244. Zhu, G., Zhang, B., Yang, H., Su, J., Liu, K., Zhu, Y., 2014. Secondary alteration to ancient oil reservoirs by late gas filling in the Tazhong area, Tarim Basin. J. Pet. Sci. Eng. 122, 240e256. Zhang, S., Huang, H., Su, J., Liu, M., 2015. Ultra-deep liquid hydrocarbon exploration potential in cratonic region of the Tarim Basin inferred from gas condensate genesis. Fuel 160, 583e595.
Please cite this article in press as: Zhu, D., Discussion for comments of Ehrenberg and Bjørlykke on paper “Formation mechanism of deep Cambrian dolomite reservoirs in the Tarim basin, northwestern China”, Marine and Petroleum Geology (2015), http://dx.doi.org/10.1016/ j.marpetgeo.2015.12.020
Contents lists available at ScienceDirect
Marine and Petroleum Geology journal homepage: www.elsevier.com/locate/marpetgeo
Discussion
Discussion for comments of Ehrenberg and Bjørlykke on paper “Formation mechanism of deep Cambrian dolomite reservoirs in the Tarim basin, northwestern China” Dongya Zhu No. 31 Xueyuan Road, Haidian District, Beijing, 100083, China
a r t i c l e i n f o
a b s t r a c t
Article history: Received 22 December 2015 Accepted 24 December 2015 Available online xxx
In the paper “Formation mechanism of deep Cambrian dolomite reservoirs in the Tarim basin, northwestern China” (Zhu et al., 2015), we concluded that hydrothermal alteration further enhanced porosity in the deep Cambrian dolomite reservoirs in the Tarim Basin, NW China. Professor Ehrenberg and Bjørlykke made comments that the hydrothermal dolomitization and increase in porosity were not well supported and casted doubt on the exploration potential. We insist the influence of hydrothermal alteration on and large exploration potential in the deep Cambrian dolomite reservoirs due to the unique geological conditions and the recent exploration results. © 2015 Elsevier Ltd. All rights reserved.
Keywords: Tarim basin Cambrian Deep dolomite reservoir Hydrothermal dissolution
1. In the paper, we demonstrated that the hydrothermal activity in the deep Cambrian dolomite in the Tarim Basin was related to magmatism in the Permian. Even though the homogenization temperatures (80e160 C, maximum frequency 110e130 C) of the fluid inclusions in the Cambrian dolomite are not greater than the present bottom-hole temperature, they are even greater than the burial temperature in the Permian. The burial depth was around 3.0 km in the Permian and the burial temperature was around 95 C, in that most of the homogenization temperatures are greater than the burial temperature. Zhang et al. (2009) and Dong et al. (2013) presented similar fluid inclusion temperatures for the hydrothermal in the Cambrian dolomite in the Tarim Basin. The 87Sr/86Sr ratios of the porefilling dolomite are not considerably higher than the matrix dolomite, indicating that the hydrothermal fluid was originated within or heavily contaminated by the Cambrian stratum. Zhang et al. (2009) also noticed the relatively low 87Sr/86Sr ratios and attributed to hydrothermal activity within the Cambrian. 2. Due to limitation of core samples from the deep Cambrian dolomite, only six porosity data could be measured and presented. As Ehrenberg and Bjørlykke pointed out, it may be not suitable to construct the trend line of porosity increase with depth within a large depth range (7104.7e8407.56 m). However, the deep dolomite reservoir around 8000 m does have relatively
E-mail address: [email protected].
high porosity. Hydrothermal alteration may be an important factor for the development of porosity especially in the Tarim Basin. 3. According to statistical evidence presented by Nadeau et al. (2005) and Nadeau (2011), few reservoirs at temperatures greater than 120 C can contain commercial quantities of oil or gas. However, recent explorations in the Tarim Basin discovered large amount commercial oil and gas in the Paleozoic carbonate reservoirs within depth between 6000 and 7000 m, and the reservoir temperatures are about 140e170 C (Zhu et al., 2014; Wang et al., 2015). Well ZS1 and ZS1C in the central Tarim Basin discovered liquid hydrocarbons in the Cambrian dolomite reservoirs at depth 6456.50 m and 6902.50 m (Zhang et al., 2015). The reservoir temperature in ZS1C is 169 C (Wang et al., 2015), much higher than 120 C. Hence, the hydrocarbon potential in the deep Cambrian dolomite reservoirs in the Tarim Basin are undoubled.
References Dong, S., Chen, D., Qing, H., Jiang, M., Zhou, X., 2013. In situ stable isotopic constraints on dolomitizing fluids for the hydrothermally-originated saddle dolomites at Keping, Tarim Basin. Chin. Sci. Bull. 58 (23), 2877e2882. Nadeau, P.H., Bjorkum, P.A., Walderhaug, O., 2005. Petroleum system analysis: impact of shale diagenesis on reservoir fluid pressure, hydrocarbon migration, , A.G., Vining, B.A. (Eds.), Petroleum Geology: and biodegradation risks. In: Dore North-West Europe and Global PerspectivesdProceedings of the 6th Petroleum Geology Conference. The Geological Society, London, pp. 1267e1274.
http://dx.doi.org/10.1016/j.marpetgeo.2015.12.020 0264-8172/© 2015 Elsevier Ltd. All rights reserved.
Please cite this article in press as: Zhu, D., Discussion for comments of Ehrenberg and Bjørlykke on paper “Formation mechanism of deep Cambrian dolomite reservoirs in the Tarim basin, northwestern China”, Marine and Petroleum Geology (2015), http://dx.doi.org/10.1016/ j.marpetgeo.2015.12.020
2
D. Zhu / Marine and Petroleum Geology xxx (2015) 1e2
Nadeau, P.H., 2011. Earth's energy “Golden Zone”: a synthesis from mineralogical research. Clay Min. 46, 1e24. Wang, M., Zhu, G., Ren, L., Liu, X., Zhao, S., Shi, Q., 2015. Separation and characterization of sulfur compounds in ultra-deep formation crude oils from Tarim Basin. Energy Fuels 29 (8), 4842e4849. Zhang, J., Hu, W., Qian, Y., Wang, X., Cao, J., Zhu, J., Li, Q., Xie, X., 2009. Formation of saddle dolomites in Upper Cambrian carbonates, western Tarim Basin (northwest China): implications for fault-related fluid flow. Mar. Pet. Geol. 26 (8), 1428e1440.
Zhu, D., Meng, Q., Jin, Z., Liu, Q., Hu, W., 2015. Formation mechanism of deep Cambrian dolomite reservoirs in the Tarim basin, northwestern China. Mar. Petrol. Geol. 59, 232e244. Zhu, G., Zhang, B., Yang, H., Su, J., Liu, K., Zhu, Y., 2014. Secondary alteration to ancient oil reservoirs by late gas filling in the Tazhong area, Tarim Basin. J. Pet. Sci. Eng. 122, 240e256. Zhang, S., Huang, H., Su, J., Liu, M., 2015. Ultra-deep liquid hydrocarbon exploration potential in cratonic region of the Tarim Basin inferred from gas condensate genesis. Fuel 160, 583e595.
Please cite this article in press as: Zhu, D., Discussion for comments of Ehrenberg and Bjørlykke on paper “Formation mechanism of deep Cambrian dolomite reservoirs in the Tarim basin, northwestern China”, Marine and Petroleum Geology (2015), http://dx.doi.org/10.1016/ j.marpetgeo.2015.12.020