Sedimentary and geochemical characteristics of the Triassic Chang 7 Member shale in the Southeastern Ordos Basin,Central China
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摘要
The Ordos Basin is the largest petroliferous basin in China, where the Chang 7 Member shale serves as the major source rock in the basin, with an area of more than 100,000 km~2 So far, sedimentary and geochemical characterizations have rarely been conducted on the shale in shallow(< 1000 m) areas in the southeastern part of the basin, but such characterizations can help identify the genesis of organic-rich shale and promote the prediction and recovery of shale oil. In this paper,several outcrop sections of the Chang 7 Member in the Tongchuan area were observed and sampled, and sedimentary and geochemical characterizations were conducted for the well-outcropped YSC section. The study results show that the Chang7 Member shale is widely distributed laterally with variable thickness. The organic-rich shale is 7-25 m thick in total and exhibits obvious horizontal variation in mineral composition. In the eastern sections, the shale contains organic matter of TypeⅡ_2-Ⅲ and is low in thermal maturity, with high clay mineral content, low K-feldspar content, and no pyrite. In the western sections, the shale contains Type Ⅱ_1 organic matter and is low in thermal maturity, with high clay mineral, K-feldspar, and pyrite contents. The YSC section reveals three obvious intervals in vertical mineral composition and organic abundance.The Chang 7 Member organic-rich shale(TOC > 10%) contains mainly sapropelite and liptinite, with Type Ⅱ kerogen. It is generally characterized by a hydrocarbon potential of more than 70 mg/g, low maturity, and shallow-semideep lacustrine facies. In the western sections, the shale, still in a low maturity stage, has a higher hydrocarbon potential and is optional for shale oil recovery. However, the Chang 7 Member shale in the study area is highly heterogeneous and its shale oil recovery is practical only in the organic-rich intervals.
The Ordos Basin is the largest petroliferous basin in China, where the Chang 7 Member shale serves as the major source rock in the basin, with an area of more than 100,000 km~2 So far, sedimentary and geochemical characterizations have rarely been conducted on the shale in shallow(< 1000 m) areas in the southeastern part of the basin, but such characterizations can help identify the genesis of organic-rich shale and promote the prediction and recovery of shale oil. In this paper,several outcrop sections of the Chang 7 Member in the Tongchuan area were observed and sampled, and sedimentary and geochemical characterizations were conducted for the well-outcropped YSC section. The study results show that the Chang7 Member shale is widely distributed laterally with variable thickness. The organic-rich shale is 7-25 m thick in total and exhibits obvious horizontal variation in mineral composition. In the eastern sections, the shale contains organic matter of TypeⅡ_2-Ⅲ and is low in thermal maturity, with high clay mineral content, low K-feldspar content, and no pyrite. In the western sections, the shale contains Type Ⅱ_1 organic matter and is low in thermal maturity, with high clay mineral, K-feldspar, and pyrite contents. The YSC section reveals three obvious intervals in vertical mineral composition and organic abundance.The Chang 7 Member organic-rich shale(TOC > 10%) contains mainly sapropelite and liptinite, with Type Ⅱ kerogen. It is generally characterized by a hydrocarbon potential of more than 70 mg/g, low maturity, and shallow-semideep lacustrine facies. In the western sections, the shale, still in a low maturity stage, has a higher hydrocarbon potential and is optional for shale oil recovery. However, the Chang 7 Member shale in the study area is highly heterogeneous and its shale oil recovery is practical only in the organic-rich intervals.
The Ordos Basin is the largest petroliferous basin in China, where the Chang 7 Member shale serves as the major source rock in the basin, with an area of more than 100,000 km~2 So far, sedimentary and geochemical characterizations have rarely been conducted on the shale in shallow(< 1000 m) areas in the southeastern part of the basin, but such characterizations can help identify the genesis of organic-rich shale and promote the prediction and recovery of shale oil. In this paper,several outcrop sections of the Chang 7 Member in the Tongchuan area were observed and sampled, and sedimentary and geochemical characterizations were conducted for the well-outcropped YSC section. The study results show that the Chang7 Member shale is widely distributed laterally with variable thickness. The organic-rich shale is 7-25 m thick in total and exhibits obvious horizontal variation in mineral composition. In the eastern sections, the shale contains organic matter of TypeⅡ_2-Ⅲ and is low in thermal maturity, with high clay mineral content, low K-feldspar content, and no pyrite. In the western sections, the shale contains Type Ⅱ_1 organic matter and is low in thermal maturity, with high clay mineral, K-feldspar, and pyrite contents. The YSC section reveals three obvious intervals in vertical mineral composition and organic abundance.The Chang 7 Member organic-rich shale(TOC > 10%) contains mainly sapropelite and liptinite, with Type Ⅱ kerogen. It is generally characterized by a hydrocarbon potential of more than 70 mg/g, low maturity, and shallow-semideep lacustrine facies. In the western sections, the shale, still in a low maturity stage, has a higher hydrocarbon potential and is optional for shale oil recovery. However, the Chang 7 Member shale in the study area is highly heterogeneous and its shale oil recovery is practical only in the organic-rich intervals.
引文
Bai YL,Ma L,Wu WJ,Ma YH. Geological characteristics and resource potential of oil shale in Ordos Basin. Geol China.2009;36(5):1123-37(in Chinese).
Bai WH,Wu YB,Gao ZL,Sun SS. Study on the mechanism of oil shale minerogenetic enrichment in the arm of shallow to half-deep lake depositional environment. Geol Surv Res. 2010;33(3):207-14(in Chinese).
Cashion WB. Geology and fuel resources of the Green River Formation, Southeastern Uinta Basin, Utah and Colorado. US, Geological Survey professional paper 548,1967. https://doi.org/10.3133/pp548.
Clarkson CR, Nobakht M, Kaviani D. Production analysis of tightgas and shale-gas reservoirs using the dynamic-slippage concept. SPE J. 2012;17(01):230-42. https://doi.org/10.2118/144317-PA.
Cui JW, Zhu RK, Li SX, Yang Z, Zhang ZY. Movable oil and its controlling factors in tight sandstone. Pet Geol Exp. 2016;38(4):536-42. https://doi.org/10.11781/sysydz201604536(in Chinese).
Deng XQ, Lin XF, Liu XY, Pang JL, Lu JW, Li SX, Liu X. Discussion on relationship between sedimentary evolution of Triassic Yanchang Formation and the early Indosinian movement in Ordos Basin. J Palaeogeogr. 2008;10(2):159-66(in Chinese).
Deng XQ, Liu XS, Li SX. The relationship between compacting history and hydrocarbon accumulating history of the super-low permeability reservoirs in the Triassic Yanchang Formation in the Ordos Basin. Oil Gas Geol. 2009;30(2):156-61(in Chinese).
Donovan AD, Staerker TS, Pramudito A, Li WG, Gorbett MJ, Lowery CM, Romero AM, Gardner RD. The Eagle Ford outcrops of West Texas:a laboratory for understanding heterogeneities within unconventional mudstone reservoirs. GCAGS J. 2012;1:162-85.
Frogner P, Gislason SR, Oskarsson N. Fertilizing potential of volcanic ash in ocean surface water. Geology. 2001;29(6):487-90.https://doi.org/10.1130/0091-7613(2001)029%3c0487:FPOVA I%3e2.0.CO;2.
Huang SJ, Huang KK, Feng WL, Tong HP, Liu LH, Zhang XH.Mass exchanges among feldspar, kaolinite and illite and their influences on secondary porosity formation in clastic diagenesis-A case study on the Upper Paleozoic, Ordos Basin and Xujiahe Formation, Western Sichuan depression. Geochimica.2009;38(5):498-506(in Chinese). https://doi.org/10.19700/j.0379-1726.2009.05.009.
Jarvie DM(2012)Shale resource systems for oil and gas:part 2—shale-oil resource systems. In:Breyer JA, editor. Shale reservoir-Giant resources for the 21st century. AAPG Memoir 97;2012. p. 89-119. https://doi.org/10.1306/13321447m973489.
Lazar OR, Bohacs KM, Macquaker JH, Schieber J, Demko TM.Capturing key attributes of fine-grained sedimentary rocks in outcrops, cores, and thin sections:nomenclature and description guidelines. J Sediment Res. 2015;85(3):230-46. https://doi.org/10.2110/jsr.2015.11.
Lu JC, Li YH, Wei XY, Wei JS. Research on the depositional environment and resources potential of the oil shale in the Chang7Member, Triassic Yanchang Formation in the Ordos Basin. J Jilin Univ(Earth Sci Ed). 2006;36(6):928-32(in Chinese). https://doi.org/10.13278/j.cnki.jjuese.2006.06.010.
Li YH,Jiang T,Wu FL,Zhang HY,Yao ZG,Wang BW. Evaluation methods and results of oil shale resources in southeastern Ordos Basin. Geol Bull China. 2014;33(9):1417-24(in Chinese).
Li YH, Li JC, Jiang T, Wei JS, Lu JC, Hang J. Characteristics of the Triassic oil shale in the Hejiafang area, Ordos Basin. J Jilin Univ(Earth Sci Ed). 2009;39(1):65-71(in Chinese).
Miller BA, Paneitz JM, Yakeley S, Evans KA. Unlocking tight oil:Selective multistage fracturing in the Bakken Shale. In:SPE annual technical conference and exhibition. 2008. https://doi.org/10.2118/116105-ms.
Ren LJ. Characteristics and resource evaluation of the Mesozoic oil shales in Binxian-Tongchuan, Ordos Basin. Masters Dissertation,Jilin University, 2008(in Chinese).
Schieber J, Southard J, Thaisen K. Accretion of mudstone beds from migrating floccule ripples. Science. 2007;318(5857):1760-3. https://doi.org/10.1126/science. 1147001.
Smith JW. Ultimate composition of organic material in Green River oil shale. Bureau of Mines, Laramie, Wyo.(USA). Petroleum Research Center. 1960.
Sonnenberg SA, Vickery J, Theloy C, Sarg JF. Middle Bakken facies,Williston basin, USA:a key to prolific production. AAPG Annual Convention and Exhibition, Huston, USA. 2011.
Sruoga P, Rubinstein N, Hinterwimmer G. Porosity and permeability in volcanic rocks:a case study on the Serie Tobifera, South Patagonia, Argentina. J Volcanol Geoth Res. 2004; 132(1):31-43. https://doi.org/10.1016/S0377-0273(03)00419-0.
Wang DY, Xin BS, Yang H. Zircon SHRIMP U-Pb age and geological implication of tuff at the bottom of Chang-7 member of Yanchang Formation in the Ordos Basin. Sci China Earth Sci. 2014;44(10):2160-71. https://doi.org/10.1007/sll430-014-4979-0.
Yang Y, Li W, Ma L. Tectonic and stratigraphic controls of hydrocarbon systems in the Ordos Basin:a multicycle cratonic basin in central China. AAPG Bull. 2005;89(2):255-69. https://doi.org/10.1306/10070404027.
Yang Z,Hou LH,Tao SZ,Cui JW,Wu ST,Lin SH,Pan SQ. Formation conditions and"sweet spot"evaluation of tight oil and shale oil. Pet Explor Dev. 2015;42(5):609-20. https://doi.org/10.11698/PED.2015.05.02.
Yang H, Zhang WZ, Peng PA, Liu F, Luo LR. Oil detailed classification and oil-source correlation of Mesozoic lacustrine oil in Ordos Basin. J Earth Sci Environ. 2016;38(2):196-205(in Chinese).
Yang H,Li SX,Liu XY. Characteristics and resource prospects of tight oil and shale oil in Ordos Basin. Acta Pet Sin. 2013;34(1):1-11.https://doi.org/10.7623/syxb201301001.
Yang H,Dou WT,Liu XY,Zhang CL. Analysis on sedimentary facies of Member 7 in Yanchang Formation of Triassic in Ordos Basin.Acta Sedimentol Sin. 2010;28(2):254-63(in Chinese).
Zimmerle W. New aspects on the formation of hydrocarbon source rocks. Geol Rundsch. 1985;74(2):385-416. https://doi.org/10.1007/BF01824905.
Zou CN,Yang Z,Cui JW,Zhu RK,Hou LH,Tao SZ,Yuan XJ,Wu ST,Lin SH, Wang L, Bin B, Yao JL. Formation mechanism, geological characteristics and development strategy of nonmarine shale oil in China. Pet Explor Dev. 2013;40(1):15-27.
Zou CN, Zhang XY, Luo P, Wang L, Luo Z, Liu LH. Shallow-lacustrine sand-rich deltaic depositional cycles and sequence stratigraphy of the Upper Triassic Yanchang Formation, Ordos Basin,China. Basin Res, 2010;22(1):108-25. https://doi.org/10.1111/j.1365-2117.2009.00450.x.
Zhang WZ, Yang H, Peng PG. Influence of volcanism on development of Chang7 hydrocarbon source rock. Geochimica.2009;38(6):573-82(in Chinese). https://doi.org/10.19700/j.0379-1726.2009.06.007.
Zhang WZ, Li SP, Xu ZQ. Analysis of industrial utilization prospect of Upper Triassic Chang-7 oil shale in Ordos Basin. Low Permeability Oil Gas Field. 2006;11(1):13-7(in Chinese).
Zhang WZ, Yang H, Yang WW, Wu K, Liu F. Assessment of geological characteristics of lacustrine shale oil reservoir in Chang7member of Yanchang Formation, Ordos Basin. Geochimica.2015;44(5):505-15(in Chinese). https://doi.org/10.19700/j.0379-1726.2015.05.010.
Zhang W, Yang H, Xie L, Yang Y. Lake-bottom hydrothermal activities and their influence on high-quality source rock development:A case from Chang 7 source rocks in Ordos Basin. Petrol Explor Dev. 2010;37(4):424-429.
Zhang WZ, Li JF. Oil and gas source of Ordos Basin. China Pet Explor.2001;6(4):28-36(in Chinese).
Bai WH,Wu YB,Gao ZL,Sun SS. Study on the mechanism of oil shale minerogenetic enrichment in the arm of shallow to half-deep lake depositional environment. Geol Surv Res. 2010;33(3):207-14(in Chinese).
Cashion WB. Geology and fuel resources of the Green River Formation, Southeastern Uinta Basin, Utah and Colorado. US, Geological Survey professional paper 548,1967. https://doi.org/10.3133/pp548.
Clarkson CR, Nobakht M, Kaviani D. Production analysis of tightgas and shale-gas reservoirs using the dynamic-slippage concept. SPE J. 2012;17(01):230-42. https://doi.org/10.2118/144317-PA.
Cui JW, Zhu RK, Li SX, Yang Z, Zhang ZY. Movable oil and its controlling factors in tight sandstone. Pet Geol Exp. 2016;38(4):536-42. https://doi.org/10.11781/sysydz201604536(in Chinese).
Deng XQ, Lin XF, Liu XY, Pang JL, Lu JW, Li SX, Liu X. Discussion on relationship between sedimentary evolution of Triassic Yanchang Formation and the early Indosinian movement in Ordos Basin. J Palaeogeogr. 2008;10(2):159-66(in Chinese).
Deng XQ, Liu XS, Li SX. The relationship between compacting history and hydrocarbon accumulating history of the super-low permeability reservoirs in the Triassic Yanchang Formation in the Ordos Basin. Oil Gas Geol. 2009;30(2):156-61(in Chinese).
Donovan AD, Staerker TS, Pramudito A, Li WG, Gorbett MJ, Lowery CM, Romero AM, Gardner RD. The Eagle Ford outcrops of West Texas:a laboratory for understanding heterogeneities within unconventional mudstone reservoirs. GCAGS J. 2012;1:162-85.
Frogner P, Gislason SR, Oskarsson N. Fertilizing potential of volcanic ash in ocean surface water. Geology. 2001;29(6):487-90.https://doi.org/10.1130/0091-7613(2001)029%3c0487:FPOVA I%3e2.0.CO;2.
Huang SJ, Huang KK, Feng WL, Tong HP, Liu LH, Zhang XH.Mass exchanges among feldspar, kaolinite and illite and their influences on secondary porosity formation in clastic diagenesis-A case study on the Upper Paleozoic, Ordos Basin and Xujiahe Formation, Western Sichuan depression. Geochimica.2009;38(5):498-506(in Chinese). https://doi.org/10.19700/j.0379-1726.2009.05.009.
Jarvie DM(2012)Shale resource systems for oil and gas:part 2—shale-oil resource systems. In:Breyer JA, editor. Shale reservoir-Giant resources for the 21st century. AAPG Memoir 97;2012. p. 89-119. https://doi.org/10.1306/13321447m973489.
Lazar OR, Bohacs KM, Macquaker JH, Schieber J, Demko TM.Capturing key attributes of fine-grained sedimentary rocks in outcrops, cores, and thin sections:nomenclature and description guidelines. J Sediment Res. 2015;85(3):230-46. https://doi.org/10.2110/jsr.2015.11.
Lu JC, Li YH, Wei XY, Wei JS. Research on the depositional environment and resources potential of the oil shale in the Chang7Member, Triassic Yanchang Formation in the Ordos Basin. J Jilin Univ(Earth Sci Ed). 2006;36(6):928-32(in Chinese). https://doi.org/10.13278/j.cnki.jjuese.2006.06.010.
Li YH,Jiang T,Wu FL,Zhang HY,Yao ZG,Wang BW. Evaluation methods and results of oil shale resources in southeastern Ordos Basin. Geol Bull China. 2014;33(9):1417-24(in Chinese).
Li YH, Li JC, Jiang T, Wei JS, Lu JC, Hang J. Characteristics of the Triassic oil shale in the Hejiafang area, Ordos Basin. J Jilin Univ(Earth Sci Ed). 2009;39(1):65-71(in Chinese).
Miller BA, Paneitz JM, Yakeley S, Evans KA. Unlocking tight oil:Selective multistage fracturing in the Bakken Shale. In:SPE annual technical conference and exhibition. 2008. https://doi.org/10.2118/116105-ms.
Ren LJ. Characteristics and resource evaluation of the Mesozoic oil shales in Binxian-Tongchuan, Ordos Basin. Masters Dissertation,Jilin University, 2008(in Chinese).
Schieber J, Southard J, Thaisen K. Accretion of mudstone beds from migrating floccule ripples. Science. 2007;318(5857):1760-3. https://doi.org/10.1126/science. 1147001.
Smith JW. Ultimate composition of organic material in Green River oil shale. Bureau of Mines, Laramie, Wyo.(USA). Petroleum Research Center. 1960.
Sonnenberg SA, Vickery J, Theloy C, Sarg JF. Middle Bakken facies,Williston basin, USA:a key to prolific production. AAPG Annual Convention and Exhibition, Huston, USA. 2011.
Sruoga P, Rubinstein N, Hinterwimmer G. Porosity and permeability in volcanic rocks:a case study on the Serie Tobifera, South Patagonia, Argentina. J Volcanol Geoth Res. 2004; 132(1):31-43. https://doi.org/10.1016/S0377-0273(03)00419-0.
Wang DY, Xin BS, Yang H. Zircon SHRIMP U-Pb age and geological implication of tuff at the bottom of Chang-7 member of Yanchang Formation in the Ordos Basin. Sci China Earth Sci. 2014;44(10):2160-71. https://doi.org/10.1007/sll430-014-4979-0.
Yang Y, Li W, Ma L. Tectonic and stratigraphic controls of hydrocarbon systems in the Ordos Basin:a multicycle cratonic basin in central China. AAPG Bull. 2005;89(2):255-69. https://doi.org/10.1306/10070404027.
Yang Z,Hou LH,Tao SZ,Cui JW,Wu ST,Lin SH,Pan SQ. Formation conditions and"sweet spot"evaluation of tight oil and shale oil. Pet Explor Dev. 2015;42(5):609-20. https://doi.org/10.11698/PED.2015.05.02.
Yang H, Zhang WZ, Peng PA, Liu F, Luo LR. Oil detailed classification and oil-source correlation of Mesozoic lacustrine oil in Ordos Basin. J Earth Sci Environ. 2016;38(2):196-205(in Chinese).
Yang H,Li SX,Liu XY. Characteristics and resource prospects of tight oil and shale oil in Ordos Basin. Acta Pet Sin. 2013;34(1):1-11.https://doi.org/10.7623/syxb201301001.
Yang H,Dou WT,Liu XY,Zhang CL. Analysis on sedimentary facies of Member 7 in Yanchang Formation of Triassic in Ordos Basin.Acta Sedimentol Sin. 2010;28(2):254-63(in Chinese).
Zimmerle W. New aspects on the formation of hydrocarbon source rocks. Geol Rundsch. 1985;74(2):385-416. https://doi.org/10.1007/BF01824905.
Zou CN,Yang Z,Cui JW,Zhu RK,Hou LH,Tao SZ,Yuan XJ,Wu ST,Lin SH, Wang L, Bin B, Yao JL. Formation mechanism, geological characteristics and development strategy of nonmarine shale oil in China. Pet Explor Dev. 2013;40(1):15-27.
Zou CN, Zhang XY, Luo P, Wang L, Luo Z, Liu LH. Shallow-lacustrine sand-rich deltaic depositional cycles and sequence stratigraphy of the Upper Triassic Yanchang Formation, Ordos Basin,China. Basin Res, 2010;22(1):108-25. https://doi.org/10.1111/j.1365-2117.2009.00450.x.
Zhang WZ, Yang H, Peng PG. Influence of volcanism on development of Chang7 hydrocarbon source rock. Geochimica.2009;38(6):573-82(in Chinese). https://doi.org/10.19700/j.0379-1726.2009.06.007.
Zhang WZ, Li SP, Xu ZQ. Analysis of industrial utilization prospect of Upper Triassic Chang-7 oil shale in Ordos Basin. Low Permeability Oil Gas Field. 2006;11(1):13-7(in Chinese).
Zhang WZ, Yang H, Yang WW, Wu K, Liu F. Assessment of geological characteristics of lacustrine shale oil reservoir in Chang7member of Yanchang Formation, Ordos Basin. Geochimica.2015;44(5):505-15(in Chinese). https://doi.org/10.19700/j.0379-1726.2015.05.010.
Zhang W, Yang H, Xie L, Yang Y. Lake-bottom hydrothermal activities and their influence on high-quality source rock development:A case from Chang 7 source rocks in Ordos Basin. Petrol Explor Dev. 2010;37(4):424-429.
Zhang WZ, Li JF. Oil and gas source of Ordos Basin. China Pet Explor.2001;6(4):28-36(in Chinese).