Characteristics and genesis of the Feixianguan Formation oolitic shoal reservoir, Puguang gas field, Sichuan Basin, China

Abstract

The Lower Triassic Feixianguan Formation at the well-known Puguang gasfield in the northeastern Sichuan Basin of southwest China produces a representative oolitic reservoir, which has been the biggest marine-sourced gasfield so far in China (discovered in 2003 with proven gas reserves greater than 350×10⁸ m³). This study combines core, thin section, and scanning electron microscopy observations, and geochemical analysis (C, O, and Sr isotopes) in order to investigate the basic characteristics and formation mechanisms of the reservoir. Observations indicate that platform margin oolitic dolomites are the most important reservoir rocks. Porosity is dominated by intergranular and intragranular solution, and moldic pore. The dolomites are characterized by medium porosity and permeability, averaging at approximately 9% and 29.7 mD, respectively. ⁸⁷Sr/⁸⁶Sr (0.707536–0.707934) and δ¹³C_PDB (1.8‰–3.5‰) isotopic values indicate that the dolomitization fluid is predominantly concentrated seawater by evaporation, and the main mechanism for the oolitic dolomite formation is seepage reflux at an early stage of eodiagenesis. Both sedimentation and diagenesis (e.g., dolomitization and dissolution) have led to the formation of high-quality rocks to different degrees. Dolomite formation may have little contribution, karst may have had both positive and negative influences, and burial dissolution-TSR (thermochemical sulfate reduction) may not impact widely. The preservation of primary intergranular pores and dissolution by meteoric or mixed waters at the early stage of eogenesis are the main influences. This study may assist oil and gas exploration activities in the Puguang area and in other areas with dolomitic reservoirs.

Keywords

oolite shoal reservoir / carbonate / diagenesis / Triassic Feixianguan Formation / Puguang gas field / Sichuan Basin

References

[1] Anderson T F, Arthur M A (1983). Stable isotopes of oxygen and carbon and their application to sedimentologic and paleoenvironmental problems∥Arthur M A. Stable Isotopes in Sedimentary Geology, Tulsa. SEPM Short Course, 10: 15–32

[2] Beach D K (1982). Depositional and Diagenetic History of Pliocene-Pleistocene Carbonates of Northwestern Great Bahama Bank: Evolution of A Carbonate Platform. Dissertation for Ph. D degree. Miami: University of Miami, 600

[3] Brasher J E, Vagle K R (1996). Influence of lithofacies and diagenesis on Norwegian North Sea chalk reservoirs. AAPG Bull, 80(5): 746–769

[4] Budd D A (1988). Petrographic products of freshwater diagenesis in Holocene ooid sands, Schooner Cays, Bahamas. Carbonates and Evaporites, 3(2): 143–163

[5] Duggan J P, Mountjoy E W, Stasiuk L D (2001). Fault-controlled dolomitization at Swan Hills Simonette oil field (Devonian), deep basin west-central Alberta, Canada. Sedimentology, 48(2): 301–323

[6] Dunham R J (1962). Classification of carbonate rocks according to depositional texture. In: Han W E, ed. Classification of Carbonate Rocks. AAPG Mem, 1: 108–121

[7] Ehrenberg S N, Nadeau P H, Aqrawi A A M (2007). A comparison of Khuff and Arab reservoir potential throughout the Middle East. AAPG Bull, 91(3): 275–286

[8] Feng J L, Cao J, Hu K, Peng X Q, Chen Y, Wang Y F, Wang M (2013). Dissolution and its impacts on reservoir formation in moderately to deeply buried strata of mixed siliciclastic-carbonate sediments, northwestern Qaidam Basin, northwest China. Mar Pet Geol, 39(1): 124–137

[9] Fu Q L, Qing H R, Bergman K M (2006). Early dolomitization and recrystallization of carbonate in an evaporite basin: the Middle Devonian Ratner laminite in southern Saskatchewan, Canada. J Geol Soc London, 163(6): 937–948

[10] Gale J F W, Gomez L A (2007). Late opening-mode fractures in karst-brecciated dolostones of the Lower Ordovician Ellenburger Group, west Texas: recognition, characterization, and implications for fluid flow. AAPG Bull, 91(7): 1005–1023

[11] Glumac B, Spivak-Birndorf M L (2002). Stable isotopes of carbon as an invaluable stratigraphic tool: an example from the Cambrian of the northern Appalachians, USA. Geology, 30(6): 563–566

[12] Guo X S, Guo T L (2012). Exploration Theory and Practice of Large Scale Carbonate Platform Margin Gas Field of Puguang and Yuanba. Beijing: Science Press, 159–163 (in Chinese)

[13] Hao F, Guo T L, Du C G, Zou H Y, Cai X Y, Zhu Y M, Li P P, Wang C W, Zhang Y C (2009). Accumulation mechanisms and evolution history of the giant Puguang gas field, Sichuan Basin, China. Acta Geol Sin, 83(1): 136–145

[14] Hao F, Guo T L, Zhu Y M, Cai X Y, Zou H Y, Li P P (2008). Evidence for multiple stages of oil cracking and thermochemical sulfate reduction in the Puguang gasfield, Sichuan Basin, China. AAPG Bull, 92(5): 611–637

[15] Hardie L A (1987). Dolomitization: a critical view of some current views. J Sediment Res, 57(1): 166–183

[16] Harrison R S (1975). Porosity in Pleistocene Grainstones from Barbados: some preliminary observations. Bull Can Pet Geol, 23(2): 383–392

[17] Huang S J (1990). Cathodoluminescence and diagenetic alteration of marine carbonate minerals. Sedimentary Geol and Tethyan Geol, 4: 9–15

[18] Jiang L, Cai C F, Worden R H, Li K K, Xiang L (2013). Reflux dolomitization of the Upper Permian Changxing Formation and the Lower Triassic Feixianguan Formation, NE Sichuan Basin, China. Geofluids, 13(2): 232–245

[19] Kaufman A J, Knoll A H (1995). Neoproterozoic variations in the C-isotopic composition of seawater: stratigraphic and biogeochemical implications. Precambrian Res, 73(1–4): 27–49

[20] Korte C, Kozur H W, Bruckschen P, Veizer J (2003). Strontium isotope evolution of Late Permian and Triassic seawater. Geochim Cosmochim Acta, 67(1): 47–62

[21] Li K K, Cai C F, Jiang L, Cai L L, Jia L Q, Zhang B, Xiang L, Yuan Y Y (2012). Sr evolution in the Upper Permian and Lower Triassic carbonates, northeast Sichuan basin, China: constraints from chemistry, isotope and fluid inclusions. Appl Geochem, 27(12): 2409–2424

[22] Ma Y S, Mou C L, Guo X S, Yu Q, Tan Q Y (2006a). Sedimentary facies and distribution of reservoir rocks from the Feixianguan Formation in the Daxian-Xuanhan region, NE Sichuan. Acta Geol Sin, 80(1): 137–151

[23] Ma Y S, Guo T L, Cai X Y (2006b). Petroleum geology of the Northeastern Sichuan Basin and the characteristics of Puguang Gas Field, China. AAPG International Conference (Perth, Australia) Technical Program

[24] Ma Y S, Guo T L, Zhao X F, Cai X Y (2008). The formation mechanism of high-quality dolomite reservoir in the deep of Puguang Gas Field. Sci China Ser D, 51(S1): 53–64

[25] Ma Y S, Guo T L, Zhu G Y, Cai X Y, Xie Z Y (2007a). Simulated experiment evidences of the corrosion and reform actions of H₂S to carbonate reservoirs: an example of Feixianguan Formation, east Sichuan. Chin Sci Bull, 52(S1): 178–183

[26] Ma Y S, Guo X S, Guo T L, Huang R, Cai X Y, Li G X (2007b). The Puguang gas field: new giant discovery in the mature Sichuan Basin, southwest China. AAPG Bull, 91(5): 627–643

[27] Machel H G, Lonnee J (2002). Hydrothermal dolomite-a product of poor definition and imagination. Sediment Geol, 152(3–4): 163–171

[28] Mazzullo S J, Harris P M (1992). Mesogenetic dissolution; its role in porosity development in carbonate reservoirs. AAPG Bull, 76(5): 607–620

[29] Meyers W J, Lu F H, Zachariah J K (1997). Dolomitization by mixed evaporative brines and freshwater, upper Miocene carbonates, Nijar, Spain. J Sediment Res, 67(5): 898–912

[30] Moore C H (1989). Carbonate Diagenesis and Porosity. New York: Elsevier, 338

[31] Moore C H, Druckman Y (1981). Burial diagenesis and porosity evolution, upper Jurassic Smackover, Arkansas and Louisiana. Am Assoc Pet Geol Bull, 65(4): 597–628

[32] Moradpour M, Zamani Z, Moallemi S A (2008). Controls in reservoir quality in the Lower Triassic Kangan Formation, Southern Persian Gulf. J Pet Geol, 31(4): 367–385

[33] Scholle P A, Halley R B (1985). Burial diagenesis: out of sight, out of mind. In: Schneidermann N, Harris P M, eds. Carbonate Cements. Society of Economic Paleontologists and Mineralogists Special Publication, 36: 309–334

[34] Steinen R P (1974). Phreatic and vadose diagenetic modification of Pleistocene limestone: petrographic observations from subsurface of Barbados, West Indies. AAPG Bull, 58(6): 1008–1024

[35] Swei G H, Tucker M E (2012). Impact of diagenesis on reservoir quality in ramp carbonates: Gialo Formation (Middle Eocene), Sirt Basin, Libya. J Pet Geol, 35(1): 25–47

[36] Swirydczuk K (1988). Mineralogical control on porosity type in Upper Jurassic Smackover ooid grainstones, Southern Arkansas and Northern Louisiana. J Sediment Petrol, 58(2): 339–347

[37] Tan X C, Liu H, Li L, Luo B, Liu X G, Mou X H, Nie Y, Xi W Y (2011). Primary intergranular pores in Oolitic Shoal Reservoir of Lower Triassic Feixianguan Formation, Sichuan Basin, Southwest China: fundamental for reservoir formation and retention diagenesis. Journal of Earth Science, 22(1): 101–114

[38] Tan X C, Zhao L Z, Luo B, Jiang X F, Cao J, Liu H, Li L, Wu X B, Nie Y (2012). Comparison of basic features and origins of oolitic shoal reservoirs between carbonate platform interior and platform margin locations in the Lower Triassic Feixianguan Formation of the Sichuan Basin, Southwest China. Petroleum Science, 9(4): 417–428

[39] Veizer J, Hoefs J (1976). The nature of ¹⁸O/¹⁶O and ¹³C/¹²C secular trends in sedimentary carbonate rocks. Geochim Cosmochim Acta, 40(11): 1387–1395

[40] Walkden G M, Williams O (1991). The diagenesis of the late Dinantian Derbyshire-East Midland carbonate shelf, central England. Sedimentology, 38(4): 643–670

[41] Wang F, Lu X X, Lo C H, Wu F Y, He H Y, Yang L K, Zhu R X (2007a). Post-collisional, potassic monzonite–minette complex (Shahewan) in the Qinling Mountains (central China): ⁴⁰Ar/³⁹Ar thermochronology, petrogenesis, and implications for the dynamic setting of the Qinling orogen. J Asian Earth Sci, 31(2): 153–166

[42] Wang S Y, Jiang X Q, Guan H L, Bao Y J (2009). Pore evolution of reservoirs of Feixianguan Formation in Puguang gas field in Northeastern Sichuan. Petroleum Geology & Experiment, 31(1): 26–30 (in Chinese)

[43] Wang S Y, Jiang X Q, Guan H L, Bao Y J (2010). Diagenesis effects of Lower Triassic Feixianguan Formation reservoir in Puguang gas field, Northeast Sichuan. Petroleum Geology & Experiment, 32(4): 366–372 (in Chinese)

[44] Wang X Z, Zhang F, Ma Q, Yang M P, Wang Y G, Wen Y C, Yang Y, Zhang J (2002). The characteristics of reef and bank and the fluctuation of sea-level in Feixianguan Formation period of Late Permian-Early Triassic, East Sichuan basin. Acta Sedimentologica Sinica, 20(2): 249–254 (in Chinese)

[45] Wang Y G, Wen Y C, Hong H T, Xia M L, He T T, Song S J (2007b). Diagenesis of Triassic Feixianguan Formation in Sichuan Basin, Southwest China. Acta Sedimentologica Sinica, 25(6): 831–839 (in Chinese)

[46] Warren J (2000). Dolomite: occurrence, evolution and economically important associations. Earth Sci Rev, 52(1–3): 1–81

[47] Zhao W Z, Xu C C, Wang T S, Wang H J, Wang Z C, Bian C S, Li X (2011). Comparative study of gas accumulations in the Permian Changxing reefs and Triassic Feixianguan oolitic reservoirs between Longgang and Luojiazhai-Puguang in the Sichuan Basin. Chin Sci Bull, 56(31): 3310–3320

[48] Zheng R C, Dang L R, Wen H G, Chen Z W, Chen F M, Zhang H J (2011). Diagenesis characteristics and system for dolostone in Feixianguan Formation of Northeast Sichuan. Earth Science-Journal of China University of Geoscience, 36(4): 659–669 (in Chinese)

[49] Zhu G Y, Zhang S C, Liang Y B, Dai J X, Li J (2005a). Isotopic evidence of TSR origin for natural gas bearing high H₂S contents within the Feixianguan Formation of the northeastern Sichuan Basin, southwestern China. Sci China Ser D, 48(11): 1960–1971

[50] Zhu G Y, Zhang S C, Liang Y B, Dai J X, Li J (2005b). Origins of high H₂S-bearing natural gas in China. Acta Geol Sin, 79(5): 697–708

[51] Zou H Y, Hao F, Zhu Y M, Guo T L, Cai X Y, Li P P,Zhang X F (2008). Source rocks for the Giant Puguang Gas Field Sichuan Basin: implication for petroleum exploration in marine sequences in South China. Acta Geologica Sinica, 82(3): 477–486

Acknowledgements

We thank the SINOPEC Zhongyuan Oilfield Company for providing the raw data used in this study and for permission to publish this work. This work was supported by the Major State Basic Research Development Program (No. 2012CB214803), China’s National Science & Technology Special Project (Grant Nos. 2011ZX05017 and 2011ZX05049), the PetroChina Research Fund (Grant No. 2011D-5006-0105), and the Key Subject Construction Project of Sichuan Province, China (Grant No. SZD 0414). Dr. Jian Cao at Nanjing University is thanked for his enthusiastic support and collaboration during this project.

RIGHTS & PERMISSIONS

2014 Higher Education Press and Springer-Verlag Berlin Heidelberg