Improvement of reservoir quality of ultra-deep tight sandstones by tectonism and fluid: A case study of Keshen gas field in Tarim Basin, western China

Abstract

The Keshen gas field is one of the most important natural gas supply sources in the Tarim basin, western China. The main gas producing interval there is the Lower Cretaceous Bashijiqike Formation(K₁bs), it is an ultra-deep tight reservoir whose buried depth exceeds 6000 m, and it shows a low matrix porosity (<10%) and extremely low matrix permeability (<0.1mD). However, this reservoir can supply extremely high and stable gas production due to improvement of reservoir quality by tectonism and fluid.

Based on tectonic evolution analysis by plenty of lab data of core plugs or thin sections, the enhancement models of tectonism and fluid are built, evidence suggests both tectonism and fluid improve the reservoir quality greatly. Tectonic evolution produces lots of natural fractures in 3stages which promote the ultra-deep tight reservoir permeability 10-200 times, then, testing results of new boreholes without fracturing show reservoir permeability underground can reach 20 mD. Furthermore, fluid dissolution increases reservoir porosity 1-2 times, the main dissolved mineral is feldspar, all fluid dissolution came from the unconformity controlling the dissolution distance. Tectonism and fluid interact on each other: Tectonism controls fracture distribution and types of diagenic fluid in reservoir, but fluids influence fracture cements and dissolution. Both tectonic folding and the fluid flow control the sweet point reservoir located in upper 150 m formation.

Keywords

Reservoir quality / Fluid interaction / Tectonism / Diagenesis / Deep gas

Declaration of competing interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper

Acknowledgement

The authors greatly acknowledge the PetroChina Tarim Oilfield Company for providing information and other support. We are thankful for Stephen Ernest Laubach, Bo Ren and Qiqi Wang from Bureau of Economic Geology, for providing constructive comments and suggestions, which improve our manuscript significantly. This work was supported by the reservoir research project of PetroChina (No. 2021DJ0302).

References

[1] J.M. Ajdukiewicz, P.H. Nicholson, W.L. Esch, Prediction of deep reservoir quality from early diagenetic process models in the Jurassic eolian Norphlet Formation, Gulf of Mexico, AAPG Bull. 94 (8) (2010) 1189-1227.

[2] B.F. Cao, G.P. Bai, Y.F. Wang, More attention recommended for global deep reservoirs, Oil Gas J. 111 (9) (2013) 78-85.

[3] C.Z. Jia, X.Q. Pang, Research processes and main development direction of deep hydrocarbon geological theories, Acta Pet. Sin. 36 (12) (2015) 1457e1469 (in Chinese with English abstract).

[4] Ministry of Land and Resources of the People's Republic of China, Regulation of Petroleum Reserves Estimation (DZ/T 0217-2005), Standards Press of China, Beijing, 2005.

[5] J.P. Wang, R.H. Zhang, J.L. Zhao, Characteristics and evaluation of fractures in ultra-deep tight sandstone reservoir: taking Keshen gasfield in Tarim Basin, NW China as an example, Nat. Gas Geosci. 25 (11) (2014) 1735-1745.

[6] J.A. Masters, Deep Basin gas trap, western Canada, AAPG (Am. Assoc. Pet. Geol.) Bull. 63 (1979) 152-181. J.D. Walls, Tight gas sands-permeability, pore structure, and clay, J. Pet. Technol. 34(1982), 2707-2714.

[7] Q.M. Zhang, Investigation report of geopressured gas and deep basin gas in North America, China Offshore Oil Gas 4 (1990) 55-66.

[8] S.E. Laubach, K. Diaz-Tushman, Laurentian paleostress trajectories and ephemeral fracture permeability, Cambrian Eriboll Formation sandstones west of the Moine thrust zone, northwest Scotland, J. Geol. Soc. (Lond.) 166 (2) (2009) 349-362.

[9] S.E. Laubach, R.H. Lander, L.J. Criscenti, L.M. Anovitz, J.L. Urai, R.M. Pollyea, The role of chemistry in fracture pattern development and opportunities to advance interpretations of geological materials, Rev. Geophys. 57 (2019).

[10] N.C. Davatzes, P. Eichhubl, A. Aydin, Structural evolution of fault zones in sandstone by multiple deformation mechanisms: moab fault, southeast Utah, Geol. Soc. Am. Bull. 117 (2005) 35.

[11] P. Eichhubl, W.L. Taylor, D.D. Pollard, A. Aydin, Paleo-fluid flow and deformation in the Aztec Sandstone at the Valley of Fire, Nevadadevidence for the coupling of hydrogeologic, diagenetic, and tectonic processes, Geol. Soc. Am. Bull. 116 (2004) 1120.

[12] P. Eichhubl, J.N. Hooker, S.E. Laubach, Pure and shear-enhanced compaction bands in Aztec Sandstone, J. Struct. Geol. 32 (2010) 1873-1886.

[13] S.M. Schmalholz,3D numerical modeling of forward folding and reverse unfolding of a viscous single-layer: implications for the formation of folds and fold pattems, Tectonophysics 446 (1) (2008) 31-41.

[14] J.E. Olson, S.E. Laubach, P. Eichhubl, Estimating natural fracture producibility in tight gas sandstones: coupling diagenesis with geomechanical modeling, Lead. Edge 29 (2010) 1494-1499.

[15] S.E. Laubach, J. Lamarche, B.D.M. Gauthier, W.M. Dunne, D.J. Sanderson, Spatial arrangement of faults and opening-mode fractures, J. Struct. Geol. 108 (2018) 2-15.

[16] N.J. Price, Fault and Joint Development in Brittle and Semi-brittle Rock, 1966.

[17] D.W. Steams, M. Friedman, Reservoirs in Fractured Rocks, 16, American Association of Petroleum Geologists Memoir, 1972, pp. 82-100.

[18] Z. Ismat, Folding kinematics expressed in fracture patterns: an example from the Anti-Atlas fold belt, Morocco, J. Struct. Geol. 30 (11) (2008) 1396-1404.

[19] A. Awdal, D. Healy, G.I. Alsop, Fracture patterns and petrophysical properties of carbonates undergoing regional folding: a case study from Kurdistan, N Iraq, Mar. Petrol. Geol. 71 (2) (2016) 149-167.

[20] N. Su, L. Zou, X. Shen, Fracture patterns in successive folding in the western Sichuan basin, China, J. Asian Earth Sci. 81 (4) (2014) 65-76.

[21] M.P. Fischer, M.S. Wilkerson, Predicting the orientation of joints from fold shape: results of pseudo-three-dimensional modeling and curvature analysis, Geology 28 (1) (2000) 15-18.

[22] M.L.E. Guiton, W. Sassi, Y.M. Leroy, Mechanical constraints on the chronology of fracture activation in folded Devonian sandstone of the western Moroccan Anti-AtIas, J. Struct. Geol. 25 (8) (2003) 1317-1330.

[23] A.N. Hughes, N.P. Benesh, J.H. Shaw, Factors that control the development of fault-bend versus fault-propagation folds: insights from mechanical models based on the discrete element method (DEM), J. Struct. Geol. 68 (2014) 121-141.

[24] G. Strijker, F. Beekman, G. Bertotti, FEM analysis of deformation localization mechanisms in a 3-D fractured medium under rotating compressive stress orientations, Tectonophysics 593 (3) (2013) 95-110.

[25] J.X. Shi, X.Y. Zhao, R.F. Pan, L.B. Zeng, W.J. Luo, Natural fractures in the deep Sinian carbonates of the central Sichuan Basin, China: implications for reservoir quality, J. Petrol. Sci. Eng. 216 (2022). Article ID. 110829.

[26] S.E. Laubach, Practical approaches to identifying sealed and open fractures, AAPG (Am. Assoc. Pet. Geol.) Bull. 87 (2003) 561-579.

[27] V. Schmidt, D.A. McDonald, The rate of secondary porosity in the course of sandstone diagenesis, Soc. Econ. Paleontol. Mineral. Spec. Publ. 26 (1979) 175-208.

[28] R.C. Surdam, S.W. Boese, L.J. Crossey, The chemistry of secondary porosity, in: D. A. McDonald, R.C. Surdam (Clastic Diagenesis,Eds.), AAPG Memoir, 37, 1984, pp. 127-149.

[29] C.F. Jové Colón, E.H. Oelkers, J. Schott, Experimental Investigation of the Effect of Dissolution on Sandstone Permeability, Porosity, and Reactive Surface Area, 68, 2004, pp. 805-817, 4.

[30] R.H. Lander, S.E. Laubach, Insights into rates of fracture growth and sealing from a model for quartz cementation in fractured sandstones, Geol. Soc. Am. Bull. 127 (3-4) (2015) 516-538.

[31] B. Thyberg, J. Jahren, T. Winje, K. Bjørlykke, J.I. Faleide, Ø. Marcussen, Quartz cementation in Late Cretaceous mudstones, northern North Sea: changes in rock properties due to dissolution of smectite and precipitation of microquartz crystals, Mar. Petrol. Geol. 27 (2010) 1752-1764.

[32] J.E. Amthor, J. Okkerman, Influence of early diagenesis on reservoir quality of Rotliegende sandstones, northern Netherlands, AAPG (Am. Assoc. Pet. Geol.) Bull. 82 (12) (1998) 2246-2265.

[33] L.B. Zeng, L. Gong, C. Guan, B.J. Zhang, Q.Q. Wang, Q. Zeng, W.Y. Lyu, Natural fractures and their contribution to tight gas conglomerate reservoirs: a case study in the northwestern Sichuan Basin, China, J. Petrol. Sci. Eng. 210 (2022). Article ID. 110028.

[34] F.A. Gahtani, Diagenetic controls on evolution of porosity in the permian illawarra goal measures, southern sydney basin, Australia, Arabian J. Geosci. 7 (12) (2014) 5473-5494.

[35] A. Okamoto, R. Yamada, H. Saishu, Porosity and permeability evolution induced by precipitation of silica under hydrothermal conditions, Procedia Earth Planetary Sci. 17 (2017) 249-252.

[36] G.Q. Wei, J.P. Wang, L.B. Zeng, Structural reworking effects and new exploration discoveries of subsalt ultra-deep reservoirs in the Kelasu tectonic zone, Nat. Gas. Ind. 40 (1) (2020) 20-30.

[37] K. Wang, R.H. Zhang, Y. Tang, Structural diagenesis and reservoir prediction of Lower Jurassic Ahe Formation in the northern structural belt of Kuqa depression, Acta Pet. Sin. 43 (7) (2022) 925-940.

[38] H.J. Yang, R.H. Zhang, X.Z. Yang, K. Wang, J.P. Wang, Y.G. Tang, L. Zhou, Characteristics and reservoir improvement effect of structural fracture in ultra-deep tight sandstone reservoir: a case study of Keshen Gasfield, Kuqa Depression, Tarim Basin, Nat. Gas Geosci. 29 (7) (2018) 942-950.

[39] J.P. Wang, H.L. Zhang, R.H. Zhang, Enhancement of ultra-deep tight sandstone reservoir quality by fractures: a case study of Keshen gas field in Kuqa Depression, Tarim Basin, Oil Gas Geol. 39 (1) (2018) 77-88.

[40] R.H. Zhang, H.J. Yang, J.P. Wang, J.F. Shou, Q.L. Zeng, Q. Liu, The formation mechanism and exploration significance of ultra-deep, low-porosity and tight sandstone reservoirs in Kuqa Depression, Tarim Basin, Acta Pet. Sin. 35 (2014) 1057-1069.

[41] K.J. Smart, D.A. Ferrill, A.P. Morris, Impact of interlayer slip on fracture prediction from geomechanical models of fault-related folds, AAPG (Am. Assoc. Pet. Geol.) Bull. 93 (11) (2009) 1447-1458.

[42] C.Z. Jia, H.L. Chen, S.F. Yang, H.F. Lu, Y.Z. Zhou, Late Cretaceous uplifting process and its geological response in Kuqa Depression, Acta Pet. Sin. 24 (2003) 1-5.

[43] C.Z. Jia, Q. Li, Petroleum geology of Kelae2, the most productive gas field in China, Mar. Petrol. Geol. 25 (2008) 335-343.

[44] Y.R. Zou, C. Zhao, Y. Wang, W. Zhao, P. Peng, Y. Shuai, Characteristics and origin of natural gases in the Kuqa depression of Tarim Basin, NW China, Org. Geochem. 37 (2006) 280-290.

[45] G. Zhu, S. Zhang, J. Su, S. Meng, H. Yang, J. Hu, Y. Zhu, Secondary accumulation of hydrocarbons in Carboniferous reservoirs in the northern Tarim Basin, China, J. Petrol. Sci. Eng. 102 (2013) 10-26.

[46] Y. Li, S. Guo, X. Wang, Y. Hou, Y. Neng, Z. Wang, L. Zhou, W. Yang, C. Tan, Stratification model of an ultra-deep tight sandstone fracture reservoir under tectonic stress: a case study of a Cretaceous reservoir in the Kuqa foreland thrust belt of the Tarim Basin, J. Nat. Gas Sci. Eng. 45 (2017) 53-64.

[47] G. Shi, X. Zhou, G. Zhang, X. Shi, H. Li, The use of artificial neural network analysis and multiple regression for trap quality evaluation: a case study of the Northern Kuqa Depression of Tarim Basin in western China, Mar. Petrol. Geol. 21 (2004) 411-420.

[48] S. Xu, X. Lu, Z. Sun, X. Pi, L. Liu, Q. Li, H. Xie, Kela-2: a major gas field in the Tarim Basin of west China, Petrol. Geosci. 10 (2004) 95-106.

[49] L.B. Zeng, H.J. Wang, L. Gong, B.M. Liu, Impacts of the tectonic stress field on natural gas migration and accumulation: a case study of the Kuqa Depression in the Tarim Basin, China, Mar. Petrol. Geol. 27 (2010) 1616-1627.

[50] W.Z. Zhao, S.C. Zhang, F.Y. Wang, B. Cramer, J.P. Chen, Y.G. Sun, B. Zhang, M.J. Zhao, Gas systems in the Kuche Depression of the Tarim basin: source rock distributions, generation kinetics and gas accumulation history, Org. Geochem. 36 (2005) 1583-1601.

[51] J.M. Eiler, Clumped-isotope” geochemistrydthe study of naturally-occurring, multiply-substituted isotopologues, Earth Planet Sci. Lett. 262 (3-4) (2007) 309-327.

[52] J. Harwood, A.C. Aplin, C.L. Pialips, J.E. Iliffe, R. Kozdon, T. Ushikubo, J.W. Valley, Quartz cementation history of sandstones revealed by high-resolutions SIMS oxygen isotope analysis, J. Sediment. Res. 83 (7) (2013) 522-530.

[53] H. Yurimoto, S. Itoh, M. Zolensky, M. Kusakabe, A. Karen, R. Bodnar, Isotopic compositions of a steroidal liquid water trapped in fluid inclusions of chondrites, Geochem. J. 48 (6) (2014) 549-560.

[54] J.P. Wang, L.B. Zeng, L. Zhou, K. Wang, Q.L. Zeng, Z.Y. Zhang, R.H. Zhang, X.W. Ma, Development Models of Natural Fracture in Ultra-deep Sandstone Reservoirs with Low Porosity in the Kelasu Tectonic Belt, Tarim Basin, Earth Science, 2022 online.

[55] J. Lai, G. Wang, Y. Chai, Y. Xin, Q. Wu, X. Zhang, Y. Sun, Deep burial diagenesis and reservoir quality evolution of high-temperature, high-pressure sandstones: examples from Lower Cretaceous Bashijiqike Formation in Keshen area, Kuqa depression, Tarim basin of China, AAPG (Am. Assoc. Pet. Geol.) Bull. 101 (2017) 829-862.

[56] X.Z. Li, D.T. Lu, R.L. Luo, Y.P. Sun, W.J. Shen, Quantitative criteria for identifying main flow channels in complex porous media, Petrol. Explor. Dev. 46 (5) (2019) 998-1005.