Effects of mechanical layering on hydraulic fracturing in shale gas reservoirs based on numerical models
- 53 Downloads
Generally, induced hydraulic fractures are generated by fluid overpressure and are used to increase reservoir permeability through forming interconnected fracture systems. However, in heterogeneous and anisotropic rocks, many hydraulic fractures may become arrested or offset at layer contacts under certain conditions and do not form vertically connected fracture networks. Mechanical layering is an important factor causing anisotropy in sedimentary layers. Hence, in this study, with a shale gas reservoir case study in the Longmaxi Formation in the southeastern Chongqing region, Sichuan Basin, we present results from several numerical models to gain quantitative insights into the effects of mechanical layering on hydraulic fracturing. Results showed that the fractured area caused by hydraulic fracturing indicated a linear relationship with the neighboring layer’s Young’s modulus. An increase of the neighboring layer’s Young’s modulus resulted in better hydraulic fracturing effects. In addition, the contact between two neighboring layers is regarded as a zone with thickness and mechanical properties, which also influences the effects of hydraulic fracturing in reservoirs. The initial hydraulic fracture was unable to propagate into neighboring layers under a relatively low contact’s Young’s modulus. When associated local tensile stresses exceeded the rock strength, hydraulic fractures propagated into neighboring layers. Moreover, with the contact’s Young’s modulus becoming higher, the fractured area increased rapidly first, then slowly and finally became stable.
KeywordsHydraulic fracturing Numerical models Longmaxi Formation Mechanical layering Shale gas reservoir Chongqing region Sichuan Basin
We would like to express our gratitude to Dr. Barry Jay Katz and the anonymous reviewers for offering constructive suggestions and comments which improved this manuscript in many aspects.
This work was financially supported by the Fundamental Research Funds for the Central Universities (2018QNA44).
- Aguilera R (2000) Well test analysis of multi-layered naturally fractured reservoirs. J Can Pet Technol 39:31–37Google Scholar
- Economides MJ, Nolte KG (2000) Reservoir stimulation, (3rd edition) edn. John Wiley and Sons, New York, p 792Google Scholar
- Fan WF, Hou DJ, Liang Y (2015) Comparative study on reservoir forming conditions between Niutitang and Longmaxi Formation of shale gas in South China: taking Southeast Chongqing area for example. Science Technology and Engineering 15:13–22 (in Chinese with English abstract)Google Scholar
- Guo XS, Hu DF, Wen ZD, Liu RB (2014) Major factors controlling the accumulation and high productivity in marine shale gas in the Lower Paleozoic of Sichuan Basin and its periphery: a case study of the Wufeng-Longmaxi Formation of Jiaoshiba. Geol China 41:893–901 (in Chinese with English abstract)Google Scholar
- Hutchinson JW (1996) Stresses and failure modes in thin films and multilayers. Notes for a DCAMM course. Technical University of Denmark, Lyngby, pp 1–45Google Scholar
- Li XT, Shi WR, Guo MY, Liu X, Zhao HY, Chen X, Ren Y, Shi YH (2014) Characteristics of marine shale gas reservoirs in Jiaoshiba area of Fuling shale gas field. Journal of Oil and Gas Technology 36:11–15 (in Chinese with English abstract)Google Scholar
- Liu RB (2015) Typical features of the first giant shale gas field in China. Nat Gas Geosci 26:1488–1498 (in Chinese with English abstract)Google Scholar
- Nie HK, Zhang JC, Zhang PX, Song XW (2009) Shale gas reservoir characteristics of Barnett Shale Gas Reservoir in Fort Worth Basin. Geological Science and Technology Information 28:87–93 (in Chinese with English abstract)Google Scholar
- Warlick D (2006) Gas shale and CBM development in North America. Oil and Gas Financial Journal 3:1–5Google Scholar
- Yew CH, Weng XW (2015) Mechanics of hydraulic fracturing, 2nd edn. Gulf Publishing, Houston, p 234Google Scholar
- Zhang JC, Jiang SL, Tang X, Zhang PX, Tang Y, Jing TY (2009) Accumulation types and resources characteristics of shale gas in China. Nat Gas Ind 29:109–114 (in Chinese with English abstract)Google Scholar
- Zhang JC, Li YX, Nie HK, Long PY, Tang Y, Tang X, Jiang WL (2010) Geologic setting and drilling effect of the shale cored well Yuye-1, Pengshui County of Chongqing. Nat Gas Ind 30:114–118 (in Chinese with English abstract)Google Scholar