Three-dimensional numerical solution and stress cage analysis of high conductive fractures pressure sealing

Abstract

Aiming at the main problems in the design and analysis of well wall strengthening for fractured formations, a three-dimensional (3D) numerical simulation scheme is proposed. The three-dimensional finite element software is used to analyze the mechanical behavior of fractures and the pressure sealing process, and evaluate the stress cage effect. The main features of the model are as follows: (1) The equivalent fractures in the analytical model represent the function sum of the mechanical behavior of all fractures on the well wall, which is a functionally equivalent crack.(2) When evaluating the stress cage effect, the shape of the crack wedge filled with the plugging agent particles is formed by simulating the fractures opening process under the injection pressure, not a given regular shape.(3) In the model of calculating bull heading of block agent, the liquid pressure on the well wall is the injection pressure, which is a variation increased with time. The fluid pressure on the well wall in the stress cage calculation model is generated by the initial pore pressure. (4) The numerical evaluation of the stress cage effect is achieved by calculating the increase amplitude FX of the minimum hoop stress on the well wall. Using this model, several sets of injection pressure design values can be used for pressure plugging numerical simulation and stress cage effect evaluation calculation, and then the optimal and accurate quantitative value of “injection pressure, block agent particle size, safe mud window upper bound” are found through comparison. Finally, through an engineering example of horizontal well drilling pressure sealing in a shale gas reservoir developed by a fracture, we use the above theoretical tools to introduce the process and results of the numerical analysis of the extended mud window drilled in the shale gas fissure reservoir.

Keywords

Well wall strengthening / Pressure sealing / Stress cage / Extended mud window / Numerical simulation / Natural crack / Quasi-brittle / Damage mechanics

Acknowledgements

Thanks to the general project of national natural science foundation of China (11272216) for the financial support of this paper.

References

[1] Wang Gui, Theory and Technology on Drilling Fluids for Wellbore Strengthening, Doctoral Dissertation, Southwest Petroleum University, Chengdu, China, 2012.

[2] Donald L. Whitfill, Hemphill Terry, All Lost-Circulation Material and Systems Are Not Created Equal, SPE Annual Technical Conference and Exhibition, Denver, Colorado, 2003.

[3] G. Shen, X. Shen, Widened Safe Mud Window for Subsalt Well Sections: a Workflow and Case Study, Offshore Technology Conference, Houston, Texas, USA, 2016.

[4] Ettehadi Ali G. Altun, Plugging performance of sepiolite drilling mud with calcium carbonate, Petrol. Explor. Dev. 44 (3) (2017) 446-455.

[5] Junwei Fang, He Zhong, Hanqiao Xiang, Sealing technology to control gas cut for fractured carbon and high pressure, Sci. Technol. Eng. 19 (4) (2019) 93-98.

[6] Hongtao Gu, Hang Yuan, Haibang Xia, Application of shooting technology of horizontal wells in Pengshui shale gas area, Reservoir Eval. Develop. 5 (6) (2015) 76-80.

[7] C. Lederer, S. Altstadt, S. Andriamonje, API Filtrate and Drilling Fluid Invasion: Is There Any Correlation? Latin American and Caribbean Petroleum Engineering Conference, Caracas, Venezuela, 1999.

[8] Mark W. Alberty, Michael R. McLean, A Physical Model for Stress Cages, SPE Annual Technical Conference and Exhibition, Houston, Texas, 2004.

[9] M.W. Alberty, M.R. McLean, Fracture Gradients in Depleted Reservoirs-Drilling Wells in Late Reservoir Life, SPE (Society of Petroleum Engineers)/IADC (International Association of Drilling Contractors) Drilling Conference, Amsterdam, the Netherlands, 2001.

[10] Gui Wang, Xiaolin Pu, Plugging mechanism of drilling fluid by enhancing wellbore pressure, Acta Pet. Sin. 31 (6) (2010) 1009-1012.

[11] Xiaochuan Lu, Baitao Fan, Hailaing Wang, New progress in shaft wall strengthening technology, Drill. Fluid Complet. Fluid 29 (6) (2012) 74-78.

[12] Dingding Song, Zhengsong Qin, Can Wang, Junyi Lin, Numerical simulation of borehole wall strengthening using ABAQUA, Drill. Fluid Complet. Fluid 33 (3) (2016) 15-19.

[13] Li Jia, Zhengsong Qin, Numeric simulation of factors affecting the strengthening of borehole wall, Drill. Fluid Complet. Fluid 34 (2) (2017) 1-8.

[14] Olivier Lietard, Mike Hoder, Tessa Unwin, Fracture Width LWD and Drilling Mud/LCM Selection Guidelines in Naturally Fractured Reservoirs, European Petroleum Conference, Milan, Italy, October 1996, pp. 22-24.

[15] Douglas E. Caughron, Douglas K. Renfrow, Unique Crosslinking Pill in Tandem with Fracture Prediction Model Cures Circulation Losses in Deepwater Gulf of Mexico, IADC/SPE Drilling Conference, Dallas, TX, USA, February 2002, pp. 26-28.

[16] S.T. Edwards, Accidental Geomechanics-Capturing In-Situ Stress from Mud Losses Encountered while Drilling, SPE/ISRM Rock Mechanics Conference, October 2002, pp. 20-23. Irving, TX, USA.

[17] S. Salehi, R. Nygaard, Numerical Modeling of Induced Fracture Propagation: a Novel Approach for Lost Circulation Materials (LCM) Design in Borehole Strengthening Applications of Deep Offshore Drilling, SPE Annual Technical Conference and Exhibition, San Antonio, TX, USA, October 2012, pp. 8-10.

[18] A. Mehrabian, D.E. Jamison, S.G. Teodorescu, Geomechanics of lost-circulation events and wellbore-strengthening operations, SPE J. 20 (6) (2015) 1305-1311.

[19] A. Hillorberg, M. Modeer, P.E. Petersson, Analysis of crack formation and crack growth in concrete by means of fracture mechanics and finite elements, Cement Concr. Res. 6 (6) (1976) 773-781.

[20] G.A.O. Davies, Stability of structures: elastic, inelastic, fracture and damage theories, Aeronaut. J. 116 (1176) (2010) 218-219.

[21] G. Cocchetti, G. Maier, X.P. Shen, Piecewise linear models for interfaces and mixed mode cohesive cracks, Comput. Model. Eng. Sci. 3 (3) (2002) 279-298.

[22] Jueshi Qian,Understanding brittle failure of concrete again, J. Chongqing Inst. Architect. Eng. 14 (3) (1992) 9-16.

[23] ABAQUS,Analysis User’s Manual, vol. 3, Dassault Systems Simulia Corp., Providence, RI, USA, 2011.

[24] H Liu, Heping Wang, WZhang, et al., Predicting Sand Production Rate in High-Pressure, High-Temperature Wells in the Tarim Basin[J], SPE production & operations (2020).

[25] Zhiping Long, Yanqi Wang, Yucang Zhou, Key drilling technologies for shale gas well longye 1HF, Petrol. Drilling Tech. 44 (2) (2016) 16-21.

[26] Anming Chen, Zhiping Long, Yucang Zhou, Discussion on low-cost drilling technologies of normal pressure shale gas in the outer margin of the sichuan basin, Petrol. Drilling Tech. 46 (6) (2018) 9-14.

[27] Xipeng He, Guisong He, G.A.O. Yuqiao, Geological characteristics and enrichment laws of normal-pressure shale gas in the basin-margin transition zone of SE Chongqing, Geol. Exploration 38 (12) (2018) 1-14.