Research Article Pore Pressure Disturbance Induced by Multistage Hydraulic Fracturing in Shale Gas: Modelling and Field Application Yijin Zeng, 1,2 Zizhen Wang , 3,4 Yanbin Zang , 1,2 Ruihe Wang , 3,4 Feifei Wang , 5 Xinming Niu , 1,2 and Feng Niu 3,4 1 State Key Laboratory of Shale Oil and Gas Enrichment Mechanisms and Effective Development, Beijing, China 2 Sinopec Research Institute of Petroleum Engineering, Beijing, China 3 Key Laboratory of Unconventional Oil & Gas Development (China University of Petroleum (East China)), Ministry of Education, Qingdao, China 4 School of Petroleum Engineering, China University of Petroleum (East China), Qingdao, China 5 College of Pipeline and Civil Engineering, China University of Petroleum (East China), Qingdao, China Correspondence should be addressed to Zizhen Wang; wangzzh@upc.edu.cn Received 20 January 2019; Revised 20 March 2019; Accepted 26 March 2019; Published 12 May 2019 Guest Editor: Andrew Bunger Copyright © 2019 Yijin Zeng et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Currently, there is no proper method to predict the pore pressure disturbance caused by multistage fracturing in shale gas, which has challenged drilling engineering in practice, especially for the infilling well drilling within/near the fractured zones. A numerical modelling method of pore pressure redistribution around the multistage fractured horizontal wellbore was put forward based on the theory of fluid transportation in porous media. The fracture network of each stage was represented by an elliptical zone with high permeability. Five stages of fracturing were modelled simultaneously to consider the interactions among fractures. The effects of formation permeability, fracturing fluid viscosity, and pressure within the fractures on the pore pressure disturbance were numerically investigated. Modelling results indicated that the pore pressure disturbance zone expands as the permeability and/or the differential pressure increases, while it decreases when the viscosity of the fracturing fluid increases. The pore pressure disturbance level becomes weaker from the fracture tip to the far field along the main-fracture propagation direction. The pore pressure disturbance contours obviously have larger slopes with the variation of permeability than those of the differential pressure. The distances between the pore pressure disturbance contours are smaller at lower permeability and higher viscosity. The modelling results of the updated pore pressure distribution are of great importance for safe drilling. A case study of three wells within one platform showed that the modelling method could provide a reliable estimation of the pore pressure disturbance area caused by multistage fracturing. 1. Introduction Shale gas becomes more and more important worldwide. The shale gas production reached 7500 × 10 8 m 3 in America in 2016, which made up more than 40% of the total natural gas production of America [1]. The horizontal well factory and multistage hydraulic fracturing are the two most important technologies for shale gas production commer- cially [2–4]. There is over sixty years of history in the study of fracture propagation in porous media, and many models have been developed, such as the PKN model [5, 6], KGD model [7, 8], and some three-dimensional models [9, 10]. Recently, more complex models for multiple-fracture propagation in horizontal wells have been built, such as the Unconventional Fracture Model (UFM) [11, 12]. In order to obtain complex fracture networks in low permeable shale reservoirs through multistage hydraulic fracturing, many studies have been done to analyze the stress distribution around the fractured horizontal wellbore [13], which is mainly focused on the extent of stress reversal [14] and the effect of stress shadow [15]. Besides the analysis of fracture initiation and propaga- tion, the stress redistribution results are further used to opti- mize the stage spacing [14, 16, 17] and well space [18]. Such Hindawi Geofluids Volume 2019, Article ID 1315451, 11 pages https://doi.org/10.1155/2019/1315451