Propagation and aperture of staged hydraulic fractures in unconventional resources in toughness-dominated regimes  

作　　者：Ali Taghichian Hamid Hashemalhoseini Musharraf Zaman Saied Beheshti Zavareh 

机构地区：[1]Department of Civil Engineering, Isfahan University of Technology [2]Mewbourne School of Petroleum and Geological Engineering, Sarkeys Energy Center,University of Oklahoma [3]Department of Mining Engineering, Isfahan University of Technology

出　　处：《Journal of Rock Mechanics and Geotechnical Engineering》2018年第2期249-258,共10页岩石力学与岩土工程学报（英文版）

基　　金：Oklahoma Department of Transportation (ODOT);Oklahoma Transportation Center for their financial support during the course of this study

摘　　要：Simultaneous multistage hydraulic fracturing of unconventional gas shale in parallel multilateral wells is an effective technique to raise the connectivity of the reservoir to the wellbore and improve reservoir permeability for an economical production. However, this technique should be accompanied with some optimization procedures to obtain an efficiently fractured reservoir with the highest production and the lowest cost. In unconventional hydraulic fracturing, fracture deviation/collapse and trapping are familiar phenomena which occur when a non-optimized fracturing pattern is used. These problems occur respectively when stress shadow size has not been considered in optimization and fracturing pressure is higher than the available pressure in the sealed section. Therefore, in an optimized hydraulic fracturing,having straight fractures with no deviation or collapse needs consideration of stress shadow effect(SSE).Apart from that, having efficiently propagated fractures to the extent of the reservoir without any fracture trap requires consideration of stress intensity factor(SIF) and aperture. SSE was studied and published by the authors in 2014. For the case of SIF, investigating any change in mode I SIF and aperture with different influencing variables such as fracture geometry and pattern are studied in the current research work. Three different fracturing techniques are assumed as multistage fracturing, simultaneous single-stage fracturing, and simultaneous multistage fracturing techniques. Since obtaining SIF for threedimensional fractures is a challenging issue, a stress ratio technique is used for calculation of SIF ratios of different fracturing scenarios compared to the case of a single fracture. Therefore, changes of SIF for different fracturing schemes are estimated and analyzed to understand whether or not a fracturing scheme is efficient and all the spaced perforations are activated and change to hydraulic fractures.Simultaneous multistage hydraulic fracturing of unconventional gas shale in parallel multilateral wells is an effective technique to raise the connectivity of the reservoir to the wellbore and improve reservoir permeability for an economical production. However, this technique should be accompanied with some optimization procedures to obtain an efficiently fractured reservoir with the highest production and the lowest cost. In unconventional hydraulic fracturing, fracture deviation/collapse and trapping are familiar phenomena which occur when a non-optimized fracturing pattern is used. These problems occur respectively when stress shadow size has not been considered in optimization and fracturing pressure is higher than the available pressure in the sealed section. Therefore, in an optimized hydraulic fracturing,having straight fractures with no deviation or collapse needs consideration of stress shadow effect(SSE).Apart from that, having efficiently propagated fractures to the extent of the reservoir without any fracture trap requires consideration of stress intensity factor(SIF) and aperture. SSE was studied and published by the authors in 2014. For the case of SIF, investigating any change in mode I SIF and aperture with different influencing variables such as fracture geometry and pattern are studied in the current research work. Three different fracturing techniques are assumed as multistage fracturing, simultaneous single-stage fracturing, and simultaneous multistage fracturing techniques. Since obtaining SIF for threedimensional fractures is a challenging issue, a stress ratio technique is used for calculation of SIF ratios of different fracturing scenarios compared to the case of a single fracture. Therefore, changes of SIF for different fracturing schemes are estimated and analyzed to understand whether or not a fracturing scheme is efficient and all the spaced perforations are activated and change to hydraulic fractures.

关 键 词：Hydraulic fracturing Stress intensity factor(SIF) APERTURE Numerical analysis Gas shale 

分 类 号：O3[理学—力学]