Numerical analysis of the material parameter effects on the initiation of hydraulic fracture in a near wellbore region

Abstract

Please cite this article as: Li, Q., Xing, H., Numerical analysis of the material parameter effects on the initiation of hydraulic fracture in a near wellbore region, Journal of Natural Gas Science & Engineering (2015), doi: 10.1016/j.jngse.2015 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. Abstract: Hydraulic fracturing is recognized as a key method to enhance unconventional reservoirs, but it is also quite complicated and challenging due to so many affecting factors such as the formation material parameters, fluid behaviors and geological setting/conditions. However, in unconventional reservoirs, in the near wellbore region, the rock may consist of different materials, and the stress is redistributed during drilling and fracturing process, so the preferable hydraulic fracture path is hard to predict. This paper aims to study the effects of formation material parameters, including drilling effects, on the hydraulic fracturing process in unconventional reservoirs. First, hydraulic fracturing has been simulated in nine cases with different parameters specifically permeability, porosity, Young's modulus, and Poisson's ratio. Then hydraulic fracturing has been studied by a heterogeneous model with multiple zones and layers, and complex stress condition. It is found that under a constant hydraulic pressure boundary, when the values of permeability, porosity, Young's modulus, and Poisson's ratio are higher, hydraulic fracturing initiates earlier; with a heterogeneous distribution of materials, stress concentration is formed between different materials, and the tensile stress concentrated areas become the preferable paths of hydraulic fracturing. M A N U S C R I P T A C C E P T E D ACCEPTED MANUSCRIPT

Numerical modelling of acoustic stimulation induced mechanical vibration enhancing coal permeability

“…CSG widely exists in pores and fractures/cleats of coal in adsorption state but is difficult to exploit due to the low permeability of coal reservoirs. Therefore, enhancing the permeability and desorption rate of coal are critical for improvement of CSG extraction amount (Gandossi 2013;Li et al, 2015). Many methods such as hydraulic fracturing, high-pressure water jet and blasting vibration (Shen et al, 2012;Li et al, 2009;Shimizu et al, 2011;Li and Xing 2015), have been tested and applied to achieve these goals.…”

“…Therefore, enhancing the permeability and desorption rate of coal are critical for improvement of CSG extraction amount (Gandossi 2013;Li et al, 2015). Many methods such as hydraulic fracturing, high-pressure water jet and blasting vibration (Shen et al, 2012;Li et al, 2009;Shimizu et al, 2011;Li and Xing 2015), have been tested and applied to achieve these goals. The desorption rate and permeability of CSG can also be significantly increased by physical stimulation through changing the thermal field, stress field, electrical and magnetic field (Pan et al, 2012;Azmi et al, 2006;Hol et al, 2011;Charriére et al,2010;Liu et al, 2006) and their coupling effects.…”

Numerical simulation of acoustic stimulation for enhancing coal seam gas reservoir permeability

“…Many methods such as hydraulic fracturing, high-pressure water jet and blasting vibration (Li et al, 2009;Shen et al, 2012;Li and Xing, 2015;Shao and Pyrak-Nolte, 2016), have been tested and applied to achieve these goals. The desorption rate and permeability of CSG can also be significantly increased by physical stimulation through changing the thermal field (Azmi et al, 2006;Charrié re and Pokryszka, 2010;Pan et al, 2012), stress field (Hol et al, 2011), electrical and magnetic field (Liu et al, 2006) and their coupling effects.…”

“…Therefore, enhancing the permeability and desorption rate of coal are critical for improvement of CSG extraction amount (Gandossi, 2013). Many methods such as hydraulic fracturing (Li and Xing, 2015), hydraulic slotting (Shen et al, 2012) and blasting vibration (Li et al, 2009), have been tested and applied to achieve these goals. The desorption rate and permeability of CSG can also be significantly increased by physical stimulation through changing the thermal field (Azmi et al,2006), stress field (Hol et al, 2011), electrical and magnetic field (Liu et al, 2006) and their coupling effects.…”

“…Therefore, enhancing the permeability and desorption rate of coal reservoirs are critical for improvement of CSG extraction amount (Gandossi, 2013). Traditional enhancing methods such as hydraulic fracturing (Li and Xing, 2015), which design hard formation reservoir like sandstone, cannot be well applied to coal reservoir. Coal medium has special properties like high-density fracture/cleat with strong heterogeneity and relatively lower density; the special features of coal cleat structure need to be fully taken into consideration to improve the designation of new enhancement technology.…”