Numerical study on hydraulic fracturing in different types of georeservoirs with consideration of H2M-coupled leak-off effects

With the increase in the world’s energy consumption and the change in climate, unconventional energy resources become more and more popular. Since geological formations of low or ultra-low permeability are usually involved, hydraulic fracturing is one of the most important tools for their exploitation. The objective of this paper is to investigate hydraulic fracturing and its hydro-mechanical influences on different types of georeservoirs, including tight gas, oil, and geothermal reservoirs. Based on the previous work of hydraulic fracturing simulation with FLAC3Dplus, the multi-phase multi-component flow simulator TOUGH2MP is coupled for the numerical study. A new coupling approach is designed with special consideration of the H2M-coupled process in different types of georeservoirs. For the simulation, a generic 3D ¼ model (200 × 300 × 200 m, consisting of 50 m caprock, 100 m reservoir formation, and 50 m base rock) is adopted. The simulations are run under comparable reservoir and operative conditions. The results show that fracture propagation and proppant concentration are comparable with a short period of slurry injection (80 min × 6 m3/min). The fracturing fluid does not penetrate deep into the formation. Due to the high compressibility of gas, the induced pore pressure is much lower than that in oil and geothermal reservoirs, although the final leak-off ratio is comparable. The hydraulic fracturing causes stress reorientation in georeservoirs. According to the criterion of 5° stress reorientation, the minimum fracture spacing for a multiple fracture system in the assumed geothermal reservoir is 73 m, while that in an oil and gas reservoir is 66 and 60 m, respectively. This work expands on the numerical simulator as well as the understanding of hydraulic fracturing in unconventional georeservoirs. The results of this study can be used further to optimize the fracture spacing in a multiple hydraulic fracture system in different reservoir types.

[1]  K. Kobe.  The properties of gases and liquids , 1959 .

[2]  Yang Gou,et al.  Numerical investigation of a low-efficient hydraulic fracturing operation in a tight gas reservoir in the North German Basin , 2014 .

[3]  Yong Wang,et al.  3D Reservoir Geomechanics Workflow and Its Application to a Tight Gas Reservoir in Western China , 2013 .

[4]  Lei Zhou,et al.  A new numerical 3D-model for simulation of hydraulic fracturing in consideration of hydro-mechanical coupling effects , 2013 .

[5]  C. Tsang,et al.  A study of caprock hydromechanical changes associated with CO2-injection into a brine formation , 2002 .

[6]  Yueming Cheng.  Boundary Element Analysis of the Stress Distribution Around Multiple Fractures: Implications for the Spacing of Perforation Clusters of Hydraulically Fractured Horizontal Wells , 2009 .

[7]  EGS Designs with Horizontal Wells , Multiple Stages , and Proppant , 2014 .

[8]  Dennis Denney,et al.  Thirty Years of Gas-Shale Fracturing: What Have We Learned? , 2010 .

[9]  Olubunmi O. Owolabi,et al.  Can Shale-Like Stimulations Unlock the Potential of Extremely Low Permeability Tight Gas Reservoirs? , 2013 .

[10]  Terry Palisch,et al.  Hydraulic Fracture Optimization in Unconventional Reservoirs , 2013 .

[11]  Deepak Tapriyal,et al.  Prediction of hydrocarbon densities at extreme conditions using volume-translated SRK and PR equations of state fit to high temperature, high pressure PVT data , 2012 .

[12]  Jennifer L. Miskimins,et al.  Optimization of Hydraulic Fracture Spacing in Unconventional Shales , 2012 .

[13]  Mark A. McHugh,et al.  Equation of state modeling of high-pressure, high-temperature hydrocarbon density data , 2010 .

[14]  J. Olson,et al.  Simultaneous Multifracture Treatments: Fully Coupled Fluid Flow and Fracture Mechanics for Horizontal Wells , 2015 .

[16]  Charles E. Brown.  World Energy Resources , 2011 .

[17]  Gudmundur S. Bodvarsson,et al.  A modeling approach for analysis of coupled multiphase fluid flow, heat transfer, and deformation in fractured porous rock , 2002 .

[18]  K. Schetelig,et al.  Hydraulic fracturing in unconventional gas reservoirs: risks in the geological system part 1 , 2013, Environmental Earth Sciences.

[19]  S. Finsterle,et al.  T2VOC user`s guide , 1995 .

[20]  K. Pruess,et al.  TOUGH2 User's Guide Version 2 , 1999 .

[21]  Mohamed Y. Soliman,et al.  Geomechanics Aspects of Multiple Fracturing of Horizontal and Vertical Wells , 2008 .

[22]  George J. Moridis,et al.  EOS7C Version 1.0 TOUGH2 Module for Carbon Dioxide or Nitrogen in Natural Gas , 2008 .

[23]  Rainer Helmig,et al.  Hydraulic fracturing in unconventional gas reservoirs: risks in the geological system, part 2 , 2013, Environmental Earth Sciences.

[24]  Karsten Pruess,et al.  User's Guide for TOUGH2-MP - A Massively Parallel Version of the TOUGH2 Code , 2008 .

[25]  M. B. Geilikman,et al.  Interaction of Multiple Hydraulic Fractures in Horizontal Wells , 2013 .

[26]  Mukul M. Sharma,et al.  Optimizing Fracture Spacing and Sequencing in Horizontal-Well Fracturing , 2011 .