Numerical Simulation on Propagation Mechanism of Hydraulic Fracture in Fractured Rockmass

2014 ◽  
Vol 488-489 ◽  
pp. 417-420 ◽  
Author(s):  
Xiao Xi Men ◽  
C.A. Tang ◽  
Zhi Hui Han
Keyword(s):  
Hydraulic Fracturing ◽  
Fracture Initiation ◽  
Coupling Model ◽  
Natural Fracture ◽  
Tensile Fracture ◽  
Propagation Mechanism ◽  
Initiation And Propagation ◽  
Fracturing Process ◽  
Two Factors ◽  
Seepage Characteristics

Hydraulic fracturing process in fractured rockmass which with an existing single natural fracture at its various conditions: its different angles and different lengths was simulated by using RFPA2D(2.0)-Flow version which adopts the finite element method and considers the heterogeneous characteristics of rock in meso-scale, creates seepage-stress-failure coupling model. The effect tendency of natural fractures angle and length on the seepage characteristics of fractured rockmass was given through the description of tensile fracture initiation and propagation in the rock specimens. The simulation results show that the effect of these two factors on fractures initiation, propagation and rockmass stability under the hydraulic fracturing could be remarkable.

scholarly journals A Modeling Study of the Productivity of Horizontal Wells in Hydrocarbon-Bearing Reservoirs: Effects of Fracturing Interference

Geofluids ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-13
Author(s):  
Lei Huang ◽  
Peijia Jiang ◽  
Xuyang Zhao ◽  
Liang Yang ◽  
Jiaying Lin ◽  
...  
Keyword(s):  
Hydraulic Fracturing ◽  
Horizontal Well ◽  
Finite Difference Methods ◽  
Horizontal Wells ◽  
Fracture Initiation ◽  
Design Parameters ◽  
Porous Media Flow ◽  
Propagation Mechanism ◽  
Well Productivity ◽  
Fracturing Process

Commercial production from hydrocarbon-bearing reservoirs with low permeability usually requires the use of horizontal well and hydraulic fracturing for the improvement of the fluid diffusivity in the matrix. The hydraulic fracturing process involves the injection of viscous fluid for fracture initiation and propagation, which alters the poroelastic behaviors in the formation and causes fracturing interference. Previous modeling studies usually focused on the effect of fracturing interference on the multicluster fracture geometry, while the related productivity of horizontal wells is not well studied. This study presents a modeling workflow that utilizes abundant field data including petrophysical, geomechanical, and hydraulic fracturing data. It is used for the quantification of fracturing interference and its correlation with horizontal well productivity. It involves finite element and finite difference methods in the numeralization of the fracture propagation mechanism and porous media flow problems. Planar multistage fractures and their resultant horizontal productivity are quantified through the modeling workflow. Results show that the smaller numbers of clusters per stage, closer stage spacings, and lower fracturing fluid injection rates facilitate even growth of fractures in clusters and stages and reduce fracturing interference. Fracturing modeling results are generally correlated with productivity modeling results, while scenarios with stronger fracturing interference and greater stimulation volume/area can still yield better productivity. This study establishes the quantitative correlation between fracturing interference and horizontal well productivity. It provides insights into the prediction of horizontal well productivity based on fracturing design parameters.

Fracture Initiation and Propagation in a Deep Shale Gas Reservoir Subject to an Alternating-Fluid-Injection Hydraulic-Fracturing Treatment

SPE Journal ◽  
2019 ◽  
Vol 24 (04) ◽  
pp. 1839-1855 ◽  
Author(s):  
Bing Hou ◽  
Zhi Chang ◽  
Weineng Fu ◽  
Yeerfulati Muhadasi ◽  
Mian Chen
Keyword(s):  
Hydraulic Fracturing ◽  
Shale Gas ◽  
Fracture Initiation ◽  
Fluid Injection ◽  
Hydraulic Fractures ◽  
Stress Difference ◽  
Gas Reservoirs ◽  
Complex Fracture ◽  
Initiation And Propagation

Summary Deep shale gas reservoirs are characterized by high in-situ stresses, a high horizontal-stress difference (12 MPa), development of bedding seams and natural fractures, and stronger plasticity than shallow shale. All of these factors hinder the extension of hydraulic fractures and the formation of complex fracture networks. Conventional hydraulic-fracturing techniques (that use a single fluid, such as guar fluid or slickwater) do not account for the initiation and propagation of primary fractures and the formation of secondary fractures induced by the primary fractures. For this reason, we proposed an alternating-fluid-injection hydraulic-fracturing treatment. True triaxial hydraulic-fracturing tests were conducted on shale outcrop specimens excavated from the Shallow Silurian Longmaxi Formation to study the initiation and propagation of hydraulic fractures while the specimens were subjected to an alternating fluid injection with guar fluid and slickwater. The initiation and propagation of fractures in the specimens were monitored using an acoustic-emission (AE) system connected to a visual display. The results revealed that the guar fluid and slickwater each played a different role in hydraulic fracturing. At a high in-situ stress difference, the guar fluid tended to open the transverse fractures, whereas the slickwater tended to activate the bedding planes as a result of the temporary blocking effect of the guar fluid. On the basis of the development of fractures around the initiation point, the initiation patterns were classified into three categories: (1) transverse-fracture initiation, (2) bedding-seam initiation, and (3) natural-fracture initiation. Each of these fracture-initiation patterns had a different propagation mode. The alternating-fluid-injection treatment exploited the advantages of the two fracturing fluids to form a large complex fracture network in deep shale gas reservoirs; therefore, we concluded that this method is an efficient way to enhance the stimulated reservoir volume compared with conventional hydraulic-fracturing technologies.

scholarly journals Numerical Modeling on Hydraulic Fracturing in Coal-Rock Mass for Enhancing Gas Drainage

2018 ◽  
Vol 2018 ◽  
pp. 1-16 ◽  
Author(s):  
Zhigang Yuan ◽  
Yaohua Shao
Keyword(s):  
Mathematical Model ◽  
Rock Mass ◽  
Hydraulic Fracturing ◽  
Gas Flow ◽  
Numerical Solutions ◽  
Fracture Initiation ◽  
Engineering Practice ◽  
Gas Drainage ◽  
Fracturing Process ◽  
Coal Rock

The mechanism of how hydraulic fracturing influences gas drainage in coal-rock mass is still not clear due to its complex mechanism. In this work, statistical distributions are firstly introduced to describe heterogeneity of coal-rock mass; a novel simultaneously coupled mathematical model, which can describe the fully coupled process including seepage-damage coupling during hydraulic fracturing process and subsequent gas flow during gas drainage process, is established; its numerical implementation procedure is coded into a Matlab program to calculate the damage variables, and it partly uses COMSOL solver to obtain numerical solutions of governing equations with damage-flow coupling; the mathematical model and its implementation are validated for initial damage pressure and mode of a single solid model without considering flow-damage coupling, as well as fracture initiation pressure and influence of heterogeneity on damage evolution of hydraulic fracturing considering flow-damage coupling; and finally, based on an engineering practice of hydraulic fracturing with two boreholes, the mechanism of how hydraulic fracturing influences gas drainage is investigated, numerical simulation results indicate that coal-rock mass pore-fissure structure has been improved, and there would exist a gas migration channel with characteristics of higher porosity and lower stresses, which demonstrates significant effects and mechanism of hydraulic fracturing on improving coal-rock permeability and enhancing gas drainage. The research results provide a guide for operation of hydraulic fracturing and optimal layout of gas drainage boreholes.

Hydraulic Fracturing Process: Roles of In Situ Stress and Rock Strength

2012 ◽  
Vol 616-618 ◽  
pp. 435-440
Author(s):  
Yan Jun Feng ◽  
Xiu Wei Shi
Keyword(s):  
Hydraulic Fracturing ◽  
Analytical Model ◽  
Field Experiments ◽  
Rock Strength ◽  
Fracture Initiation ◽  
In Situ Stress ◽  
Experimental Investigations ◽  
Propagation Process ◽  
Fracturing Process

This paper presents results of a comprehensive study involving analytical and field experimental investigations into the factors controlling the hydraulic fracturing process. Analytical theories for fracture initiation of vertical and horizontal borehole are reviewed. The initiation and propagation process of hydraulic fracturing is performed in the field by means of hydraulic fracturing and stepwise hydraulic fracturing, the effect of factors such as in-situ stress and rock strength on fracture propagation process is studied and discussed. The fracture initiation pressures estimated from the analytical model and field experiments are compared as well as the fracturing process during case 1and case 2. Results from the analytical model and field experiments conducted in this study are interpreted with a particular effort to enlighten the factors controlling the hydraulic fracturing process.

scholarly journals Simulation of Hydraulic Fracturing Using Different Mesh Types Based on Zero Thickness Cohesive Element

Processes ◽  
2020 ◽  
Vol 8 (2) ◽  
pp. 189
Author(s):  
Chen ◽  
Li ◽  
Wu ◽  
Kang
Keyword(s):  
Hydraulic Fracturing ◽  
Pore Pressure ◽  
Fractured Reservoirs ◽  
Fracture Initiation ◽  
Fluid Simulation ◽  
Naturally Fractured Reservoirs ◽  
Natural Fracture ◽  
Petroleum Engineering ◽  
Contact Friction ◽  
Triangle Mesh

Hydraulic fracturing is a significant technique in petroleum engineering to enhance the production of shale gas or shale oil reservoir. The process of hydraulic fracturing is extremely complicated, referring to the deformation of solid formation, fluid flowing in the crack channel, and coupling the solid with fluid. Simulation of hydraulic fracturing and understanding the course of the mechanism is still a challenging task. In this study, two hydraulic fracturing models, including the Khristianovic–Geertsma–de Klerk (KGD) problem and the hydraulic fracture (HF) intersection with the natural fracture (NF), based on the zero thickness pore pressure cohesive zone (PPCZ) element with contact friction is established. The element can be embedded into the edges of other elements to simulate the fracture initiation and propagation. However, the mesh type of the elements near the PPCZ element has influences on the accuracy and propagation profile. Three common types of mesh, triangle mesh, quadrangle mesh, and deformed quadrangle mesh, are all investigated in this paper. In addition, the infinite boundary condition (IBC) is also discussed in these models. Simulation indicates that the results of pore pressure for zero toughness regime simulated by the triangle mesh are much lower than any others at the early injection time. Secondly, the problem of hydraulic fracturing should be better used with the infinite boundary element (IBE). Moreover, suggestions for crack intersection on the proper mesh type are also given. The conclusions included in this article can be beneficial to research further naturally fractured reservoirs.

scholarly journals A criterion for identifying a mixed-mode I/II hydraulic fracture crossing a natural fracture in the subsurface

2020 ◽  
Vol 38 (6) ◽  
pp. 2507-2520
Author(s):  
Yijin Zeng ◽  
Wan Cheng ◽  
Xu Zhang ◽  
Bo Xiao
Keyword(s):  
Hydraulic Fracturing ◽  
Hydraulic Fracture ◽  
Mixed Mode ◽  
Petroleum Reservoirs ◽  
In Situ Stress ◽  
Natural Fracture ◽  
Mode I ◽  
Pure Mode ◽  
True Triaxial ◽  
Fracturing Process

Hydraulic fracturing has been proven to be an effective technique for stimulating petroleum reservoirs. During the hydraulic fracturing process, the effects of the natural fracture, perforation orientation, stress reorientation, etc. lead to the production of a non-planar, mixed-mode I/II hydraulic fracture. In this paper, a criterion for a mixed-mode I/II hydraulic fracture crossing a natural fracture was first proposed based on the stress field around the hydraulic and natural fractures. When the compound degree (KII/KI) approaches zero, this criterion can be simplified to identify a pure mode I hydraulic fracture crossing a natural fracture. A series of true triaxial fracturing tests were conducted to investigate the influences of natural fracture occurrence and in situ stress on hydraulic fracture propagation. These experimental results agree with the predictions of the proposed criterion.

scholarly journals A multi-perforation staged fracturing experimental study on hydraulic fracture initiation and propagation

2020 ◽  
Vol 38 (6) ◽  
pp. 2466-2484
Author(s):  
Jianguang Wei ◽  
Saipeng Huang ◽  
Guangwei Hao ◽  
Jiangtao Li ◽  
Xiaofeng Zhou ◽  
...  
Keyword(s):  
Hydraulic Fracturing ◽  
Hydraulic Fracture ◽  
Oil And Gas ◽  
Fracture Initiation ◽  
Fracture Network ◽  
Hydraulic Fractures ◽  
Breakdown Pressure ◽  
Tight Sandstone ◽  
Heterogeneous Samples ◽  
Initiation And Propagation

Hydraulic fracture initiation and propagation are extremely important on deciding the production capacity and are crucial for oil and gas exploration and development. Based on a self-designed system, multi-perforation cluster-staged fracturing in thick tight sandstone reservoir was simulated in the laboratory. Moreover, the technology of staged fracturing during casing completion was achieved by using a preformed perforated wellbore. Three hydraulic fracturing methods, including single-perforation cluster fracturing, multi-perforation cluster conventional fracturing and multi-perforation cluster staged fracturing, were applied and studied, respectively. The results clearly indicate that the hydraulic fractures resulting from single-perforation cluster fracturing are relatively simple, which is difficult to form fracture network. In contrast, multi-perforation cluster-staged fracturing has more probability to produce complex fractures including major fracture and its branched fractures, especially in heterogeneous samples. Furthermore, the propagation direction of hydraulic fractures tends to change in heterogeneous samples, which is more likely to form a multi-directional hydraulic fracture network. The fracture area is greatly increased when the perforation cluster density increases in multi-perforation cluster conventional fracturing and multi-perforation cluster-staged fracturing. Moreover, higher perforation cluster densities and larger stage numbers are beneficial to hydraulic fracture initiation. The breakdown pressure in homogeneous samples is much higher than that in heterogeneous samples during hydraulic fracturing. In addition, the time of first fracture initiation has the trend that the shorter the initiation time is, the higher the breakdown pressure is. The results of this study provide meaningful suggestions for enhancing the production mechanism of multi-perforation cluster staged fracturing.

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