The onshore oil and natural gas industries of China have started a large-scale development when crude oil reserves have been difficult to recover. The stratum Fracture modification is an indispensable measure to efficiently develop oil and gas fields. Hydraulic fracturing is the most important reservoir stimulation technique, but it is still faced with various problems such as the failure to Fracture the target reservoir, long fracturing duration, and short efficient length of the Fracture. High Energy Gas Fracturing (HEGF) can easily break down the high-Fracture-pressure oil reservoir and generate multiple Fractures free of in-situ stress. Moreover, HEGF entails no large-scale devices, and this method is strongly adaptable to the environment without causing environmental pollution. After combining the two technologies (HEGF and the other), then they can complement each other with their strengths. That is, both of them decrease the Fracture initiation pressure of (or caused by) hydraulic fracturing on the one hand, and to extend, gather, and support multiple radial Fractures of gas fracturing on the other hand. Thus, a Fracture zone with a large radius is finally formed, and the percolating resistance of the fluid is significantly decreased. Moreover, in this study, a Dynamic model related to the drainage flow of the perforated holes in a gas well, fluid pressure distribution in the Fracture, fluid seepage on the Fracture wall, Fracture initiation criterion, and Fracture Propagation velocity during the HEGF process has been presented. Consequently, a gas/liquid/solid coupling Fracture Dynamic Propagation model during the HEGF process can be built to provide a theoretical basis for the accurate simulation of the Fracture form changes during this process.

In this work, we used a grain-based numerical model based on the concept of lattice. The modelling was done to simulate the lab experiments carried out on the mortar samples. Also the analytical solutions corresponding to the viscosity-dominated regime were used to estimate the Fracture length and width, and the results obtained were compared with the numerical simulations. As the analytical solutions are proposed for a penny-shaped Fracture with no presence of any obstacle such as natural interfaces, in this work, we presented the results of lattice simulations for hydraulic fracturing in the cement sample, similar to the lab, but with no natural Fractures, and compared the results obtained with analytical solutions. The results indicated that in the case of a continuous medium, the analytical solutions may present a reasonable estimation of the Fracture geometry. Also the viscosity-dominated leak-off model showed a better match between the analytical solutions and the numerical simulation results, confirmed by observing fluid loss into the sample in the lab post-experiment. In the case of assuming leak-off, the results indicated that the Fracture width and length would reduce. However, it should be noted that in real cases, rock formations exhibit Fractures and inhomogeneity at different scales so that the applications of the analytical solutions are limited.

In this article, we studied the Dynamic Fracture process of Bam earthquake. In two presented models stress heterogeneity on the fault plain was modeled as barrier or asperity and friction included as slip-weakening relationship. Results of models were constrained by near field ground motion recorded in Bam station. In the first model, Fracture starts form a weak asperity which its waves surround the neighbor barrier and break it down. In the second model, another asperity is included in southern part of the fault. Breaking barrier releases two Fracture fronts traveling in two different regimes. One of them travels faster than shear waves and goes to the intersonic velocity. The other front travels with 0.74 shear wave velocity and makes the largest pulse of the record. Both models predict the slip rate successfully, but the second model is more consistent with the real data.

A pipeline is considered as shell structure so its design is based on stability concepts; due to the exerted high pressure, local instability is probable to occur and so prevention of its occurrence and Propagation are important subjects in its design. In this paper, Dynamic buckle Propagation has been modeled by 3D finite element method, results are verified with experimental tests and velocity of Dynamic buckle Propagation is calculated for pipes with different diameter to thickness ratios. Due to the effect of velocity in designing of marine pipelines, separate relations based on the initiation pressure are derived for the velocity of Propagation and the influence of diameter to thickness ratio on the Propagation velocity is studied.

In this study, a series of laboratory tests using a real Tri-axial Hydraulic Fracture System were performed to investigate the mechanism of Fracture initiation and Propagation on the cement blocks in different reservoirs in normal and tectonic stress regimes. The influences of crustal stress field, confining pressure, and natural Fractures on the Fracture initiation and Propagation were discussed. Experimental results demonstrate that stress concentration around the hole would significantly increase the Fracture pressure of the rock. At the same time, natural Fractures in the borehole wall would eliminate the stress concentration, which leads to a decrease about two thirds in the Fracture initiation pressure. Two interaction types between induced Fractures with pre-Fracture were observed including crossing and opening the pre-existing Fracture. In a normal stress regime, hydraulic Fracture crossed the pre-Fracture. But in tectonically stressed or shallow reservoirs, due to high interaction between hydraulic and natural Fractures, hydraulic Fracture was arrested by opening of the pre-Fracture.

In many cases some barriers like low permeability, secondary porosity and decreasing in formation permeability due to damages casued by drilling, asphaltene and other problems confine oil production rate in unacceptable region and These problems reduce percentage of oil recovery from these reservoirs, These problems can be solved by utilizing hydraulic Fracture method. A new model based on cohesive zone method coupling stress-seepage damage filed is developed to simulate the interaction between hydraulic Fracture and natural Fracture with using ABAQUS software. The effect of differential stress and approaching angle on the intersection between hydraulic Fracture and natural Fracture, as well as the effect of natural Fracture cementing strength on the geometry of  hydraulic Fracture Propagation, have been investigated. While the hydraulic Fracture initiates, propagates, and intersects with the natural Fracture, it can either deflect into it or cross it by severing the natural Fracture. The greater the approaching angle and differential stress , the easier it is for the hydraulic Fracture to cross the natural Fracture.The behavior of hydraulic Fracture changes from deflection to crossing as the natural Fracture cementing strength is increased.

In the process of hydraulic Fracture, various physical parameters such as; viscosity, inertia of fluid and toughness of rock do not influence the Fracture Propagation identically, and it is probable that one or more of the parameters be more pronounced. Therefore, it may persuade one special regime which is named base on dissipation of energy. In an impermeable rock, the two limiting regimes can be identified with the dominance of one or the other of the two energy dissipation mechanisms corresponding to extending the Fracture in the rock and to flow of viscous fluid in the Fracture, respectively. In the viscosity-dominated regime, dissipation in extending the Fracture in the rock is negligible compared to the dissipation in the viscous fluid flow, and in the toughness-dominated regime, the opposite holds. Here, it is supposed that the flow of incompressible fluid in the Fracture is unidirectional and laminar. Besides, the Fracture is fully fluid-filled at all times and Fracture Propagation is described in the framework of linear elastic Fracture mechanics (LEFM). In this paper, a new semi-analytical method has been introduced for solving the plane-strain fluid-driven Fracture propagating in an impermeable medium in viscosity-toughness dominated (the MK-edge solution). Standard methods of analysis and improvement of diverging series have been applied on the expansion series method to gain the more convergence for the viscosity series diverge due to a nearest (non-physical) singularity on the negative real axis of the viscosity parameter for larger viscosity. For more explanation, Euler transformations have been suggested in terms of small parameter which is a function of viscosity parameter. Compared to the other analytical solution (e. g. Garagash, 2006), the new M-K edge solution represents a significant improvement in term of convergence. In addition to, the results have been compared to the numerical solution (e. g. Adachi, 2000) and it is shown good agreement in the light of quantity and quality. Contrary to numerical methods, the new proposed method can pragmatically be used for the range of M-K edge.

Statement of Problem: In a previous study it was reported that a durable resin-ceramic tensile bond could be obtained by an appropriate silane application without the need for HF acid etching the ceramic surface. Evaluation of the appropriate application of silane by other test methods seems to be necessary.Purpose: The purpose of this study was to compare the interfacial Fracture toughness of smooth and roughened ceramic surfaces bonded with a luting resin.Materials and Methods: Ceramic discs of 10 mm in diameter and 2 mm in thickness were prepared.Four different surface preparations (n=10) were carried out consisting of (1) ceramic surface polished to a 1µm finish, (2) gritblasted with 50µm alumina, (3) etched with 10% HF for 2 min, and (4) gritblasted and etched. The ceramic discs were then embedded in PMMA resin. For the adhesive area, the discs were masked with Teflon tapes. A circular hole with diameter of 3 mm and chevron-shaped with a 90° angle was punched into a piece of Teflon tape. The exposed ceramic surfaces were treated by an optimised silane treatment followed by an unfilled resin and then a luting resin cylinder of 4mm in diameter and 11 mm in length was built. Specimens were stored in two different storage conditions: (A): Distilled water at 37°C for 24 hours and (B): Distilled water at 37°C for 30 days. The interfacial Fracture toughness (GIC) was measured at a cross-head speed of 1 mm/min. The mode of failure was examined under a stereo-zoom microscope and Fracture surfaces were examined under Scanning Electron Microscope.Results: The mean interfacial Fracture toughness values were; Group A: 1) 317.1±114.8, 2) 304.5±109.2, 3) 364.5±169.8, and 4) 379.4±127.8 J/m2±SD. Group B: 1) 255.6±134.4, 2) 648.0±185.1, 3) 629.3±182.6 and 4) 639.9 ±489.0 J/m2±SD. One way Analysis of Variance showed that there was no statistically significant difference in the mean interfacial Fracture toughness for groups A1-A4 (P>0.05). However, the mean interfacial Fracture toughness for group B1 was significantly different from that for groups B2, B3 and B4 (P<0.05). Independent-ٍٍٍSamples T-Test results showed that there was a significant increase in the GIC mean value for groups B2 and B3 after 30 days water storage (P<0.05). The modes of failure were predominantly interfacial or cohesive within the resin.Conclusions: The Fracture toughness test method used in this study would be appropriate for analysis of the adhesive zone of resin-ceramic systems. From the results, it can be concluded that micro-mechanical retention by gritblasting the ceramic surfaces could be sufficient with no need for HF acid etching the ceramic surfaces when an appropriate silane application procedure is used.

In this study, a series of laboratory tests using a hydraulic fracturing system were conducted to examine the behavior of an induced hydraulic Fracture as it approached a cemented natural Fracture. To achieve this, sheet-like test specimens were cast with natural Fractures of varied mechanical properties, thickness, and relative position to a fluid injection port. A tendency for the induced hydraulic Fracture was shown to cross thick natural Fractures filled with softer materials than the host rock and to be diverted by thick natural Fractures with harder filling materials. The induced hydraulic Fracture also tends to cross hard natural Fractures when the natural Fractures are relatively thin. In addition, the induced hydraulic Fracture from the injection port was shown to be diverted by a thin, hard natural Fracture that was placed relatively close to the injection port but crosses the same natural Fracture when placed farther away from the injection port. Finally, the results provide a novel evidence of the impact of natural Fracture filling materials on the outcome of hydraulic Fracture Propagation at its interaction with natural Fractures.