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| 1 | Evolution of a mining induced fracture network in the overburden strata of an inclined coal seam显示文摘The geological conditions of the Pingdingshan coal mining group were used to construct a physical model used to study the distribution and evolution of mining induced cracks in the overburden strata.Digital graphics technology and fractal theory are introduced to characterize the distribution and growth of the mining induced fractures in the overburden strata of an inclined coal seam.A relationship between fractal dimension of the fracture network and the pressure in the overburden strata is suggested.Mining induced fractures spread dynamically to the mining face and up into the roof as the length of advance increases.Moreover,the fractal dimension of the fracture network increases with increased mining length,in general,but decreases during a period from overburden strata separation until the main roof collapses.It is a1so shown that overburden strata pressure plays an important role in the evolution of mining induced fractures and that the fractal dimension of the fractures increases with the pressure of the overburden. | Wei Xiujun Gao Mingzhong Lv Youchang Shi Xiangchao Gao Hailian Zhou Hongwei | 2012 | International Journal of Mining Science and Technology2012，22，6： | 7 |
| 2 | Effects of inhibitor KCl on shale expansibility and mechanical properties显示文摘The expansibility and mechanical properties of shale are significantly influenced by water-based muds(WBMs);thus,it is necessary to mitigate this effect to avoid borehole instabilities in drilling operation.Potassium chloride(KCl)is usually used as inhibitor to reduce hydration of shales.In this study,we investigated the inhibitory efficiency of KCl on shale through a series of experiments,including dynamic linear swelling(DLS)tests and uniaxial compressive strength(UCS)tests,to provide reference for the design of WBMs.These tests were conducted on shale samples soaked in KCl solution for 24,48,72,and 96 h with saline concentrations of 0%,2%,4%,6%,and 8%.Experimental results show that samples with microcracks and bedding fissures have the highest swelling increase and the largest strength reduction after immersion in solution.The swelling potential decreased with increasing KCl concentration.In addition,KCl exhibited a certain inhibitory effect on the weakening of the mechanical properties of samples.An increase in the KCl concentration increases the compressive strength and elastic modulus,and decreases the Poisson's ratio.However,in terms of homogeneous samples,the UCS test results show that exposure to water is weakly related to weakening of the mechanical properties of shale samples.We found that immersing the shale in KCl solution for a longer time decreases the compressive strength,increases the Poisson's ratio,and decreases the elastic modulus. | Xiangchao Shi Lei Wang Jianhua Guo Qiang Su Xiao Zhuo | 2019 | Petroleum2019，5，4： | 2 |
| 3 | Wellbore stability analysis of layered shale based on the modified Mogi-Coulomb criterion显示文摘Borehole instability was frequently encountered during shale gas drilling.Most conventional models are not applicable to layered formation's wellbore stability analysis on account of anisotropic strength characteristic.In this study,an empirical equation for predicting anisotropic strength was implemented in the Mogi–Coulomb criterion to describe variations of cohesive strength and friction angle of shale formations.A collapse pressure model and its appropriate solution method for layered shale formations were proposed.The impact of different strength criteria and rock anisotropy type on rock strength and collapse pressure was investigated.The analysis indicated that the predicted strength of our modified criterion was usually higher than the weak plane failure criteria.The collapse pressure calculated by the modified Mogi–Coulomb criterion was lower than the weakplane failure criteria.Furthermore,it was more consistent with real mud weight.Additionally,the anisotropy type of rock notably influences wellbore stability.More significant anisotropy coefficients correspond to higher strengths,which results in smaller collapse pressure values.Improper anisotropy coefficients can over-or underpredict the collapse pressure.Reasonable estimates of collapse pressure of anisotropic rocks can be made through the modified Mogi–Coulomb criterion using limited experimental data and the anisotropy rock type. | Xu Yang Xiangchao Shi Yingfeng Meng Xiaoyong Xie | 2020 | Petroleum2020，6，3： | 1 |
| 4 | Confined compressive strength model of rock for drilling optimization显示文摘The confined compressive strength(CCS)plays a vital role in drilling optimization.On the basis of Jizba's experimental results,a new CCS model considering the effects of the porosity and nonlinear characteristics with increasing confining pressure has been developed.Because the confining pressure plays a fundamental role in determining the CCS of bottom-hole rock and because the theory of Terzaghi's effective stress principle is founded upon soil mechanics,which is not suitable for calculating the confining pressure in rock mechanics,the double effective stress theory,which treats the porosity as a weighting factor of the formation pore pressure,is adopted in this study.The new CCS model combined with the mechanical specific energy equation is employed to optimize the drilling parameters in two practical wells located in Sichuan basin,China,and the calculated results show that they can be used to identify the inefficient drilling situations of underbalanced drilling(UBD)and overbalanced drilling(OBD). | Xiangchao Shi Yingfeng Meng Gao Li a Jiaxue Li Zuwen Tao Shandong Wei | 2015 | Petroleum2015，1，1： | 1 |
| 5 | The Mechanism of TBM Cutter Wear in Mixed Ground 显示文摘 | GAO Mingzhong LI Chao SHI Xiangchao | 2012 | Advanced Materials Research2012，446，： | 1 |
| 6 | Effects of a polyamine inhibitor on the microstructure and macromechanical properties of hydrated shale显示文摘China is rich in shale gas resources,however,wellbores in shale gas reservoirs are frequently unstable.This has a serious impact on the shale gas drilling cycle.Polyamine,a common additive in water-based shale drilling fluids,can effectively inhibit shale hydration.However,there is a lack of quantitative research on the effect of polyamine inhibitors on the microstructure and macromechanical properties of shale.Therefore,this study investigated those issues via a systematic hydration experiment carried out on shale from the Longmaxi Formation.The results show that microfractures are created and expand during shale hydration,that they also connect to form a complex microfracture network,and that 3%polyamine inhibitors(polyamine solution with volume fraction of 3%)can effectively inhibit their evolution.The ultrasonic velocities and UCS of the Longmaxi shale are significantly anisotropic;the former first increases and then decreases with the laminae angle,reaching its maximum when the laminae angle is 30°.The UCS of the shale is highest and lowest,respectively,when the laminae angles are 0°or 90°and 30°.In general,these UCS appear as a'U'pattern,high on two sides with a dip in the center.Polyamines can effectively inhibit both the expansion of shale and the reduction of P-wave and S-wave velocities,the UCS,and elastic modulus.The UCS of a shale sample was reduced by 28%e40%after immersion for 96 h in water,compared to 2%e20%after immersion in a 3%polyamine inhibitor for the same amount of time.The inhibiting effect of the polyamine was remarkable. | Yunlei Hu Xiangchao Shi Qingling Li Leiyu Gao Feng Wu Gang Xie | 2022 | Petroleum2022，8，4： | 0 |
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