Hole cleaning evaluation and installation spacing optimization of cuttings bed remover in extended-reach drilling

In extended-reach or long-horizontal drilling,cuttings usually deposit at the bottom of the annulus.Once cuttings accumulate to a certain thickness,complex problems such as excessive torque and drag,tubing buckling,and pipe stuck probably occur,which results in a lot of non-productive time and remedial operations.Cuttings bed remover can efficiently destroy deposited cuttings in time through hydraulic and mechanical stirring effects.This paper aims to build a method for hole cleaning evaluation and installation spacing optimization of cuttings bed remover to improve the wellbore cleaning effect.Firstly,a Computational Fluid Dynamics approach with Eulerian—Eulerian multiphase model was utilized to investigate the mechanism of cuttings transportation,and a new type of cuttings bed remover was designed.Next,an evaluation method of hole cleaning effect of remover was established.After that,the effects of several drilling parameters on hole cleaning including flow rate of drilling fluid,rotational speed of drillpipe,rate of penetration,wellbore size,rheological property of drilling fluid,and remover eccentricity on the performance of cuttings bed remover were investigated.The results demonstrate that the new type of remover with streamline blade performs better than conventional removers.The efficiency of hole cleaning is greatly improved by increasing the rotational speed of drillpipe,flow rate of drilling fluid,remover eccentricity,and 6 rpm Fann dial reading for drilling fluid.While higher rate of penetration and large wellbore size result in worse hole cleaning.These findings can serve as an important guide for the structure optimization design of cuttings bed remover and installation spacing of removers.

Theoretical and numerical simulation investigation of deep hole dispersed charge cut blasting

Drilling and blasting methods have been used as a common driving technique for shallow-hole driving and blasting in rock roadways.With the advent of digital electronic detonators and the need for increased production efciency,the traditional blasting design is no longer suitable for deep hole blasting.In this paper,a disperse charge cut blasting method was proposed to address the issues of low excavation depth and high block rate in deep hole undercut blasting.First,a blasting model was used to illustrate the mechanism of the deep hole dispersive charge cut blasting process.Then,continuous charge and dispersed charge blasting models were developed using the smooth particle hydrodynamics-fnite element method(SPHFEM).The cutting parameters were determined theoretically,and the cutting efciency was introduced to evaluate the cutting efect.The blasting efects of the two charging models were analyzed utilizing the evolution law of rock damage,the number of rock particles thrown,and the cutting efciency.The results show that using a dispersed charge improves the cutting efciency by about 20%and the rock breakage for the deep hole cut blasting compared to the traditional continuous charge.In addition,important parameters such as cutting hole spacing,cutting hole depth and upper charge proportion also have a signifcant impact on the cutting efect.Finally,the deep hole dispersed charge cut blasting technology is combined with the digital electronic detonator through the feld engineering practice.It provides a reference for the subsequent deep hole cutting blasting and the use of electronic detonators in rock roadways.

Experimental Study Optimizing Hole Cleaning-Cuttings Transport in Oil Drilling Engineering

With a clear understanding of the drilling fluid techniques and the cutting taking mechanism, a new advanced model is set up for analyzing field data and quantitative forecast of cutting taking mechanism. Therefore, a number of values affecting the drilling rate and the hole cleaning are studied over a wide range of parameters. Drilling data obtained under high borehole pressure conditions are analyzed to determine the causes of the reduction in rate of penetration (ROP) as the borehole pressure increases, which in some cases is caused by the buildup of rock debris under the bit. The theoretical achievement and testing conclusions can be very instructional for horizontal well drilling. Much higher annular velocities are required for effective hole cleaning in directional wells than in vertical wells. High viscosity muds are observed to provide better transport than low viscosity muds.

Endoscopic ultrasound-guided cutting of holes and deep biopsy for diagnosis of gastric infiltrative tumors and gastrointestinal submucosal tumors using a novel vertical diathermic loop

AIM To report on a more accurate diagnostic possibility offered by endoscopic ultrasound-guided cutting of holes and deep biopsy (EUS-CHDB) for pathologic diagnosis of gastric infiltrative tumors and gastrointestinal submucosal tumors. METHODS Ten consecutive patients who were suspected of having gastric invasive tumors or gastrointestinal submucosal tumors underwent EUS-CHDB with a novel vertical diathermic loop. We reviewed their medical data and analysed the effectiveness and safety of this new method. The final diagnosis was based on the surgical pathology or clinical/imaging follow-up. RESULTS EUS-CHDB was performed successfully in all the ten patients. Neither severe haemorrhage nor perforation occurred in any patient. Among the ten patients, there were three cases of gastric linitis plastica, one case of gastric lymphoma, five cases of gastrointestinal stromal tumors (GISTs), and only one case of chronic non-atrophic gastritis. That is, nine (90%) of the cases CONCLUSION EUS-CHDB may be a technically feasible and safe option for patients with gastric infiltrative tumors or gastrointestinal submucosal tumors. EUS-CHDB may be used as a remedial or even preferred biopsy method for submucosal lesions.

Numerical simulation of parallel hole cut blasting with uncharged holes

The cavity formation and propagation process of stress wave from parallel hole cut blasting was simulated with ANSYS/LS-DYNA 3D nonlinear dynamic finite element software. The distribution of element plastic strain, node velocity, node time-acceleration history and the blasting cartridge volume ratio during the process were analyzed. It was found that the detonation of charged holes would cause the interaction of stress wave with the wall of uncharged holes. Initial rock cracking and displacement to neighboring uncharged holes become the main mechanism of cavity formation in early stage.2008 University of Science and Technology Beijing. All rights reserved.

Mechanism and practice of rock control in deep large span cut holes

Deep large span cut holes are difficult to stabilize. The 7801 cut hole in the Lu'an Wuyang Mine was used as this project's background. The main factors affecting large span cut hole stability are analyzed. Pre- stressed bolting theory was used to design a roof control method for a large span roadway. By reducing the span and applying equal strength coordinated supports the rock could be stabilized. The control prin- ciples and methods are given herein along with the analysis. A double micro arch cross section roadway is defined and its use in solving the current problem is described. Beam arch theory was used to build a model of the double micro arch cross section roadway. A support reverse force model for the arch foot intersection was also derived. A support method based upon reducing the width of the large span in the cut hole is presented. These results show that the reduced span of the roadway roof plus the use of cable anchors and single supports gives an effective way to control the large span cut hole. On site monitoring showed that the reduced span support from the double micro arch cross section roadway design had a significant effect. The roadway surface displacement was small and harmful deformation of the cut hole was effectively controlled. This will ensure its long term stability.

Experimental research on characteristics of hole reaming and side cutting of one-cone bits

The hole reaming and side cutting characteristics of offset one-cone bit and conventional one- cone bit were investigated on simulated drilling experimental equipment. The borehole diameter was a little larger than the bit diameter due to side force. However, the reaming effect was not very apparent, whether drilling with an offset or conventional one-cone bit. The side cutting displacement increased gradually with increasing depth of drilling and side force. The side cutting displacement of offset onecone bits was larger than that of conventional ones under the same conditions of weight-on-bit （WOB）, rotary speed, side force and borehole depth.

Influence of delay interval on blasting efficiency of parallel hole cuts with an empty hole

Time interval of short delay ignition is an important factor to affect theefficiency of blasting cuts. The motion process of rock pieces in the cut cavity is analyzed, amechanical model to calculate the delay time of parallel hole cuts is presented for tunnel blasting,and a theoretical method to determine the volume ratio (the clearage rate) of the rock pieceswithin the cut cavity at different moments is proposed for the blasting cut with an empty hole.Numerical analysis results show that the optimal delay interval is proportional to the boreholedepth. The suggested results are of practical value to the optimal design of the delay interval inmillisecond blasting related to the parallel hole cuts with an empty hole.

Cuttings transport: Back reaming analysis based on a coupled layering-sliding mesh method via CFD

Inadequate hole cleaning is one of the main reasons for inefficient operations in extended-reach drilling.The mechanism of cuttings transport under the back reaming operation,which is frequently adopted to remove the cuttings,has been investigated in this study.To this end,a coupled layering-sliding mesh method with the Eulerian-Granular approach has been established innovatively.The dynamic layering method has been employed to simulate the axial motion of the pipe,whereas the sliding mesh method has been used to simulate the pipe rotation.The back reaming operation of a connector-furnished pipe has been simulated,and the sensitive parameter analysis has been conducted.The results thus obtained demonstrate that the increase in the initial bed height,inclination,and the diameter and length of the connector causes a significant increase in the cuttings concentration.In addition,the cuttings concentration is observed to decrease significantly with the pipe rotation speed.Furthermore,two main factors contribute towards the cuttings accumulation around the connector,namely,the difference in the cross-sectional area and the pushing effect of the connector—like a“bulldozer”.The“bulldozer”effect of the connector dominates when the tripping velocity is significant compared to the velocity of the cuttings.Conversely,the effect of the difference in the cross-sectional area becomes the leading factor for cuttings accumulation.The“bulldozer”effect of the connector causes a more severe impact on hole cleaning.In both cases,increasing the tripping velocity only mildly affects the cuttings concentration.It is therefore suggested that the tripping velocity should be slower than that of the sand during the back reaming operation.Furthermore,increased fluid velocity might lead to a higher accumulated cuttings concentration around the connector when the cuttings bed has not entirely passed through the connector.A significant flow rate can be safely applied after the cuttings have passed through the connector furnished with a large diameter,such as the bottom hole assembly.This exploration serves as an essential guide to predicting and controlling tight spots while back reaming.

Fatigue Behavior of Open-Holed CFRP Laminates with Initially Cut Fibers

Carbon fiber-reinforced plastic (CFRP) laminates with initially cut fibers (ICFs) have good formability without large degradation of static strength;however, their fatigue behavior has not been investigated thus far. In this paper, we investigated fatigue behavior and damage progress of open-holed CFRP laminates with ICFs having interlayers. Three types of CFRP laminates were employed: a laminate without ICF fabricated using an autoclave (Continuous-A), a laminate with ICF fabricated using an autoclave (ICF-A) and a laminate with ICF fabricated using press molding (ICF-P). First, fatigue test was conducted to obtain S (maximum stress)-N (the number of cycles to failure) curves in order to reveal fatigue strength. The fatigue tests for several specimens were interrupted at three prescribed numbers of cycles to observe damage progress. It is found that the Continuous-A laminate shows little strength degradation in the S-N curve while fatigue strength in both ICF laminates is decreased by approximately 30% at N of 106. In contrast, the damage progress of the ICF-P laminate is the least among the three laminates while the delamination progress at both edges and around the hole in the Continuous-A laminate is the most prominent.

沿空留巷密集钻孔切顶机理及关键参数确定方法

为实现密集钻孔切顶条件下沿空留巷顶板结构安全稳定,研究正常情况与密集钻孔条件下顶板岩层结构受力状况,基于岩石断裂理论和弹性理论分析回采前后顶板密集钻孔孔间围岩受力分布及其破断过程,明确密集钻孔切顶机理及相邻钻孔的孔间集中应力相互作用机制,推导工作面端头弧形三角板结构巷道侧边界密集钻孔孔间围岩的拉剪应力计算公式。在此基础上,分析不同参数对孔间围岩所受拉剪应力的影响作用,提出沿空留巷密集钻孔切顶关键参数确定方法。研究表明:密集钻孔主要通过回采前后钻孔周围应力条件改变来增加钻孔围岩拉剪应力集中程度,引起孔间裂隙扩张联通,形成切缝线破断关键岩层。回采前钻孔主要受水平挤压应力影响,回采后钻孔受力逐渐转变为采空区顶板回转下沉产生的拉剪应力为主,钻孔孔间围岩状态随之由孔间围岩弱化阶段过渡到孔壁裂纹成形阶段,再转变为孔间围岩破断阶段。密集钻孔孔间围岩所受拉剪应力大小主要取决于关键岩层厚度及钻孔孔径与孔间距之比,与钻孔高度及间距成负相关,与角度及直径正相关。据此提出了密集钻孔关键参数确定方法,并根据龙滩矿3124 N工作面坚硬顶板条件设计了密集钻孔切顶留巷方案,确定钻孔长度为8.3 m,角度为15°,钻孔直径为48 mm,间距为500 mm。留巷后巷道顶帮变形可控且整体稳定性较好,由此可证明密集钻孔布置参数较为合理,密集钻孔关键参数确定方法有效可行。

大直径空孔对掏槽爆破效果的影响机理研究

针对大红山铜矿巷道掘进爆破出现炮孔利用率低、单次循环进尺低、现场半孔率低、超欠挖严重及轮廓面不平整等问题,通过数值模拟软件LS-DYNA,构建三、四、五、六个大直径空孔四种掏槽爆破模型,对四种大直径空孔数量条件下的掏槽爆破成腔效果进行数值模拟研究,为后续掏槽布孔设计提供指导。研究表明:大直径空孔对岩体爆破损伤有导向作用,六个大直径空孔诱导形成的爆腔面积最大,约0.1321 m^(2),比五个大直径空孔的爆腔面积增长了8.55%,比四个大直径空孔的爆腔面积增长了2%,比三个大直径空孔的爆腔面积增长了8.01%;大直径空孔的阻隔作用明显,空孔的存在可以使得爆破振动峰值下降51.63%,有效应力峰值下降67.24%。

井底流固耦合环境下PDC钻头切削齿冷却仿真实验

PDC钻头已成为开发深部资源的主体钻头,但在钻井过程中产生的热损伤是影响钻进效率及钻头寿命的重要因素之一。该文针对PDC钻头切削齿热损伤问题,开展基于不同影响因素的井底流固耦合环境下切削齿冷却仿真实验。建立了PDC钻头井底冷却流固耦合模型,结合实际钻井工况制定了数值仿真方案,根据仿真实验结果分析了井底流固耦合环境中不同影响因素下钻头切削齿的温度变化规律,并通过正交试验对钻头冷却效果与各影响因素间的敏感性进行了评价。切削齿冷却敏感因素从大到小依次为:钻井液排量>钻井机械参数、钻井液温度>地层温度。研究成果为探索井底工况下钻头破岩过程中切削齿热损伤问题和优化PDC钻头设计提供了理论依据。

孔洞缺陷对TC4切削加工影响的仿真研究

为研究孔洞缺陷对TC4材料切削加工的影响,使用有限元切削仿真方法对切削过程的应力应变、切屑形态和切削力特点和规律进行研究。通过热力耦合仿真、数据分析、时频分析等方法对含缺陷材料切削过程中的参数的研究,研究结果表明:位于切削路径上的缺陷,在切削完后缺陷处表面出现应力集中,位于切削路径上的缺陷处表面应力值相比无缺陷时明显减大;缺陷位于表层区域时,由于缺陷导致材料内部结构变化,切屑断裂,切屑形态剧烈变化;当缺陷位于切削路径上和表层区域时,切削至缺陷处时切削力发生突变,切削状态发生失稳,并且位于表层区域的缺陷对切削力的突变影响最大;最后通过Choi-Williams时频分析对含不同位置缺陷切削仿真得到的切削力信号进行分析,观察到不同位置缺陷情况下切削力波动的时频信号,判断缺陷的位置。

渠式切割水泥土连续墙的应用和发展

作为超深、等厚、连续、可靠的截水挡土帷幕,渠式切割水泥土连续墙在国内有广泛应用。本文概括了渠式切割水泥土连续墙在国内的引进、应用和发展历程。结合对国内200多个既有应用案例的统计分析,研究了渠式切割水泥土连续墙的施工设备保有情况、成墙深度范围、常用墙体厚度和主要应用场景;罗列了渠式切割水泥土连续墙在复杂地层施工的辅助措施以及典型案例;指出了渠式切割水泥土连续墙在敏感环境微扰动施工的控制要点;介绍了渠式切割预制装配式混凝土连续墙的设计要求和用途,尤其是内插预制板材的截面设计和制造工艺;最后用工程实例表明渠式切割预制装配式混凝土连续墙同时继承了渠式切割微扰动和地下连续墙支护刚度好的特点,无论是切割成墙期间还是土方开挖期间,施工对周边环境的影响都较小。

石门揭煤局部防突措施研究进展及展望

随着矿井开采深度的增加,瓦斯突出问题日益凸显,如何快速安全地进行石门揭煤,是保障煤矿安全生产的重要目标。选取中国知网数据库中近30年相关文献为样本,基于图谱分析法,分析了石门揭煤局部防突领域中的研究热点;对防突措施的研究进展和不足之处进行了系统探析,分析发现低温冷冻技术从降低煤层储能及提高煤体强度2个角度实现防突。煤与瓦斯突出事故的发生是煤层储能失稳后突破了煤体抵抗能力导致的,基于目前局部防突领域存在的技术难题以及人工冻结存在的不足,结合智能化技术,提出智能“钻-抽-注”一体化措施,通过信号基站及局域网络进行实时监控及预警,实现精准防突;通过建立多物理场耦合模型、理论分析及工程实践验证3方面相结合,掌握冷冻条件下煤岩体瓦斯赋存状态及运移规律,为低温冷冻技术在石门揭煤局部防突中的应用提供理论依据;借助智能液氮冻结系统,实现“一孔多功能”,为石门揭煤局部防突工作提供新的选择和支持,从而快速、安全揭开突出危险性煤层。

深孔聚能预裂爆破切顶卸压机理与应用

为解决悬顶导致的煤柱及邻近巷道高应力和大变形问题,结合工作面顶板地质条件,提出深孔聚能预裂爆破切顶卸压专项方案,采用数值模拟及现场试验对卸压效果开展综合研究。研究结果表明,煤层顶板在切顶后垂直应力减幅为21.62%,预裂切顶措施可显著降低煤柱及邻近巷道围岩应力水平。试验发现,炮孔内轴向贯穿裂缝明显,可实现采空区顶板及时垮落。顶底板在切顶后累计位移量减幅达59.27%,巷道两帮及顶底板移近变形得到有效控制,煤柱垂直应力增量显著降低。实践证明,采用深孔聚能预裂爆破切顶卸压效果显著,可大幅提高作业效率,为类似矿压防治工程提供借鉴。

金属矿山硬岩巷道分阶段掏槽爆破数值模拟研究

针对地下金属矿山深部硬岩强度高,掏槽难度大,掘进效率低下的问题,以首钢杏山地下铁矿巷道掘进项目为背景,基于数码电子雷管精准逐孔起爆,提出针对直眼桶形掏槽爆破的掏槽区孔内分段与孔间、孔内延时相结合的分阶段爆破方案。采用数值模拟以及现场试验方式,在现场原传统方案的基础上,对掏槽区炮孔进行孔内分段、孔间以及孔内微差起爆的分阶段起爆设置。通过LS-DYNA数值模拟软件建立掏槽区三维模型,设置了原传统方案和3种分阶段方案进行模拟计算,对比分析了原传统爆破方案和分阶段方案在掏槽区的有效应力峰值演化情况。数值模拟结果表明:采用孔间短延时分阶段爆破方案能够改变有效应力峰值波动形态,与原传统方案相比,掏槽区沿炮孔方向岩体的有效应力峰值状态提升40%~57%,炮孔底部0~30 cm半径岩体有效应力峰值状态提升幅度在84%~92%。在数值模拟结果的基础上,开展了现场试验验证,现场试验表明:在矿石点位掘进中,采用孔间短延时微差起爆能够改善碎石挤死的现象,采用孔内短延时微差起爆能够提高抛掷能力,改善上段炮孔爆破后产生碎石的抛掷效果,避免影响后续炮孔爆破,在硬岩爆破中二者结合可以明显改善爆破效果,掏槽进尺提高28%;在岩石点位掘进中,采用孔间短延时,孔内长延时设置能获得良好的掘进效果。

高温合金小孔微细螺旋铣削工艺参数研究

高温合金具有良好的耐高温性、抗氧化性和耐腐蚀性,广泛应用于航空航天、能源工业等领域。由于高温合金抗拉强度高、导热系数低、在切削加工中发生塑性变形的抗力大以及切削热集聚和加工硬化严重,是典型的难加工材料,故采用切削方式在高温合金零件上制作小孔具有挑战性。采用螺旋铣孔的方式对钴基高温合金GH605进行小孔加工,设计并进行微细螺旋铣孔正交试验,探究关键铣削参数(主轴转速n、进给速度v f和螺距s)对切削力F、切削温度T和孔壁表面粗糙度Ra的影响规律。基于试验数据极差分析的结果,并进行螺旋铣削关键参数优化,成功实现高质量直小孔和斜小孔的微细螺旋铣削加工。

切割井中深孔孔内分段爆破一次成井数值模拟

为分析中深孔孔内分段爆破一次成井的爆破效果,采用ANSYS/LS-DYNA有限元数值模拟软件,对孔内分段装药和不分段装药2种不同装药结构下中深孔爆破切割井处应力变化、损伤区域进行模拟计算研究。结果表明:孔内分段装药爆破时切割井中部两侧应力更集中,炸药爆炸产生的应力波更多的作用于炮孔顶部岩石处,使其受到的应力更大;分段装药时炮孔下层炸药首先起爆为上层炸药爆炸创造了良好的自由面,炸药爆炸产生的能量更多作用于岩石两侧及顶部,导致其损伤区域高度更高,模型底部产生的裂纹较密集,并且模型外侧边界处裂纹衍生的数量以及裂纹宽度和长度明显较高,证明孔内分段装药对切割井爆破一次成井具有更优的效果。最后,应用此方案在矿山现场成功施工1条高度为13.2 m、断面为2.1 m×2.2 m的切割天井,表明该方案具有较好的工程意义和推广价值。