1.Introduction

Applying high pressure water jets to penetrate rocks is extensively studied since the middle of the 20th century(e.g.Farmer and Attewell,1965).Applications range from cutting/carving applications(e.g.Harris and Mellor,1974;Summers and McGroarty,1982;Hagan,1992)to downhole drilling(e.g.Maurer et al.,1973;Deily,1977;Pols,1977a,b).In recent years,the application of the radial water jet drilling(RJD)technology is increasingly investigated to perforate and stimulate low performing wells(e.g.Buset et al.,2001;Bruni et al.,2007;Cirigliano and Talavera Blacutt,2007;Seywald and Marschall,2009;Abdel-Ghany et al.,2011;Elliott,2011;Cinelli and Kamel,2013).For the RJD technology,a bottom hole assembly,generally referred to as ‘def l ector shoe’,is connected to a tubing and lowered to the target depth.For cased hole intervals,a coiled tubing conveyed milling assembly is lowered through the tubing.At the bottom,the def l ector shoe def l ects the milling bit towards the casing.After milling a hole into the casing,a jetting assembly is lowered through the tubing.The coiled tubing conveyed jetting assembly consists of a self-propelled jetting nozzle attached to a flexible hose.This assembly is capable of jetting up to 100 m into the formation.

Recently,the RJD technology has gained considerable interest for stimulating low performing geothermal wells,motivating numerical investigations to estimate the benefit from applying this technology(e.g.Peters et al.,2015).For enhanced or engineered geothermal systems,it is considered as a viable alternative to conventional hydraulic stimulation technologies and has triggered several research projects(e.g.Reinsch and Bruhn,2016).As one of the first applications in a geothermal environment in Europe,RJD stimulation was performed in a low performing injection well in Klaipeda,Lithuania.RJD was applied to jetting 12 laterals with a length up to 40 m each,leading to an increase of injectivity of about 14%although a maximum increase of 57%was suggested by numerical modeling(Nair et al.,2017).Analysing the sensitivity to different model parameters like lateral direction and length,which influences the predicted increase by up to 10%for individual parameters,underlines the importance of proper monitoring equipment to measure the laterals’geometry(Nair et al.,2017).

While rock penetration experiments can be performed in the laboratory with good access to the process parameters as well as the jetted holes afterwards,RJD operations are performed downhole with limited access to process parameters and no option to investigate the jetted holes(fora review on different laboratoryand field experiments,please see Blöcher et al.,2016).In order to bridge this gap,we performed a jetting experiment in a quarry with the state-of-the-art RJD technology.Monitoring and in fl uencing process parameters like fluid pressure and fl ow rate could easily be implemented.In addition,the jetted holes were accessible afterwards for geometry measurements and could be surveyed visually.Although jetting individual holes at ambient surface conditions is not comparable to downhole applications with regard to the reservoir pressure and temperature conditions as well as saturation and stress conditions within the rock,various aspects of the technology can be investigated:

(1)To control jetting parameters(pressure and f l ow rate)and monitor their effects on process parameters such as rate of penetration(ROP),fluid return,and cutting return.

(2)To monitor the direction of a jetted hole by acoustic/seismic measurements at the surface during the jetting process.

(3)To inspect the inside of the jetted hole,thereby determining the shape of the jetted hole as well as its trajectory.

(4)To observe the influence of local geological or structural interfaces on the jetting process as well as the hole geometry.

(5)To determine the change in injectivity over the length of the jetted hole,especially when intersecting permeable features,e.g.a fracture.

(6)To collect eroded rock particles/cuttings for further investigation.

Reed-Muller(RM)逻辑是函数基于AND/XOR的逻辑表示，与基于AND/OR的逻辑表示相比，对于算术、校验以及通信等电路具有面积上的优势，并且能够实现具有通用测试集的可测试性电路设计[1].近几年来RM逻辑在信息安全领域的电路设计中的实际应用，如AES加密电路中的S盒电路[2]、基于FinFET的安全绝热电路[3]等，验证了对RM电路进行功耗、可靠性等优化的必要性.

(7)To analyse if the jetting process parameters can be used to infer details about the jetted formation.

1.人员素质低。基层队伍中，特别是村防疫员大多为临时雇佣人员，年龄偏大，不能独立完成移动智能识读器的信息录入和上传工作，严重影响畜禽标识数据库建设工作的落实。

(8)To test different jetting nozzles.

⑧试压合格的管道应及时进行阀门井室安装及沟槽回填，管沟分层填土并用蛙式打夯机夯实。因管线经过地段多为山区，且管道布置曲线较多，为便于以后维修查找，管沟回填后及时埋设水道标。水道标为钢筋混凝土制，沿管线间距100m埋设在管道正上方，并在管道转弯、与道路交叉处设置。水道标埋入地下0.7 m，地面以上0.5m，水道标周围填土应分层回填密实。

Overall,the trajectories seemed to be diverted upwards over the length of each hole.Even when initially directed downwards,the curvature changed towards the top of the quarry.In addition to large radius direction changes towards the top of the quarry as well as within the horizontal plane,short radius changes can be observed in the dogleg severity plot.Apart from the end of the wellheads in holes 1-3,strong change in direction was observed for hole 1,where two distinct depths at 1-2 m as well as 4-5 m were located.From the visual inspection,apart from the onset of the jetted hole at the end of the pipe,a very heterogeneous hole geometry with larger cuttings remaining inside the hole was found in the first interval.This coincides with the depth of both thin bedding as well as intersection with a fracture.From the visual inspection,none of both interfaces can be excluded to have caused the change in direction.For the change in direction observed at greater depth,a larger oval-shaped caving was observed with a diameter of more than about 5 cm.At this depth,an interface was intersected.In addition,the hole split into two arms.To remove cuttings from the hole during jetting,the jetting hose was pulled out of hole from time to time.In this depth,a‘sidetrack’was initiated due to hole cleaning.Which one of both holes was entered with the geometry sensor cannot be determined from the visual inspection.The reason for the larger excavation causing the deviation might be the intersected interface.The deviations in hole 6,although initially directed such that it does not intersect any interface,show an almost constant change in direction at a depth larger than 2 m.Visual inspection showed that several interfaces including larger excavations could be observed from that depth.Neither structural features nor any bedding was observed before that depth.In hole 4,the geometry tool was stuck in about 1 m below surface.

1.1.Selection of quarry

To ensure sufficient penetration depth and rate during the drilling experiment in a quarry,pre-quarry jetting tests were performed on different rock samples in yard tests at ambient surface conditions.Three types of sandstones were selected based on rock properties,mainly permeability and porosity,and the accessibility of the respective quarry(see Table 1).In addition,the pre-quarry tests were used to perform acoustic measurements during jetting to determine the frequency spectrum of the acoustic signal resulting from the jet-rock interaction.

During jetting and testing at one wellhead,the remaining two wellheads were plugged and pressure gauges were used to monitor any pressure changes.As none of the other wellheads was fluid fi lled and the formation was not saturated,no pressure change was measured.Fig. 4 shows the wellhead installation on the second jetted hole.High pressure hoses as well as pressure gauges and seismic receivers attached to the wall are shown.

入摩入富比例提升，国际资金加速涌入A股市场。根据MSCI的披露，2019年底将A股纳入份额由目前的5%提升到20%，届时A股占整个MSCI新兴市场指数将由目前的0.7%提升至3%。同时今年9月富时宣布将分三个阶段把A股1249只股票纳入富时全球市场指数，第一阶段将从2019年6月开始，到2020年中国A股将占富时新兴市场指数的5.6%。随着中国股市逐步融入国际市场，海外资金将通过北上渠道源源不断流入A股。高盛预计2019年因为MSCI纳入比例提升和纳入富时罗素导致的北上资金将达到650亿美元，相对于2017、2018年的300亿美元和400亿美元有较大增长。

Table 1 Rock samples and respective quarries tested in the yard tests.The last column gives the International Geo Sample Number(IGSN).

Sandstone Quarry Maximum ROP(m/h)IGSN Triassic Sandstone Bad Dürkheim,Germany 0.17 GFTRE0040 Middle Buntsandstein 0.46 GFTRE0060 Cretaceous Sandstone Friedewald,Germany Gildehaus,Germany 4.28 GFTRE0073

(1)Accelerometers for frequencies up to 800 Hz(Sercel DSU-3,200-800 Hz).

(2)Geophones for frequencies up to 5000 Hz(GS-14).

(3)Piezo-elements for frequencies up to 10,000 Hz(BK 4514-B).

Due to the full overlap in frequency response of the geophones with the other two instruments,the geophones were considered redundant and not used for monitoring in the quarry experiment.Table 1 lists the maximum ROP achieved during the yard tests.It is shown that the highest ROP was obtained for the Cretaceous Sandstone from Gildehaus,Germany.For a static nozzle,significantly lower ROPs were observed compared to a nozzle with a selfpropelled rotating head,referred to as rotation nozzle.Therefore,it was decided to perform the jetting experiment mainly with a rotating nozzle in the Gildehaus quarry,Germany.

Based on previous studies by Hardy Jr.(2003),Kovacevic et al.(1998),and Rabani et al.(2012)and on the pre-quarry rock jet tests in Bochum,the signal of the jetting activity in the quarry experiment was expected to lie in the frequency range of 500-10,000 Hz.Based on this,we decided to deploy three-component accelerometers combined with piezo-elements in the quarry,since they can together properly span the expected frequency band of the acoustic activity.

1.2.Description of quarry and geology

The quarry Gildehaus is located in North-West Germany,3.5 km west of Bad Bentheim and close to the border with the Netherlands(52°18′8.42′N,7°6′18.76′E).It is located about 50 m above mean sea level between the Ems-and Münsterland,within the Westfälische Bucht.The stratigraphyof the sandstone canbe classified as Lower-Valanginian,Lower Cretatious(Haack,2007).

Fig. 14 shows the results of the localisation of the acoustic signal received by the piezo-elements and accelerometers while the radial drill at hole 1 was performed.The localisation result in Fig. 14 is shown at the start and termination of the jet,illustrating the source location with highest probability indicated in yellow.The figure shows increased probability(yellow)at the location where the radial is placed,and the estimated location remains close to the quarry wall during drilling.These results are based on a specific data selection with source-receiver offsets of 1-5 m and data inversion is based on a uniform velocity model of 1500 m/s.This velocity was determined from velocity analysis of a hammercalibration shotline conducted along the quarry wall.The location estimations found with the piezo-element and the accelerometer data agree with each other.Their estimated locations have an offset of 5 m compared to the final location as measured with the in situ accelerometer tool.

The quarry Gildehaus covers an area of about 18,000 m2with a length of about 300 m.It can be subdivided into five excavation sites.At its lowest point,the quarry is about 30 m deep.Our jetting experiments were performed in the central part of the quarryat the southern side.

Fig. 1.View to the east onto the quarry wall used for the jetting experiments.Subvertical red lines indicate major fracture zones.The sub-horizontal yellow line indicates the direction of the layering,whereas the thick sandstone layer can be seen below and the interlayered section can be seen above.

Fig. 2.Fracture face in Gildehaus quarry.Reddish-brown colours originate from ironmanganese minerals.

On average,individual sandstone layers have a strike and dip of about 183°/28°.Fractures instead show a strike and dip of 25°/76°.Due to the anticline structure,individual fracture faces can dip to the south/south-west,rotated by 180°.Individual larger fractures show an offset of about 1-3 cm.The aperture of the individual fractures varies from＜0.1 mm to 1 cm at the quarry wall.A single major fracture zone with a width of 17 cm was observed,which is divided into multiple smaller fractures.Individual fractures have a terraced,undulating,and smooth surface.The mainly well sorted fine-to-medium size grained sandstone is free of lime and consists of 95%quartz grains which are moderately rounded and cemented with a siliciclasic cement.The sandstone has a feldspar content of about 2%and can be classi fi ed as Arenite(DIN,2003;Stow,2008).A porosity up to 22.8%is reported(Klein et al.,2001).

Although the ROP was measured during jetting in different lithologicalsettings,with differentnozzle geometries and changing fluid pressures,a conclusive result could not be obtained.Neither jetting in the homogeneous rock formation(e.g.in the first 2 m of hole 6),nor varying nozzle pressure(e.g.in hole 2,where 50 m and 15 m high fluid pressures were used),nor changing the nozzle geometry from a nozzle with 4 to a nozzle with 3 forward directed orif i ces changed the ROP significantly.Individual high ROP values cannot be attributed to any specific downhole situation.One reason might be the spatial and temporal resolution of the ROP measurements.As individual measurements were taken every 25-50 cm,small-scale features like the effect of bedding or fractures on the ROP are obscured.From the geometry,it is known that all holes tend to be directed upwards into the part of the quarry with inter-bedded clay layers.An effect of the lithology on the ROP was not observed with the current set-up.Compared to a real field scale application,ROP values in the quarry were significantly lower than expected but corresponded to the ROPs observed during laboratory experiments at surface conditions.

The outcropping sandstone consists of a homogeneous,weakly weathered,and non-graded sandstone.The lower part of the wall is made of a massive sandstone layer with a thickness of up to 10 m which is currently quarried,mainly in the western part of the quarry.It is overlain by a unit of about 5 m in thickness,consisting of 5-20 cm thick sandstone layers separated by thin clay layers(Fig. 1).On top,a massive sandstone with little layering can be found.

2.Experimental set-up

2.1.Hydraulic set-up

Before the jetting experiment,three ‘wellheads’were prepared at the quarry wall.A coring machine was used to drill 67 mm diameter holes up to 30 cm into the quarry wall.Into these holes,2′′(≈5.08 cm)WECO 1502 pup-joints with a length of about 0.6 m were cemented with composite mortar.After drying,a hand-held drilling machine was used to penetrate the mortar at the bottom of the WECO tubes.During jetting,a hydraulic system was attached to the pup-joints.Borrowing terminology fromoilfield applications,the necessaryset-up is herereferred toas X-mas tree.Fig. 3 shows a schematic overview of the set-up together with different sensors installed in the hydraulic system.

Fig. 3.Wellhead set-up during jetting operation.For details on the geometry,please see Table 2.

Table 2 Length information(m)for the different jetted holes.See Fig. 3 for the nomenclature of different components.The depth(m)of the holes(e)is evaluated using information from drilling and subsequent logging campaigns.

Hole a(approximately) b c d e(drilling) e(visual log) e(geometry log) f(initial) g Hole 1 0.22 0.38 0.35 1.27 5.35 4.97 5.17 50 0.067 Hole 2 0.22 0.38 0.36 1.24 3.86 4.12 4.27 50 0.067 Hole 3 0.255 0.345 0.34 1.2 2.5 2.735 3.3 15 0.067 Hole 4 - - 0.15 - 12.3 7.49 1.05 50 0.02 Hole 5 - - 0.15 - 0.15 - - - 0.02 Hole 6 - - 0.15 - 7.8 5.25 5.55 15 0.02

The X-mas tree started with a T-piece.The downward facing part redirected the back- fl ow including the cuttings from jetting.This fluid went through a valve and a crossover to a 1′hose.It was fi ltered to retrieve the cuttings and directed into a 1 m3Intermediate Bulk Container(IBC).Here,the return fluid volumes could be measured.On the collinear side of the T-piece,another T-piece was connected.The downward facing part was connected to a blind-cap with a 1/2′NPT thread,allowing for injection testing through this inlet.The collinear connection was connected to a valve.Through this valve,the jetting hose was fed into hole.During injection testing,both valves at the end of the X-mas tree as well as at the fluid return were closed.

For jetting and injection testing,two pumps were used.For the injection testing,we used a ‘low pressure’pump.This pump is capable of delivering 60-200 L/min at a maximum pressure of 600 bar(1 bar=100 kPa).The maximum pressurewas set to 50 bar.For the jetting,a ‘high pressure’pump capable of delivering 11-30 L/min at a maximum pressure of 1000 bar was used.Due to the pressure rating of the equipment,the maximum operating pump pressure was set to 700 bar.

The ‘low pressure’pump was connected to the wellhead via a 100 barrated 3/4′ID hose.The ‘high pressure’pump was connected to the jetting hose via a 700 bar rated flexible hose with a pressure gauge before the jetting hose.The jetting hose itself was a 700 bar rated flexible hose.For the first jetting experiments,we used a length of 50 m.Later,we shortened it to 15 m to increase the available fluid pressure at the nozzle.For RJD applications,pressure friction loss within the CT as well as the flexible hose determines the available pressure at the nozzle.In downhole applications,the pressure at the nozzle can be increased by decreasing the length of the CTor the flexible hose or by increasing diameters.In our jetting experiment,wedid notaim fora specific pressure at the nozzle.The experiment,therefore,can only give indications on performance parameters,e.g.for the ROP,when compared to downhole applications.Parameters like hole geometry and hole survey,however,should be comparable.

Either a static or a rotating RJD nozzle was attached to a flexible high pressure hose and connected to a high pressure triplex pump.To control the stand-off distance between the nozzle andthe rock surface,the nozzle was clamped to a hydraulic piston capable of steering it towards the rock surface.The rock samples were neither saturated nor immersed in water during the tests.Rock samples of approximately 50 cm×50 cm×50 cm were positioned in front of the nozzle and equipped with three types of acoustic sensors:

As we were not able to jet the planned 25 m in holes 1-3,it was decided to jet two more holes,i.e.holes 4 and 6.For holes 4 and 6,no wellhead with X-mas tree was installed.For holes 4 and 6,pilot holes were drilled with a 20 mm diameter rotary bit down to 15 cm and a 16 mm rotary bit down to 30 cm,respectively.Due to the missing wellhead,no injection tests could be performed.Cuttings were collected using a bucket placed along the vertical rock surface beneath the drilled hole.The position and direction of the pilot holes 4 and 6 were chosen not to intersect with any interfaces(bedding or fractures)within the surrounding rock mass.Hole 5 was marked but not drilled.

建立一套行之有效的规章制度，对于提高管理效率，明确责任分工，逐级落实，人人有责，各负其责方面具有重大意义。以创新能力培养为中心的实验室建设最重要的是制度保障，主要包括安全管理制度、设备管理制度、信息管理制度、团队管理制度和奖励激励制度等5个方面。

2.2.Acoustic monitoring

The acquisition layout is shown in Fig. 5.The monitoring Instrumentation consisted of three-component accelerometers and unidirectional piezo-elements.Sensors were deployed with 2 m spacing along two lines termed L1 and L2 that were approximately parallel to ground level.Along line L1,both accelerometers and piezo-elements were placed to compare the performance of the two types and test the localisation method.Line L1 was used as a proxy for a downhole application where sensors can only be placed vertically in a well.In the quarry,we used the possibility to sample the acoustic wavefield in another plane,by placing accelerometers along line L2.

Fig. 4.Wellhead of hole 2 installed in quarry wall.Wellhead 1 was equipped with a pressure sensor.Three-component geophones were cemented into the quarry wall(red)together with piezo-elements for high frequency recording.Hole numbers are indicated.

Fig. 5.Geometry of sensors relative to individual jetted holes.The sensors are subdivided into a L1-and a L2-line.For the x′z and y′z projections,the coordinate system was rotated by-45°.

During the jetting process,we expected a more or less continuous acoustic signal,and therefore needed to adopt techniques that are capable of processing continuous signals into finite signals to provide information on source location.The localisation technique thatweusedhererelied ondrill-bit interferometryas applied in the oil and gas industry,which was thoroughly explained and demonstrated byRectorand Marion(1991),and Polettoet al.(2004,2010,2014).

We implemented the following workf l ow to estimate the location of the radial path:

(1)Recorded data are conditioned by suppressing harmonic or cultural noise and isolating signal that comes directly from the interaction between nozzle jet and rock.Therefore,we compared data acquired during jetting periods to data from periods when there was no activity.We used a Butterworth bandpass f i lter to reject undesired signal.

(2)Synthetic travel times of the P-wave arrival are calculated for all stations using a P-wave velocity model derived from active hammer shot data acquired at the quarry wall.Synthetic travel time data are calculated for all relevant source-receiver combinations.

(3)The continuous data are divided into distinct files of specific duration.The duration is chosen such that it represents a time window within which we can assume that the nozzle source is at a stationary location.

(4)Data of all station pairs are cross-correlated.Subsequently,the envelope of the resulting cross-correlated data is calculated,along which energy is stacked along synthetic delay times per synthetic source location.

(5)This yields a maximum value for the synthetic source location for each time window that best explains the observed travel time data.

2.3.Jetting program

It was planned to jet three holes with different angles towards the local fracture network as well as the bedding with a length up to 25 m.After every 4 m,it was planned to perform a short-terminjection test.We assumed a decreasing injection pressure for a specific f l ow-rate over the length of the jetted hole.In case a fracture was intersected,this pressure was assumed to drop drastically.Data were supposed to show if any permeable features within the quarry wall were intersected.Between individual jetting intervals,the holes were inspected with a camera.During the tests,static and rotating nozzles were tested.Table 3 gives an overview of the different nozzle geometries tested during the experiment.Table 4 displays an overview about the different activities during the quarry experiment.

Table 3 Nozzles to be tested.

Nozzle Number of frontward orif i ce Number of backward orif i ce Quantity Standard static(StS) 4 5 1 Buckman static(BS) 1(vortex)6 1 Standard rotary(SR3) 3 2 2 Custom rotary(CR3) 3 2 1 Custom rotary(CR4) 4 2 1

3.Results

We were able to jet individual holes with a length up to 12.3 m during the experiment.As we were not able to reach the anticipated 25 m,we decided to jet the additional holes 4 and 6.Injection tests into the unsaturated large open fractures,connected to the surface of the quarry wall,did not produce an evaluable dataset.Injection tests were therefore only performed in holes 1 and 2.In holes 4 and 6,total circulation loss was observed at a depth of 10.25 m and 2.9 m,respectively,indicating the connection to a high permeable fracture.For holes 1-3,the return f l ow data were inconclusive and a total circulation loss was not detected.Table 2 lists the geometric information for different holes that were jetted during the quarry experiment.

3.1.Jetting performance

During jetting,we measured the ROP in relation to jetting pressure and nozzle geometry.Using static nozzles(Table 3),we observed no ROP in the quarry.Individual ROP measurements were averaged over 25-50 cm intervals.For the rotating nozzles with 3 and 4 forward directed orif i ces,no conclusive results were obtained that favour one geometry over the other(Fig. 6).In addition,the length of the jetting hose was reduced from 50 m to 15 m during the experiment.Reducing the length of the hose decreased the pressure friction loss by about 100 bar at the maximum f l ow rate.For the additional pressure of 100 bar at the nozzle,a significant and sustainably increased ROP was not observed.On average,the ROP was a couple of cm/min.Anincreased ROP was observed in the first section of hole 1(0-3.5 m depth),the second interval in hole 2(1-2 m depth)and the single interval in hole 3.Holes 4 and 6,intentionally inclined not to intersect any structural feature(bedding or fracture),show a more stable ROP.

Table 4 List of experiments performed in different holes(Y=yes,N=no).

Test Hole 1 Hole 2 Hole 3 Hole 4 Hole 5 Hole 6 Nozzle rotary Y Y Y Y - Y Nozzle BS Y Y N Y - N Nozzle StS N N N Y - N Hose 50 m Y Y N Y - N Hose 15 m N N Y Y - Y Injection test Y Y N N - N

Fig. 6.Rate of penetration for the different holes calculated for individual sections along each hole.The number associated to each bar indicates the number of forward directed orif i ces for the nozzle used in the test.‘l’and ‘s’indicate the length of the high pressure hose(long:50 m,and short:15 m).

3.2.Inspection of jetted holes

3.2.1.Visual inspection

或许，文化研究与台湾“重写文学史”思潮的耦合，与其说是文化研究在理论旅行过程之中开拓出了新的问题场域和批判空间，不如将之视为建构起了一种“阐释台湾”的新范式。而我们对于这一“耦合”与“新范式”应该坚持“历史性的思考”[17]14，因为“历史性的思考”意味着语境化和持续批判性。

《路线图》的编制坚持“科学性、前瞻性、创造性、引导性相统一”这一基本原则，按照“印刷传媒、包装印刷、印刷制造、数字印刷、绿色印刷、印刷设备与器材”六个主要产业板块，分析市场、技术、管理、投资与风险管控等几大方面的需求变化，不仅着眼于解决当前产业发展问题，更重要的是着眼于未来中长期技术发展趋势和方向。可以说，凝聚行业智慧和社会力量来组织编制技术路线图，对于我国众多印刷企业认清发展趋势、寻求发展路径、直面产业变革的挑战、把握产业发展的机遇，具有积极而重要的意义。

Each hole was inspected with an endoscope made from a USB camera fastened to a f i bre glass rod here referred to as endoscope(Fig. 7).The endoscope was pushed into each hole until the total depth or until a narrow spot prohibited the endoscope to progress deeper into the hole.Overa largeinterval of each hole,the diameter was a little larger than 20 mm(Fig. 8).However,the drift is significantly smaller.We were not able to push an 18 mm rod for more than 17 cm in any of the holes.On the other hand,a geometry sensor of 10 cm length and 12 mm diameter could be pushed along the holes.In individual intervals,although not very prominent,a star-shape profile was observed,indicating erosion caused by the backward directed nozzles.

历史唯物主义是中国特色社会主义的底色。中国特色社会主义既不是翻版，更不是再版，而是新版。之所以说是新版，就在于中国开辟出了一条有中国特色的社会主义道路。中国道路彰显了中国共产党和中国人民的“首创精神”。中国人民应该有这个自信，“坚定中国特色社会主义道路自信、理论自信、制度自信，说到底是要坚定文化自信。文化自信是更基本、更深沉、更持久的力量。”[26]如今，“历史终结论”终结了，“社会主义失败论”失败了，“中国崩溃论”崩溃了。

Fig. 9 shows the endoscopic view of three fractures that were intersected during jetting.Each fracture was intersected under a different angle varying from an estimated 25°to almost 90°.On the fracture faces,iron-manganese minerals can be observed.Before the 90°fracture,a larger excavated volume can be observed indicating that the fracture face was harder to penetrate.Without ROP in front of the fracture face,the weaker sandstone was eroded.

Fig. 10 showsthe bottomof hole 2,wherea larger void spacewas hit.In front of the endoscope,the sandstone surface was slightly eroded.However,the nozzle did not further penetrate into the formation at this depth.From the visual inspection,it is hard to determine if a fracture or a bedding feature was intersected.Although,for individual fracture faces,the brownish colour is a good indicator for a fracture interface,thin layers of less resistant mudstone were washed out during jetting.If an offset corresponds to a fracture or a washed out lithological layer,it is difficult to distinguish.

Fig. 7.Home-made endoscope used for inspecting holes.A USB camera was attached to a f i bre glass rod and pushed into all holes.

3.2.2.Trajectory

事情很快败露。妈用笤帚狠狠抽打三哥，他哭着却不躲，死心塌地接受惩罚。哥哥姐姐拼命护着三哥，也跟着哭了起来。妈打着打着却一把搂过我们兄妹也哭了，比我们更伤心。

The geometry was measured with a three-dimensional(3D)accelerometer combined with a 3D magnetic field sensor.The sensor was attached to a f i bre glass rod and pushed into the hole.While pulling out of hole,a measurement of azimuth and inclination was performed every 25 cm.

None of the measured trajectories is completely straight.All trajectories either have a rather constant change in direction over the entire length of each hole,or short radius changes at specific depths.An overview about the individual geometries is given in Fig. 11,where different two-dimensional(2D)projections are shown together with the dogleg severity,to indicate the change in direction per depth interval.For holes 1-3,the metal pipe was magnetized and in fl uenced the trajectory measurement.For the fi rst depth interval,where elevated magnetic field data indicated a strongly magnetized pipe,the initial direction was estimated to be normal to the quarry wall.When leaving the pipe,all holes show a high dogleg severity indicating that the jet hole was initiated slightly deviated from the axis of the wellhead.

Fig. 8.Endoscopic view into the jetted hole.The red lines indicated the hole geometry.It has a diameter of about 20 mm.

Fig. 9.Selected endoscopic view into two holes.(a)A fracture was intersected at an angle of about 45°.The fracture face is characterized by brownish colours.(b)A fracture was intersected at an angle close to 90°.A large volume was excavated before the fracture.The fracture face is characterized by brownish colours.And(c)A fracture was intersected at an estimated angle of 25°.The fracture is indicated by the dashed red line.

Fig. 10.Endoscopic view into the second jetted hole.The jetting nozzle hit a larger void space.Here,ROP decreased to zero and the hole was terminated.

石黑一雄在这部小说里所采用的整体式悬念、顶针式悬念和切入式悬念从三个角度展现了事件悬念与小说情节的内在关联，使读者产生“山穷水尽疑无路，柳暗花明又一村”的艺术感受。其笔下扣人心弦的事件悬念设计使读者的心与小说人物的心一起跳动，淋漓尽致地展现了事件悬念设计的独特艺术效果。

现代医院管理制度包括3个层面的逻辑架构[4]：宏观层面的政府治理机制、中观层面的法人治理机制和微观层面的医院内部管理制度。

Fig. 11.Survey of jetted holes projected to a single reference point.

3.2.3.Cutting analysis

Fig. 12 shows the grain size distribution of cuttings retrieved from holes 1-3 where a reliable sampling was guaranteed by the hydraulic set-up.For all three holes,the grain size distribution is similarly corresponding to a medium-grained sand.From the grain size distribution,permeability values were calculated according to empirical formulas derived by Hazen(1893),Seelheim(1880),Beyer(1964),Bialas and Kleczkowski(1970)for unconsolidated sediments as reported in Hölting(1996).For each of the three holes,the calculated permeability values are in the range of 3-17 Darcy(Table 5).This value is very close to permeability values derived from laboratory experiments on intact rock samples of 0.8 Darcy at 50 bar of confining pressure(IGSN:GFTRE0066).

3.3.Acoustic monitoring

During the jetting tests at the Gildehaus quarry,acoustic signal resulting from jetting activity was successfully recorded using accelerometer and piezo-element instruments.Here,we demonstrate the localisation technique for the piezo-element and accelerometer measurements acquired while jetting in hole 1,where a penetration of 5.4 m was reached.Fig. 13 shows the data recorded bypiezo-elementsand accelerometerswhilethe maximum penetration at hole 1 was reached.Both datasets were frequency f i ltered in the same bandpass of 350-950 Hz for comparison.

用ZMD-2型电子密度计，采用排水法测量烧结试样的烧结密度；用Leica DM4000型显微镜，对烧结试样的横截面进行孔隙度测试；用DM400M型金相显微镜，对烧结试样进行显微组织分析；用HR-150A型洛氏硬度计，测量试样的硬度(HRB)．

Fig. 12.Grain size distribution of cuttings sampled during the RJD operation from holes 1-3.

Table 5 List of formation permeability in Darcy calculated from grain size distribution of the cuttings as an average and standard deviation from holes 1-3.

Sources Permeability(Darcy)Hazen(1893)14.24±2.79 Seelheim(1880) 8.64±0.06 Bialas and Kleczkowski(1970) 3.31±0.14 Beyer(1964) 13.54±2.65

At the onset of the Cretaceous time,a continental landmass developed in the northern part of Germany.Therefore,siliciclastic sediments were deposited.During the subsequent subsidence of the area,the Niedersächsische Transtensionsbecken as well as the Münsterländer Kreidebucht was formed and a shelf sea,the chalk sea,was able to transgress.Within the Lower Cretaceous,diagenetic processes formed the up to 70 m thick Bentheimer sandstone.Onto the Bentheimer sandstone,marl and limestones were deposited within a depth up to 250 m in the sea.Climate changes at the end of the Cretatious led to a regression of the Cretaceous sea.Due to the periodical trans-and regression of the North Sea,successive sedimentary layers were deposited during the Tertiary age.Since the Quaternary,Tertiary and Cretaceous sediments were almost entirely eroded,in some locations such as Bad Bentheim,Cretaceous sediments are outcropping within sediments of mainly glacial and f l uviatile origin(Meschede,2015).Due to the uplift of a salt-diapir beneath Bad Bentheim,an anticline formed.The layering of the Bad Bentheim sandstone therefore dips to the south.

4.Discussion

4.1.The ROP

Overall,the colour of the Bad Bentheim sandstone is grey-beige to brownish if weathered and light-grey to beige on fresh surfaces.Individual clay layers can clearly be identified by their darker appearance.On fracture faces,iron-manganese minerals are abundant and can be identified by their reddish-brown colour(see Fig. 2).

For the jetting experiments,rotating nozzles were applied.The nozzles created a mainly roundish hole geometry.Before individual fracture faces,larger excavations were observed,indicating a very slow ROP through the interface.Individual clay layers could not be observed visually.The soft clay was likely washed out,making it very difficult to distinguish between a fracture or several closely spaced fractures with a certain aperture and individual clay layers.From the visual inspection,however,it was observed that distinct interfaces can be intersected under different angles without changing the direction of the jetting nozzle.From the visual inspection combined with the geometry information,it can be concluded that all holes tend to orient themselves towards the bedded quarry interval,wherepotentiallysofterformations prevail.A clear indication from the ROP,however,was not observed.In larger cavities,either washed out by the jetting operation or naturally existent within the rock,the orientation seems to be influenced,as the backwards directed nozzles cannot orient the nozzle sufficiently.

Fig. 13.Acoustic data acquired during jetting hole 1 along L1.(a)Acoustic waveform data recorded at 16 piezo-element stations.The vertical component data are plotted having the same orientation as the piezo-elements.(b)Acoustic waveform data recorded at 16 accelerometer stations.Both datasets were passed within the frequency band of 350-950 Hz.

Fig. 14.Results of localization of acoustic data from hole 1.(a,b)Estimated location based respectively on the piezo-element and the accelerometer data during the start of the jetting.(c,d)Estimated location based respectively on the piezo-element and the accelerometer data when maximum penetration was reached.

From the cutting analysis,assuming an unconsolidated sand,permeability values could be calculated.For the very homogenous,high porosity sandstone in Gildehaus,the calculated permeability values correspond very well to permeability data measured on intact rock samples under laboratory conditions.Although a sandstone as homogeneous as the Gildehaus sandstone will likely not be found in typical downhole applications,valuable data might be gathered from the cuttings.

4.2.Acoustic monitoring

Careful inspection of the acoustic data proved that only a limited part of the data was suited to perform inversion of continuous signal data to location estimation.Careful selection of data turned out to be especially important.Data should contain a minimum amount of undesired noise,such as man-made activity along the wall.Additionally,the strength and signature of acoustic data showed significant variations during individual jetting tests,which might be related to the various speeds at which the nozzle moved as well as the inhomogeneities within the rock.These signal variations appeared to have a significant effect on the robustness of the location estimates.This is partially related to the simpleone-dimensional(1D)velocitymodelusedherefor inverting travel times to source location estimations.The actual structure of the quarry wall is more complex,containing a number of fractures that will affect transmission and reflection behaviours of propagating waves.This will result in biases of measured travel times obtained from recorded station data,with respect to simulated travel times of the best fitting source location.Furthermore,reflections occurring along the free surface of the quarry wall may complicate an accurate estimation of the nozzle location and reconstruction of the jet path.Additionally,by using higher frequency information for small source-receiver offsets,the source estimation might be improved.A challenge here is that the accuracy of the geometry(source,receivers and geology)becomesincreasinglyimportantwhen considering higher frequencies to correctly predict time differences in travel time arrivals between stations.The accuracy of estimation of the jetted path is significantly smaller compared to the in situ location measurements.However,the acoustic localization can provide a mean of identifying zones where the nozzle has passed,and provides a clue in which direction the path has been set.It is encouraging that the inversion results of part of the piezoelement and accelerometer data agree with each other.The offset in location between acoustic inversion and accelerometer tool probably results from the simplif i ed homogeneous velocity model that we assumed.

5.Conclusions

(1)Monitoring the acoustic activity generated by the jetting process can in principle provide location estimations of the jetting nozzle within the rock mass.The success of this location method at the quarry site mainly depends on careful data selection,suppression of undesired noise,and the degree of realism accommodated in the forward velocity model used to calculate synthetic travel times that are in turn used to estimate the nozzle locations.A downhole application of geophones can provide insight in the approximate spatial distance towards the nozzle,provided that a sufficient aperture and sensor distribution can be reached within the well.At this stage,however,the accuracy of the jet geometry estimated from downhole acoustic measurements with the current data analysis procedure will be limited compared to in situ measurements.

(2)The jetted holes have a round geometry but a limited drift close to the diameter of the nozzle itself.Intersecting various geological boundaries,the trajectory of the hole is far from straight.Although data suggest that interfaces can be intersected under different angles,it cannot be excluded that structural features caused the deviation of the hole.For this experiment,the spatial resolution of the geometry measurement was to low(25 cm),and the geometry information reasonably gained for individual interfaces(plural)from geological mapping at the rock surface was not accurate enough when projected to depth.

可对路基的宽度、边坡进行自动设置，也可设置路段中心线的挖填深度，确保中心线的坡度大小能满足要求。在进行开挖与填筑平衡设计的过程中，自动寻找并确定能确保开挖与填筑保持平衡的深度值，当该值为正时为开挖；当该值为负时，为填筑，结果应精确至0.1m。设计成果需要存储在磁盘当中[4]。

(3)The pressure information from injection experiments alternating with the jetting could not be used to evaluate downhole permeabilities due to large void spaces and multiple high conductive features intersecting the holes.It cannot be excluded that pressure information during the jetting process downhole can be used to have an online information about permeability variations within the formation.Performance parameters like ROP,jetting pressure,fluid velocity,and return fluid volume,however,could not be used to assess the hydraulic variability downhole within the quarry.

(4)As already observed in the pre-quarry tests,rotating nozzles proved to generate the highest ROP values in the quarry.

(5)Collected rock cuttings could be used to accurately assess the permeability of the penetrated rock mass.It remains to be proven that this can be applied to the downhole situation as well.

(6)To reduce the curvature of the jetted hole,the jetting nozzle should be stabilized.

Conflict of interest

The authors wish to confirm that there are no known Conflicts of interest associated with this publication and there has been no significant financial support for this work that could have influenced its outcome.

Acknowledgements

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