頂進回拖王望(英文翻譯原文).pdf

UKKeywords:Horizontal directional drillingSteering responseDown-hole motorsdirectional drilling installations and the potential inability to maintain such positional control is a factorisof HDD in various ground conditions. The installations investigatedused tri-cone roller (TCR) bits without stabilising elementsbent-sub; the geology in which the installation takes place. Priorto the presentation of the results from the investigation of thesefactors, a brief summary on the use of down-hole assemblies inHDD installations and the need to control steering in HDD is given.2. Control of steering in HDD installations using down-holemotorsPositive displacement down-hole motors are incorporated intodrill strings, with bent-subs, to power rotary drill bits that areAbbreviations: BUR, build up rate (C176/m); DBR, drilling build rate (C176/m); DTR,drilling turn rate (C176/m); HDD, horizontal directional drilling (dimensionless); MT,mill-tooth (TCR bit) (dimensionless); PDC, polycrystalline diamond compact(dimensionless); ROP, rate of penetration (m/min); SBE, sliding build effectiveness(dimensionless); STE, sliding turn effectiveness (dimensionless); SBR, sliding buildrate (C176/m); STR, sliding turn rate (C176/m); TCR, tri-cone roller (dimensionless); TCI,tungsten carbide insert (TCR bit) (dimensionless); WOB, weight on bit (kN).* Corresponding author. Tel.: +44 (0) 121 414 5141; fax: +44 (0) 121 414 3675.Tunnelling and Underground Space Technology 25 (2010) 754765Contents lists availableTunnelling and Undergroujournal homepage: www.eE-mail address: a.c.royalbham.ac.uk (A.C.D Royal).adapted from oilfield technology, that is increasingly being usedto install cables and pipes under rivers and infrastructure. HDD tra-ditionally uses two cutting tools; shaped blades (that jet-cut withdrilling mud) for soft soils and down-hole drill bits, powered bymud-motors, for stronger formations.This paper focuses upon the control of steering HDD pilot borescreated using down-hole mud-motors. Fifty-four HDD installa-tions, comprising 86 drives over 42 km, were investigated; usingsite investigation survey data, HDD operators steering records(developed prior to installation to ensure that the desired borepathis achieved) and recorded drilling data, to analyse the performancenot investigated.The data for each drive was organised into sections describingeach length of rotary drilling and slide drilling used to establishthe borepath. The ratio of actual steering performance against pre-dicted performance was identified for each of the sections to deter-mine the factors that impact upon steering control in HDDinstallations (following the approach by Lesso et al., 1999; Studeret al., 2007). The study identified a number of factors that impactupon the ability to control steering in HDD, including; the lengthof slide drilled sections; the distance from the drilling rig to thedown-hole assembly; the drill bit type and bend angle of the1. IntroductionHorizontal directional drilling (HDD)0886-7798/$ - see front matter C211 2010 Elsevier Ltd. Alldoi:10.1016/j.tust.2010.06.004that prevents the widespread adoption of this technique in place of traditional open cut methods.Two types of drill bit are commonly used in horizontal directional drilling; shaped jet-cutting bits andbits mounted on bent-subs and driven by mud-motors, the former being utilised in weak ground condi-tions and the latter in stronger formations. This paper analyses a dataset of survey data from pilot boresfor fifty-four HDD installations that used mud-motors to investigate the parameters that impact uponthe control of the position of the drilling bit. The drives are broken down into sections of rotary and slidedrilledborepathandtheseareinvestigatedseparately.Drillingpractice,drillingequipment,lengthofdriveand the geology in which the bore is being established will have an effect upon the ability to control theposition of the drilling bit.C211 2010 Elsevier Ltd. All rights reserved.a versatile technique,within the down-hole assembly. Those installations using poly-crystalline diamond compact (PDC) bits, stabilisers or were identi-fied as being undertaken in problematic ground conditions wereReceived 9 June 2009Received in revised form 25 January 2010Accepted 17 June 2010Available online 17 July 2010in urbanised environments or in locations where trenching is difficult, such as under rivers or railways.This technique utilises down-hole bits to create the bore before it is expanded with back-reamers to allowinstallationoftheproductpipe.ControllingthepathoftheboreiscriticaltothesuccessofmanyhorizontalAnalysis of steering in horizontal directionalusing down-hole motorsA.C.D Royala,*, T.J. Riggallb, D.N. ChapmanaaSchool of Civil Engineering, University of Birmingham, Edgbaston, Birmingham B15 2TT,bRiggall & Associates Limited, Nailsworth GL6 0DT, UKarticle infoArticle history:abstractHorizontal directional drillingrights reserved.drilling installationsis becoming an increasingly popular technique for the installation of /locate/tustat ScienceDirectnd Space Technologyefficient at cutting through rock formations. Incorporating a drillbit that can be rotated irrespective of the rotation of the drill stringhas resulted in the development of two drilling practices; drilling(or rotary drilling) and sliding (or slide drilling) (Fig. 1). Drilling re-fers to the rotation of the drill string whilst providing thrust fromthe drilling rig and sliding refers to the provision of thrust only. Insignificant torque and have side cutting capabilities, and in thecomparatively weak geological conditions associated with HDDbehind the bit (Fig. 2). Thus the operator does not accurately knowthe position of the bit in real time and must wait until the sensorof short alternating drive lengths of drilling and sliding in prefer-ence to continuous slide drilling. This is due to the concernsregarding the ability to accurately control the position of thedown-hole assemblies whilst sliding over long distances.Data collected from the sensors in the down-hole assembly canbe compared to the steering patterns to monitor the down-holeassembly location; provided that the azimuth, inclination, distanceto bit, distance to sensor and tool face angle are known. The fre-quency, and adopted strategy, of surveying the position of thedown-hole assembly can lead to deviations from the desired bore-path. Current practice is to take static surveys at set points (everytime a new drill rod is introduced into the string, or after a set pen-etration distance; a maximum of 10 m between survey points isgenerally used in the HDD industry). Stockhausen and Lesso(2003a,b,c) undertook continuous surveying of oilfield boring andwere able to illustrate that assuming the drill bit must cut a pre-dictable bore between two surveyed points (approximate surveydistance of 30 m) is invalid and can lead to significant deviationswithin the bore if the deviations are not identified and are allowedto combine over the length of the bore. It was recommended that aA.C.D Royal et al./Tunnelling and Underground Space Technology 25 (2010) 754765 755reaches the desired point to obtain accurate positional data. Clearlythere is the potential for the drill to deviate from the desired pathand the operator must either withdraw the drill string and re-drillthe bore or correct the position of the drill as it moves forward. Theincorporation of deviations from line and level (known as dog-legs)has the potential to damage the drill string or the product pipe dur-ing subsequent installation. Royal et al. (2006, 2010) and Chapmanet al. (2007) have argued for the need for research to improve thecontrol of the position of down-hole assemblies if HDD is to be-come universally adopted, in place of open cut methods, andachieve long distances in continuous drives.installations PDC bits suffer from excessive bit-walk. Bit-walk de-scribes the lateral drift of the drill bit due to rotational forces actingon the bit (Liu and Shi, 2002). TCR bits will experience bit-walk butat a lower level to the PDC bit, due to the reduced level of torquegenerated by the bit (Norris et al., 1998) and the reduced side-cutting potential (Ernst et al., 2007). However, TCR bits experiencereduced rate of penetration (ROP) and require a greater minimumforce applied to the bit; known as the weight on bit (WOB) (kilo-newtons), in order to cut effectively, when compared to PDC bits.4. Monitoring the position of the down-hole assemblyThe use of down-hole motors within a drilling assembly is notwithout its problems as the sensors used to monitor the positionof the drill suffer from interference generated by the motor (usingconventional HDD equipment) and must be placed several metresboth cases the mud-motor drives the drill bit. Drilling createsstraight sections of bore whereas sliding creates the curved sec-tions (which are orientated by managing the angle of the tool faceand controlled by the angle of the bent-sub). The presence of thebent-sub within the drill string results in rotary drilled sectionshaving greater bore diameters than those created by slide drilling(Fig. 1), this can have an impact on the ability to control the posi-tion of the drill bit. Equipment is available that attaches to thedown-hole assembly and allows for the creation of curved sectionswhilst rotary drilling, although this is rarely incorporated into HDDinstallations and is not considered herein.3. Bit types commonly used in HDDThe oilfield industry utilises either PDC bits (these shear the for-mation), or TCR bits (which gouge and crush the formation); mill-tooth bits (MT) or tungsten carbide insert bits (TCI). However,HDDinstallationstendtobedominatedbyTCRbitsasPDCgenerateFig. 1. Illustration of drilling (rotary drilling, left)5. Establishing the desired borepath during pilot drillingSteering patterns are often developed by the HDD operatorsprior to pilot boring to guide the drillers, allow for the predictionof the location of the down-hole assembly at any point duringthe drive, and ensure that the desired borepath is established.These steering patterns are created in accordance with manufac-tures technical data for the down-hole assembly in question.When developing steering patterns for curved sections withinthe borepath, HDD operators have traditionally utilised sequencesFig. 2. Configuration of down-hole assembly, the tool face convention (lookingfrom the surface down into the bore) and the components used to describe a 3-Dcurve (drawing not to scale).and sliding (slide drilling, right) in HDD.veying, tied into static surveys every 10 m (or at the installationbly, the drill bit type and the stated performance of the down-holerate; DTR and DBR, respectively) and sliding (sliding turn rateand sliding build rate; STR and SBR, respectively). The measuredassembly, the bend angle of the bent-sub. The methodology usedto create the modelled data and the outcomes of the parametricstudy are reported in the following sections of the paper.7. Analysis of steering HDD pilot boresThe data used in this study comprised three formats; drillinginformation (location, drilling conditions, drilling mud pressuresand flow rates, down-hole assembly used, bit to sensor length,of a new drill rod into the drill string), would be equally applicableto HDD installations and would provide increased certainty in thepositional control of the down-hole assembly.6. Factors identified in oilfield drilling that impact upon thecontrol of steeringPrevious research undertaken in positional control of down-hole assemblies tends to refer to oilfield applications and focusupon the use of PDC bits, which is not felt to be directly relevantto the HDD industry. However, a number of factors have been iden-tified that may be relevant to HDD installations and include; thecompressive strength of the rock (Lesso et al., 1999; Harelandet al., 2000); changes in rock strength (both laminations and inter-bedding within the strata, Boualleg et al., 2006); the dip of the for-mation (Stockhausen and Lesso, 2003b); the type of down-holeassembly used (Lesso et al., 1999; Studer et al., 2007); the ROP(Ernst et al., 2007; Lesso et al., 1999), the WOB (Lesso et al.,1999; Studer et al., 2007); bit-walk (Liu and Shi, 2002); tool faceangle (Lesso et al., 1999; Studer et al., 2007); stabilisers (that am-plify the size of dog-legs created by migration away from line andlevel).Lesso et al. (1999) and Studer et al. (2007) both developed ap-proaches to investigate the relationship between the apparatusused (within the oilfield industry) and steering response. Lessoet al. (1999) investigated 4600 drives by averaging the steeringperformance for the drive and then undertaking a cluster analysis.Finite element models were created to predict the behaviour oftypical down-hole assemblies (based on the results of the clusteranalysis) and the models were used to undertake a parametricstudy to identify important parameters on steering response (asdescribed above). Studer et al. (2007) developed a program thatcan be used in post-analysis to investigate drilling performance.The model breaks a drive into segments and compares predictedperformance (derived from user supplied variables) with actualperformance.In light of the previous research undertaken on steering controlin oilfield drilling, the analysis of control of steering in HDD instal-lations reported in this paper broadly follow the approach under-taken by Lesso et al. (1999) and Studer et al. (2007). The datasetswere broken down into sections and the surveyed values werecompared to theoretical values. The modified datasets were thenused in a parametric study to assess the relative importance of var-ious factors on the control the position of HDD down-hole assem-blies. The parametric study included the length of slide drilledsections, the distance from the drilling rig to the down-hole assem-change in survey strategy is needed, i.e. to increase survey fre-quency or move towards continuous surveying, to improve thecontrol of bit positioning. The authors of this paper believe that,whilst the surveying distance in HDD is less than in the oilfieldindustry (10 m intervals instead of every 30 m), continuous sur-756 A.C.D Royal et al./Tunnelling and Undergroundetc.), steering information (formalised description of operatorsprocedures throughout the installation) and the surveyed data.The data spans a 10 year period and describes HDD installationsdistance in Table 2 refers to the distance travelled during eachphase of drilling and sliding (calculated from the change in dis-tance from drilling rig to bit). The ability to achieve the desired cur-vature during the drive was assessed by dividing the curve ratesachieved in each section (STR and SBR) by the predicted curve rateof the down-hole assembly in the turn and build planes. The pre-being undertaken in 13 countries by 20 companies. It is understoodthat in 10 years changes in technology or practice could have an ef-fect upon the analysis. However, the data was included as a signif-icant dataset was required to investigate which parameters havean effect on the control of steering and it was felt that HDD steer-ing technology had not changed significantly within this period.8. Preparation of the dataset for use in the studyThe majority of bits used in this study were TCR without stabil-isers. Therefore datasets based on PDC, drag-bit, or stabiliseddown-hole assemblies were removed from the dataset used inthe study. Data was also removed if the information providedwas insufficient for the needs of the project. Occasionally, the dril-ling records would state that conditions encountered were diffi-cult or problematic, although further information providinginsight as to why this may be the case were not supplied.In these instances, the drilling records were also rejected fromthe dataset because it was not possible to quantify why the groundwas problematic, nor how difficult ground impacted upon steer-ing control, and it was felt that it would be inappropriate to includesuch data within the analysis.It is understood that difficult ground conditions would be ofinterest to any investigation that considered the control of HDDsteering; as such cases could result in extreme deviations from de-sired borepath. Difficult ground is a term often used to describewhen cavities, fractures, faults, boulders, and cobbles wereencountered. Deviations caused by these structures are difficultto estimate without prior knowledge of their orientation relativeto the drill alignment. Prediction of deviations in difficult groundis believed to be impractical without detailed mapping of the geo-logical structures in which the borepath is being drilled. A poten-tial method to compile such information would be to pullgeophysical logging equipment through the completed borepath;something the authors are unaware of being undertaken in HDD,and certainly had not been undertaken in the installations investi-gated herein.In total approximately 16 installations were removed as notbeing suitable for this study (72 installations, with 130 drives wereinitially investigated). The HDD project location, number of drivesundertaken during the installation and approximate maximumdrive length within the installation can be found in Table 1. Forthe purposes of analysis the installation data was tabulated and di-vided into sections describing changes in the drilling or sliding (in-formed by the drillers logs) during installation. The survey data(azimuth and inclination data) combines to form the 3-D borepathcreated during the installation, although for the purposes of thisstudy the data was analysed in two planes (horizontal and vertical,termed turn and build respectively, Fig. 2). The sign convention forbuild and turn is defined herein as: build is positive when movingtowards the high side and negative towards the low side; turn ispositive turning to the