A Theoretical Study of Rock Drilling with a High Pressure Water Jet

Based on analyses of experimental results of water jet drilling, the fluid motion law in rock pores and the tendency of energy distribution, the rock-breaking process under high pressure water jet drilling has been studied systematically. The research indicates that the main interaction between the rock and water jet is interface coupling, that the impacting load and the static pressure of the water jet act together to make the rock break, and that the stress wave is the main factor. Water jet drilling can be divided into two stages: At the initial stage, the stress wave plays the main role and most of the rock breaking takes place; at the later stage, the existing rock defects, for instance, micro-holes and micro-cracks, are propagated and merged to make macroscopic damage, and then the diameter of the jet-drilled hole is expanded.

Micro-macro fracture mechanism of heterogeneous granite in percussive drilling

The conventional rotary rock breaking method faces a technical bottleneck in improving the rate of penetration(ROP)in deep hard formations.Percussive drilling is the most potential approach to increase rock-breaking efficiency and ROP.However,the rock-breaking mechanism of percussive drilling is still unclear enough,especially the micro-fracture mechanism of rock under confining pressure(under lateral pressure and hydraulic pressure).In this paper,the impact rock breaking experiments by four kinds of Polycrystalline Diamond Compact(PDC)cutters are carried out using a drop-weight impact testing machine and an acoustic emission(AE)recording system,the influence of parameters such as cutter shape,rake angle,and impact energy on rock-breaking are systematically analyzed.This study includes a numerical simulation to examine the process of crack initiation,propagation,and cuttings formation during the impact process with the consideration of confining pressure.The results show the conicalshaped cutter is the most aggressive with high breaking efficiency.The penetration depth of the cutter is mainly influenced by the impact energy and cutter shape than the rake angle of the cutter.There exists critical impact energy makes the rock breaking efficiency the highest.The critical impact energy is about 40 J when using the conical-shaped cutter with a rake angle of 15°.The rock mainly failed in tensile mode,and the inter-grain crack is the main crack.Hydraulic pressure can inhibit the formation of horizontal cracks,while lateral pressure can inhibit the formation of vertical cracks and reduce the proportion of tensile cracks.The research results can provide some reference and basis for improving the rock-breaking efficiency in deep hard formations.

Deformation Mechanisms and Safe Drilling Fluids Density in Extremely Thick Salt Formations

Hydrocarbons are very often associated with salt structures. The oil and gas industry is often required to drill along and through long salt sections to reach and recover hydrocarbons. The unique physical properties of salt require special techniques to ensure borehole stability and adequate casing design. This paper assumed that the mechanical behavior of salt is regulated by the magnitude of mean stress and octahedral shear stress and under the influence of different stress conditions the deformation of rock salt can be represented by three domains, i.e. compression domain, volume unchanged domain, and dilatancy domain, which are separated by a stress dependent boundary. In the compression domain, the volume of salt decreases until all microcracks are closed, with only elastic deformation and pure creep; in the volume unchanged domain the deformation is considered steady incompressible flow controlled by pure creep; and in the dilatancy domain the volume of salt increases during deformation due to micro-cracking, causing damage and accelerating ＂creep＂ until failure. This paper presents a hypothesis that the borehole is stable only when the magnitude of octahedral shear stress is below the dilatancy boundary. It gives the design method for determining drilling fluids density, and calculates the closure rate ofborehole with the recommended drilling fluids density. If the closure rate of the borehole is less than 0.1%, the drilling fluids density window can be used during drilling through extremely thick salt formations.

Tooth arrangement design of retractable DTH hammer bit used for drilling while casing

Down-the-hole(DTH)hammer with casing while drilling(CWD)is a technology that has been proven to be able to alleviate many of the problems faced by complex formations.However,the drill bit is suffered from rapid wear,low drilling efficiency,and high energy consumption due to the unreasonable tooth arrangement and impact energy selection in drilling process,which affect the application effect of this technology.ABAQUS software was used for numerical simulation of rock breaking behavior under impact load with the single,three,and five teeth arrangement drill bit respectively,to improve the application effect and solve the aforementioned technical problems.Based on the calculated parameters of tooth arrangement,we designed a novel drill bit for hard rocks and provided a theoretical basis for the tooth arrangement of largediameter drill bits.

Research progress and development direction of low-temperature drilling fluid for Antarctic region

By combing the characteristics of drilling in Antarctic region, performance requirements on drilling fluid for Antarctic low temperature conditions, and research progress of low temperature drilling fluid, current problems of the drilling fluid have been sorted out, and the development direction of the drilling fluid has been pointed out. Drilling in the Antarctic region mainly includes drilling in snow, ice and subglacial rock formations, and drilling in Antarctic low temperature conditions will face problems in four aspects:(1) low temperature and large temperature changes in the drilling area;(2) likely well leakage and drillstring-sticking in the snow layer, creep in the ice layer, ice chip gathering jamming in the warm ice layer, well wall collapse in the subglacial rock formations;(3) lack of infrastructure and difficulty in logistical support;(4) fragile environment and low carrying capacity. After years of development, progresses have been made on low-temperature drilling fluids for the Antarctic region. Low-temperature petroleum-based drilling fluid, ethanol/ethylene glycol-based drilling fluid, ester-based drilling fluid and silicone oil-based drilling fluid have been developed. However, these drilling fluids have problems such as insufficient low-temperature tolerance, low environmental performance and weak wellbore stability, etc. In order to meet the performance requirements of drilling fluid under low-temperature conditions in Antarctic region, the working mechanisms of low-temperature drilling fluid must be examined in depth;environment-friendly low-temperature base fluid of drilling fluid and related additives must be developed to prepare environmentally friendly low temperature drilling fluid systems;multi-functional integrated adjustment method for drilling fluid must be worked out to ensure well wall stability and improve cutting-carry capacity when drilling ice formations and ice-rock interlayers;and on-site support operation codes must be established to provide technical support for Antarctic drilling.

Mechanism of drilling rate improvement using high-pressure liquid nitrogen jet

To address the high rock strength and low drilling rate issues in deep oil/gas and geothermal exploitation, we performed mechanical property tests on three kinds of rock samples(granite, shale and sandstone) subjected to liquid nitrogen(LN2) cooling and conducted rock-breaking experiments using LN2 jet. Rock-breaking characteristics and mechanisms of LN2 jet, heat transfer features between LN2 and rock and thermal stress evolution in rock were analyzed. A novel high-pressure LN2 jet assisted drilling method was proposed accordingly. The study results show that LN2 thermal shock can significantly reduce uniaxial compression strength and elastic modulus of rock. Rock damage and corresponding mechanical deterioration become more pronounced with increasing rock temperature. The LN2 jet has merits of high rock-breaking efficiency and low threshold rock-breaking pressure. Rock failure under LN2 jet impact is characterized by large volume breakage and the rock-breaking performance becomes more significant with increase of rock temperature. Under the impact of LN2 jet, the damage of granite is the most remarkable among the three rock samples. Thus, this method works better for high temperature granite formations. It has a good application prospect in speeding up drilling rate in deep hot dry rock geothermal reservoirs.

冲击破岩钻井提速技术研究现状与发展建议

提高钻井速度不仅是提高我国油气效益开发及深地勘探等方面的重要技术手段,同时对保障国家能源安全意义重大。冲击破岩钻井技术在国内外油田现场应用并获得了良好的提速效果,持续开展此类技术攻关有望攻克当下我国深地高温高压硬岩地层进尺低、提速难的技术痛点。介绍和分析了轴向冲击、扭力冲击和轴-扭耦合冲击辅助钻头破岩钻进技术方面的实践及发展动态。结合冲击破岩钻井技术现状,阐明了冲击辅助钻头破岩力学原理是冲击破岩钻井提速技术的关键问题,综述了国内外研究学者在冲击辅助钻头破岩物理实验、理论模型和数值模拟等研究方法上取得的科学进展。针对冲击破岩钻井提速技术的发展提出了相关建议,即加强在材料结构优化设计、智能化控制、多元技术融合和井场应用优化等方面的研究力度,为我国能源高效开发做出贡献。

干热岩定向钻井关键技术研究与应用

为推动干热岩产业化步伐,中国地质调查局在青海共和盆地部署了我国首例干热岩试验性开发工程,采用一口直井注入和两口定向井采出的开发模式,文章就定向井钻井关键技术进行研究与应用。青海共和盆地干热岩主要为花岗岩,地层硬度大、研磨性强、温度高,加上大规模储存改造的影响,定向井钻井作业存在机械钻速低、碎岩工具寿命短、测量仪器耐温差、信号不稳定、井眼轨迹控制难度大等技术难题。为保证钻井作业顺利推进,从井眼轨迹控制、提高井下工具耐温耐磨能力、提高钻井液高温流变性能、钻井液主动降温等技术手段入手,创新研发了耐高温MWD、抗高温聚合物钻井液体系、螺旋板式钻井液冷却装置等关键技术与装备,优选了“牙轮钻头+单弯螺杆+MWD”钻具组合,安全高效地完成了双靶点定向井施工,AB靶心的中靶精度分别为4.85 m和8.97 m,钻井周期缩短20%以上,并取得了最高进尺175.00 m、最快机械钻速3.74 m/h的提速增效成果。

基于仿真的复合冲击破岩流固热耦合场分析

为了揭示复合冲击载荷下全尺寸PDC钻头破岩机理,以温度为纽带,通过迭代算法建立复合冲击载荷下PDC钻头破岩流固热耦合仿真分析模型,同时以PDC钻头切削齿温度为评价指标验证仿真模型;从动态破岩过程、力学变化行为、温度演化规律和流场分布特征等4个方面完成复合冲击载荷下全尺寸PDC钻头破岩工作特性分析。分析结果表明:PDC钻头破岩流固热耦合仿真分析模型误差在10%以内,满足工程分析精度需求;PDC钻头破岩过程分为单齿破岩、平面破岩和深度破岩3个阶段,增加复合冲击载荷后PDC钻头最大扭矩增大66.3%,平均扭矩增大28.0%;PDC钻头的高温区域分布在钻头最底部切削齿表面,最高温度达到166.9℃;钻井液在PDC钻头刀翼外侧切削齿产生高压区域,最大压力达到107.9 kPa;钻井液在喷嘴出口处流速最大,达到6.1 m/s。研究结果可为揭示复合冲击破岩机理、开发高效PDC钻头提供理论指导和技术支持。

高压电脉冲破碎非均质花岗岩数值模拟

对高压电脉冲破碎机制的研究是提高钻井破岩效率和优化电脉冲电参数的关键。利用颗粒流离散元软件及Voronoi划分建立非均匀介电性质的花岗岩模型,从电流场、电路场、电击穿场进行等离子通道生长过程仿真,并分析非均质度对击穿路径的影响;对比不同花岗岩的电破岩效率和电脉冲破岩效果。结果表明:花岗岩的非均质度增大使得初始电场极值增大,相应地降低了电破岩的能量需求;等离子通道的生长方向存在优先发展区域,等离子通道的生长过程体现出通道尖端处电场集中现象强于通道躯干处;花岗岩非均质度的差异使得等离子通道的总长度和平均贯穿深度存在显著差异,在一定非均质度范围内电脉冲破碎效果和非均质度呈正相关;不同非均质度花岗岩的单脉冲电破岩效率差异不大,等离子通道的总长度越长,电破岩效率越高。

自控型粒子冲击钻井系统研制与现场试验

我国油气资源勘探开发中常规钻井技术在钻遇石英砂岩、燧石、高硅质砂岩、黄铁矿和火成岩等难钻地层时,面临“钻速慢、进尺短”的钻井瓶颈。为此,基于粒子高频冲击破岩原理,借鉴高层建筑混凝土配浆-注浆和常压混凝土储存方法,设计了双活塞换向机构、防粒子沉淀物料罐、动态回收储存装置、高效分离装置和2D/3D自动化监控系统,研制了1套自控型粒子冲击钻井系统,并在江沙X1井对其进行了现场试验。试验结果表明:该系统运行稳定可靠,粒子回收率达到98.7%,平均机械钻速15 m/h,与邻井同地层螺杆配PDC钻头钻进方式相比平均机械钻速提高1.52倍。所得结论可为深层及复杂坚硬地层钻井提速提供技术支撑。

油基钻井液乳化剂的制备与性能评价

钻井液乳化剂是油井钻探中的重要化学品之一,其性能评价对于钻井工程的成功进行具有重要意义。优秀的乳化剂能确保钻井液的稳定性和流变性能。在选择乳化剂时,应充分考虑其理化性能和体系综合性能,以确保钻井工程的成功进行。本研究以植物油酸、二乙烯三胺、马来酸酐为主要原料,制备了6种乳化剂产品,并对其进行理化性能评价和体系综合性能评价。实验结果显示,乳化剂PF-MOEMUL1、PF-MOCOAT1、PF-MOEMUL2、PF-MOCOAT2满足所有指标要求,在理化性能评价和体系综合性能评价的关键指标上有良好的性能,为钻井工程提供可靠的保证。而乳化剂PF-MOEMUL3、PF-MOCOAT3在倾点和塑性黏度方面未能达到指标要求。可能导致乳液不稳定、流变性能不佳等问题,从而影响钻井工程的顺利进行。通过对钻井液乳化剂的性能评价,对乳化剂的选择和应用提供了有效的参考指导。

旋冲钻具凸轮-滚轮冲击机构工作特性分析

旋冲钻具能有效提高深层、硬地层的破岩效率,具有广阔的应用前景。凸轮-滚轮是实现冲击动作的关键机构,但复杂多变的井下环境导致机构损伤严重,进而影响破岩效率。基于旋冲钻具多井次的试钻数据,建立凸轮-滚轮动力学模型,通过显式动力学(Autodyn)分析不同冲程、转速、钻压下的工作特性,总结机构的形变特征提出优化方法。分析结果与试验数据和理论数值对比,验证了计算模型的准确性。结果表明:冲程增大可提高冲击效果,但高于10 mm冲程的滚子实际运动轨迹受钻速、滚轮尺寸、凸轮轮廓曲率影响其轨迹将变平缓。转速在9~18 rad/s时轴向加速度波动幅度较大,对钻具的稳定性具有一定影响。钻压增大凸轮内缘处形变特性明显,其形变量与钻压成正比,25 kN钻压下凸轮的形变量约是10 kN的2.6倍。凸轮齿顶、滚轮内缘处为易变形点,在齿顶处安装可换滚筒同时改变滚轮为鼓轮构型并对抛物线-直线-抛物线、2次多项式、摆线、7次多项式4类凸轮轮廓线型进行特性分析。选用摆线及7次多项式凸轮座轮廓和鼓轮可提高冲击效果,计算结果可为旋冲钻具设计提供参考依据。

旋冲钻井技术研究现状与展望

随着中国资源勘探开发面向深层、超深层发展以及对应急钻孔救援水平保障能力的更高需求,旋冲钻井技术成为高效钻井领域的研究热点.旋冲钻井技术相较于传统旋转钻井技术,具备硬岩地层钻进效率高、钻压调控灵活、黏滑振动强度低等优势,广泛应用于深海深地资源勘探开采、应急钻孔救援等领域,具有广阔的应用前景.现阶段,在复杂岩层以及多变工况等条件下,进一步提高旋冲钻进效率、降低成本成为深井、超深井钻井过程中面临的首要任务.文中首先介绍了旋冲钻井技术的基本概念及优势;其次,综述了液动和气动2种冲击器的研制情况及结构特点;再次,讨论了高效破岩机制的研究进展和优化策略;从次,阐述了钻进效率关键影响因素方面的研究成果;最后,基于旋冲钻井技术研究成果和面临的挑战,对其未来研究方向进行了分析和展望.

高阻地层HDIL阵列感应影响因素分析与校正方法

近年来,四川盆地川中深层灯影组和龙王庙组天然气勘探中越来越多地使用油基泥浆,使得裸眼井电阻率测井只能选择阵列感应仪器。该地区目的层致密碳酸盐岩普遍表现为中高电阻率,典型气层的电阻率一般在500Ω·m以上甚至高达2000Ω·m,使得测量电导率的感应测井仪器接收的信号弱,叠加深层高温等因素的影响,采集的信号常出现负值,软件聚焦处理结果常出现平头现象,不能用于储层识别和气层评价。采用有限元模拟算法,分析泥浆电阻率、侵入半径及原状地层电阻率等单因素对阵列感应测井响应的影响规律,明确了各环境因素对感应测量信号的影响规律。结果表明,地层与泥浆电阻率对比度对测量信号有明显影响,当对比度接近于1时,各子阵列的误差较小,而侵入深度是另一个重要影响因素。总体上,较长源距的子阵列受各种因素的影响相对较小。针对实际资料的特点,提出一种基于Archie公式的原始电导率信号约束校正方法,对约束校正后的数据再开展软件聚焦,其结果得到明显改善。

多热源影响下双深双高钻井井筒瞬态传热模型

为准确分析钻井液高温高压物性参数、钻柱偏心、旋转和钻头破岩多种热源因素对环空温度剖面的影响,基于井筒和周围环境传热机理和流动过程,建立了一种适用于双深双高钻井的井筒瞬态传热模型。利用有限体积法对该模型进行数值求解,并将现场实测数据分别与软件Drillbench和该模型进行对比验证。结果表明,该模型的预测与现场实测数据拟合效果更佳。研究发现:综合考虑多种热源因素会使环空温度更接近井筒真实值,井底环空温差达到8.43℃;当考虑钻井液高温高压物性参数变化时,下段环空温度随井深的增加而显著减小,井底处环空温差为3.48℃;相较钻柱偏心,旋转和钻头破岩作用对环空温度的影响更显著,井底环空温差分别为6.20和6.56℃。研究结果可为双深双高钻井井筒温度预测和控制提供理论指导。

电脉冲破岩钻井地层主要参数敏感性分析

岩石的硬度、耐磨性等严重限制了深层超深层油气资源的高效开采,而电脉冲破岩钻井技术在破碎硬岩方面具有独特优势。为探究地层特性对电脉冲破岩效果的影响,根据电脉冲破岩的基本原理,并基于基本破岩单元建立了动态电损伤模型。基于动态电损伤模型,讨论了特定高压脉冲电源参数下,岩石特性对电脉冲破岩效果的影响。通过讨论分析可知,相对介电常数越大,岩石内部发生电击穿的时间成本越低,破坏深度与损伤总量也会越大;电击穿时间、破坏深度会随泊松比和弹性模量的变化出现小幅波动,但不具有规律性;岩石的密度不会对电脉冲破岩造成影响。相关结论可为电脉冲破岩钻井技术的进一步工业化应用提供一定参考。

基于力-构-能模型的钻井法凿井钻进参数设计思路与方法

竖井钻机钻井法是实现井筒机械化、无人化和智能化建设的重要技术之一。西部弱胶结地层钻井法凿井基岩破碎难、刀具损坏率高、糊齿和吸渣口堵塞等现象突出,高钻压、排渣不及时、泥包钻头易导致钻头憋死,而大扭矩钻进又发生了钻杆断裂、钻具掉落等事故,进尺缓慢和反复提钻维修、钻具打捞导致钻井工效极低,主要原因是钻头结构及其刀具布置不合理、钻进参数与岩石条件不匹配、破岩与排渣效率不协调。为解决弱胶结地层钻井法凿井“破不掉、排不出、进尺慢、能耗高”的现实难题,梳理了竖井钻机钻头破岩钻进技术现状及存在的问题,以“系统”和“过程”为基本观点,提出了基于力-构-能协调模型的钻进参数设计思路与方法,应重点围绕弱胶结地层钻井法凿井钻头结构设计及其力学特征、基于钻头滚刀运动轨迹的滚刀布置、基于气-液-固耦合流场的排渣效率优化以及基于能量转化机制的钻进参数优化4个主要方面开展研究,进而形成融合钻头结构、滚刀布置、洗井排渣和能量消耗等多因素的钻头高效钻进参数设计方法,为西部弱胶结地层钻井法凿井低能耗破岩、高效率排渣和破-排效率协调作业提供支撑,推动竖井钻机钻井法在西部弱胶结地层凿井中的应用。

非常规油气田开发含油岩屑环保无害化处理技术

非常规油气田的勘探开发通常使用大量的油基钻井液,在钻井过程中不可避免地产生较多的含油岩屑,给周边生态环境带来了较大的污染威胁。为了提高此类含油岩屑的处理效率,达到含油岩屑环保无害化处理的目的,采用超声波辅助化学清洗法对含油岩屑进行了清洗处理,并优化了处理工艺参数。结果表明:液固质量比越大、清洗剂质量分数越高、实验温度越高,经过超声-化学清洗处理后的岩屑含油率相对就越低;而随着清洗时间的延长以及超声功率的增大,处理后的岩屑含油率则呈现出“先降低后升高”的趋势。当实验液固质量比为4∶1、清洗剂质量分数为8%、清洗温度为40℃、清洗时间为30 min、超声功率为300 W时,对目标含油岩屑的清洗处理效果最好,处理后的岩屑含油率可以降低至0.22%,能够达到国家标准GB 18599—2020中的排放要求。研究结果可为非常规油气田开发含油岩屑的高效处理提供一种参考。

陕西榆林废弃钻井液固液分离技术研究

采用稀硫酸作为破胶剂,通过室内抽滤实验对各种常用絮凝剂进行了优选,优化了废弃钻井液固液分离配方,即采用酸化破胶后加入3.09 g/L硫酸铝和3.09 g/L硫酸铁,能够将废弃钻井液进行脱稳分离。经陕西榆林现场应用表明,废弃钻井液应用此技术脱稳后,一次压滤成功,滤饼中平均含水量为31.79%。与前期固液分离效果相比,滤饼平均含水量降低了17.90%,废弃钻井液处理成本降低了10.21%。