High quality and cost effective drilling system for prebored pressuremeter testing

A prebored pressuremeter test (PMT) requires a predrilled vertical smooth surface borehole of a constant diameter. Two methods for the preparation of predrilled boreholes are included in ASTM D4719. The first method is drilling a borehole using a rotary rig. While this method provides a constant diameter and a vertical borehole, it is costly and time consuming. The second method is the drilling of a borehole by a hand auger (Iwan type). While this is a low cost, rapid method, it may not provide a vertical borehole of constant diameter in a variety of soils.An innovative mechanical drilling system (MDS) has been developed for the preparation of vertical smooth surface borehole of constant diameter for the pressuremeter testing. The PMT was conducted in boreholes drilled by MDS, rotary rig (RR) and hand auger (HA) at a site that comprised clayey silt (CL-ML) and sandy silt (ML) deposits. The PMT curves thus obtained were compared in terms of quality, cost and time. The comparison indicates that good quality and cost effective PMT curves can be obtained by using MDS in broader strain range (up to 40%) for the stiffness and limit pressure determination.     

Modeling of annular fluid pressures in horizontal boring

Horizontal directional drilling (HDD) is minimally-intrusive construction method for installing underground utilities and pipelines. Today, HDD is becoming widely accepted as a cost-effective alternative to traditional open-cut construction. The occurrence of hydraulic fracturing, resulting in the migration of drilling fluid to the surface, has placed the HDD process under scrutiny, especially when considered for projects in environmentally sensitive areas. Hydraulic fracturing results when fluidic pressure within the borehole exceeds the shear strength or undrained cohesion of the strata. Models have been developed to predict borehole pressures; however, there is only limited information available on the properties of drilling returns obtained during HDD installations. A research program was undertaken to determine flow characteristics for drilling returns under a variety of soil conditions and bore penetration rates. Soil samples were gathered based on the Unified Soil Classification System (USCS) and their rheological properties were obtained for different drilling fluids and slurry densities. Presented in this paper is a methodology for predicting borehole fluid pressures over a wide range of project parameters that can be used as a guide to minimize the occurrence of hydraulic fracturing.     

Effective use of water in a system for water driven hammer drilling

Drilling with water driven down-the-hole (DTH) hammers is a recently developed method for competitive production of boreholes. In order to prevent large amounts of water being used during operation, the drilling fluid is here directly processed into a quality acceptable for reuse. The effectiveness is evaluated in well drilling with a mobile prototype water cleaning and pressurising unit. Especially the presence of abrasive particles in the fluid can drastically reduce tool life and make the method inefficient. The vital significance of this relation has called for detailed studies and a process simulation model for determining particle concentration and size distribution has been developed. This paper describes the model and how it is applied. Simulation results of different system configurations are also presented.     

Prediction of rotational torque and design of reaming program using horizontal directional drilling in rock strata

Horizontal directional drilling (HDD) has been widely used to efficiently and cost-effectively install pipelines in a variety of conditions. In particular, during application of HDD in the recent West-East Natural Gas Transmission Project in China, rocky conditions were encountered. In such difficult situations, it is necessary to predict the torque required for performing the reaming operation, as well as to select the appropriate type and size of reamers. However, there is presently not an appropriate and convenient method to accomplish these tasks, especially for large pipelines, such as 1219 mm (48 in.) diameter, which typically require a borehole of approximately 1600 mm (64 in.). The process of expanding the initial borehole to the ultimate required diameter in rocky strata is often a complicated procedure involving several passes of intermediate size reamers. Although available information for drilling techniques does provide some means of predicting the torque, it is not sufficient for meeting the present needs, including providing guidelines for determining the corresponding reaming program. Therefore, the results of recent research, which addresses rock crushing energy, have been incorporated to develop an improved prediction method. The results reflect rock characteristics collected at different job sites, which may be applied to new projects containing similar rock strata. The improved methodology is a valuable aide for engineers in their selection of an appropriate back-reaming program.     

Analysis of formation fracturing for the Maxi-HDD Qin River crossing project in China

A new irrigation pipeline was installed using the Horizontal Directional Drilling (HDD) method in order to alleviate the water shortage situation in Jiaozuo City, Henan Province, China. This pipe installation project included two parallel HDD crossings, with a pipe diameter of 1016 mm and a driven length of 1750 m for both of them. Based on the preliminary detailed geological survey report of the riverbed, hydro-fracturing control under high slurry pressure would be a big challenge for this project. This paper summarizes the prediction methods for the maximum allowable mud pressure in the borehole based on different mechanisms of formation fracturing. Based on the geological data of this crossing project, the Delft equation and another prediction method based on tensile failure (termed here the Xia method) were used to calculate the maximum allowable annular pressure. The real pumping pressure of this project was recorded by the contractor. By comparing the theoretical predictions of allowable pressure with the actual pressures for the horizontal section of the borehole, it indicated that the Xia method is conservative and the limits of the Delft equation could not be verified in this project. As a solution dealing with potential hydro-fracturing, finite element modeling shown that increasing the ground surface load would rise the borehole allowable pressure at which fracturing would occur. This solution was used to deal with a blow-out in the entry section of one pilot hole on this project. Under the guidance of the theoretical and numerical simulation results, the Qin River crossing project was successfully completed.     

Stability analysis of a borehole wall during horizontal directional drilling

In this paper, numerical simulation strategies are proposed and numerical analyses are performed to investigate the stability of a borehole wall during horizontal directional drilling in loose sand with an emphasis on the role of the filter cake in borehole stability. Two computational scenarios, one in the absence of a filter cake and one with the presence of a filter cake in a borehole wall, are investigated by considering both deep and shallow borehole situations. In the case where no filter cake is formed, the soil–drilling fluid interaction analysis shows that the effective pressure on soil particles will quickly decrease to zero even at a low drilling fluid pressure because of the rapid drainage of the drilling fluids into the loose sands. This conforms to the classical liquefaction criterion, indicating that static (flow) liquefaction-based soil crumbling and sloughing will occur even at a very low drilling fluid pressure if an effective filter cake is not formed. Soil’s permeability effect on pore pressure and the transition to a steady flow are also studied. In the second scenario in which a filter cake is formed, the hydraulic fracture failures around the bores are investigated, which are caused by the expansion of the yielding zones. The yield zone sizes and critical drilling fluid pressures at the moment of hydraulic fracturing failure are calculated from the finite element analyses and the closed-form solution, which is based on classical plasticity theories. The critical fluid pressures from the finite element analyses and the closed-form solutions are very close, but there is a large discrepancy between the yield zone sizes.     

基于非线性反演的井壁稳定随钻预测方法

常规井壁稳定预测方法计算量大、操作繁琐、适用范围有限,严重影响其实钻应用效果。通过考察声波速度、地震记录及井壁稳定参数之间的定量关系,建立起利用地震资料直接反演孔隙压力、地应力、岩石强度的模型。根据反演模型的非线性特征,结合井壁稳定参数的地质统计特性,运用随机地震反演方法预测待钻地层的孔隙压力、地应力、岩石强度,并根据反演结果进一步预测井壁稳定性。在实钻过程中,利用录井资料的实时分析和井壁稳定参数的分层地质统计模型,对钻头前方地层的井壁稳定性进行随钻预测。在川东北元坝气田的应用情况表明,本方法的综合性能相比常规方法有明显提高,具有较强的随钻预测能力。     

流固耦合作用下水平定向孔壁稳定性分析

孔壁失稳是目前水平定向钻进工程中经常遇到的一个实际问题,尤其是在地表的第四纪松散地层中钻进孔壁失稳更是屡见不鲜,严重影响工程施工。针对以往研究中没有考虑渗流场对孔壁稳定性的影响问题,本文在Biot固结理论的基础之上,建立了应力场和渗流场耦合数学模型,采用有限元方法对所建立的模型进行求解。通过对某一水平定向钻进孔壁稳定性进行数值模拟,分析了在流固耦合作用下地层孔隙压力、有效应力和位移的变化规律,并分析了在不同的冲洗液压力下,地层沉降情况。研究发现,在定向钻进过程中,流固耦合作用对地层特别是井壁附近围岩的应力和变形影响很大。研究结果为钻进过程中避免孔壁失稳,合理选择冲洗液及冲洗液压力提供理论依据。     

Marine Water Quality Assessment Of Synthetic-Based Drilling Waste Discharges

Drilling muds or fluids used in drilling operations serve several functions: they lubricate the drill bit; maintain borehole pressure; clean and condition the hole; and flush rock cuttings to the surface. Drilling mud also adheres to rock cuttings, as can formation oil. Barite is used as a weighting agent, which approximately makes up approximately 33% of synthetic mud. It contains traces of heavy metals, which contribute to the toxicity of drilling waste. As environmental issues attract increasing public awareness, the treatment and disposal of spent drilling fluids and contaminated rock cuttings from drilling operations have become sensitive issues for offshore operations around the world. Within the last decade, the oil and gas industry has introduced synthetic-based drilling fluids as substitutes for oil-based fluids. This pollution prevention measure has been complemented by improvements in solid control systems technology. This paper adopts the current U.S. Environmental Protection Agency methodology for a hypothetical case study of an oil field on the East Coast of Canada to determine the water quality impacts of disposal of drilling wastes. The concentration of pollutants at the edge of the mixing zone in the water column and pore water are estimated and compared with Canadian water quality guidelines for protection of aquatic life.     

Drilling-induced tensile wall-fractures: implications for determination of in-situ stress orientation and magnitude

Detailed investigation of failure of the borehole wall in two scientific drilling projects, the German KTB (Kontinentales Tiefbohrprogramm der Bundesrepublik Deutschland) and the European geothermal research project at Soultz-sous-Forêts, France, has lead to new insight in the phenomena of tensile fractures induced in the wellbore wall during drilling. Comparison of the orientation of the fractures with the orientation of the horizontal principal stress known from breakout and hydraulic fracturing analysis demonstrates that these fractures are reliable indicators of the orientation of the maximum horizontal principal stress S_H. A model for the initiation of the fractures is presented which points out the important influences of (a) the tectonic stress state, (b) increased mud pressures during drilling operation and (c) thermal stresses induced by circulation of relatively cold drilling mud. Analysis of drilling-induced fractures in the GPK1 borehole at Soultz-sous-Forêts (where the magnitude of S_H is known from hydraulic fracturing experiments) demonstrates the validity of this model for the initiation of the fractures. Further, a new method is proposed to estimate the magnitude of S_H from the occurrence of drilling-induced fractures and knowledge of thermally induced stress and pumping pressure during drilling. The method is successfully applied to both KTB boreholes. An independent method to estimate the magnitude of S_H based on the analytical calculation of the stress intensity factor for drilling-induced fractures taking into consideration both, increased mud pressure and thermal stress, is also presented. Application of this method confirms the results derived with the analysis described above. Additionally, the evaluation of the orientation of the fractures with respect to the wellbore axis indicates that over major depth sections of the investigated wells the vertical stress is a principal stress.     

A decision support system for horizontal directional drilling

Horizontal directional drilling (HDD) was pioneered in the US in the early 1970s. Through the integration of vertical oil well drilling technology with modern survey and steering techniques, horizontal directional drilling methods have the capability of undertaking a wide range of pipe installations, from large-diameter river crossings to small-diameter cable pipes. HDD has gained in popularity, as it is able to install underground pipes with minimum impact on society and the environment. Although HDD has been used for over three decades, it is necessary to evaluate the suitability and appropriateness of HDD methods on a project-to-project basis by considering a large number of factors that influence this decision-making. The lack of a systematic tool contributes to the difficulty of making effective decisions. This paper discusses the development of the framework for a decision support system (DSS) to assist in the selection of appropriate equipment/technique for HDD projects. Decision making criteria and rules are developed through literature review, analysis of field data compiled from the completed HDD projects, and investigations of ongoing projects. This DSS is most appropriate for use by contractors and asset managers at project planning stages.     

Practical application of failure criteria in determining safe mud weight windows in drilling operations简

Wellbore instability is reported frequently as one of the most significant incidents during drilling operations. Analysis of wellbore instability includes estimation of formation mechanical properties and the state of in situ stresses. In this analysis, the only controllable parameter during drilling operation is the mud weight. If the mud weight is larger than anticipated, the mud will invade into the formation, causing tensile failure of the formation. On the other hand, a lower mud weight can result in shear failures of rock, which is known as borehole breakouts. To predict the potential for failures around the wellbore during drilling, one should use a failure criterion to compare the rock strength against induced tangential stresses around the wellbore at a given mud pressure. The Mohr–Coulomb failure criterion is one of the commonly accepted criteria for estimation of rock strength at a given state of stress. However, the use of other criteria has been debated in the literature. In this paper, Mohr–Coulomb, Hoek–Brown and Mogi–Coulomb failure criteria were used to estimate the potential rock failure around a wellbore located in an onshore field of Iran. The log based analysis was used to estimate rock mechanical properties of formations and state of stresses. The results indicated that amongst different failure criteria, the Mohr–Coulomb criterion underestimates the highest mud pressure required to avoid breakouts around the wellbore. It also predicts a lower fracture gradient pressure. In addition, it was found that the results obtained from Mogi–Coulomb criterion yield a better comparison with breakouts observed from the caliper logs than that of Hoek–Brown criterion. It was concluded that the Mogi–Coulomb criterion is a better failure criterion as it considers the effect of the intermediate principal stress component in the failure analysis.     

控制油井盐层段流变缩径的泥浆密度的计算方法

利用模拟地下温压条件下的盐岩三轴蠕变试验装置,通过试验确定出中原油沙三段盐层的流变本构关系,研究出一种控制井眼收缩的泥浆密度的计算方法,并且据此绘制了相应的泥浆密度随地温及深度的变化曲线。经现场初步验证表明,曲线的预测值与现场数据具有很好的吻合。     

地面钻孔抽放采空区瓦斯及其稳定性分析

随着放顶煤开采技术在我国的迅速普及，采煤工作面及采空区的瓦斯涌出量不断增加。传统的高位钻孔、（本）煤层钻孔及穿层钻孔抽放技术有时不能完全满足现代化煤矿生产对瓦斯抽放的要求。采用地表垂直钻孔抽放采空区内的瓦斯是瓦斯治理技术的另一选择。煤层开采后，采窄区上覆岩层将发生非连续破坏和连续移动。在长壁工作面通过的过程中，地面垂直钻孔可能随岩层移动而发生破坏。据此，介绍一种进行地面抽放采空区垂直钻孔的应用及稳定性分析的方法及用于确定钻孔及套管直径的应用实例。采用提出的计算方法可避免由于受采动影响对地表瓦斯抽放钻孔引起的过大变形及其所造成的破坏。通过计算地表钻孔在不同深度的水平位移和垂直变形可确定钻孔直径和所需安设套管的直径及套管外充填材料的性能。     

超前地质钻探技术在齐岳山隧道中的运用

以齐岳山隧道进口施工为例,介绍了超前地质钻探技术在岩溶富水、高压突水、突泥的复杂地质条件下的施工工艺、成果分析、技术特点,从而为以后同类隧道施工奠定了基础。     

水基钻井液转变为水泥浆的实验研究

分析了矿渣的化学组成,碱催化下的水化反应机理及矿渣、钻井液混合浆的固化机理,并采用淡水泥浆和人工海水泥浆,进行了转变水泥浆实验,实践证明水基钻井液转换为水泥浆的技术具有经济效益和社会效益。     

基于围岩本体Mogi-Coulomb强度准则的层理性岩层斜井井壁稳定模型

 层理性地层中进行大斜度井施工的井壁失稳问题较为突出,在传统井壁稳定模型基础上,以弱面对岩石强度的弱化作用实验为依据,引入欧拉变换充分考虑三维地应力方向的任意性,利用Mogi-Coulomb准则强化中主应力对围岩本体强度的影响,结合单弱面强度准则建立分析层理性地层斜井井壁稳定问题的模型,并进一步给出计算斜井坍塌压力与破裂压力的方法与公式。实验与计算结果表明：当加载方向与弱面夹角为30°时岩石强度最低;Mogi-Coulomb准则因考虑了中主应力的影响而对围岩本体强度的估计更为有效;考虑层理弱面影响的井壁坍塌破坏区域明显增大,破坏位置也发生改变;取得最小坍塌压力值的钻井方向在空间中与层理面并非简单的垂直关系;空间中关于地应力主平面对称的井孔破裂压力相同。利用所建模型进行安全泥浆压力窗口的计算可为安全钻井以及斜井轨迹设计提供理论依据。     

Sanierung der Drainage- und Kontrollbohrungen im Untergrund der Sorpetalsperre

Remediation of the underground drainage and control system of the Sorpe dam To ensure the structural stability of the Sorpe dam, the Ruhrverband is remediating the no longer fully functional underground drainage and control system. Built between 1926 and 1935, the 69 m high rockfill dam with a concrete core seal was damaged during the Second World War, which led to increased seepage water in the inspection gallery. In the 1950s the original drainage system was therefore grouted and a new system created. In the 2010s it was discovered that the boreholes in the bedrock were no longer at their original depth due to sediments containing iron and manganese. In the current remediation the existing drainage and monitoring boreholes are either being widened by drilling or filled with cement suspension and replaced with new borehole profiles. All boreholes will then be converted into measuring points for monitoring the water level, seepage water and pressure. The drilling work poses a particular challenge due to the limited space within the dam structure. In July 2022 the remediation work was temporarily halted due to the occurrence of chemical injection agents containing PAHs. The work is expected to continue in the first quarter of 2024 using strict separation of clean and contaminated areas with artificial ventilation as well as a flocculation and activated carbon filter system for the drilling fluid.     

锚杆扩孔技术应用于某高层建筑基础加固

通过某高层建筑基础加固实例,介绍一种先在建筑物筏板钻小直径孔(φ150),然后利用锚杆扩孔技术在筏板下施工较大直径(φ400)桩基础的建筑基础加固方法,该加固方法对原基础的损伤小,成桩直径可控,单桩承载力高,加固速度快,工程实例表明,加固效果理想.     

深厚块石堆填层覆盖的岩溶地区冲孔桩施工

块石堆填地层由漂石、碎块石混少许粘性土组成,粒径大小不一,结构松散,孔隙大;岩溶地区基岩多发育溶洞、溶沟、溶槽、裂隙等形态,岩面坡度大。在厚层块石堆填物覆盖的岩溶地区,桩基选型相对容易,但桩基成孔施工往往成为制约工程工期的关键因素及工程的难点。应用泥浆护壁冲击成孔工艺配合合适的工艺控制手段,可以很好解决类似地层的桩基施工难点问题。实践证明,手动冲击钻机对类似地层更为高效。