Drilling Quality Research Articles

Problems in the wellbore integrity of a shale gas horizontal well and corresponding countermeasures

In the Changning–Weiyuan national shale gas demonstration area, SW Sichuan Basin, the wellbore integrity damage occurs in some shale gas wells and has direct effect on the gas production rate of single shale gas horizontal well. After statistics analysis was performed on the problems related with wellbore integrity, such as casing damage, casing running difficulty and cement sheath blow-by, the multi-factor coupling casing stress calculation and evaluation mode laws established. Then study was conducted on the influential mechanism of multi-factor coupling (temperature effect, casing bending and axial pressure) on casing damage. The shale slip mechanism and its relationship with casing sheared formation were analyzed by using the Mohr–Coulomb criterion. Inversion analysis was performed on the main controlling factors of casing friction by using the developed casing hook load prediction and friction analysis software. And finally, based on the characteristics of shale gas horizontal wells, wellbore integrity control measures were proposed in terms of design and construction process, so as to improve the drilling quality (DQ). More specifically, shale gas well casing design calculation method and check standard were modified, well structure and full bore hole trajectory design were optimized, drilling quality was improved, cement properties were optimized and cement sealing integrity during fracturing process was checked. These research findings are significant in the design and management of future shale gas borehole integrity.

Reliability Analysis of Double Derrick Based on Stress Analysis

The double derrick as an important part of the drilling rig hoisting system in deep sea oil and gas development, its working environment is much more complex than land rigs working environment. Therefore, in order to ensure the quality of drilling, it is very important to analyze the reliability of the deep double derrick structure and its dynamic load characteristic. Based on the ANSYS software to establish finite element model of double derrick, through the static analyzing to the derrick, get the stress distribution of the derrick structure in static action and the derrick stress deformation trend, provided a reference for evaluation of derrick. Selected the calculation method of double derrick overall reliability index, and according to the results of the finite element calculation of static strength calculated the double derrick overall reliability index, compared with the general standard, know that double derrick with high reliability.

Effects of applying electric and magnetic fields on laser drilling

To reduce defects and improve the quality of laser drilling, the electric and magnetic (EM) field-assisted laser drilling has been tested. For different industrial applications, we performed microlaser drilling and macro-through-hole drilling under different EM fields using two different lasers (ns and ms). Drilling was performed on a custom apparatus that can produce static and rotating EM fields. The motion of the plasma strongly affected the drilling quality. In an EM field, both the ns and ms lasers produced holes with smaller diameters, better surface quality, and fewer hole wall defects. The drilling defects were mainly caused by the plasma-based multi-shock effect. The EM field can influence the motion of the plasma and minimize defects.

Tuberculosis y embarazo

Se ha realizado el estudio de 597 casos de pacientes con tuberculosis pulmonar y embarazo, predominando los procesos pulmonares avanzados y de evolución crónica en 48.9 %. Del total de pacientes, fueron internadas 63 % en los últimos meses de gestación. Se instituyó en todos los casos la terapia tuberculostática actualmente en uso; la vigilancia del embarazo estuvo a cargo del obstetra. No obstante ello, las reactivaciones o extensiones lesionales en el puerperio sólo han alcanzado el 2 %. Las distocias ocurrieron en 4.4 % de casos, casi la totalidad por causa obstétrica; en dos pacientes, la insuficiencia cardio-respiratoria demandó la operación cesárea. Fallecieron tres pacientes por extensión del proceso pulmonar, una de las cuales ingresó en trabajo de parto en marcada insuficiencia respiratoria debido a la extensa calidad lesional y grave, complicada con perforación pulmonar unilateral. El promedio general de peso de los niños al nacer mostró tendencias, en general, a ser menor en los hijos de madres portadoras de formas pulmonares avanzadas que en las moderadamente avanzadas. El estudio anatomopatológico de placenta no reveló lesión tuberculosa en caso alguno; el cultivo de este material fue positivo en seis muestras, en cinco de ellas tan solo una o dos colonias. El líquido amniótico fue positivo para B.K. en cuanto casos; en tres solamente una o dos colonias. La duda sobre la asepsia necesaria en la recepción de las muestras no permite emitir juicio definitivo al respecto; el cuarto caso correspondió al de un niño que falleció dos meses después del parto en otro hospital con tuberculosis generalizada.

A New Method for Improving the RQD Determination of Rock Core in Borehole

Rock mass soundness is typically measured by engineers using the rock quality designation (RQD) combined with their own experience (Choi and Park 2004). Many researchers have established empirical models to estimate mechanical properties from the RQD (Zhang and Einstein 2004; Jiang et al. 2009), rock mass rating (RMR) (Bieniawski 1978; Nicholson and Bieniawski 1990; Chun et al 2009; Hoek and Brown 1997), or Q methods (Barton et al. 1974; Barton 1983, 2002) and the cumulative core index (Sen 1990). Considering its worldwide acceptance and usage in major rock mass classifications such as Q and RMR, RQD is among the practical useful parameters, especially when the geological strength index (GSI) is concluded from the RMR. Applications of RQD have also been quickly extended to other areas of rock mechanics, so that it is now among the fundamental parameters of geotechnical engineering (Hoek and Brown 1980; Hoek and Bray 1981). The RQD index is affected by a number of well-known factors and limitations; For example, it yields different values for a given location when samples are extracted from cores with different drilling orientations. Moreover, factors such as the quality of drilling and logging, rock strength and core size, water conditions, joint apertures, alteration, and roughness affect RQD values. Another significant limitation of the RQD definition is its dependence on the selected threshold length of unbroken rocks (Priest and Hudson 1976; Harrison 1999; Hack 2002; Chen et al. 2005). Therefore, RQD values for the same core typically vary for different threshold lengths. In practice, a familiar observation associated with this drawback is that RQD values tend to be either high or low (often above 70 % or below 10–20 %) in most rock engineering projects. Some values (e.g., between 40 and 60 %) are less frequently encountered, due to the customarily and universally adopted, but very arbitrarily selected, threshold value of 10 cm (for NX cores) in the assessment of RQD (Harrison 1999). To obtain a wider range of RQD values, Harrison (1999) proposed a technique for determining the optimal threshold length. However, this approach is only appropriate for a particular rock mass. Besides, this technique requires the determination of the minimum and maximum values of the discontinuity frequency in the rock mass, which generally means that the simplicity of the original RQD is lost. It is concluded that, since RQD measurements are encumbered by several limitations, they should be used with caution. Limitations of the RQD index influence engineering results when applied in classification systems, numerical modeling, and other engineering assessments (Palmstrom, 2005). Thiswork aims to describe the deficiencies of the RQD and propose a new, straightforward method for calculation of borehole RQD. This method also enables removal of the effect of joint orientation and piece length on RQD values.

Modelling of Nonlinear Torsional-Flexural Vibrations of Drill Strings

Nonlinear flexural-torsional vibrations of shallow drill-strings are investigated. The drill-string is represented as an elastic rod rotating at constant angular velocity under the action of the longitudinal compressive force. The nonlinear model of flexural and torsional vibrations of drill-string is constructed on the basis of the theory of finite deformations of V.V. Novozhilov and its second system of simplifications. The numerical analysis of the model is carried out in the environment of symbolic mathematical computations - Wolfram Mathematica. The dominance of flexural vibrations of the drill-string over torsional vibrations is established. The influence of drill-string parameters on its oscillatory processes is investigated. It will allow to build up the modes of the drill-string movements to improve the quality of drilling of wells.

Influence of nanofillers on the quality of CO2 laser drilling in vinylester/glass using Orthogonal Array Experiments and Grey Relational Analysis

Abstract This paper presents the influence of nanofillers on the CO 2 laser drilling of vinylester/glass based on L 9 Orthogonal Array Experiments and Grey Relational Analysis. Three nanofillers such as nickel nanopowder, carbon black and Closite 15-A were studied. Multiple responses such as Damage Width, Surface Damage Width and Taper Angle were optimised using the Grey–Taguchi method for laser power, cutting speed, air pressure and nanofiller content. Heat affected zone along with char due to the complete burning of the matrix was largest and caving through the depth of the hole was observed in vinylester/glass. Nickel nanopowder effectively reduced the heat affected zone and improved the quality of the hole due to the absence of char. Closite 15-A reduced the surface damage and the char was thicker and distributed as globules. Carbon black caused greater surface damage at the entry of the hole due to the burning of the fibres and very thin char covered the fibres through the length of the hole. Regression models were developed to predict the laser drilling responses.

Incapability of Drilling With a High-Power-Density Beam

This paper theoretically identifies the factors affecting the keyhole collapse during drilling with a high-power density laser or electron beam from fundamental principles of thermal physics. Laser drilling is widely used in components, packaging, and manufacturing technologies. The approach adapted in this paper is to probe the quasi-steady 1-D supersonic or subsonic flow behavior of the two-phase vapor-liquid dispersion in a vertical keyhole of varying cross section, paying particular attention to the transition between the annular and slug flows. Drilling with a pulsed laser beam can evidently change Mach number, ejected mass flux at the keyhole base, energy absorption and evolution in the keyhole, drilling speed, and surrounding pressure. The results find that thermal drilling is susceptible to becoming incapable for higher absorbed energy, drilling velocity, and Mach number, ejected mass flux at the keyhole base, and lower surrounding pressure resulting in a shock wave for a supersonic flow in the keyhole. A subsonic flow usually gives rise to keyhole collapse. The predicted results agree with physical intuition and exact closed-form solutions derived in the absence of friction, entrainment and energy absorption. Controlling the factors to enhance efficiency and quality of drilling is therefore provided in this paper.

Drilling Performance Investigations on Hybrid Composites by Using D-Optimal Design

The present study is carried out to study the damage observed at entrance and exit of the hole during drilling and surface quality of drilled hole on newly developed natural hybrid composites. Hybrid composite samples are prepared by using vinyl ester resin and three types of reinforcements namely, randomly oriented vetiveria zizanioides, woven jute and woven glass. The natural fibers are pre-treated with alkali and furnace heating in order to improve its surface properties. Three samples are developed by varying the composition of fibers in each one. Machinability study is done by drilling a series of 28 holes based on D-optimal design. Three output responses namely, damage factor at entrance and at exit and surface roughness are measured and optimized with an objective of minimizing the damages. Confirmatory runs are conducted and the responses are measured. The results are validated by calculating the average percentage of error between the model and confirmatory runs. The error was found to be minimal and hence the optimization is highly satisfactory.

Effect of ultrasonically-assisted drilling on carbon-fibre-reinforced plastics

This research focuses on the effect of ultrasonically-assisted drilling (UAD) on carbon fibre-reinforced plastics. High-frequency vibration was used to excite a drill bit during its standard operation. An extensive experimental study of drilling forces, temperature, chip formation, surface finish, circularity, delamination and tool wear was conducted using ∅3mm drill and presented here. UAD showed a significant improvement in drill quality when compared to conventional drilling processes. A finite-element study was also conducted to understand the nature of drilling-force reduction in UAD.

Quality Control for Weathered Rock Directional Drilling Pilot Hole Construction

Directional Drilling Technology originated from the oil drilling industry, combining industrial and public utility construction technology, after the evolution of modern horizontal directional drilling technology, which is widely used in the construction of municipal pipelines, oil and gas pipeline industry, and is a kind of trenchless surface through the construction technology. At present, there is more weathering rock to pass through in the oil and gas pipeline construction, so a higher requirements for the construction of directional drilling mud. The weathering degree of heterogeneity of the rock at the same time and also caused great difficulties to construction, and the guide hole construction in the construction of directional drilling is the key control to the key working procedure, after the guide hole is dragged back reaming and pipe at all levels, the basis of the guide hole quality directly affects the pipeline back to success, is the most important factor in engineering which can be successfully completed, so how to control the construction quality of directional drill guide hole is particularly important. Key words : Weathered rock; Directional drilling; Pilot hole; Mud

Mechanism of damage generation during drilling of carbon/epoxy composites and titanium alloy stacks

Composite/metal stacks are widely used in aerospace structures. To study the mechanism of damage generation during drilling of carbon/epoxy composites and titanium alloy stacks, both traditional drilling and orbital drilling were used. Because the cutting parameters of the two drilling processes were different from each other, an appropriate comparing method was proposed based on the analysis of kinematics of orbital drilling and traditional drilling. The results show that high cutting temperature is the main reason for the damage generation during drilling of composite/titanium stacks. Cutting heat generated during machining of titanium alloy conducts to the composites and leads to the increase of composite temperature. High cutting temperature induces the degradation of carbon/epoxy composite properties, which results in the generation of damage during machining of composites. The cutting force in axial direction during orbital drilling is generally as high as that during traditional drilling. However, the temperature during orbital drilling is 36.3% less than that during traditional drilling. High cutting temperature and continuous chip generated during traditional drilling cause the high hole-wall roughness of titanium alloy. The lower temperature during orbital drilling is responsible for the machining quality of orbital drilling being higher than that of traditional drilling.

Current rise criterion: a process-independent method for tool-condition monitoring and prognostics

Presented in this work is a novel tool-condition criterion dubbed as the current rise criterion (CRC). This criterion is based on the measured current values of the machine tool’s spindle and drive motors. The CRC comprises two components: (1) the current rise index (CRI) and (2) a sensitivity factor (SF) indicated as a subscript to the CRI. Current rise criterion is described mathematically as CRC = CRISF. The CRI that accounts for the damage (including wear) suffered by the tool is calculated as the square root of the sum of the squared percent increase in the root mean square (RMS) current values of the spindle and drive motors. To indicate the relative contribution of each of the machine tool motors to the CRI, the sensitivity factor (SF) reflects the ratio of the drive motor current percent rise to that of the spindle motor. The reference current used in calculating the percent rise of the motor current for both CRI and SF is measured at the first cut of the fresh tool. The versatility of the CRC was demonstrated here using two different machining processes: milling and drilling. Quantitative polar maps of the CRI and the associated sensitivity factor of cutting tools as well as qualitative descriptions of the various modes of tool condition afflicting the cutting tools are presented. CRC is demonstrated to be capable of monitoring the tool condition for a variety of cutting parameters of speeds and feeds. Another study demonstrated the versatility of CRC as a discriminator of the quality of chisel drills. It was found that the criterion successfully tracks the tool condition along a variety of process levels. CRC may be used to monitor tool condition and prognostics across practically all machining operations and process parameters, thus rendering the criterion “process independent.” CRC can also be used to monitor the change in power consumption of machine tools while cutting with worn tools.

Study on the 3D Pattern of Hole Wall in Drilling Carbon Fiber Reinforced Plastics Using Orthogonal Experiment

The drilling damage forms of hole wall is presented and the reasons for drilling quality are analyzed in drilling carbon fiber reinforced plastics. Based on the study of experiments, the relationship between the drilling damage and the drilling parameters are obtained. The results indicate that the drilling hole wall forms drawn fiber and fallen off fiber bundle more easily and the surface roughness of hole wall becomes worse with the increase of the spindle speed, and the final drilling surface presents obvious anisotropy. In order to obtain good drilling quality, lower spindle speed should be selected on the premise of lower feed rate.

The AMT Features Extraction from Batch Drilling Step Monitor Signals and its Applications

Angle Measure Technique (AMT) algorithm is proposed to analyze the quality of batch drilling process in this paper. The groups spindle power (SP) signals of batch drilling were preprocessed by the normalization method, and then the AMT was used to extract the scale features of monitor signals from local to global. By the method of Principal Component Analysis (PCA), the dimensionality of these scale features was reduced to obtain a distribution of the step quality of batch drilling. The results indicate that this method can be used for observation of high precision cutting step quality.

Investigation on Delamination Factor in Drilling Medium Density Fiberboards with Variable Feed Pressure Using Multi-Spindle Drill

Abstract．Drilling quality in manufacturing medium density fiberboards (MDF) is greatly affected by delamination. In multi-spindle drill machine, the feed is provided by feed pressure generated by air compressor. This study focus on relation between delamination and machining parameters in drilling MDF with variable feed pressure. The relation is investigated by establishing second order polynomial models using response surface methodology, and the analysis of variance (ANOVA) is employed to verify the validity of the models. It is found that the delamination factor increases with the decrease of drill hardness and with the increase of feed pressure both at entry and exit of MDF. However, at low level hardness and high level feed pressure, the delamination factor is insensitive with variation of drill hardness and feed pressure.

プリント基板の微細穴加工技術に関する研究

The smaller through holes of printed circuit boards (PCBs) are required for the multifunctional information communication devices. This paper describes some experiments on the effect of entry sheet (E/S) on the micro drilling quality of PCB. Especially the effect of the resin painted on E/S on the micro drilling quality was investigated. The effect was examined by performing the micro drilling tests of PCB using the aluminum E/S and the resin painted aluminum E/S. Resin films used were the polyethylene-glycol (PEG) based film and the wax-based film. The effect of the E/S on the position error of hole center was determined by measuring the centripetal action with the non-contact displacement sensor. The effect of the E/S on the hole wall roughness was also determined by examining the relationship between the drill temperature decrease during drilling due to the use of E/S and the adhesion of resin film to the drill. From these experiments, the followings were obtained : (1) On the position error of hole center, the wax-based film is better than the PEG-based film. (2) On the hole wall roughness, the PEG-based film is better than the wax-based film.

Çeşitli Delme İşlemlerine Tabii Tutulan Sığır Tibia Kemiklerinin Yapısal ve Histopatolojik Değişimleri

Bone tissue damages such as fractures, bone tissue losses, osteolysis and necrosis caused by temperature are the serious clinical concerns in orthopaedics. In order to show the effect of heat generation in bone drilling, temperatures were recorded and analysed for various drill speed, diameter, drilling force and bone densities on fresh calf tibial bones. This study revealed that high drill speeds increase the maximum temperature of the bone while high diameters and drill forces cause a decrease in the drilling temperature. SEM and histopathologic evaluations showed that high values of drill diameter and bone density caused greater damage to the bone and lowered the drill quality around the drilled site by producing rough surfaces and higher loss of osteocytes.

The Modeling of Multi-State Deformation in Aircraft Panel Automated Riveting System

Automatic drilling and riveting process, in order to improve the quality of drilling and riveting aircraft panel deformation are needed for compensation. Due to panels in automatic drilling and riveting process with more posture, therefore, solving panel deformation of plates under more posture is important. This paper establishes aircraft panel in the automatic drilling riveting process multiple posture deformation model. Firstly, simplify the manner of support, locate and clamping between the panel and the splints, supportive of integral panel at each location are calculated using three-moment theory to provide data reference for spacing between splints. Then, deformation results are calculated using flat shell theory to provide data reference for error compensation in automated riveting system, thus, drilling and riveting quality are improved.

Influence of Cutting Heat on Quality of Drilling of Carbon/Epoxy Composites

Cutting heat generated during drilling of carbon/epoxy composites has been recognized as a factor to influence the machine quality. This research aims to study the damage induced by cutting heat during drilling. A temperature-dependent experiment was carried out. The temperature of specimen was changed, and the machine parameter was constant in the experiment. The material temperature near exit was measured. Besides, the machine quality was detected, and the failure mode of the machined surface was observed. The results show that the decrease of material stiffness with increasing temperature induces the decrease of machine quality. Furthermore, delamination, transverse crack, high porosity, and fuzzing are mainly caused by low material stiffness. The transverse cracks which join together under cutting force lead to the generation of spalling on exit surface. As temperature increases, the failure modes of the machined surface changes from matrix dominant failure to interface dominant failure. It is predicted that the critical material temperature of damage-free is 186°C.