Sharif Digital Repository

In this research work, an ultrasonic assisted drilling system is employed to apply both rotation and vibration to drill bits. The transducer horn transfers power very efficiently and changes tools effortlessly. The setup used to conduct drilling tests is Inconel 738LC with depth-to-diameter ratios from 2 to 10 by conventional drilling (CD), ultrasonic assisted drilling (UAD), and electro discharge drilling (EDD). The effects of ultrasonic vibration amplitude, spindle speed, and number of steps to drill each hole on machining force and surface roughness in UAD are investigated. The results demonstrate not only a significant improvement in tool life (by applying ultrasonic vibration to the... 

In this paper a nonlinear dynamic model for drill string in inclined well drilling is developed. Effects of drilling mud flow rate, weight on bit, angular velocity along with viscous damping on stability and vibration of the drill string are studied. Findings indicate the nonlinear effects are significant on the results. The effects of drilling mud flow rate and weight on bit on the natural frequencies and time responses are evaluated. Enhancement of drilling mud flow rate results in decreasing of natural frequencies and vibrational amplitude, while increasing the weight on bit, leads to decrease of the natural frequencies and increase the vibrational amplitude. © JVE INTERNATIONAL LTD  

Increasing cuttings bed height is a serious concern during extended-reach well drilling. In order to predict and prevent cuttings bed height increase, it is essential to study how the critical parameters influence the cuttings transport, especially the drill pipe rotation effects on the cuttings transport process. In conventional models for cuttings transport, the dynamic behavior of particles due to drill pipe rotation is neglected or empirically simplified. This paper presents a coupled Computational Fluid Dynamics and Discrete Element Method (CFD-DEM) approach to simulate the cuttings transport considering the dynamic collision process. The fluid phase is treated as an Eulerian continuum... 

Supercritical fluid extraction is a new technology that could be effectively used to treat oil-contaminated drill cuttings generated during drilling for oil and gas. In this work, the solubility of oil-contaminated drill cuttings in supercritical carbon dioxide is obtained by an experimental flow type apparatus. The solubility was measured at 200 bar pressure, over a temperature range of 55-79.5°C. The measured solubility and experimental data for oil in drill cuttings were correlated using the PC-SAFT, PR and SRK EOS models, without any adjustable parameters. Average absolute derivations of less than 15.1 %, 98.7 %, and 99.3 % are achieved between predicted and experimental values for the... 

Cutting transport is an important goal in drilling operation especially in horizontal and deviated wells since it can cause problems such as stuck pipe, circulation loss and high torque and drag. To this end, this article focused on the affecting parameters on the cutting transport by computational fluid dynamic (CFD) modeling and real operational data. The effect of drilling fluid and cutting density on the pressure drop, deposit ratio and string stress on the cutting transport has been investigated. A systematic validation study is presented by comparing the simulation results against published experimental database. The results showed that by increasing two times of drilling fluid... 

To improve the thermal stability of starch in water-based drilling fluid, monoethanolamine (MEA) was added, and the effect was investigated by laboratory experiment. The experimental results show that the addition of monoethanolamine (MEA) increases the apparent viscosity, plastic viscosity, dynamic shear force, and static shear force of the drilling fluid, and reduces the filtration rate of drilling fluid and thickness of mud cake apparently. By creating hydrogen bonds with starch polymer, the monoethanolamine can prevent hydrolysis of starch at high temperature. Starch, as a natural polymer, is able to improve the rheological properties and reduce filtration of drilling fluid, but it works... 

Nowadays, economical extraction of the oil and gas, and their products is an important problem. Up to now, vertical wells have been used for oil extraction but some wells exist that they cannot be reached by using the vertical drilling. Horizontal and directional drillings are some techniques to reach these wells. In this article, dynamics of the horizontal drill string is studied. According to the forces that affect the dynamics of drilling, its longitudinal vibration is analyzed. After determination of the boundary conditions and normal modes of the system with using mode summation method, displacement of the bit is obtained. Finally, dynamics of the horizontal drill string is simulated... 

In drilling oil wells a system of complex fluids and chemical additives is used. Losses of these fluids in the well during drilling or disposal of them in well site could transfer pollutants to groundwater. In the present study a number of well sites, located in South of Iran, were studied to indicate types and magnitude of various pollutant materials that remain in the environment undestroyed and have considerable impacts on the underground water resources. Hydrocarbons used in Oil Base Muds (OBM) that can't be biodegrade readily in nature found to be the most severe pollutant material caused by disposal of Drilling Mud and Cuttings. Volume of drilling waste for these oil wells evaluated to... 

To improve the thermal stability of starch in water-based drilling fluid, monoethanolamine (MEA) was added, and the effect was investigated by laboratory experiment. The experimental results show that the addition of monoethanolamine (MEA) increases the apparent viscosity, plastic viscosity, dynamic shear force, and static shear force of the drilling fluid, and reduces the filtration rate of drilling fluid and thickness of mud cake apparently. By creating hydrogen bonds with starch polymer, the monoethanolamine can prevent hydrolysis of starch at high temperature. Starch, as a natural polymer, is able to improve the rheological properties and reduce filtration of drilling fluid, but it works... 

In recent years, growing interest in underbalanced drilling has resulted in the rapid development of its associated equipment technology, practices, and procedures. Underbalanced drilling is used to avoid lost circulation, formation damage, and decreasing weight on bit. However, the risk of wellbore collapse due to lake of hydrostatic mud pressure is high; therefore, using good geo-mechanical model may avoid wellbore instability problems. In order to evaluate the potential for wellbore instability, it is necessary to use an elastoplastic model to compute the stresses and strains around the bore hole. Furthermore, it should be mentioned that the laser drilling process depends extremely on the... 

Superalloys have a poor machinability and are often drilled using Electro Discharge Machining (EDM) methods. However EDM is a time-consuming process and has low surface integrity. Ultrasonic Assisted Drilling (UAD) technology is a modern method of drilling such materials. Although this method has very high capabilities, it has not been introduced widely to industry. In this study a special horn is designed and used to apply both rotation and vibration to drill bits. It can transfer power with high efficiency and has the capability to change tools easily. The setup is used to conduct deep drilling tests on Inconel 738LC with depth-to-diameter ratio of 10. The effect of ultrasonic vibration... 

Delamination is a major problem in drilling of fiber-reinforced composite materials. Thrust force is an important factor leading to propagation of delamination during drilling process. One of effective methods to reduce machining forces is application of ultrasonic vibrations. In this study ultrasonic assisted drilling is applied to reduce thrust force in drilling of GFRP laminates. In order to conduct experiments a setup is designed and fabricated to apply both vibrations and rotation to drill bits. Using Taguchi method, a set of experiments is conducted with feed rate, spindle speed, and ultrasonic vibration amplitude as control factors. The results show that applying ultrasonic vibration... 

The capability level of rotary as well as first generation drilling operation could not be matched for deeply drilling programs. To reach that deep, the increasing in drill string length could also cause an additional constraint on hydraulic performance. The operation of slim hole drilling has significant potential to reduce well costs. This cost might be savings are especially important with increased demand for reduced capital finance under current economic conditions in the Iranian oil and gas industry. This savings achievement could be caused by use of smaller drilling rigs, work over rigs, reduced casing size, reducing requirement for drilling consumables and other costs associated with... 

Metal matrix composites (MMCs) have received considerable attention due to their excellent engineering properties. Accuracy and surface finish play an important role in modern industry. Undesired projections of materials, known as burrs, reduce the part quality and negatively affect the assembly process. In this study, reducing burr size in drilling of MMC is performed by adding ultrasonic vibration to the process. Al/SiC p MMC with 5 wt% of SiC particulates in dry drilling operation with HSS drill tools coated with TiN was investigated. The effect of ultrasonic assistance on burr size was studied. The results demonstrate that under suitable ultrasonic vibration conditions, in comparison... 

The influence of deep cryogenic treatment on wear resistance and tool life of M2 HSS drills in high-speed dry drilling configuration of carbon steels was studied. The experimental results indicated 77 and 126% improvement in cryogenic-treated and cryogenic- and temper-treated drill lives, respectively. The results of wear rate test were in agreement with drill life test. Chemical composition of chips were also reported to show the onset of seizure in drilling test and the consequence of seizure in promoting dissolution wear by diffusion mechanism. Wear resistance improvement was mainly attributed to the resistance of cryogenically treated drills against diffusion wear mechanism, due to the... 

In offshore Iran, wellbore instability is quite common and the main cause for most of problems during drilling operations. In this study, the existing relevant logs, drilling and other data from offset well were analyzed and integrated to construct a precise Mechanical Earth Model (MEM) describing pore pressure, stress magnitudes and orientation, and formation mechanical properties of the South Pars Gas field. Then, the constructed MEM was refined and calibrated using the existing caliper, image logs, rock mechanical core test and drilling data and through history matching to constrain and reduce the uncertainties associated with limitations and availability of the existing data. Using the... 

Burr in drilling plays an important role on product quality, so analysis the burr height is essential at the final production. This paper presents the application of Taguchi method for survey the burr height by adding ultrasonic vibration to the process. In this paper L18 orthogonal array based on Taguchi techniques was used in the design of experiments. Analysis of Variance (ANOVA) was used to determination the effect of drilling parameter on burr formation. Influence of spindle speed, feed rate and percentage of SiC particle was investigated in with and without ultrasonic assisted drilling. In this paper drilling of Al/SiCp MMCs with 5, 15 and 20 wt% of particulate SiC in dry drilling... 

In this paper, the impact of three parameters including nanoparticles geometry, particles aggregation and borehole inclination on induced formation damage from water based drilling fluids were investigated by means of experimental studies. Accordingly, we designed a dynamic filtration setup capable to rotate and change well inclination. Nano-based drilling fluids consisting of spherical, cubical and tubular shapes nanoparticles as fluid loss additives were used. Mud cake quality, core permeability impairment and degree of formation damage at various well inclinations were examined. The cluster structure of aggregated particles were determined using fractal theory and applying dynamic light...