Drill Collar Research Articles

EVALUASI NILAI CUTTING CARRYING INDEX PADA LUMPUR DIESEL OIL

Evaluation of Cutting Carrying Index when using Diesel Oil base mud in well T is carried out on section 12-1 / 4 ", 8-1 / 2", and 5-3/4 ". This is because the use of mud on the previous section did not use Diesel Oil base mud, but only used native mud and KCL Polymer base mud. In the CCI evaluation of the Diesel Oil mud, several parameters included, Equivalent Circulating Density and rheology of diesel oil base mud. Based on the primary data on well T the ECD calculation can be done by calculating the average annulus velocity, velocity critical around annulus hole, and the pressure loss in it. The value of ECD obtained on section 12-1 / 4 "ranges from 14 ppg to 15 ppg, section 8-1/2” has 16,08 ppg to 16,4 ppg, and section 5-3 / 4" reaching 14,72 ppg as the biggest value. Based on the ECD, CCI value is obtained, this is because the ECD value describes the mud weight around the annulus hole. A good CCI value must be greater than or equal to 1, then evaluated with the results of CCI on route 12-1 / 4 "obtaining the greatest CCI value 1.6 in the jar and drill collar I. On route 8-1 / 2", CCI value evaluated in the heavyweight drill pipe section with a change in the value of 0,76 to 1,08. The CCI value on section 5-3 / 4“ changes in value from 0,65 to 1,19 in heavyweight drill pipe section.

크레인 중량물 낙하사고에 대응한 설계개념과 간이 해석법에 대한 연구

This paper is about design concept and simplified analysis method against dropped object events. The ships and offshore structures are exposed to various types of dropped object accidents such as laydown area struck by drill collar and topside deck hit by food container during their lifetime. Mitigation can be accomplished by proper facility layout and designing structures to safely absorb energy from accidental loads. It shall be designed to avoid loss of life, environmental pollution and loss of assets. Impact loads can lead to structural global collapse of the main structure or punching of a local barrier type structure with potential to escalate directly or indirectly to a global collapse of the structure. This study provides the background information on the issue of dropped object of the shipyard and also focuses on structural assessment of the local individual component such as deck plate, stiffener and web/girder by using simplified analysis method. The results of the simplified analysis method were compared with numerical results using non-linear finite element simulation.

Simulations of collar waves for acoustic logging while drilling in the frequency and the spatial domains

Tool waves generated by the presence of the drill collar can cover the formation signals we need. The suppression for those collar waves has been a challenge for designing acoustic logging while drilling (ALWD) tools. To study the collar wave characteristics, we evaluate the excitation intensity of the modes with varying frequencies and positions by solving the elastic wave equations. Analysis results show that the collar wave energy concentrates in the cylindrical tool model. And the radial location of its peak gradually moves from the inner surface to the outer wall with the increasing frequency. The particle vibration trajectories contributed by the collar wave are also investigated. It is revealed that the collar mode in the lower frequency range has an approximately longitudinal polarization, while it tends to the transverse-wave-like motion at high frequencies. According to these features, we propose strategies on the tool structure designs to suppress the collar waves in the lower- and the higher- frequency ranges, respectively. Numerical examples further validate that the proposed collar structures with interlayers or grooves can well attenuate the collar wave propagation.

Vibration characteristics of the stepped drill string subjected to gas-structure interaction and spinning motion

This paper studies the vibration characteristics of a drill string in gas drilling under gas-structure interactions, and affected by the combined effects of several parameters including the spinning motion, the weight on bit, the hydrodynamic force, the damping force of drilling fluid and the stabilizer. Based on the Hamilton's principle, the dynamic equations of the spinning drill string subjected to the weight on bit and gas-structure interaction are established and solved by using the Galerkin's method. The exact solutions of the i-th natural frequencies of the drill string with uniform section are derived considering the gas-structure interaction and the spinning motion, and the characteristic curves of the non-dimensional natural frequencies versus different parameters are obtained respectively. The results show that the spinning angular speed, the weight on bit, the flow velocity, the viscous damping force of drilling fluid, the ratio of the external diameter of drill pipe to that of the drill collar and different installation positions of the stabilizer have significant influences on the dynamic characteristics of the drill string. In addition, the effects of the gas drilling fluid and the mud drilling fluid on the system vibration characteristics are discussed and compared, which reveal that natural frequencies of the drill string in gas drilling are higher than that in mud drilling.

A novel approach in high performance deep hole drilling of Inconel 718

Application of deep holes is extensively found in the oil and gas industry to manufacture downhole equipment. These deep holes are fabricated in drill collars to deploy delicate sensors downhole for obtaining vital information like temperature, pressure and other geo-physical data from the bottom of the hole. High temperature and corrosion resistant materials like Inconel 718 is often used for drill collars to shield these sensitive communication equipment from the hostile downhole environment. Gundrilling is an established hole making method known for drilling precise and high aspect-ratio (AR>10) holes in conventional materials such as steels, cast iron and aluminium alloys etc. However, gundrilling of Inconel 718 offers unprecedented challenges like excessive tool wear, hole straightness deviation due to poor thermal conductivity and work-hardening tendency of the alloy. Moreover, as the drilling depth increases the deviation is further exacerbated due to the low rigidity of long gundrill shafts. The present study in the Phase 1 introduces a dynamic model using multispan Euler-Bernoulli beam theory to evaluate the effectiveness of coolant pressure and rotation speed during deep hole fabrication in Inconel 718. In addition, experimental investigations have been conducted to validate the model by studying the effects of coolant pressure and rotation speed on straightness of the fabricated holes. It was found that the straightness deviation was 0.37 mm corresponding to 137.89 bar and 1600 rpm coolant pressure and rotation speed respectively. In Phase 2, a non-contacting EDM process was used to fabricate a straight guide hole followed by conventional gundrilling (CG) with optimum pressure (137.89 bar) and speed (1600 rpm) obtained from the Phase 1 trials. The experimental results revealed that the thrust force reduced drastically from 800 N (CG) to 250 N (EDMG). Moreover, a significant improvement in both rake wear and flank wear was also observed. Finally, a straightness deviation of 0.19 mm was recorded for a maximum drilling depth of 350 mm which is 48.65% lesser than CG. From the study, it was found that this novel EDMG process improved the drilling capability of Inconel 718 by reducing the thrust force generated, enhancing tool life and minimizing the straightness deviation.

АПАРАТУРНО-МЕТОДИЧНИЙ КОМПЛЕКС ДЛЯ ВИЗНАЧЕННЯ ПАРАМЕТРІВ НАФТОГАЗОВИХ КОЛЕКТОРІВ У ПРОЦЕСІ БУРІННЯ ГОРИЗОНТАЛЬНИХ СВЕРДЛОВИН

The paper is devoted to the basic principles of the trend of logging, namely logging while drilling (LWD), which is new for Ukraine. The LWD technology has a number of advantages over other logging types, in particular, in supplementary exploration and production of hydrocarbons in fields that are in longterm development. In this case, the drilling of horizontal wells, which by productivity is much higher than the vertical ones, is important. For the investigations of horizontal wells, we proposed a universal compact radioactive logging tool with small diameter, which is placed in entire drill collar just before drilling. The combined radioactive logging tool LWD-КПРК-48 (48 mm in diameter) contains dual-spacing modules of neutron logging, neutron-gamma logging, density logging, as well as separately placed gamma-logging unit. Calibration works with the developed combined tool were carried out on physical models of reservoirs in the presence of drill collars and corresponding calibration dependences on porosity and density were obtained. They, together with the developed methods and other data, allow us to determine an extended set of petrophysical parameters, namely, the porosity of water-, oil- and gas-saturated reservoirs, the identification parameters of fluid: water – oil and water – gas, oil-, gas- and water saturation, volume content of oil and gas, etc. Test of a logging tool LWD-КПРК-48 when drilling a horizontal well in an oil-bearing bed showed high informativity and efficiency of product. The created apparatus and methodical complex for the investigation of horizontal oil and gas wells while drilling has several advantages over known analogues, in particular, is universal, convenient, more available to mining and well logging oil and gas companies.

The research of LWD acoustic isolator based on SAW spatial separation

Acoustic logging while drilling (LWD) can extract P-wave and S-wave information from the formation. However, the transmission of the collar wave propagated directly from the emitter to the receiver may interfere with the P-wave and S-wave and affect the extraction of formation information. Therefore, it is necessary to design a suitable acoustic isolator between the transmitter and the receiver to attenuate the drill waves. The commonly used acoustic LWD isolator is that the outer surface of the drill collar is evenly grooved to attenuate the collar wave. However, there are still disadvantages such as the lack of mechanical strength of the evenly grooved acoustic insulators and the ability to extract clean longitudinal wave under certain circumstances. Therefore, there is an urgent requirement to design a new type of acoustic LWD isolator with sufficient strength and acoustic insulation requirements. In recent years, spoof surface acoustic waves (SSAWs) generated by periodic corrugated surface rigid plates have attracted the attention of many researchers, who can spatially separate the surface waves to attenuate acoustic waves. In this paper, a new type of acoustic LWD insulator based on SAW space separation structure is proposed. The finite element software ANSYS is used for acoustic analysis.

Research on a rotational speed control strategy of the mandrel in a rotary steering system

AbstractRotary steering systems are cutting-edge, intelligent oil drilling and steering equipment developed at the end of the twentieth century. The core function of the bit pointing rotary steering system is to control the eccentric shaft with bit pointing function to track the outer drill collar for reverse rotation [1]. When the relative speed thereof is offset, the mandrel tool face remains stationary, and the directive function of the drill bit is realized [2]. Therefore, it is important to precisely control mandrel rotational speed and make it follow the outer drill collar to conduct face-to-face rotation at all times. A double closed loop control method for realizing rotational speed loop and position loop through controlling mandrel rotational speed is proposed in this paper. Relative rotational speed of drill bit shaft (or mandrel) and drill collar of zero can be realized within the shortest time, thereby realizing rapid and precise rotational speed tracking. Relative positions of mandrel and drill collar at several angles on 360° circumferences, thereby proving the feasibility of the method. The method can provide a technical reference and basis for prototype production of directional rotary steering system [3].

Non-magnetic drill collar failure analysis and prevention measures

Non-magnetic drill collar is a kind of drill collar made of high quality stainless steel in drilling tool. It is widely used in oil fields, but its failure rate is rising directly, and the oil well is safe. In order to better the failure reasons explored, this article through to the non-magnetic drill collar failure parts of the macroscopic characteristics, chemical composition, mechanical properties and metallographic analysis, study the cause of non-magnetic drill collar failure and failure causes and failure process for seeking the non-magnetic drill collar failure before the defects of some form of expression and master some regularity of no magnetic drill collar failure, for we can effectively prevent the non-magnetic drill collar failure accidents mat set a foundation, but also effectively control magnetic drill collar failure accidents occur frequently.In view of the above analysis conclusion, this paper puts forward a set of non-magnetic drill collar failure prevention measures, it effectively avoid due to its failure will continue to use with the hidden trouble of non-magnetic drill collar failure risk.

Fatigue resonant tests on drill collar rotary shouldered connections and critical thread root identification

A fatigue test series on a drill collar rotary shouldered connection, thread type 5-1/2 FH MOD, was performed with a dedicated alternating bending resonant test rig. Compared to a quasi-static testing approach, the dynamic loading allowed high testing frequency and a relatively light supporting structure. Crack initiation was identified as the onset of a discrepancy between two strain gauge signals which were monitored throughout the test. A through-wall crack condition was assumed as the effective fatigue failure. The stress distribution in the connection was then analysed with a finite element plane harmonic axisymmetric model, taking into account both the initial make-up torque and the alternating bending load during the test. In these simulations, the most critical stress between the pin or box, in terms of fatigue, mainly depended on the preload. The modelled contact behaviour of the incomplete threads of the box played a significant role in predicting the position of the crack initiation thread root, which was then compared with the test results.

Tribological characterization of the drill collars and casing friction couples

Drill collars are special pipes used in the drilling of wells for weighting the drill bit, enabling it to drill through the rock. In the drilling process, the drill collars are exposed to an intensive wear due to friction on inner surface of casing wall. In order to evaluate the tribological behaviour of this friction couple, paper presents the drill collars parent material, reconditioned and casing pipe chemical composition, microstructures, hardness and friction tests. For friction tests were prepared samples extracted from new and reconditioned drill collars and from casing pipes and tested on a universal tribometer. Were used plane-on-disk surface friction couples and tests were conducted at two sliding speeds and three normal loads for each materials couple. Plane static partner samples were extracted from casing pipes and disks samples were extracted from new and reconditioned drill collars. Were obtained friction coefficients values and also the temperatures increasing values due to friction working tests parameters. The temperature increasing values were obtained by measuring it with an infrared thermographic camera.

Development of Work Flow To Manage Fatigue of Bottomhole Assemblies

This article, written by Special Publications Editor Adam Wilson, contains highlights of paper IPTC 18682, “Development and Utilization of BHA-Fatigue-Management Work Flow,” by Hendrik Suryadi, SPE, and Phan Van Chinh, SPE, Schlumberger, prepared for the 2016 International Petroleum Technology Conference, Bangkok, Thailand, 14–16 November. The paper has not been peer reviewed. Copyright 2016 International Petroleum Technology Conference. Reproduced by permission. A new fatigue-management work flow provides drillers with a tool to simulate and predict the life expectancy of bottomhole assemblies (BHAs) before fatigue causes problems. This new feature allows engineers to calculate and monitor the fatigue life. It also helps engineers to take appropriate action before a failure occurs downhole or to provide information to the maintenance team for preventive maintenance. Overall, this new approach allows engineers to manage drilling risks related to fatigue before any negative consequences. Introduction The oil and gas industry continues to drill wells that are deeper, more complex, and have greater extended reach and dogleg severity. These wells expose drillstring elements to higher loads and several kinds of cyclic stresses. The success of drilling operations relies on maintaining the integrity of the BHA and the drillstring. One of the more common catastrophic events related with BHA integrity is twistoff, where the BHA component parts from the drillstring downhole. Twistoff can be caused by the load exceeding the collar strength or by high shock, vibration, or corrosion, but the primary cause of twistoff is fatigue failure. With fatigue failure, the drillstring fails downhole despite the stress being below the material-strength specification. This is caused by fatigue accumulated over time. According to some reports, fatigue failure contributes to more than 60% of total drillstring failures. Fatigue failure can occur under a wide range of conditions and environments; however, a higher risk of fatigue failure always exists when rotating drill collars and tools through high-dogleg intervals during the drilling. With high rig operating costs and increasing BHA and wellbore complexity, increased focus has been placed on avoiding twistoff-related expenses such as Cost associated with time required to trip out of the hole Cost of fishing operations and to repair or replace failed equipment Cost to perform sidetracking Engineers attempt to prevent drillstring failures by optimizing the drill-string and trajectory designs.

Design of a continuous wave mud pulse generator for data transmission by fluid pressure fluctuation

High-speed downhole transmission technology is in high demand for measurement while drilling (MWD) and logging while drilling (LWD) systems which have had major roles in increasing the geo-steering and formation evaluation capacity of reach wells, difficult horizontal wells and branch wells as well as increasing drilling rates. This paper presents the conceptual design and performance of a novel continuous wave mud pulse generator with the goal of transmitting data using hydraulic pressure waves. The generator includes the rotary valve, drive shaft and bearings, rotary and static seals, motor and reducer, resolver, pressure balance structure and lower centralizer; all of these components are mounted within a rotary drill collar. In particular, the rotary valve is the key important part of the continuous wave mud pulse generator. Based on the concept of a sinusoidal signal output, an improved arc-fillet-line triangular valve orifice is designed according to the relationships between the fluid differential pressure of a thin-walled cutting edge and the fluid flow area calculated from the relative rotation angle of the rotor to the stator through the established polar coordinate equations. The highly similar sinusoidal pressure signals can be achieved by optimized valve structures, which were verified by computational fluid dynamics (CFD) simulations, where the valve flow pattern characteristics and the impact law between the gap of the stator/rotor and pressure waveform were also obtained. Moreover, the drive capability response curves of the motor driver unit with and without a load are precisely determined, and current ground hydraulic experiments indicate that the designed continuous wave mud pulse generator performs well as a whole. The generated real pressure waves exhibit clear spectrum structures with a distinctive characteristic signal.

Whirl Simulation of Drill Collar and Estimation of Cumulative Fatigue Damage on Drill-Collar Connection

Summary Most drill-collar-connection failures are attributed to cumulative fatigue caused by bending vibration. An important class of bending vibration is whirl, which is formed by the eccentricity of the rotational drill collar. The contact between the drill collar and the borehole causes extreme harmful backward whirl, even chaotic whirl. A two-degree-of-freedom nonlinear lumped-mass model is used to represent the drill collar in whirl. Unlike other studies, the stick/slip vibration causing fluctuation of rotary speed is taken into account. In this lumped-element model, the contact forces obey the Hertzian contact law, which leads to lateral bounce of the drill collar and affects the borehole wall chaotically. The modified Karnopp friction model is adopted to simulate the stick/slip rotary vibration of the bottomhole assembly (BHA). On the basis of the time-domain responses of whirl, the continuous-bending-stress history is broken down into individual stress ranges with an associated number of stress cycles using the rainflow-counting method. The cumulative fatigue damage is estimated using Miner's rule. The conclusion of this paper indicates that chaotic lateral vibration and fatigue damage happen at a lower rotational speed than previously reported.

Detection of formation S-wave in a slow formation using a monopole acoustic logging-while-drilling tool

Acoustic logging-while-drilling (LWD) is a technology that is used to measure formation elastic properties during drilling. When the formation shear slowness is smaller than the borehole fluid slowness (i.e., fast formation), monopole logging can be used to obtain formation compressional and shear slownesses by measuring the corresponding refracted waves. In a slow formation in which the shear slowness is larger than the borehole fluid slowness, other logging methods, such as quadrupole LWD, are used instead for shear slowness measurement due to the lack of a fully refracted S-wave. Through modeling analysis, we find that the transmitted S-wave generated by a monopole LWD tool in a slow formation can be detected and used to measure the formation shear slowness. This phenomenon can be explained by Huygens’ principle, which states that every point on a wavefront can be considered as a secondary source that induces particle motion. It is hard to discern the transmitted S-wave in monopole wireline data because it strongly interferes with the Stoneley mode in wireline logging. However, the transmitted S-wave decouples from the Stoneley in the LWD environment because the drill collar slows down the low-frequency part of the Stoneley mode. The nondispersive nature of the transmitted S-wave makes it suitable for shear slowness extraction using time semblance analysis, but sophisticated signal preprocessing might be needed because this wave is generally weak compared with the Stoneley wave. Moreover, our study helps us better understand how the Stoneley mode behaves and interferes with other modes in a slow formation under LWD conditions.

Dynamic stability of a stepped drillstring conveying drilling fluid

Taking into account differences between a drill pipe (DP) and a drill collar (DC), the drillstring in a vertical well is modeled as a stepped pipe conveying a drilling fluid downwards to the bottom inside the string and then upwards to the ground from the annulus. An analytical model that describes lateral vibration of the drillstring and involves the drillstring gravity, weight on bit (WOB), hydrodynamic force and damping force of the drilling fluid is established. By analysis of complex frequencies, the influences of WOB, borehole diameter, DP length, velocity and density of the drilling fluid on the stability of the system are discussed.

An Analysis of Common Drill Stem Vibration Models

Excessive drill stem (DS) vibration while rotary drilling of oil and gas wells causes damages to drill bits and bottom hole assemblies (BHAs). In an attempt to mitigate DS vibrations, theoretical modeling of DS dynamics is used to predict severe vibration conditions. To construct the model, decisions have to be made on which beam theory to be used, how to implement forces acting on the DS, and the geometry of the DS. The objective of this paper is to emphasize the effect of these assumptions on DS vibration behavior under different, yet realistic, drilling conditions. The nonlinear equations of motion were obtained using Hamilton's principle and discretized using the finite element method. The finite element formulations were verified with uncoupled analytical models. A parametric study showed that increasing the weight on bit (WOB) and the drill pipe (DP) length clearly decreases the DS frequencies. However, extending the drill collar length does not reveal a clear trend in the resulting lateral vibration frequency behavior. At normal operating conditions with a low operating rotational speed, less than 80 RPM, the nonlinear Euler–Bernoulli and Timoshenko models give comparable results. At higher rotational speeds, the models deliver different outcomes. Considering only the BHA overestimates the DS critical operating speed; thus, the entire DS has to be considered to determine the critical RPM values to be avoided.

Dynamic model for 3D motions of a horizontal oilwell BHA with wellbore stick-slip whirl interaction

Failure of horizontal oilwell drilling equipment, in particular the bottom-hole-assembly, is very costly. Vibration causes tool joint failure, twist-off, and bit-damage, and has motivated extensive research on understanding and predicting the dynamic shock-loading response of the bottom-hole-assembly. This paper presents a model to analyze the dynamics of a horizontal oilwell bottom-hole-assembly. A nonlinear three-dimensional multibody shaft model has been verified and extended to include stick-slip whirl phenomena due to the contact between the rotating bottom-hole-assembly and wellbore. The model has been verified with a dynamic finite element analysis through comparisons of the response of an enclosed shaft under axially compressive load rotating inside the wellbore. Finally, a complete deviated drillstring has been simulated by combining the bottom-hole assembly model with a model of the drill pipe and collars. The pipe and collars are modeled using a lumped-segment approach that predicts axial and torsional motions. The model can predict how axial and torsional bit-rock reactions are propagated to the surface, and the role that lateral vibrations near the bit play in exciting those vibrations and stressing components in the bottom-hole-assembly. The proposed model includes the mutual dependence of these vibrations, which arises due to bit-rock interaction and friction dynamics between the drillstring and wellbore wall. A force excitation source, which simulates an axially-vibrating downhole tool, has been implemented in the horizontal section of the virtual drillstring. Simulations show a better weight transfer to the bit due to the tool, with a low frequency and high amplitude force excitation giving best performance but potentially increasing the severity of lateral shock. The model, implemented using the bond graph formalism, is a useful tool for design and sensitivity analysis due to its physically meaningful parameters and low simulation times on a personal computer.

LWD-DATC: Logging-While-Drilling Dipole Shear Anisotropy estimation from Two-Component waveform rotation

Sonic dipole shear anisotropy orientation in subsurface formations is key information for a complete characterization of rock mechanical models for well planning. In Wireline logging, it is estimated with the well-known Alford rotation on four-component inline and crossline waveforms from two orthogonal dipole firings. In contrast, shear orientation estimation is more challenging in Logging-While-Drilling (LWD) operations because of the following reasons:—No exactly orthogonal cross-dipole firings in LWD tools due to tool rotation while drilling;—Coupling between the formation flexural mode and the strong collar flexural mode propagating through the stiff drill collar;—Unavoidable tool eccentering;—Strong drilling noise from vibration, shock, and the turbulent mud flow around the tool; To overcome the aforementioned challenges, this paper describes a new technique to estimate the LWD dipole shear orientation with two-component waveforms obtained from a single dipole firing. It is accomplished by maximizing the projected energy of the two-component waveforms into a subspace defined by two eigenfunctions (the Bessel functions of the first- and second-kinds) accounting for the propagation of the two coupled flexural modes over multiple frequency points. By resorting to the subspace estimation, the new technique has been successfully validated on synthetic data and tested on field data sets.

Downhole vibration causing a drill collar failure and solutions

In large borehole drilling of some blocks or formations, due to serious downhole vibration, fatigue failure of a drill collar occurs frequently and most washouts and fractures are in thread root. An analysis of the above failure shows that the drill collar fatigue failure is caused by the cyclic bending stress due to serious downhole vibration. Therefore, downhole vibration modes were theoretically analyzed in terms of axial vibration, lateral vibration, stick-slip, and the physical model established by the mechanical vibration field. Then the resonance damage caused by the actual different downhole vibrations and its theoretical basis were analyzed; and according to the downhole drill string lateral vibration and whirling law, the best area to ensure drilling parameter stability based on the given boundary conditions was figured out, and the theory was clarified that in the best area of drilling, the maximum ROP will be achieved by maintaining the drill string stable or eliminating the vibration/stick-slip, meanwhile the stress fatigue of BHA will be reduced or eliminated especially for drill collar. Finally, solutions were provided as follows: (1) According to the special BHA, drilling conditions, together with physical and mathematical models listed above, downhole resonance speed and related parameters to be avoided can be easily figured out. It was also clarified that resonance speed is exactly the vibration speed that need to be avoided; and that the resonance frequency can be avoided with software for vibration analysis in BHA design and application at well sites; (2) V-Stab is a new and efficient tool which can reduce or eliminate downhole lateral vibration and stick-slip.