Hole Assembly Research Articles

Experimental study and mechanism analysis of the motion states of bottom hole assembly during rotary drilling

Lateral vibration of bottom hole assembly (BHA) severely affects the drilling efficiencies of downhole tools and even leads to downhole accidents. To further study the lateral motion states of BHA during rotary drilling, a new experimental setup was built based on the similarity criterion that was derived using the Buckingham π-theorem. Meanwhile, four characteristic parameters were introduced to distinguish the types of motion states and highlight their dynamic characteristics. Moreover, a systematical experiment was conducted to analyze the effects of well inclination, rotation speed, weight on bit (WOB), measurement position, and friction coefficient on the motion states. In addition, the occurrence mechanism of the motion states was explained through the principle of least energy dissipation, and the numerical simulation was conducted to calculate the energy dissipation. The results show that the motion states in vertical wells contain forward whirl, random motion, and backward whirl, and the main motion state in deviated wells is circular arc swing. The rotation speed and friction coefficient have major effects and WOB has moderate effects on the motion states in vertical wells. The larger rotation speed, friction coefficient, and WOB, the easier is the occurrence of backward whirl. Meanwhile, well inclination has suppressing effects on lateral vibration, while rotation speed and friction coefficient have promoting effects. WOB has promoting effects on lateral vibration in vertical wells and relatively small effects in deviated wells. The stabilizer can effectively limit lateral vibration. Moreover, the change of the motion states depends on which motion state consumes the least external work. In particular, the conditions of forming backward whirl are more rigorous than those of maintaining backward whirl. Thus backward whirl is a stable motion state and is difficult to stop once it occurs. In this paper, the study can help to understand the dynamic characteristics and occurrence mechanism of the motion states during rotary drilling.

Torsional model of the drill string, and real-time prediction of the bit rotational speed and the torque on bit, in an oil well drilling tower

In an oil well drilling tower, the Bottom Hole Assembly (BHA) data is needed to optimize the controllable variables such as weight on bit and bit rotational speed for obtaining the optimum drilling rate. In order to acquire the data of the BHA, a simple and low-cost method, can be predicting of these parameters. In this study, first the torsional modelling of the drill string is implemented by dividing its length to some equal sections, then the effects of dividing on the estimation accuracy are evaluated. Using an ADRC (Active Disturbance Rejection Controller) in the vertical and rotational motions dynamics, some proper observers to predict the bit rotational speed, rock stiffness and torque on bit, in real-time are designed and presented. Dividing the drill string length to more sections, leads to design high order observer, so the performance of the designed observers with different orders, are compared and analysed. Employing the integral square error analysis, it is revealed, dividing the drill string length to more sections, leads more accurate in the prediction of bit rotational speed, but not more effect on the estimated rock stiffness, and torque on bit. Also it is shown that increasing of the observer bandwidth, leads to more accurate in the estimation, but concludes the estimation be more sensitive to the sensor noise. Employing the presented observers in this study to estimate the BHA data, in addition to enhance the drill quality and safety, the controllable variables are optimized, and consequently the whole drilling process can be robustly controlled, with no needs to the expensive measurement systems at the BHA.

Interaction of N-succinyl-diaminopimelate desuccinylase with flavonoids

DapE is an enzyme that belongs to the meso-diaminopimelate/Lysine pathway. It is recognized as an antimicrobial target, hence compounds that inhibit its catalytic activity are required. The principal features considered in the selection of potential inhibitors for this enzyme are compounds containing metal binding groups that could block access of the substrate to the Zinc metal centers and/or block the assembly of the oxyanion hole. We show the interaction of DapE from Enterococcus faecium, Staphylococcus aureus, Klebsiella aerogenes, Pseudomonas aeruginosa and Escherichia coli with flavonoids: quercetin, catechin, luteolin, rutin and hesperidin. Flavonoids contain several oxygen atoms distributed along their structure in a pattern that may be considered for the development of new antibiotics. Docking experiments suggest that these compounds containing metal binding groups that interact with metal centers of DapE and binding experiments indicate that glycoside flavonoids are preferred by DapE.

The Assembly of the First Massive Black Holes

The existence of ∼109M⊙supermassive black holes (SMBHs) within the first billion years of the Universe has stimulated numerous ideas for the prompt formation and rapid growth of black holes (BHs) in the early Universe. Here, we review ways in which the seeds of massive BHs may have first assembled, how they may have subsequently grown as massive as ∼109M⊙, and how multimessenger observations could distinguish between different SMBH assembly scenarios. We conclude the following: ▪ The ultrarare ∼109M⊙SMBHs represent only the tip of the iceberg. Early BHs likely fill a continuum from the stellar-mass (∼10M⊙) to the supermassive (∼109) regimes, reflecting a range of initial masses and growth histories. ▪ Stellar-mass BHs were likely left behind by the first generation of stars at redshifts as high as ∼30, but their initial growth typically was stunted due to the shallow potential wells of their host galaxies. ▪ Conditions in some larger, metal-poor galaxies soon became conducive to the rapid formation and growth of massive seed holes, via gas accretion and by mergers in dense stellar clusters. ▪ BH masses depend on the environment (such as the number and properties of nearby radiation sources and the local baryonic streaming velocity) and on the metal enrichment and assembly history of the host galaxy. ▪ Distinguishing between assembly mechanisms will be difficult, but a combination of observations by the Laser Interferometer Space Antenna (probing massive BH growth via mergers) and by deep multiwavelength electromagnetic observations (probing growth via gas accretion) is particularly promising.

Vibration analysis of simultaneous drilling and reaming BHA

The drillstring used in the oil and gas exploration is a complex structure due to the different forces acting on it. One of the primary sources of drillstring vibrations is the cutting forces caused by the drill bit contact with the rock formation. In some drilling applications, such as hole enlargement and underreaming, the source of the cutting action originates from the drill bit as well as the reamer which increases the dynamic complexity of the drillstring. This paper’s objective is to investigate the torsional vibration behaviors of the bottom hole assembly (BHA) under simultaneous drilling and reaming. More specifically, it addresses the effect of the reamer interaction with the wellbore during drilling operations on the overall torsional vibrations of the BHA. The BHA was modeled as a torsional shaft subjected to a localized external force due to the reamer cutting action, and a point load external force due to the drill bit interaction with the formation. The equation of motion was obtained using Hamilton’s principle, and modal expansion was used to solve the equation of motion. The results showed that the location of the reamer within the BHA plays an important role in vibrations response. It was found that vibration modes that exhibit symmetry within the reamer location show a negligible effect on the overall BHA torsional response. Reamers with aggressive cutters cause higher vibration response when compared with a drill bit with the same cutter aggressiveness. The simplified model reveals the significance of properly matching the drill bit and the reamer to reduce the overall BHA torsional vibrations.

Applying modern technologies when drilling directional wells with long horizontal boreholes

Introduction. Directional drilling of wells is currently carried out by a rotary steerable system and conventional equipment including a mud motor with an adjustable skew angle. Either of the two methods has particular advantages. Research aim is to analyze the technologies provided by various service companies in the field of directional and horizontal wells drilling in order to provide means of improving the utilization capacity of the conventional bottom hole assembly in long horizontal boreholes. Methodology. When drilling directional wells with a small departure from the vertical and wells with horizontal boreholes up to 500 m long, a preference is given to a mud motor as far as a change in deviation parameters is concerned. This is due to the fact that the mud motor has a significant economic advantage. However, when drilling directional well with complex planned profile or a well with a horizontal borehole of more than 500 m, the mud motor may cause a variety of problems, while a rotary steerable system will allow to avoid some of them. Results. The rotary steerable system is not always economically feasible suggesting a need for an alternative technology with a more advantageous offer on the market of services. A system of pulsed controlled drilling will allow the adjustment of the trajectory of the wellbore when drilling in a rotary mode with conventional equipment for directional drilling, reduce rig time, and improve the borehole quality. Summary. The given technology will make it possible to improve the efficiency of conventional equipment which includes the mud motor for directional wells drilling with complex planned profile and long horizontal boreholes of more than 500 m, as soon as the technology provides the possibility of adjusting the trajectory in a rotary mode. The system of pulsed controlled drilling is developed as an alternative to the rotary steerable system making it possible to significantly reduce construction expenses for wells with complex geological conditions of drilling

Time-dependent cuttings transport modeling considering the effects of eccentricity, rotation and partial blockage in wellbore annuli

This paper presents a new cuttings transport model that captures the time-dependent effects of pipe rotation, drillpipe eccentricity and annulus blockage on hole cleaning. By integrating the time-dependent model with well construction data, the level of cuttings deposition along the trajectory of the wellbore can be simulated in real-time. The model recalculates its hole cleaning assessment at every time-step, and can use real-time drilling data at pre-determined time/depth intervals for calibration purposes.The integrated, real-time hole cleaning model was applied to a field case. Field data from an actual stuck pipe event was used to calculate the behavior of the cuttings profile in time along the wellbore. The data show that a high rate of penetration whilst sliding with a directional motor in the near-horizontal section of the well resulted in a significant amount of cuttings buildup around the bottom hole assembly (BHA). Unsurprisingly, the drillstring packed off and became stuck on the final trip out of the hole. Moreover, the casing-hole annulus packed off and caused induced losses while cementing because of the cuttings bed left in the hole. If the proposed time-dependent cuttings transport model had been utilized, these well problems and associated non-productive time (NPT) could have been better predicted and possibly avoided.

From galactic nuclei to the halo outskirts: tracing supermassive black holes across cosmic history and environments

ABSTRACT We study the mass assembly and spin evolution of supermassive black holes (BHs) across cosmic time as well as the impact of gravitational recoil on the population of nuclear and wandering BHs (wBHs) by using the semi-analytical model L-Galaxies run on top of Millennium merger trees. We track spin changes that BHs experience during both coalescence events and gas accretion phases. For the latter, we assume that spin changes are coupled with the bulge assembly. This assumption leads to predictions for the median spin values of z = 0 BHs that depend on whether they are hosted by pseudo-bulges, classical bulges or ellipticals, being $\overline{a} \sim 0.9$, 0.7 and 0.4, respectively. The outcomes of the model display a good consistency with $z \le 4$ quasar luminosity functions and the $z = 0$ BH mass function, spin values, and BH correlation. Regarding the wBHs, we assume that they can originate from both the disruption of satellite galaxies (orphan wBH) and ejections due to gravitational recoils (ejected wBH). The model points to a number density of wBHs that increases with decreasing redshift, although this population is always $\rm {\sim}2\, dex$ smaller than the one of nuclear BHs. At all redshifts, wBHs are typically hosted in $\rm {\it M}_{halo} \gtrsim 10^{13} \, M_{\odot }$ and $\rm {\it M}_{stellar} \gtrsim 10^{10} \, M_{\odot }$, being orphan wBHs the dominant type. Besides, independently of redshift and halo mass, ejected wBHs inhabit the central regions (${\lesssim}\rm 0.3{\it R}_{200}$) of the host DM halo, while orphan wBH linger at larger scales (${\gtrsim}\rm 0.5{\it R}_{200}$). Finally, we find that gravitational recoils cause a progressive depletion of nuclear BHs with decreasing redshift and stellar mass. Moreover, ejection events lead to changes in the predicted local BH–bulge relation, in particular for BHs in pseudo-bulges, for which the relation is flattened at $\rm {\it M}_{bulge} \gt 10^{10.2}\, M_{\odot }$ and the scatter increase up to ${\sim}\rm 3\, dex$.

Finite Element Analysis of Effect of Flexible Pupjoints on Push-the-Bit Rotary Steering Deflecting Force

As one of the most advanced international drilling technologies at present, rotary steering has been extensively applied to large-displacement, long-distance horizontal, and complex structural wells with numerous advantages, such as strong steering deflecting capacity and good borehole quality. Push-the-bit rotary steering is nowadays commercially applied on a large scale. In the bottom hole assembly (BHA) design of push-the-bot rotary steering drilling, flexible pup joints are the main components that exert an important effect on the exertion of steering deflecting capacity of push-the-bit rotary steering tools. The effect of flexible pup joints on steering capacity of BHA used in the push-the-bit rotary steering drilling process was investigated through a finite element analysis and their action laws were summarized. The results indicated that in order to optimize the deflecting capacity of rotary steering drilling tools, flexible pup joints should be installed cooperatively so as to obtain greater steering drilling capacity. In the rotary steering drilling process, as the outer diameter of flexible pup joints increased, the maximum stress of the BHA decreased. Side cutting force of the drill would increase with the length of pup joints, but this would result in degradation of anti-torsion performance of the BHA.

A New Model for Predicting Rate of Penetration Using an Artificial Neural Network.

The drilling rate of penetration (ROP) is defined as the speed of drilling through rock under the bit. ROP is affected by different interconnected factors, which makes it very difficult to infer the mutual effect of each individual parameter. A robust ROP is required to understand the complexity of the drilling process. Therefore, an artificial neural network (ANN) is used to predict ROP and capture the effect of the changes in the drilling parameters. Field data (4525 points) from three vertical onshore wells drilled in the same formation using the same conventional bottom hole assembly were used to train, test, and validate the ANN model. Data from Well A (1528 points) were utilized to train and test the model with a 70/30 data ratio. Data from Well B and Well C were used to test the model. An empirical equation was derived based on the weights and biases of the optimized ANN model and compared with four ROP models using the data set of Well C. The developed ANN model accurately predicted the ROP with a correlation coefficient (R) of 0.94 and an average absolute percentage error (AAPE) of 8.6%. The developed ANN model outperformed four existing models with the lowest AAPE and highest R value.

Isolation through a viscoelastic surfactant of a fracable hydrocarbon-containing formation

In this paper water cut of well products problem is considered. To solve this problem it is proposed to use a technology of water inflows isolation during the drilling process developed by the authors. Not only does our approach stimulates the production of hard-to-recover hydrocarbons but it also protects local water and undisturbed geological formations against the impact of hydraulic fracturing operations. This approach also enables higher well potential due to a longer service life of the wellbore. The use of a device-pressure regulator with synchronous injection of the developed blocking fluid is presented. Mathematical modeling of the experiment was performed, aimed at determining the dependence of the change in pressure drop in the annular space of the well on the flow conditions of the blocking composition with a device installed in the bottom hole assembly that will effectively apply the controller device, taking into account the drilling parameters of a particular well. The novelty of this approach lies in the fact that this work offers an aquifer isolation technology, which suggests applying a pressure regulating device, and provides a layout of a blocking viscoelastic system.

Dynamic analysis of the longitudinal vibration on bottom drilling tools

With extreme complexity, the drilling process is a dynamic process which is severely influenced by longitudinal vibration. Longitudinal vibration, as one of the most important reason, is directly generated by the fatigue failure of the bottom hole assembly. In this paper, the natural frequencies of longitudinal vibration along the drillstring are analyzed by the finite element method. The deformed plot, stress nephogram, and displacement contour map under 1 to 4 ordered the natural frequency of the longitudinal vibration are obtained. The analysis results show that the maximum deformation always appears in the central part of the string so that some technological process on these positions is required to reduce the collision between the string and wellbore wall. Additionally, a time series of longitudinal vibration of a bottom rotating drillstring is extracted from real-time field data, which is measured while drilling near the drill bit. Then the time-frequency and energy spectrum analysis of the longitudinal vibration is carried out. The results of the statistical analysis show that, when the drillstring uniformly rotates, the longitudinal vibration can be considered as a kind of random vibration. However, if the stick-slip phenomenon occurs during the drilling process, the energy concentration will appear in the time series spectrum of the longitudinal vibration, by which means the vibration could be regarded as random no longer.

Application of Composite Deflecting Model in Horizontal Well Drilling

Based on current issues of difficulties in controlling horizontal well trajectory and high cost in drilling deflecting, a compound deflecting BHA (bottom hole assembly) with diameter-adjustable stabilizer (DAS) and bending-adjustable housing (BAH) is presented. According to the DAS operational principles and the stress condition in operation, the computational formula of wedge’s axial moving displacement and piston’s radial telescopic displacement of the DAS driven by drilling fluid pressure is presented. This formula is verified by lab experimental simulation. Three-points-circle method is utilized to calculate geometrical build up rate of compound deflecting BHA, and the result is verified by field data. The method is utilized to make design and calculate for compound BHA. The research can be used as a reference for compound deflecting drilling in horizontal wells. The flow rate and pressure difference have a very serious impact on the flow regulator erosion, so the flow rate and pressure difference should be controlled when the DAS works, and it is suggested that the flow regulator should maintain and replace frequently when in service.

Study on acoustic transmission characteristics of BHA in directional well

Acoustic telemetry technology while drilling may effectively solve the practical and speed bottleneck of downhole information transmission, but its channel characteristics are subject to the influence of drill string structure in the channel. According to the requirements of reservoir exploitation and drilling technology, the directional well technology is becoming more complex, and the changeable bottom hole assembly (BHA) in the well causes the aperiodicity of acoustic channel. Through the modeling and analysis of BHA under different drilling technology, the characteristics of various aperiodic channels are obtained, and compared with the characteristics of ideal periodic channels, the acoustic transmission characteristics of drill string in directional well are obtained. The aperiodicity brought by BHA makes the high frequency section of the channel seriously attenuated, so the number of aperiodic drilling tools used in the acoustic remote transmission channel needs to be strictly controlled. It can be excluded from the channel if necessary.

Post-job Data Analysis by Python for a Miniature Recorder in Drilling Motors

A vibration recorder has been deployed to capture the dynamics data of drilling motors for their operation and health evaluation. The recorder is usually inserted inside the rotor catcher of a conventional drilling motor in such a way that no extra length is introduced to the planned bottom hole assembly (BHA). The recorder can log data over the full operation cycle of a drilling motor, including vibration during surface activities and downhole operation. A post-job data analyzer was specifically designed based on Python. The analyzer processes the recorded data and generates statistics, time plots, and the various statistical plots such as histograms. These statistics and plots help the operators and maintenance technicians to gain insights into the motor operation and performance. The analyzer can provide adequate information on a drilling motor to asset owners for maintenance and operation optimization without analysis training or qualification from operators.

Modeling and Experimental Study on Motion States of Laboratory-Scale Bottom Hole Assembly in Horizontal Wells

Motion states of bottom hole assembly (BHA) have a great effect on the trajectory control and drilling efficiency while rotary drilling. In order to study the motion states of BHA in horizontal wells, a BHA dynamic model with the finite element method was established. Meanwhile, an indoor experimental setup based on similarity criterion was designed and built to verify the numerical simulation results. Finally, the effects of measuring positions, rotate speeds, weight on bit (WOB), and friction coefficients on the motion states were analyzed in numerical simulation and experiment. The results show that the experimental results can match well with the numerical simulation results. The motion states of BHA in horizontal wells can be divided into three kinds, including circular arc swing, "8" shape swing, and dot-like circular motion. The circular arc swing mainly appears at middle section of BHA and occurs through the collective result of gravity and tangential friction. The dot-like circular motion mainly appears at near-bit or near-stabilizer area because drill bit and stabilizer can steady the BHA at the center part of the wellbore. The "8" shape swing mainly appears at the crossed area and occurs through collective disturbance of the other two motions. Moreover, rotate speed and friction coefficient have promotions on the lateral vibration while WOB have a much smaller effect. Through analyses, related suggestions are given for the drilling engineering. The related conclusions and suggestions in this paper can help to further understand the lateral dynamic characteristics of BHA in horizontal wells and select suitable parameters for drilling engineering.

Analysis of the main factors affecting bottom hole assembly Re-entry into main hole in forward drilling of fishbone wells

Wellbore re-entry is one of the critical technologies in fishbone well drilling. In the sequence of forward drilling, the main hole is designed as a low wellbore and the branched hole is designed as a high wellbore to ensure that the bottom hole assembly (BHA) can re-enter the main wellbore. However, there is no quantitative theoretical analysis regarding the reliability of wellbore re-entry at present. In order to analyze the reliability of the main hole re-entry, an analysis method was provided in this paper. Firstly, a detailed description of the wellbore model around the sidetracking point was built, which can consider the different build-up rate and bending direction of the main and branched hole. Secondly, a mechanical model based on the elastic rod theory was established to calculate the force and deformation of drill strings in the wellbore and a re-entry coefficient was introduced to evaluate the reliability of the main hole re-entry. Moreover, the effects of tool face angle, build-up rate of wellbore, junction wall geometry, and motor structure on the re-entry coefficient are analyzed. Finally, the main controlling factors were analyzed to distinguish the influence degree of different parameters on the re-entry coefficient. From the results, the angle between the bending direction of the branched hole and the tool face of the BHA is the decisive factor in the process of the main hole re-entry. The BHA should be controlled so that the angle is greater than 90° as much as possible. If such angle is less than 90°, the change of wellbore build-up rate, junction wall geometry, and motor structure can be used to increase the re-entry coefficient, such as increasing the build-up rate of the branched hole, wellbore enlargement rate, depth of the slot in the junction wall, and ridge width of the junction wall. Meanwhile, decrease the angle of bent housing, distance between the bending point and the top of bit, and outer diameter of the body stabilizer of the motor can also increase the re-entry coefficient. Among the effects of re-entry coefficient, the main controlling factors are the bend point position and the angle of bent housing.

Orientation load prediction method based on randomness/stochasticity of multi-source parameters in coiled tubing drilling

Well trajectory control is always the key point of directional drilling. Downhole parameters measurements and BHA (bottom hole assembly) configuration and adjustment have the vital and coupling effect on realizing effective and efficient trajectory control. However, error exists universally in both of these phases. Compared with previous fixed value prediction models on controlling parameters prediction, uncertainty analysis based method will make the prediction results more reasonable and meaningful to control the BHA performance. With the consideration of the randomness of downhole multi-source parameters in coiled tubing drilling, an uncertainty prediction method for orientation load at a certain confidence level is proposed. Based on the beam-column theory, the probability and statistics theory is introduced and the distribution forms of main parameters are counted statistically. The probability density function and cumulative probability function of the orientation load prediction model when pump off and pump on in coiled tubing drilling are derived. The lognormal distribution has better correlation with the probability function of the orientation load, and the analysis on the confidence interval of the orientation load is described. Then, several relevant validation experiments are carried out, and the prediction of uncertain orientation load in coiled tubing drilling is also made. Several conclusions are made regarding to the field trial results. The randomness of weight on bit, friction coefficient of the interfacial between drill string and borehole wall or drill string and casing and tool face angle are the principal factors affecting the uncertainty of orientation load in coiled tubing drilling. The orientation load predicted with the uncertainty method is not a single curve or a single value, but an interval with a certain confidence level. The width of interval window is determined by the accuracy and precision of parameters information. The higher the confidence level is, the wider the predicted interval of orientation load and the larger the uncertainty range become. Compared with the predicted results of the uncertainty method, an error exists in the result of traditional single-value calculation method. The error varies with the change of weight on bit and formations and can be positive or negative. Meanwhile, retrieving more accurate principal original dada, e.g. WOB, formation properties, will make the uncertainty of the prediction lower. This orientation load prediction method is helpful to improve the efficiency of directional drilling in coiled tubing drilling.

Vibration of drilling motors in unconventional oil and gas exploration with a miniature recorder

A low-cost and miniature vibration recorder was developed to capture the vibration data of drilling motors for their health assessment. The recorder is installed in the rotor catch of a conventional drilling motor in such a way that no additional length is added to the bottom hole assembly. The recorder is fitted with two triaxial vibration accelerometers with different ranges, a rate gyroscope, a temperature sensor, and an integrated circuit (IC) for timestamps. The recorder can log data over the full operation cycle of a drilling motor, including vibration during surface activities and downhole operation. It allows the vibration recorders to be easily deployed to motor operations. The vibration recorder has been deployed to drilling motors in unconventional horizontal wells. The data analysis showed that the recorder captured vibration data from the installation of the recorder in maintenance bases until the return of the tools. Not only downhole drilling vibration data were successfully obtained, but also surface vibration data during shipment, and rig-side handling was recorded; the vibration recorders provided adequate information of a drilling motor to asset owners for maintenance and operation optimisation.

Design of bottom hole assemblies with two rock cutting tools for drilling wells of large diameter

The experimental results have been obtained without any support of grants or projects. The authors express their gratitude to Doctor of Technical Sciences, Professor I.I. Chudyk for advice and support in the process of obtaining research results.