Drilling Fluid Velocity Research Articles

OPTIMIZATION OF HYDRODYNAMIC PARAMETERS OF DRILLING FLUIDS FOR IMPROVED CUTTINGS TRANSPORT IN HORIZONTAL WELLS

In horizontal portions of small-bore well holes, improper cuttings transportation results in high torque and raises the possibility of the drill being stuck, shortening its service life and endangering safe operation. A transport approach utilizing pulsed drilling fluid based on a shunt relay mechanism is suggested since the traditional cuttings transport method is ineffective at removing the cuttings bed. The transport of cuttings in horizontal small-bore wells is modeled numerically using three layers. The cuttings transport is examined in terms of the cuttings concentration, cuttings velocity, and cuttings bed movement distance using both numerical models and tests. The best pulse parameters are identified by adjusting the pulsed drilling fluid velocity cycle, amplitude, and duty cycle at the annulus inlet and assessing the impact on cuttings transport. The findings demonstrate that pulsed drilling fluid can be used to improve wellbore cleaning, lower cuttings concentration, and increase the cuttings bed's transport distance and moving cutting velocity. A steady flow rate of drilling fluid is used in the traditional cuttings transportation method. Simulations using the three-layer numerical model show that the cuttings bed's movement distance is decreased to the point where the wellbore's cleaning effect falls short of its intended level when the cuttings bed's height in the annulus surpasses a critical value. A technique using pulsed drilling fluid has been suggested to enhance transportation. By altering the drilling fluid's flow rate, this continuously affects the cuttings. Because pulsed jet drilling technology can effectively boost drilling speed, downhole drilling instruments that use pulsed jets are outfitted with spiral pressure intensifiers and variable-frequency pulse jet generators. According to field tests, using pulsed drilling fluid improves cuttings transport efficiency and lessens the impact of chipping. The majority of cuttings transport research to date has been on how cuttings behave under typical drilling fluid flow conditions. Relatively few studies exist about the destruction of the cuttings bed or the transportation of cuttings under conditions of pulsed drilling fluid. This research establishes a three-layer numerical model under pulsed fluid circumstances based on a shunt relay mechanism. This research describes the transport of cuttings in horizontal well sections under pulsed drilling fluid circumstances in terms of factors, such as the cuttings concentration, the cuttings bed's distance traveled, and the moving cuttings velocity, using both numerical models and tests. Furthermore, the ideal pulse parameters are found, which serves as a crucial guide for designing cuttings transport using pulsed drilling fluid tools. A three-layer numerical simulation model of cuttings transport utilizing a pulsed drilling fluid in the horizontal section of a narrow-bore hole is constructed in the second section of the article, which is based on actual onsite working conditions. The experimental apparatus and procedures are presented in the third section, and the experimental data are used to study the behavior of cuttings transport by the pulse drilling fluid. The cuttings transport behavior for various values of th is examined in the fourth section using finite element software. Keywords: CFD model, cuttings bed, pulsed drilling fluid, and horizontal well drilling

Flow Field Simulation of a Hydrogeological Exploration Drill Bit for Switching between Coring Drilling and Non-Coring Drilling

Drilling is one of the most commonly used techniques in hydrogeological exploration and is employed to obtain rock samples and create boreholes. During conventional drilling, it is necessary to raise all the drilling tools in the borehole when switching between coring drilling and non-coring drilling, which causes large auxiliary operation time consumption and poor drilling efficiency. Based on the structure of wireline coring tools, a large diameter modular drill bit was designed to switch between coring drilling and non-coring drilling without lifting the whole set of drilling tools. In the COMSOL simulation environment, a simulation model of the modular bit was constructed. Drilling fluid velocity and pressure characteristics flowing through the modular bit were studied. According to the analysis results, with the same input flow rate, similar velocities and lower pressure loss can be obtained in non-coring drilling as with the coring bit, and thus drilling cuttings can be removed effectively even if there are more cuttings produced in non-coring drilling than in coring drilling for a borehole drilled at the same diameter. When the outside diameter of the modular bit is 216 mm, the recommended clearance value is 9 mm or 10 mm in order to obtain lower pressure loss and larger diameter core. To generate low pressure loss and ensure bit strength, a layout with four nozzles on the internal non-coring bit is recommended. The modular bit enables fast switching between coring drilling and non-coring drilling without raising the drilling tools. The simulation model can be used for drilling parameter selection and drill bit optimization.

Experimental evaluation of different influencing parameters on cutting transport performance (CTP) in deviated wells

• CTP in deviated wells is affected by influencing parameters. • CTP has enhanced up to 8% by increasing viscosity with constant velocity. • Increasing additional viscosity results in a 12% reduction in CTP. • Hole inclination above 60 degrees has a positive effect on CTP which is up to 40%. • Velocity has a significant impact on CTP with a maximum of 98%. Globally, fuel energy has become a crucial issue in fulfilling energy demand; new oil/gas wells should be drilled to achieve the well target safely and efficiently. Cutting transport in deviated wells is directly affected by influencing parameters such as viscosity, annulus velocity of drilling mud, and hole inclination. Therefore, hole cleaning investigation requires a deep understanding of all influential parameters, as cuttings transport significantly affects drilling costs, time, and oil/gas well integrity. Poor hole cleaning efficiency could cause many drilling issues, including excessive torque and drag, Pipe washout and jamming, bit balling and washout, etc. The results of this study were utilized to investigate cutting transport performance, employing three different kinds of drilling mud. The investigational work was performed by a 10-feet elongated invisible pipe of 5-inch diameter and a steel pipe of 2-inch diameter as the test section. The cutting transport performance (CTP) was computed based on weight data for every single test. At different flow regimes, viscosity was examined in addition to two other influential parameters, namely fluid velocity and hole inclination. At all angles, during turbulent flow, Cutting Transport performance has enhanced up to 8% by increasing viscosity while keeping velocity constant. Nevertheless, an increasing additional amount of viscosity will turn the flow condition from turbulent to transient or laminar flow, resulting in a 12% reduction in CTP. It also shows that increasing hole angle above 60 degrees positively affects cuttings transport performance. It will be improved up to 40%. Moreover, a maximum of 98 percent CTP can be attained by drilling fluid velocity. Therefore, this study properly investigates the influence of viscosity, velocity, and hole inclination on cutting transporter performance, as a result saving drilling time and reducing hidden costs, as well as lead to a prediction of the carrying capacity of fluids and facilitating the optimum design of vertical and directional wells. Moreover, this study provides a guideline to analyze and enable the adjustment of drilling parameters to optimize the overall drilling process.

Estimation of downhole cuttings concentration from experimental data – Comparison of empirical and fuzzy logic models

Proper selection of drilling parameters during planning phase to ensure an adequately clean well is the key to avoid costly drilling operational problems such as mechanical stuck pipe and high drillstring torque and drag resulting in not reaching the drilling target for highly deviated/ERD wells. Cuttings transport is a complex phenomenon influenced by different parameters such as flow rate, drillstring rotation, rate of penetration, eccentricity, well configuration, drilling fluid properties and cuttings properties. The complexity of the cuttings transport process has led to the use of alternative modeling approaches. In this paper, a computational intelligence method, fuzzy logic (FL), is chosen to develop a model to estimate downhole cuttings concentration. FL, resembling human reasoning, is capable of modeling non-linear functions of arbitrary complexity and dealing with imprecision in data. The FL model developed in the current work is based on 509 experimental observations involving 11 independent test parameters each. 25% of the collected dataset (excluding the test dataset) is used as cross-validation dataset and the rest is used as training dataset to avoid overfitting. The test dataset comprised of nine observations is used for comparing FL model estimates for downhole cuttings concentration to those made by two published empirical models which are based on dimensional analysis and critical drilling fluid velocity concept respectively. Comparison of the models on the test dataset shows that the developed FL model performs better than the two empirical models in all the three statistical measurements namely coefficient of determination (R2), root mean square error (RMSE) and mean absolute error (MAE).

Design and Performance Research of Flexible Drill Pipe Joint Based on Bionic Theory

Fatigue fracture is the main failure form of mining drill pipe joints, which directly leads to the occurrence of drill pipe drop accidents. Based on the principle of engineering bionics, the spine structure and kinematic behavior characteristics of cheetah were studied; the bionic design and trial production of drill pipe joints were carried out. For the bionic drill pipe joint, it separates the torsion transmission function from the connection function, and when the torsion transmission function of the joint fails, the connection function is still effective, so as to achieve the effect of “breaking the bones and connecting the ribs.” The mechanical and flow field properties of the bionic drill pipe joint were analyzed. Mechanical test results showed that, for the bionic drill pipe joint, the average tensile capacity was 555.48 kN and the average torsion capacity was 8914.13 N·m, which met the mechanical performance requirements. The flow field numerical simulation results showed that, when the drilling fluid velocity field and pressure field were stable and change evenly, there is no risk of leakage. The study results can provide a new research idea for the research and development of mine drill pipe joint with long life and antidropping function.

Analysis of critical whirling velocity of drill string

ABSTRACT During the drilling process, the whirling motion often occurs, which will cause the drill string to vibrate violently, accelerate the fatigue damage of the drill string, and eventually cause the bottom hole assembly to fail. But the existing research rarely focuses on the critical whirling velocity of drill string. To solve this problem, the whirl differential equation of drill string was set up based on the D’Alembert principle, and the critical whirling speed equation of drill string was deduced according to separation variable method. Reference to actual downhole conditions, the influence of drill stem wall thickness, tension, drilling depth, drilling fluid flow rate, and other factors on the critical whirling speed of drill string are considered. Research results indicate that when n ≤ 8324, drill string has a critical whirling speed, and when n > 8324, there is no critical whirling speed. And under different orders, as drill string wall thickness and drilling depth increase, the critical whirling velocity decreases. In general, the drill string rotation rate is 0–150 rad/min. When the drilling depth is 0–500 m, the critical speed is not considered. However, as drilling depth exceeds 500 m, the critical whirling velocity is within the general range of drill string speed. Therefore, drill string velocity should be chosen reasonably to avoid resonance. When the tension increases, critical whirling velocity increases. As the drilling fluid flow rate increases, the critical whirling velocity of drill string decreases. But when drilling fluid velocity is close to 120 L·s−1, increasing the drilling fluid velocity hardly affects the critical whirling velocity of drill string. In a word, research results of this paper have certain guiding significance to drilling engineering.

Computational study of cutting transport by drilling fluids in directional wells

The paper presents the computation results of the cutting transport in directional wells. Two samples of oil-based muds were prepared. The rheological parameters, incorporated in the computation model, were measured. The geometry of the real well was used for the computation. Three well slopes equal to 15, 45, 75 degrees were studied. The sludge velocity profiles in the annular channels were obtained. The average volumetric value of the particle slip velocity was obtained (the difference between the drilling fluid velocity and the sludge velocity).

Central tube erosion investigation of torque impactor in the deep shale gas formation

ABSTRACT To figure out erosion mechanism of the torque impactor and optimize the structure of such tools, CFD (computational fluid dynamics) simulation model of the central tube is established. Results show that the location of the most serious erosion and the maximum erosion rate (4.80 × 10−4 (kg/(m2·s)) are consistent with the actual situation. Solid particles retained in the central tube are distributed unevenly. When drilling fluid velocity increases from 26 to 32 m/s, the maximum erosion rate of the central tube increases from 3.89 × 10−4 to 6.60 × 10−4 (kg/(m2·s)). As the mass flow rate of the solid particles increases from 0.2 to 0.8 kg/s, the maximum erosion rate increases from 5 × 10−4 to 28 × 10−4 (kg/(m2·s)). With increasing of particle diameter from 0.2 to 1.2 mm, the maximum erosion rate increases from 5.98 × 10−4 to 48 × 10−4 (kg/(m2·s)) and shows different upward trend in different intervals of particle diameters. As the solid particle shape coefficient increases from 0.4 to 1, the maximum erosion rate decreases from 14 × 10−4 to 1 × 10−4 (kg/(m2·s)). Grey correlation coefficient method indicates that the most relevant to the erosion rate is the drilling fluid velocity, followed by the particle shape coefficient, the particle diameter, and the solid particle mass flow rate.

Prediction of Cuttings Transport Behavior under Drill String Rotation Conditions in High-Inclination Section

Cuttings are likely to accumulate and eventually form a cuttings bed in the highly-deviated section, which usually lead to high friction and torque, slower rate of penetration, pipe stuck and other problems. It is therefore necessary to study cuttings transport mechanism and improve hole cleaning efficiency. In this study, the cuttings-transport behaviors with pipe rotation under turbulent flow conditions in the highly deviated eccentric section were numerically simulated based on Euler solid–fluid model and Realizable [Formula: see text]–[Formula: see text] model. The resulted numerical results were compared with available experimental data in reported literature to validate the algorithm, and good agreement was found. Under the conditions of drill string rotation, cuttings bed surface tilts in the direction of rotation and distributes asymmetrically in annulus. Drill string rotation, drilling fluid flow rate, cuttings diameter, cuttings injection concentration and drilling fluid viscosity affect the axial velocity of drilling fluid; whereas drilling fluid tangential velocity is mainly controlled by the rotational speed of drill string. Increase in value of drill string rotation, drilling fluid flow rate or hole inclination will increase cuttings migration velocity. Notably, drill string rotation reduces cuttings concentration and solid–fluid pressure loss, and their variations are dependent on inclination, cuttings injection concentration, cuttings diameter, drilling fluid velocity and viscosity. However, when a critical rotation speed is reached, no additional contribution is observed. The results can provide theoretical support for optimizing hole cleaning and realizing safety drilling of horizontal wells and extended reach wells.

Cuttings Transport Using Pulsed Drilling Fluid in the Horizontal Section of the Slim-Hole: An Experimental and Numerical Simulation Study

Poor transport of cuttings in horizontal sections of small-bore well holes leads to high torque and increases the risk of the drill becoming stuck, reducing its service life and posing a threat to safe operation. Because the conventional cuttings transport method cannot effectively remove the cuttings bed, a transport method using pulsed drilling fluid based on a shunt relay mechanism is proposed. A three-layer numerical simulation model of cuttings transport in horizontal small-bore wells is established. Using both experiments and numerical simulations, the cuttings transport is studied in terms of the moving cuttings velocity, cuttings concentration, and distance of movement of the cuttings bed. By varying the pulsed drilling fluid velocity cycle, amplitude, and duty cycle at the annulus inlet, their effects on cuttings transport are analyzed, and the optimal pulse parameters are determined. The results show that the use of pulsed drilling fluid can effectively enhance the moving cutting velocity and transport distance of the cuttings bed, reduce the cuttings concentration, and improve wellbore cleaning.

Investigation of cuttings transport in directional and horizontal drilling wellbores injected with pulsed drilling fluid using CFD approach

Efficient cuttings transportation is a significant issue in wellbore drilling. The pulsed jet drilling technology is known to improve the rate of penetration (ROP), but lacks targeted research into its effect on cuttings transport. We presented a CFD model based on Eulerian-Eulerian method to investigate the cuttings transport characteristics in horizontal and directional wellbores injected with pulsed drilling fluid. Kinetic theory of granular flow was used to formulate the stress tensor of cuttings particles, and sliding mesh method was used to achieve the rotation of the drill pipe. The wave propagation of the flow of cuttings particles was analyzed from the variation of amplitude and frequency of the inlet velocities of pulsed drilling fluids. Effects of drilling fluid rheological properties and hole and pipe diameters on borehole cleaning in traditional and pulsed drilling were studied. Numerical results indicated that the pulsed drilling fluid contributes to borehole cleaning because it significantly reduces the cuttings concentration in the moving bed zone and increases the velocities of cuttings in the fixed bed zone. Increasing amplitude and frequency of the inlet velocity of pulsed drilling fluid also leads to a decrease of the height of cuttings bed. The pulsed drilling fluid produces higher turbulent kinetic energy and lower turbulent dissipation rate comparing with the case with a constant drilling fluid velocity. Furthermore, pulsed drilling was also proved to be universally applicable to the improvement of cuttings transport within a wide range of drilling fluid rheological parameters and hole and pipe diameters.

Temperature and pressure effects of drilling fluid on cutting transport using CFD simulations

AbstractSimulation of liquid–solid flow in annulus of oil wells is of a great importance to predict the two‐phase flow field in wellbore accurately. In this paper, direct effects of drilling fluid rheological properties by Herschel–Bulkley model on cuttings transportation, pressure drop, and other parameters of two‐phase flow are numerically investigated at different temperatures and pressures. Recent studies have not addressed these effects. Thus, a 3D form of a steady‐state and isothermal model is used to simulate the two‐phase flow in various temperatures and pressures of drilling fluid, flow rates, and drilling pipe rotations. The governing equations created a system of coupled partial differential equations solved using the iterative finite volume method. The comparisons between the results of the model and experimental data and also analytical relation showed that the model can accurately predict two‐phase flow in the annulus. The results indicated that the elevation of temperature and reduction of pressure contributes to a decrease in the cuttings transportation. For drilling fluid velocity of 0.75 m/s, the cuttings transportation has been decreased 2.08% by increasing temperature from 70°C to 90°C in 0.1 MPa, whereas in pressure of 10 MPa, about 1.63% reduction on the transportation of cuttings yielded. © 2017 Curtin University and John Wiley & Sons, Ltd.

Impact of drilling fluid viscosity, velocity and hole inclination on cuttings transport in horizontal and highly deviated wells

Deviation from vertical path makes drill cuttings to accumulate on the lower side of the wellbore that induces the formation of cuttings bed. Subsequently, relative problems occur while drilling. Excessive torque and drag, difficulties in running casing in hole and accomplishing good cementing jobs and mechanical pipe sticking are few of the classical examples of such problems. Therefore, a comprehensive understanding of influential parameters on hole cleaning seems to be essential. This paper indicates the results of an experimental study that was carried out to evaluate cuttings removal efficiency using three types of drilling fluid. The experimental works were conducted using a 17-feet long opaque flow loop of 2-in. diameter as the test section. For each test, the amount of cuttings transport performance (CTP) was determined from weight measurements. Viscosity was investigated together with other two influential parameters, namely fluid velocity and hole inclination under various flow conditions. It is shown that the increase in drilling fluid viscosity has improved CTP by approximately 8 % at all angles provided the flow regime remained turbulent while velocity was kept constant. However, further increase of viscosity as flow regime was turning into transient or laminar flow, has lessened CTP by a total average of 12 %. It was also revealed that an incremental escalation in hole inclination from 60° to 90° has a positive effect on CTP, i.e., it will be improved up to 40 %. Drilling fluid velocity was found to have significant impact on CTP as it could attain maximum percentage of 98 %.

CFD predictions of drilling fluid velocity and pressure profiles in laminar helical flow

Fluid flow in annular spaces has received a lot of attention from oil industries, both in drilling operations and in petroleum artificial rising. In this work, through numerical simulation using the computational fluid dynamics (CFD) technique, the flow of non-Newtonian fluids through the annuli formed by two tubes in concentric and eccentric arrangements of a horizontal system has been investigated. The study analyzes the effects of viscosity, eccentricity, flow and shaft rotation on the tangential and axial velocity profiles and on the hydrodynamic losses. It evaluates the performance of the numerical method used, comparing the results obtained with those in other reported works, aiming to validate the simulation strategy by the interpolation routines as well as the couplings algorithms adopted.

A New MTV Computer Package for Hole-Cleaning Design and Analysis

Summary This paper describes a computer package that can be used to calculate the minimum transport velocity (MTV) required to ensure efficient hole cleaning during deviated drilling operations. The package was developed in the Dept. of Petroleum Engineering at Heriot-Watt U. It operates in a Windows environment and allows the user to do the following: Define, from viscometer data, the rheological model (PowerLaw, Bingham Plastic, or Herschel-Bulkley) that best describes a particular drilling fluid. Model the drilling fluid velocity profile in a defined annular geometry. Predict the minimum circulation rate required to ensure efficient cuttings transport for a wide range of operational conditions. The paper describes how the lift and drag forces on the cuttings have been determined and used in the development of the package. Case studies that demonstrate the functionality of the package are also presented.

Evaluation of jetting insertion for the self-boring pressuremeter

The primary objectives of the self-boring pressuremeter (SPBM) test are to measure, in situ, the horizontal stress and the stress–strain characteristics of soils and soft rocks. This cylindrical probe tunnels itself into the ground with a minimum disturbance. Conventionally, the advance has been performed using a cutter system housed inside a cutting shoe. Although proven effective, this method is slow and cumbersome. In response to these drawbacks, a jetting insertion method was introduced and designed to allow a faster rate of insertion using a system that is less equipment intensive and easily adapted to conventional drill rigs. To avoid similar potential inconsistencies encountered in earlier SBPM testing with the cutting method, a series of laboratory simulation tests and in situ self-boring pressuremeter tests were carried out in two soft clay deposits to assess the jetting method. The following key insertion parameters were studied: jetting nozzle type, drilling fluid velocity, jetting nozzle position, rate of advance, and jetting flushing system. The results of this study indicate that, as with the cutting method, the jetting method can be used in soft to medium clays to advance the self-boring pressuremeter with minimum disturbance. Key words : self-boring pressuremeter, soft clay, horizontal stress, jetting, cutting.

Experimental Study of Cuttings Transport in Directional Wells

Summary A large-scale study of cuttings transport in directional wells is discussed in this paper. Previous investigators used unrealistically high fluid velocities and/or short test sections where steady-state conditions had not been established. This study used a 40-ft [12.2-m] test section. Pipe rotation and eccentricity, as well as several types of drilling muds and flow regimes, were studied. Annulus angles varied from 0 to 90°, and actual drilled cuttings were used. The major factors affecting cuttings transport are drilling fluid velocity, hole inclination, and fluid rheological properties. Much higher annular velocities are required for effective hole cleaning in directional wells than in vertical wells. An increase in hole angle and/or drilling rate reduces the transport performance of drilling fluids. Hole angles of 40 to 50° are critical because of cuttings buildup and downward sliding of the bed of cuttings. High-viscosity muds were observed to provide better transport than low-viscosity muds.