Drilling Fluid Flow Research Articles

A Numerical Simulation of the Effect of Drilling Fluid Rheology on Cutting Migration in Horizontal Wells at Different Drilling Fluid Temperatures

In recent years, significant breakthroughs have been made in the exploration of deep to ultra-deep oil and gas reserves onshore in China. These conventional deep to ultra-deep reservoirs are typically buried at depths exceeding 4500 m, with bottom-hole temperatures surpassing 150 °C. The high temperatures at the bottom of the well are more likely to cause deterioration in drilling fluid properties, altering its rheological properties and reducing cutting transport efficiency, which can lead to wellbore cleaning issues. In this paper, the numerical simulation method is used to analyze the influence of cutting particle size, drilling fluid flow rate, drill pipe rotation speed, and drill pipe eccentricity on the annular cutting concentration under different wellbore drilling fluid temperature conditions. The results show that at the same cutting particle size, as the drilling fluid temperature increases, the cutting concentration in the annulus increases sharply. The increase is the largest when the particle size is 3 mm, and when the drilling fluid temperature is 220 °C, the cutting concentration increases by 79.7% compared to at 200 °C and by 279% compared to at 180 °C. When the flow rate increases from 0.5 m/s to 1.0 m/s, the annular cutting concentration at drilling fluid temperatures of 220 °C and 200 °C decreases by 70.5% and 50.4%, respectively. The higher the drilling fluid temperature, the better the cutting removal effect when increasing the drill pipe rotation speed. However, when the rotation speed exceeds 120 rpm, the change in cutting concentration with increasing rotation speed becomes insignificant. When the drill pipe eccentricity is small, an increase in drilling fluid temperature leads to a significant rise in annular cutting concentration. However, when the drill pipe eccentricity is large, changes in drilling fluid temperature have a smaller impact on cutting concentration. The research findings can provide engineering guidance and theoretical support for the design of drilling fluid hydraulic parameters for cutting transport and rheological parameters in high-temperature wellbores.

Theoretical Analysis of Drilling Fluid Flow for Maxi-Horizontal Directional Drilling

Theoretical Analysis of Drilling Fluid Flow for Maxi-Horizontal Directional Drilling

Developing a neural network model to predict the optimal minimum flow rate for effective hole cleaning

The object of the study is effective well cleaning during drilling. The subject of the study is the development of a machine learning model based on a neural network for predicting the optimal minimum drilling fluid flow rate. The challenge is the need to improve well cleaning efficiency to prevent stuck pipes and the associated downtime and costs. During the study, a neural network model was developed and tested to predict the minimum flow rate for cleaning wells. The model was trained and tested on data showing its high accuracy and reliability. The mean square error (MSE) reached 0.019169 for LSTM and 0.0828 for GRU, indicating the accuracy of the predictions. Neural network architectures such as Long-Short Term Memory (LSTM) and Gated Recurrent Unit (GRU) were used to efficiently process time series of data and consider long-term dependencies. The results are explained using advanced neural network architectures and machine learning algorithms, which made it possible to achieve good accuracy of predictions. These architectures enable efficient model training on large amounts of data, allowing complex dependencies and influencing factors to be considered. Distinctive features of the results include good accuracy of predictions and the ability to use the model in real-world conditions. The model demonstrates good performance and reliability in predicting the minimum flow rate. The results of the study can be used to optimize the processes of well drilling. Practical applications include using the model to predict the optimal minimum flow rate in various conditions, which will reduce the risks of stuck pipes and increase the efficiency of drilling operations. The model can be integrated into existing monitoring and control systems for drilling processes to improve their performance

Experimental Analysis of Shale Cuttings Migration in Horizontal Wells

The extraction of shale gas via horizontal drilling presents considerable challenges, primarily due to the accumulation of cuttings within the annular space, resulting in increased friction, torque, and potential drilling complications. To address this issue, the study proposes an experimental setup aimed at simulating cuttings transport under various operational conditions, with a particular emphasis on gas wells. The methodology encompasses the modulation of the drilling fluid flow rate and the drill’s rotational speed to examine the transport velocity of cuttings. Furthermore, the study analyzes the impact of annular eccentricity on return volume, transport time, and cuttings bed height. Critical initiation velocities for cuttings across different motion modes were also determined, and theoretical calculations were compared with empirical data. The findings indicate that an increased flow rate of drilling fluid and higher rotation speed substantially improve the transport of cuttings, thereby minimizing bed formation, whereas increased eccentricity hinders this process. The results revealed that the theoretical model showed a greater overestimation of the start-up velocity for spherical particles, with average errors ranging from 15.50% to 17.56%. In contrast, the model exhibited better accuracy for non-spherical (flaky) particles, with errors between 8.63% and 9.61%. Under non-rotating conditions, the average error of the model was approximately 8.32%, while the introduction of drill tool rotation increased the average error to 11.94%. These results have the potential to optimize operational parameters in shale gas well drilling and may contribute to the development of specialized borehole purification tools.

Model establishment and flow field simulation analysis of high torque screw motor in ultra-deep well

Abstract To explore the distribution law of the flow field in the inner annular flow channel of the stator-rotor of the high-torque screw drill tool and determine the key performance parameters of the tool under different drilling fluid densities and flow rates, a physical model for fluid simulation was established with the 7/8 head screw motor as the research object to study the distribution law of the flow field and the output torque of the rotor at different flow rates and densities, and a comparative analysis was made with the actual test. The results show that the pressure of the internal flow channel is mainly concentrated at the entrance of the flow channel and the wall of the flow channel. The flow rate in the thick fluid domain is high, the flow rate in the thin fluid domain is low, and the flow rate in the thinnest area is about zero. The relationship between displacement pressure drop and output torque presents a positive correlation. When displacement increases, the output torque of the screw increases, and the relationship between displacement and torque presents a linear increase. The torque and displacement of fluid simulation under ideal conditions are larger than the actual test parameters. In the actual test, the drilling fluid temperature and experimental equipment factors affect the performance of the screw motor. In the process of fluid simulation, the setting of boundary conditions should refer to the real situation as much as possible to improve the accuracy of simulation results. The difference between fluid simulation and actual test parameter values is small and the trend is the same, so fluid simulation can guide practical application and reduce cost to a certain extent.

Technologies to improve wellbore cleaning

Relevance. The main technological process when constructing oil and gas wells is effective wellbore cleaning, especially when drilling horizontal and deviated wells. The article deals with the peculiarities of wellbore drilling technology according to the traditional method in combination with water and hydrocarbon-based polymer-clay solutions, as well as improvement of drilling mud removal properties taking into account density, drilling pump productivity, rheological parameters of the fluid, geometry of the well annulus, shape and concentration of drill cuttings particles. Insufficient cleaning of the well bottom hole causes undesirable phenomena leading to various complications. The object of the research is the technology of cuttings transportation along the wellbore to the surface. The basic formulas characterizing the work of interchangeable hydromonitor nozzles are given. The quality of wellbore cleaning depends on the degree of flow turbulence. Aim. To develop technical solutions that contribute to improving the quality of wellbore cleaning. Methods. Optimal geometrical parameters of hydraulic nozzles for double-deck anti-vibration bit and design of drill pipes with helical ribs have been established by experimental works. Results and conclusions. A double-deck anti-vibration bit with interchangeable hydro-monitor nozzles and drill pipes with helical ribs were developed. Implementation of these developments in the practice of drilling operations will improve the quality of wellbore cleaning by creating a turbulent regime of drilling fluid flow.

Design and dynamic characteristics of automatic vertical drilling tool

Higher performance is needed in deeper and longer horizontal wellbore drilling. In vertical drilling conditions, wellbore trajectory often be led to deviation due to objective conditions. Based on the engineering issues, this paper presents a new automatic vertical drilling tool, including the innovative design and working mechanism research. This tool working mechanism are carried out, such as the mechanics model of eccentric tube and the relationships between eccentric torque and deflection angle. The eccentric tube torque increases with the wellbore deviation angle. When wellbore deviation angle is constant, the eccentric tube torque reaches maximum value when its deflection angle is 90°. The internal flow parameters are studied by fluid field simulation, such as drilling fluid flow rate, pressure drop, and pressure distribution inside this tool during downhole drilling process. The larger the diameter of switch hole, the higher is the pressure drop around, which leads to the force on push block increasing. The drilling fluid pressure increases with higher input flow rate inside this tool. The comparison of results, the data of simulation and theoretical model calculations, verified the reliability and accuracy of research. This study has provided innovative ideas and reference for drilling tool design and wellbore trajectory control methods.

Self-Stabilizing Control Strategy of Stabilized Platform for Rotary Steerable Drilling System Based on Adaptive Backstepping Control

To enhance the robustness of the toolface angle control in a fully rotary steerable drilling tool, a backstepping control law and a drilling fluid flow adaptive law are devised based on the dynamic model of the stable platform. The Lyapunov function is constructed, and it is proven that the adaptive backstepping control system of the stabilized platform is stable. Furthermore, in order to address problems such as the friction dead zone and excessive rotational kinetic energy in the stabilized platform system, which could cause toolface angle oscillations and the rapid rotation of the stabilized platform, we additionally propose an online estimation method for the balancing torque and velocity-angle control switching strategy. By combining the backstepping control law, drilling fluid flow adaptive law, and velocity-angle control switching strategy, a self-stabilizing control strategy for the stabilized platform is established. In comparison with the PID control method, the simulation results show the superiority of the proposed scheme under complex disturbances from a downhole environment. And the drilling simulation experiment results indicate that the proposed control method has a good anti-interference capability under various conditions, including drilling fluid flow rate, inclination angle, and drill collar rotational speed. Therefore, the proposed control method can improve the robustness of the stabilized platform control system.

Research on the Error Calibration Method of Rheological Parameters of Rectangular Tubular Viscometer

In order to solve the problem of high error in the process of measuring the rheology of drilling fluids by the common pipe flow method, an online measurement device for the rheology of drilling fluids with rectangular tubular drilling fluids was fabricated, and a calibration method for the measurement error of rheological parameters was proposed and corresponding experiments were carried out. By measuring the differential pressure value and flow, flow rate and other parameters when the drilling fluid flows through the measuring tube, upload them to the host computer for processing, use VMD to decompose the measured differential pressure data, remove the residual term, and then perform Hibert transform on each modal component to obtain its analytical signal, modulate the amplitude and phase of each analytical signal, and then reconstruct the signal to obtain the optimized differential data, and finally bring it into the constructed calibration model of the rheological parameter measurement error of drilling fluid to obtain the rheological parameters. The experimental results show that the proposed method can obtain more accurate rheological parameters of drilling fluid, improve the measurement accuracy of drilling fluid rheology parameters, so as to judge the downhole situation more accurately and ensure the personal safety of on-site staff.

Moore And Chien Correlation To Address The Issue Of Hole Cleaning In Guba Field – Libya

Hole cleaning and hydraulics are important part of drilling operations that need to be carefully reviewed and incorporated in drilling program. Poor hole cleaning could lead to various problems like slow rate of penetration (ROP), excessive torque and drag, excessive wear on bit, pipe sticking problems, and possibly fracturing of formation.In this work, Since hole cleaning is a major problem associated with drilling operations. There is an evaluation of the effect of the drilling fluid rheology parameters and flow rate on hole cleaning. Correlation methods such as Moore and Chien correlation have been made to provide the most suitable approach to address the issue of a hole cleaning. On the other hand, also explains the effect of the flow rate in the equivalent circulating density (ECD) in terms of frictional pressure loss in the annulus. The result of analysis demonstrates how the rheology parameters and flow do affect the hole cleaning and concludes that the ECD and frictional pressure loss in the annulus are affected by the flow rate.

Fusion model of weight on bit in horizontal exploration hole based on wavelet transform and machine learning

During the horizontal drilling of the development of energy and the geological exploration, the loss of axial feed pressure is serious due to the frictional resistance in horizontal hole. As the length of the drilling pipe increases, the problem of insufficient drilling pressure becomes increasingly prominent. It is imperative to master weight on bit (WOB) in time and accurately for the adjustment of drilling parameters. Limited by the long drilling pipe, it is difficult and costly to measure WOB directly. Therefore, a novel model of WOB prediction was established. The model realized the coupling of wavelet transform and neural network. Five easily available parameters, feed pressure, rotational speed, torque, pump pressure and drilling-fluid flow rate were selected as input to the model. The WOB was taken as the only output of model. First, Morlet wavelet was used to reform the structure of hidden layer and output layer of neural network. In the reformed model, the self-learning and adaptive ability of neural network and the ability for local information extraction of wavelet transform were fully stimulated. Then, embedded genetic algorithm (GA) was used to optimize the weights and wavelet parameters of the model, which improves the global optimization ability of the model. The established model was named GA-WNN, and the experimental results demonstrate that the R2 of prediction model reaches 0.9982. The mean absolute percentage error (MAPE) of GA-WNN prediction can yield as low as 6.22%, while the MAPE of standard neural network prediction can yield as high as 47.04%. Furthermore, the accuracy of the model was further verified by response surface methodology (RSM), and the results show that the predicted data of the model can meet the requirements of RSM for data quality. The RSM analysis of WOB based on predicted data was successfully carried out, and the interaction influence between drilling parameters on WOB were obtained, which provides reference for parameter adjustment. The high-quality algorithm of WOB prediction provides support for long-distance horizontal drilling.

Diagnosis of the structural stability of the flow of multiphase oil-based drilling fluids

Diagnosis of the structural stability of the flow of multiphase oil-based drilling fluids

Research on measurement method of drilling fluid rheological parameters based on helical pipe

Monitoring drilling fluid rheological parameters can provide a basis for assessing downhole complexities and analyzing well control risks. Among various methods for measuring drilling fluid rheological parameters, the pipe flow method allows for real-time online measurements. However, it faces limitations due to the long length of pipes and challenges in miniaturization. Based on a survey of domestic and international research, this study conducted numerical simulations to analyze the differences in flow pressure drop of drilling fluid between helical pipes and straight pipes. It clarified the impact of helical pipe structural parameters, drilling fluid process parameters, and rheological parameters on drilling fluid flow pressure drop. Utilizing the constitutive equations of Bingham, power-law, and Herschel-Bulkley fluids, a regression model was established to convert the flow pressure drop of drilling fluid between helical pipes and straight pipes. The reliability of the numerical simulation results was verified using a self-developed drilling fluid flow pressure measurement device, which yielded an average relative error of only 2.13%. These research findings provide a theoretical basis for the development of drilling fluid rheological parameter monitoring devices based on helical pipes and the corresponding software.

Analysis of seepage and temperature fields and their influence on collapse pressure while drilling in shale oil reservoirs

Shale wellbore instability poses a considerable challenge in terms of drilling efficiency. However, previous studies typically assumed single-phase flow in the seepage field, neglecting the influences of water saturation and temperature on rock mechanical properties. Furthermore, there has been a lack of quantitative analysis on the degree of correlation between various factors and collapse pressure. To address these gaps, this research introduces an oil–water two-phase seepage model to describe the water saturation distribution surrounding the wellbore,and also constructed a wellbore temperature field model that accounts for mechanical and hydraulic heat sources and validated its accuracy. Furthermore, this paper examines the effects of temperature and seepage on shale mechanical parameters. By incorporating a rock failure criterion that accounts for water saturation, a shale collapse model in thermal-seepage coupling is established, which has also been validated. Finally, this paper utilises the grey relational analysis to quantitatively assess the correlation between different variables and collapse pressure. The results indicate that the temperature field and collapse models are consistent with field data. As drilling time increases, water saturation and invasion distance grow, while the seepage radius hardly increases anymore. When porosity exceeds 0.05, its influence on water saturation weakens. Under unbalanced conditions, capillary force drives drilling fluid into the formation. The maximum wellbore temperature is found near the drill bit and exceeds the formation temperature. The bottom-hole temperature difference increases with the increase in well depth and drilling time, sometimes exceeding 20 °C. Among drilling engineering parameters, pump rate has greater influence on bottomhole temperature than WOB, RPM and ROP. Regarding drilling fluid property parameters, density, flow index and consistency coefficient considerably influence bottom-hole temperature. The influence of seepage on collapse pressure is greater than that of the temperature field. Grey relational analysis reveals that pump rate and water saturation have the highest correlation with collapse pressure. As drilling time increases, the correlation degree of pressure difference, horizontal section length and weight on bit gradually increase, while that of the mud behaviour index, consistency coefficient, rock thermal conductivity and mud yield stress slightly decreases.

Axial Impact Analysis of Torsion Impactor Based on Water Strike Effect

The stick-slip vibration phenomenon that occurs during the drilling process not only reduces the drilling speed, but also affects the performance of the drill pipe and the service life of the drill bit. In response to the problem of stick-slip vibration, a torsional impactor has been developed. The tool, through its internal throttle action, will produce a sudden change in the mass flow of fluid in the central tube and thus produce a water strike phenomenon, and the change in the axial force of the torsional impactor caused by the water strike effect can cope with the stick-slip vibration that occurs during drilling as well as increase the drilling efficiency. In this paper, the axial impact capacity of the tool is investigated based on its water impact effect. CFD simulations were used to determine the axial impact capacity of the torsional impactor at different drilling fluid flow rates, and the maximum equivalent force of the central tube under the water impact effect was analyzed and strength checks were performed. The research results show that: two axial vibrations occur in the center tube within half a working cycle; As the drilling fluid flow rate increased from 24L/s to 31L/s, the axial impact force of the torsion impactor increased from 32506N to 43189N; the maximum equivalent force of the center tube is 106.59 MPa, which meets the impact strength requirements. Finally, it was verified through field tests that the water impact effect generated inside the torsional impactor can effectively solve the stick-slip vibration problem and improve the rock-breaking efficiency under different drilling fluid flow rates.

An explainable ensemble machine learning model to elucidate the influential drilling parameters based on rate of penetration prediction

Many researchers have examined the benefits of machine learning (ML) algorithms in geothermal drilling, especially for predicting the rate of penetration (ROP) of drilling. However, little attention has been given to enhancing the explainability of ML algorithms. Motivated by this, this study examines the feasibility of an explainable ML approach for elucidating the behavior of the drilling parameters to generate explainable insights regarding the surface-controllable drilling parameters that could maximize the ROP for drilling effectiveness (DE). First, this study presents a performance analysis using hyper-parameter technique of the ensemble supervised machine learning (ESML) for ROP predictions. Secondly, this study uses an explainable ML method to explain the drilling parameters' behavior based on the ESML prediction. The results show that the ensemble CatBoost model shows the best performance for ROP prediction. Then, the explainable ML successfully revealed several influential drilling parameters that could maximize the ROP for DE. In earlier drilling (0–4,000 m in depth), temperature and pressure contribute to a lower ROP, and the drilling fluid flow rate and rotary speed contribute to a higher ROP. On the other hand, as the drills go deeper into the earth (4,000–7,536 m in depth), maximum ROP can be obtained by maximizing the drilling pressure, weight on bit (WOB), surface torque, and rotary speed (RPM) of the drill bit, while drilling fluid flow rate does not significantly contribute to ROP. The explainable ML also highlighted the drilling parameters' inflection points when a switch from low to high rates of ROP occurs. Overall, the findings show the proposed model's strength in generating explainable insights that can improve the selection of appropriate ROP settings and support future decision-making processes in geothermal drilling.

Development of annular pump to enhance drilling distance and cuttings return in horizontal directional drilling

In many shallow horizontal directional drilling (HDD) projects, the annulus fluid pressure soon reaches the blowout or frac-out pressure of the soil formation. The pressure at single-source pump therefore must be limited. This limits the maximum drilling distance (borehole length), maximum attainable rate of penetration (ROP), and maximum distance over which cuttings can be returned. A novel concept involving a series of annular pumps distributed along the borehole length to aid in generation of distributed annulus pressure boost and cuttings transport in HDD was conceived. The success of the above concept, designated as distributed pumping system (DPS), relies on the ability to design and power an annular pump that can fit in the constricted annulus geometry of HDD boreholes while satisfying the performance requirements. We present the laboratory-scale development of three annular pumps based on the turbomachinery design principle of axial blade propellers. The pump prototypes were 3D printed and tested in the laboratory test rig flow loop built to simulate the annular flow configuration of HDD boreholes. The annular pump was powered using the axial propeller turbine housed inside the hub of each annular pump. The turbine converts hydraulic energy from the inner flow (analogous to drilling fluid flow within drill rod) to power the integrated setup of the axial inner turbine and annular pump, in short, designated as integrated turbine-pump (ITP). Results from the tests on three preliminary prototypes of the annular pump using water as the medium in the test rig yielded a maximum pressure boost of 44 kPa–enough to space the annular pumps 80 m apart when designed for a typical annular pressure drop rate of 0.54 kPa/m. The performance index (i) of the ITP, defined as the ratio of pressure boost provided by the annular pump in the outer (annular) flow to the pressure drop created by an inner turbine in the inner flow, reached a maximum value of 0.6. The results from the study promise a technology that can enable long-distance HDD cuttings return without the risk of blowout or the need for an external power source.

Study on Erosion of Small-Size At-bit Azimuthal Gamma Geosteering Tool

Small-size at-bit azimuthal gamma geosteering tool is an important tool used in the process of old well sidetracking. It is significant to carry out numerical simulation analysis of erosion and life prediction to reduce development costs and excavate the remaining reservoir in old wells. By using the finite element software, we calculate and analyze the erosion characteristic of the drilling fluid flow and the sand content ratio of the geosteering tool. These results demonstrate that the water hole erosion rate is positively correlated to the flow rate and sand ratio respectively, and the maximal erosion rate all happens at the root of the female thread. When the drilling fluid flow rate is 14 L/s and the sand content ratio is 4%, its erosion life is about 743.2 h which satisfies the service life of downhole tools. The research results can provide theoretical guidance for configuring drilling fluid on-site, adjusting pump pressure, and prolonging the service life of tools.

Optimization of technological parameters of airlift operation when drilling water wells

Purpose. Development of a methodology for optimizing the technological parameters of the airlift operation, based on the analysis of the pressure balance in the annulus and in the drill string that occurs during drilling. Methodology. The tasks were solved by a complex research method, which includes a review and generalization of literary and patent sources, analytical studies on existing methods for optimizing the technological parameters of drilling with reverse circulation using an airlift. Findings. It has been established that in the study on the airlift circulation method during rotary drilling with reverse circulation, an important role is played by the analysis of the pressure balance arising in the course of drilling in the annulus and in the drill string. It takes into account both hydrostatic pressures and pressure losses for pumping water and water-air mixture. A technique has been developed for assessing the effect of rate of penetration on circulation parameters. Originality. For the first time, it has been shown that the analysis of the pressure balance makes it possible to establish, with a given accuracy, the average effective values of the output parameters: the density of the water-air mixture, its upward flow rate, and the air flow rate at a given velocity of the upward flow of water as it approaches the mixer. Practical value. The proposed technique makes it possible to establish the dependence of the values of the output parameters on the depth of the well, as well as the required compressor performance to provide a given drilling fluid flow rate.

On Nonlinear Spatial Vibrations of Rotating Drill Strings under the Effect of a Fluid Flow

In this article, the development and subsequent numerical analysis of a nonlinear mathematical model of the drill-string dynamics taking into account the effect of a drilling fluid flow and the gravitational energy of the system is carried out. Spatial lateral vibrations of the drill string modeled as a rotating elastic rod are studied. The developed nonlinear model generalizes and refines the well-known linear models of rod vibrations with the considered effect. The obtained numerical results demonstrate the influence of geometric nonlinearity, the gravitational energy of the drilling system, additional Coriolis and centrifugal forces as well as the parameters of the fluid flow on spatial vibrations of the drill strings. It allows for giving some recommendations on the choice of the drilling system parameters for ensuring safe drilling operations.