Drilling Cycle Research Articles

DESIGNING EQUIPMENT FOR SYNERGETIC CHEMICAL ENGINEERING PROCESSES ACCORDING TO DRILLING RIG MODERNIZATION RESEARCH MODELS

In the materials of the article, examples of calculations and selection of a technological complex for drilling a well with a depth of 5650 m are considered, a complex of mechanization and partial automation of lowering and lifting operations during well drilling is analyzed, the advantages of such systems are established compared to installations that are not equipped with a complex of ASP mechanisms. The justification of the feasibility and economic efficiency of the introduction of the proposed technical solutions for the development of a device for limiting the movement of the melting unit of the drilling rig was carried out, its principle and electrical diagrams were proposed, the technical feasibility was substantiated, and the economic effect of the implementation of the developed design of the device for limiting the movement of the melting unit was calculated. The components of the developed methodology for calculating energy costs and machine time costs during SPO by lifting complexes are presented, an assessment of the perfection of lifting complexes of drilling rigs with different drives in terms of machine time costs of lifting a drill string for a well drilling cycle, an assessment of the perfection of lifting complexes of drilling rigs with different drives in terms of energy consumption rise of the drill string during the well drilling cycle. The materials of the article consider examples the calculation and the chosen technological complex for wells drilling with the depth of 5650 m, analyses the complex of mechanisms to mechanise and partially automate lowering-lifting operations while wells drilling and establishes advantages of such systems, comparing to the sets not equipped with the complex of mechanisms ALL.

Drilling Rate of Penetration Prediction Based on CBT-LSTM Neural Network.

Due to the uncertainty of the subsurface environment and the complexity of parameters, particularly in feature extraction from input data and when seeking to understand bidirectional temporal information, the evaluation and prediction of the rate of penetration (ROP) in real-time drilling operations has remained a long-standing challenge. To address these issues, this study proposes an improved LSTM neural network model for ROP prediction (CBT-LSTM). This model integrates the capability of a two-dimensional convolutional neural network (2D-CNN) for multi-feature extraction, the advantages of bidirectional long short-term memory networks (BiLSTM) for processing bidirectional temporal information, and the dynamic weight adjustment of the time pattern attention mechanism (TPA) for extracting crucial information in BiLSTM, effectively capturing key features in temporal data. Initially, data are denoised using the Savitzky-Golay filter, and five correlation coefficient methods are employed to select input features, with principal component analysis (PCA) used to reduce model complexity. Subsequently, a sliding window approach transforms the time series into a two-dimensional structure to capture dynamic changes, constructing the model input. Finally, the ROP prediction model is established, and search methods are utilized to identify the optimal hyperparameter combinations. Compared with other neural networks, CBT-LSTM demonstrates superior performance metrics, with MAE, MAPE, RMSE, and R2 values of 0.0295, 0.0357, 9.3101%, and 0.9769, respectively, indicating the highest predictive capability. To validate the model's robustness, noise was introduced into the training data, and results show stable performance. Furthermore, the model's predictive results for other wells achieved R2 values of 0.95, confirming its strong generalization ability. This method provides a new solution for ROP prediction in real-time drilling operations, assisting drilling engineers in better planning their operations and reducing drilling cycles.

Research on Drillpipe Stick-slip Vibration and Its Suppression Mechanism in Deep Well Drilling

Abstract During drilling deep wells, stick-slip vibration(SSV) is a reciprocating vibration form of drill bit adhesion, sliding, re-adhesion, and re-sliding. If not suppressed, it can cause serious drilling accidents, such as accelerated wear of drilling equipment, which lead to decreased drilling safety, reduced drilling efficiency, and prolonged drilling cycle. This article establishes a SSV model of the drill string system, considering the three degrees of freedom of the rotary table/top drive, hammer, and drill bit, and analyzes the SSV characteristics of the drill bit during deep well drilling. The SSV analysis of the drill string system was carried out for well XX-X-4, and the sensitivity of rotational speed, viscous damping, drilling pressure, drill bit length, and friction torque coefficient was analyzed. The results showed that the friction torque coefficient and rotational speed are the main factors affecting stick reduction efficiency, while the length of the drill collar is a secondary factor. The WOB and viscous damping have the least impact on stick reduction efficiency. The parameters were optimized to reduce SSV as the target. This article has certain guiding significance for deep well drilling operations.

Methods for Assessing the Layered Structure of the Geological Environment in the Drilling Process by Analyzing Recorded Phase Geoelectric Signals

Assessment of the current state of the near-surface part of the geological environment and understanding of its layered structure play an important role in various scientific and applied fields. The presented work is devoted to the application of phasometric modifications of geoelectric control methods to solve the problem of the detailed complex study of the underground layers of the environment in the process of drilling operations with the use of special equipment. These studies are based on the analysis of variations in phase parameters and characteristics of an artificially excited multiphase electric field to assess poorly distinguishable details and changes in the layered structure of the medium. The proposed method has increased accuracy, sensitivity and noise proofness of measurements, which allows for extracting detailed information about the heterogeneity, composition and stratification of underground geological formations not only in the zone where the drill makes contact with the medium, but also in the entire control zone. This paper considers practical mathematical models of phase images for basic scenarios of drill penetration between the layers of the near-surface part of the geological medium with different characteristics, obtained by means of approximation apparatus based on continuous piecewise linear functions, and also suggests the use of modern machine learning methods for intelligent analysis of its structure. Studying the phase shifts in electrical signals during drilling highlights their value for understanding the dynamics of soil response to the process. The observed signal changes during the drilling cycle reveal in detail the heterogeneity in soil structure and its response to changes caused by drilling. The stability of phase shifts at the last stages of the process indicates a quasi-equilibrium state. The results make a significant contribution to geotechnical science by offering an improved approach to monitoring a layered structure without the need for deep drilling.

Study on the Law of Rock Drillability under High-Temperature and High-Pressure Conditions in the Western Margin of the Ordos Basin

The deep strata in the Ordos Basin exhibit characteristics of high temperature and high stress. Conventional methods for assessing drillability (normal temperature and pressure) fail to accurately understand the drilling resistance characteristics of deep rocks in this region, leading to improper guidance for selecting formation drilling tools and prolonging drilling cycles. This study employs physical experiments and numerical simulations to conduct drillability tests on core samples taken from the region under high-temperature and high-pressure conditions, simultaneously simulating the rock breaking process under different temperature and pressure conditions. The study investigates the variation patterns of rock drillability grade values and von Mises stress values during rock breaking under single-factor and multi-factor analyses of temperature and pressure conditions. Combining these variation patterns, an optimization analysis of the back rake angle of PDC drill bits used in drillability experiments is conducted to guide the selection of drill bits on site. The results indicate that the variation patterns of von Mises values from finite element simulations are consistent with the drillability grade values under high-temperature and high-pressure conditions. Under single-factor conditions, von Mises stress and drillability grade values generally increase with rising temperature before decreasing, while they increase with increasing confining pressure. Under multi-factor conditions, confining pressure is the primary influencing factor within the range of 0 to 50 MPa, while the influence of temperature becomes prominent between 180 °C to 200 °C, with a weakening effect of confining pressure. Model application: Selecting a back rake angle of 30° for PDC drill bits yields optimal rock-breaking results. The research findings hold significant implications for understanding the low rock-breaking efficiency of deep strata, optimizing drill bit parameters, and enhancing drilling efficiency.

Study of wellbore instability in shale formation considering the effect of hydration on strength weakening

Shale formations often contain a high proportion of clay minerals, which, upon contact with drilling fluid, undergo hydration expansion. This leads to wellbore instability, a problem that poses significant challenges globally. This study aims to investigate the variation of mechanical properties of shale with respect to hydration time. We employ an empirical model that relates shale strength parameters to the time of drilling through geological formations. Additionally, we consider both shear failure along the wellbore boundary and shear sliding along bedding planes in the analysis. We establish a predictive model for wellbore instability in shale formations. The model quantitatively analyzes the variation of wellbore collapse pressure with drilling time. The research findings indicate that, when the influence of bedding is considered, both the wellbore collapse pressure and the optimal well trajectory undergo significant changes, in addition, for some wellbore trajectories, the collapse pressure can increase by more than 30%. Therefore, it is essential to account for the influence of bedding in wellbore stability analysis in shale formations. As the bedding dip angle changes, both the numerical values and distribution range of wellbore collapse pressure and the optimal well trajectory change noticeably. Changes in bedding dip direction, however, do not affect the numerical values of collapse pressure but do influence the distribution region of the optimal well trajectory. Thus, in wellbore trajectory design within shale formations, it is crucial to determine the orientation of bedding and adjust the well trajectory accordingly to enhance wellbore stability. Furthermore, shale hydration does not impact the optimal well trajectory for a block, but with prolonged hydration, the minimum drilling fluid density required to maintain wellbore stability gradually increases. This suggests that hydration intensifies the weakening effect on bedding plane strength. The research results are helpful to understand the effect of hydration on shale wellbore stability and ensure shale wellbore stability during drilling cycle.

Research on trajectory control technology for L-shaped horizontal exploration wells in coalbed methane

Horizontal wells have significant advantages in coal bed methane exploration and development blocks. However, its application in new exploration and development blocks could be challenging. Limited geological data, uncertain geological conditions, and the emergence of micro-faults in pre-drilled target coal seams make it hard to accurately control the well trajectory. The well trajectory prior to drilling needs to be optimized to ensure that the drilling trajectory is within the target coal seam and to prevent any reduction in drilling ratio (defined here as the percentage of the drilling trajectory in the entire horizontal section of the well located in the target coal seam) caused by faults. In this study, the well trajectory optimization is achieved by implementing the following process to drill pilot hole, acquire 2D resonance, and azimuthal gamma logging while drilling. The pilot hole drilling can obtain the characteristic parameters of the target coal seam and the top and bottom rock layers in advance, which can provide judgment values for the landing site design and real-time monitoring of whether the wellbore trajectory extends along the target coal seam; 2D resonance exploration can obtain the construction of set orientation before drilling and the development of small faults and formation fluctuations in the horizontal section, which can optimize the well trajectory in advance; the azimuth gamma logging while drilling technology can monitor the layers drilled by the current drill bit in real time, and can provide timely and accurate well trajectory adjustment methods.The horizontal well-Q in the Block-W of the Qinshui Basin was taken as a case study and underwent technical mechanism research and applicability analysis. The implementation of this new innovative process resulted in a successful drilling of a 711 m horizontal section, with a target coal seam drilling rate of 80%. Compared to previous L-type wells, the drilling rate increased by about 20%, and the drilling cycle shortened by 25%. The technical experience gained from this successful case provides valuable insight for low-cost exploration and development of new coalbed methane blocks.

SUBSTANTIATION OF SOLUTIONS TO INCREASE THE DURABILITY OF THE INNER ROWS OF STEEL TEETH OF ROLLER CONE BITS DURING DRILLING OF BOULDER-PEBBLE ROCK FORMATIONS

The article deals with issues concerning the increase in the productivity of roller bits when drilling soft and soft-medium rocks with inclusions of boulder-pebble formations by justifying solutions to increase the relative safety margin of steel teeth expressed in an increase of the impact strength of the material for making cones in combination with an increase in the geometry of steel teeth. The efficiency of the rock-crushing tool and, as a result, the destruction of rock during the entire drilling cycle, directly depends on the resource and durability of the elements of the roller bit. When drilling the upper intervals of deposits in the East Siberian region, composed of soft and soft-medium rocks with inclusions of boulder-pebble deposits, there is a problem of premature wear of the drill bit. Both PDC bits are subject to catastrophic wear due to chips and fractures of PDC cutters, as well as roller bits. The use of first-class roller bits with steel teeth leads to advanced wear, expressed by the scrapping of the teeth of the inner rows. This leads to a «hanging» of the bit and a loss of mechanical penetration speed. Based on this, the work provides recommendations for increasing the durability of steel teeth for first-class roller cone bits.

Research on Vibration Accumulation Self-Powered Downhole Sensor Based on Triboelectric Nanogenerators.

In drilling operations, measuring vibration parameters is crucial for enhancing drilling efficiency and ensuring safety. Nevertheless, the conventional vibration measurement sensor significantly extends the drilling cycle due to its dependence on an external power source. Therefore, we propose a vibration-accumulation-type self-powered sensor in this research, aiming to address these needs. By leveraging vibration accumulation and electromagnetic power generation to accelerate charging, the sensor's output performance is enhanced through a complementary charging mode. The experimental results regarding sensing performance demonstrate that the sensor possesses a measurement range spanning from 0 to 11 Hz, with a linearity of 3.2% and a sensitivity of 1.032. Additionally, it exhibits a maximum average measurement error of less than 4%. The experimental results of output performance measurement indicate that the sensor unit and generator set exhibit a maximum output power of 0.258 μW and 25.5 mW, respectively, and eight LED lights can be lit at the same time. When the sensor unit and power generation unit output together, the maximum output power of the sensor is also 25.5 mW. Furthermore, we conducted tests on the sensor's output signal in conditions of high temperature and humidity, confirming its continued functionality in such environments. This sensor not only achieves self-powered sensing capabilities, addressing the power supply challenges faced by traditional downhole sensors, but also integrates energy accumulation with electromagnetic power generation to enhance its output performance. This innovation enables the sensor to harness downhole vibration energy for powering other micro-power devices, showcasing promising application prospects.

Improvement and Application of Directional Reaming While Willing Bit in Tahe Oilfield

Unlike conventional sidetracking technology, the technology of reaming while directional drilling makes it possible for us to conduct directional drilling and reaming simultaneously using dual core bit, which simplifies the construction steps and can greatly shorten the drilling cycle and reduce drilling costs. With the increasing of the tasks of sidetrack horizontal well in the old wells of Tahe Oilfield, the technology of reaming while directional drilling has become an important means for sidetrack of old wells in Tahe Oilfield. However the substratum of Bachu formation has high content of gravel with large diameter and strong consolidation, which cause severe abrasion of dual core bit, short drill life and low ROP. With the problems in the substratum of Bachu Formation, Tahe Oilfield continuously improves dual core bit based on its effect of reaming while drilling, and breaks the national records of the maxim setting depth, inclination and continuous expansion length during the operations of well TH12124CH. This paper shows the improvements of dual core bit and its application effect both in well TH10233CH and well TH12124CH, and put forward a further scheme to improve the dual core bit for the substratum of Bachu Formation of Tahe Oilfield.

Hybrid physics-machine learning models for predicting rate of penetration in the Halahatang oil field, Tarim Basin

Rate of penetration (ROP) is a key factor in drilling optimization, cost reduction and drilling cycle shortening. Due to the systematicity, complexity and uncertainty of drilling operations, however, it has always been a problem to establish a highly accurate and interpretable ROP prediction model to guide and optimize drilling operations. To solve this problem in the Tarim Basin, this study proposes four categories of hybrid physics-machine learning (ML) methods for modeling. One of which is residual modeling, in which an ML model learns to predict errors or residuals, via a physical model; the second is integrated coupling, in which the output of the physical model is used as an input to the ML model; the third is simple average, in which predictions from both the physical model and the ML model are combined; and the last is bootstrap aggregating (bagging), which follows the idea of ensemble learning to combine different physical models’ advantages. A total of 5655 real data points from the Halahatang oil field were used to test the performance of the various models. The results showed that the residual modeling model, with an R2 of 0.9936, had the best performance, followed by the simple average model and bagging with R2 values of 0.9394 and 0.5998, respectively. From the view of prediction accuracy, and model interpretability, the hybrid physics-ML model with residual modeling is the optimal method for ROP prediction.

Drill-In Fluid Optimization for Formation Damage Control Considering Salt Dissolution in Saline-Lacustrine Reservoirs

Summary Salt dissolution induced by drill-in fluid loss is a frequent occurrence in saline-lacustrine reservoirs, which can potentially result in serious formation damage. In light of this, an experimental study was conducted to investigate the salt mineral dissolution and dynamic damage in the rock samples collected from a saline-lacustrine carbonate reservoir and the response of pore-fracture structures using the in-situ drill-in fluids. The study further involved analyzing the formation-damage-control (FDC) ability of the in-situ drill-in fluids. The results indicated that although salt dissolution significantly increased the pore size of the tight matrix and the width of natural fractures, improving the conductivity of seepage channels, the increase in pore-fracture size may have greatly aggravated the drill-in fluid loss during the process. The continuous serious filtrate loss, lower pressure-bearing capacity of the plugging zone, and lower permeability recovery rate (PRR) of rock indicated poor FDC performance of in-situ brine drilling fluids for the salt-dissolved core samples. The FDC performance of drill-in fluids for saline-lacustrine carbonate reservoirs was optimized based on the response of reservoir pore-fracture structure to salt dissolution and the theory of slightly underbalanced activity. The experimental results showed that the optimized drill-in fluids had better FDC ability, with an average PRR increase of 14.04%. Field application indicated that the optimized drill-in fluids reduced the drill-in fluid loss by 76.48%, shortened the drilling cycle by 45.20%, and increased the initial production capacity per well by 7.70%. This study can provide insightful guidance to optimize the FDC performance of drill-in fluids for saline-lacustrine hydrocarbon reservoirs during drilling.

Methodology of experimental filtration studies (releases) from high-pressure inter-salt productive deposits of industrial lithium-bearing brines of the hydrogeological halogen-carbonate formation of the Siberian platform

It is known that all our knowledge about the industrial brines of the Siberian platform was obtained while drilling wells for oil and gas whereas targeted studies of brine-bearing horizons in deep wells for hydrocarbons are hardly conducted. One of the reasons is the high daily rate in the drilling cycle resulting in carrying out strictly limited additional works not related to drilling. Meanwhile, the geological results including the forecast, the estimation of the calculated parameters of the section productive intervals, the exploration and development methodology of deposits of industrial metal-bearing brines with abnormally high reservoir pressure directly depend on the data of the hydrodynamic studies. Today, large companies – subsurface users of the south of the Irkutsk region are tasked to determine the methodology of short-term pilot releases, which provides correct input data for reserve calculation of industrial brines of natural inter-salt carbonate fractured reservoirs of the hydrogeological halogen-carbonate formation. To determine a reliable permeability coefficient under the experimental filtration work, it is necessary to achieve a quasi-stationary filtration mode. The optimal mode is an intermittent one of brine release with a constant flow rate at the same time intervals with a continuous recording of pressure changes by the telemetry system. The results of pilot releases implemented at the Znamenskiy site of the Angara-Lena deposit of industrial lithium-bearing brines have been considered. The release methods enabling the performance of experimental filtration work in a short time, and applicable in well construction for hydrocarbon production have been proposed. Surface users can carry out the research using the proposed methodology in the case when the well bottom unexpectedly opens a brine formation with an abnormally high reservoir pressure of the fluid system. The implementation of experimental filtration work employing the described methods allows the subsoil users to substantiate the resource base of industrial brines and the elements in them including lithium, rubidium, cesium, bromine, iodine and other rare, trace elements and mineral salts.

Numerical Simulation and Field Test of a PDC Bit with Mixed Cutter Arrangement to Break Non-Homogeneous Granite

As the depth of petroleum drilling increases, the strata environment becomes more complex. The efficiency and lifespan of Polycrystalline Diamond Compact (PDC) drill bits fail to meet current drilling demands. However, the structure and arrangement of PDC cutters are valuable determinants of drilling efficiency, although related research still has gaps and deficiencies. This study focuses on PDC cutters in axe, triangular prism, and circular forms. It establishes an inhomogeneous granite model based on the actual measurements of granite and verifies the accuracy of this model through uniaxial compression simulation. Finite element models of three types of cutters in various combination schemes are constructed to examine rock-breaking effects, with the best scheme optimized using Box-Behnken response surface methodology. The rock-breaking process of the optimal PDC drill bit layout has been compared to that of a single cutter bit. Field drilling has demonstrated the effectiveness of a mixed cutter arrangement. The results show that the inhomogeneous granite model can be trusted. The optimal arrangement involves axe cutters in the front row and an alternate arrangement of triangular prism cutters and axe cutters in the back row. The optimal lateral and longitudinal distances for the triangular cutters from the front row of axe cutters are 10 mm and 7 mm, respectively, while those for the back row of axe cutters from the front row are 10.06 mm and 7 mm, respectively. The ROP standard deviation in the drilling process of mixed cutter bits decreases by 53.06% and 43.08% compared to axe and triangular prism cutter bits, respectively. The drilling efficiency increases by 16.8% and 16.6%, respectively, demonstrating higher efficiency and stability. Field drilling results indicate that a mixed cutter bit increases efficiency by 23.5% compared to a bit with only triangular prism cutters. This study posits that research on the combination schemes and parameters of PDC cutters can significantly enhance drilling efficiency, thereby reducing the drilling cycle and costs.

Multi-source information fusion-based dynamic model for online prediction of rate of penetration (ROP) in drilling process

Rate of penetration (ROP) accurate prediction can effectively reduce drilling cycle time and operation cost. However, the complexity and variability of drilling process is not conducive to accurate ROP modeling. The existing ROP models focus on static prediction considering drilling data, which cannot effectively solve the ROP mutation problem caused by complex formations. Some ROP online prediction studies have great real-time capture capability, but without considering the formation lithology adequately, and can be limited in practical application. In this paper, a multi-source information fusion-based dynamic model for online prediction of ROP in drilling process is proposed, which consists of three stages (drilling data pre-processing, optimized ROP modeling, and ROP model updating). In the first stage, three drilling parameters including weight on bit, rotational speed, and torque are filtered by using the outlier removing and wavelet filtering techniques. In the second stage, a novel ROP modeling method, named as hybrid bat algorithm optimized - restricted Boltzmann machine - back propagation neural network (HBAO-RBM-BPNN) is proposed to build the ROP prediction model. In the last stage, formation drillability variation and time interval are used as update conditions, and the established ROP model is updated via a moving window strategy to realize high accuracy online prediction of ROP. Multi-source (formation and drilling) information fusion is considered in this key stage. Finally, the proposed method and seven ROP prediction methods (two offline and five online) are compared through the use of industrial data from a drilling site in Dandong area, Northeast China. The comparison results verify the effectiveness of the proposed method, which lays a foundation for intelligent optimization control of complex geological drilling process.

Research solution for automatic hole quality analysis when drilling fiber-reinforced composites

Fiber-reinforced polymers are highly demanding composites in aerospace and automotive areas because of their excellent mechanical properties such as stiffness and strength-to-weight ratio. The drilling remains the major machining operation applied to composites to provide high-quality holes for joints between parts. Due to composites plied structure, the drilling is accompanied with unusual form metal cutting defects such as delamination and uncut fibers around the drilled hole. Considering that the tool life of some drills reaches over thousands of holes, the research of composites machinability becomes difficult due to demanded labor intensity in manual inspection of the hole quality. Therefore, this paper develops the research solution for automatic analysis of the hole quality in drilled fiber-reinforced materials. The paper proposes a complex of solutions aimed to speed up the analysis of the hole quality when composites drilling. The solution consists of the developed vacuum table, robot arm with high-speed camera, developed top and bottom lightning systems, and Image Processing algorithms for defect detection from captured images. The paper results show how the developed solution can be used for high routine research activities. The output data, including tested 72 cutting data parameters and full-size tool life test, allowed identifying the operational window for high-speed steel drills and the range of tool life, where drill ensures a certain hole quality. The paper shows the efficiency of the developed research solution can reach 5 s per hole including drilling and full cycle of measurements having measurement error of 1–3%.

Cutting mechanism of a special 3D concave-shaped PDC cutter applicable to the Weiyuan shale

The Weiyuan shale gas field faces problems of long drilling cycles and high development costs. Improving the drilling efficiency of polycrystalline diamond compact bits in shale formations will significantly reduce the overall well cost and duration. Previous applications have demonstrated that conventional PDC bits on the market cannot meet the demand for drilling acceleration. In this work, a new three-dimensional concave-shaped PDC cutter was proposed to improve drilling efficiency. The special 3D concave-shaped cutter has two symmetrical curved ridges on the concave surface and a circular plane at the center. The cutting mechanism of the new 3D concave-shaped cutter has been studied by laboratory experiments and numerical simulations. The research data revealed that, compared with a flat cutter, the tangential force of the original 3D concave-shaped cutter was reduced by 1.4%–35.0%, the axial force was reduced by 6.7%–37.6%, and the mechanical specific energy (MSE) was reduced by 1.6%–35.59%. Simulations showed that the shear action of the 3D concave-shaped cutter was divided into two continuous parts, with the sides and the center surface being stressed successively, which is helpful for extending shear cracks, forming trilobal cuttings, and improving cutting efficiency. With the special 3D concave-shaped cutter, an 8½-inch drill bit was designed and manufactured and tested on the Longmaxi shale in the Weiyuan block. Through field tests, we further compared the performance of the 3D concave-shaped cutter PDC bit with that of the flat cutter PDC bit. The 3D concave-shaped PDC bit had a 41.8% better footage and 22.6% better rate of penetration (ROP) in field test.

Pomiar zużycia energii w trakcie cyklu wiercenia termicznego

The work presents the issue of measuring and analyzing energy consumption during a thermal drilling cycle. A research stand based on a CNC lathe was presented, the equipment of which was an experimental energy consumption system based on an electricity meter and a force gauge. The measuring devices used allowed for recording the load on the power grid, the load on the machine tool drives, the axial force, the drill braking torque, the current rotation of the machine tool spindle, the position of the drill in relation to the workpiece and the values of auxiliary parameter registers in the strategy of adaptive feed control. Two cases of a drilling cycle were considered: making a single hole and making a series of holes in one cycle. Five feed control strategies were tested during the drilling cycle, including adaptive feed control and a recursive feed optimization method. For comparison, holes were also made with traditional HSS twist drills. Based on the obtained test results, it can be concluded that the friction drilling method can be included in the energy-saving methods of making holes in thin-walled elements.

Subsection and superposition method for reservoir formation damage evaluation of complex-structure wells

Kinds of complex-structure wells can effectively improve production, which are widely used. However, in the process of drilling and completion, complex-structure wells with long drilling cycle and large exposed area of reservoir can lead to the fact that reservoir near wellbore is more vulnerable to the working fluid invasion, resulting in more serious formation damage. In order to quantitatively describe the reservoir formation damage in the construction of complex-structure well, taking the inclined well section as the research object, the coordinate transformation method and conformal transformation method are given according to the flow characteristics of reservoir near wellbore in anisotropic reservoir. Then the local skin factor in orthogonal plane of wellbore is deduced. Considering the uneven distribution of local skin factor along the wellbore, the oscillation decreasing model and empirical equation model of damage zone radius distribution along the wellbore direction are established and then the total skin factor model of the whole well is superimposed to realize the reservoir damage evaluation of complex-structure wells. Combining the skin factor model with the production model, the production of complex-structure wells can be predicted more accurately. The two field application cases show that the accuracy of the model can be more than 90%, which can also fully reflect the invasion characteristics of drilling and completion fluid in any well section of complex-structure wells in anisotropic reservoir, so as to further provide guidance for the scientific establishment of reservoir production system.

Effects of Bit Shape of Electroplated Diamond Tool Used for Drilling Small Diameter Holes in Glass Plate on Machining Fluid Flow and Chip Discharge

Our laboratory has been exploring the development of tools for drilling holes in glass plates, and the drilling techniques to be adopted for it. A devised tool shape that could prevent the occurrence of cracks at the exit holes achieved high quality through hole drilling of 100 holes or more using only the drilling cycle. However, crack-free drilling beyond this number of holes cannot be performed. This is due to the adhesion of the residual chip on the tool surface when the number of holes increases. Therefore, further improvement of chip discharge is needed to achieve crack-free drilling. In this report, we consider that chip discharge results from the flow of the machining fluid. To investigate the cause of chip discharge, we analyzed the flow of the machining fluid in the hole using computational fluid dynamics and the supposed chip discharge conditions. The results obtained in this study are summarized as follows. (1) In the case of a cylindrical tool, the Z-axis directional flow of the machining fluid did not occur in the hole. This is because the tool does not have bumps to agitate the fluid on the side, and the gap between the tool and the inner surface of the hole is narrow. (2) The plate side widened the gap between the tool and inner surface of the hole. Therefore, the fluid was likely to flow in the Z-axis direction in the hole. (3) For the tool with the plane side bit, the flow entered the hole from one plane side and exited the hole from the other plane side. (4) When the tool end is spherical, the Z-axis directional flow of the fluid occurs at the tool end. (5) The fluid flow of the devised tool weakened as the drilling depth increased. To improve the chip discharge performance of the designed tool, the Z-axis directional flow of the machining fluid must occur in an area deeper than 2 mm.