Pipe String Research Articles

Safety analysis of pipe string strength during transient process of ultrahigh temperature and high pressure well fracturing

Safety analysis of pipe string strength during transient process of ultrahigh temperature and high pressure well fracturing

Research on Wellbore Blockage Mechanism and Blockage Removal Technology of Shale Gas Wells

Abstract With the continuous extension of development time, the production decline of single well is accelerated, and the problem of wellbore blockage in shale gas wells is prominent. The problem of wellbore blockage seriously restricts the stable production and efficient development of gas fields. In this paper, the ‘micro + macro’ analysis method is used to study the blockage. It is found that the wellbore blockage mainly includes corrosion, scaling products and a small amount of clay minerals brought by the reservoir during gas production. In the process of production, corrosion and scaling mechanism work together. Acidic gas such as CO2 in shale gas are dissolved in high-salinity formation water, causing electrochemical corrosion of the string. The formation of corrosion products will promote the deposition and adsorption of inorganic scales. The uneven accumulation of corrosion product films will enhance the surface roughness of the substrate and accelerate the deposition of scale samples around the crystal nucleus. At the same time, scaling will cause corrosion under the scale of the pipe string. Cl− can penetrate into the film through the micropores covering the product film on the metal surface, and pitting corrosion occurs to corrode the pipe string. Finally, the corrosion and scaling products together cause the pipe string to be blocked. Based on the analysis results of blockages and water samples, a blockage removal liquid system was developed according to the blockage mechanism. It has a high dissolution ability and the corrosion of 125SG, 155V and N80 steel sheets at 60°C for 4h is less than 1 g/(m2·h), which meets the requirements of industry standards. This system can inhibit the secondary precipitation of metal ions, has low corrosion damage to oil and casing, can remove wellbore blockage, does not need to flow back, will not cause secondary damage to the reservoir. It can provide guiding significance for similar shale gas well wellbore blockage removal.

Development and Application of Drilling Intelligent Assistant Decision System

Abstract In order to systematically harness the substantial volume of data generated during the drilling process and achieve intelligent analysis and auxiliary decision-making for real-time risk monitoring and warnings during drilling, an intelligent drilling auxiliary decision-making system has been developed. This system integrates various technologies, including physical models, intelligent algorithms, and trend analysis. By analyzing the characteristics of logging data under different operating conditions, an intelligent algorithm capable of automatically distinguishing six types of drilling operating conditions has been established. Taking into account the impact of rock cuttings on the stress on the pipe string and annular pressure loss during the drilling process, coupled frictional torque and cyclic pressure loss calculation models were developed under coupled conditions. Building upon this foundation and considering the trend of deviation between predicted and measured parameters, a monitoring algorithm for detecting stuck drilling, wellbore leakage, and overflow incidents was formulated. The development of the drilling intelligent decision-making system was completed based on a C/S three-layer architecture and a data center. This system has been successfully applied in more than 50 exploration wells of various types, including shale oil and gas horizontal wells and deep wells. The static analysis results demonstrated a compliance rate of 91.5% with on-site monitoring, playing a crucial role in drilling parameter optimization and risk monitoring. The practicality and feasibility of the system have been verified, providing essential support for efficient and safe drilling production.

Research and Tests on the Technology of Releasing and Fishing Stuck Throttles Under Pressure

Abstract In order to solve the problem of gas well shutdown caused by fishing failure due to stuck throttles, and to avoid situations such as the inability to lift the pipe string and high cost of handling stuck throttles, the basic structures of the slip-type throttles were analyzed. And based on the actual situation on site, it was determined that the deformation of the slip mechanism was the main cause of the throttles getting stuck. And combined with conventional bridge plug drilling and grinding, coiled tubing fishing, and steel wire fishing techniques, the technology of grinding and milling under pressure to release and fishing stuck throttles was studied. Theoretical analysis has been conducted on the feasibility of using coiled tubing mill to break the slip mechanism of the stuck throttles, including mill torque, construction displacement, drilling pressure, etc. At the same time, the technical principle and operation process of gas lift fishing throttles were introduced. Two three-packer string wells were successfully tested in the field. After the stuck throttles were milled and unblocked by the coiled tubing, the stuck throttles of Φ73.0 mm tubing were successfully salvaged, one of which was fished by gas lift. The average construction time is less than 2.5 days. The research results show that the technology of grinding and milling with pressure to release and fishing stuck throttles is safe and efficient, providing a new technical means for dealing with stuck throttles and has good promotion and application value.

A Super Vibration Drag Reduction System Based on Drilling Robot

Summary For directional or horizontal wells, friction between the drillstring and the borehole wall has become a significant factor in reducing the rate of penetration, leading to a decrease in weight on bit (WOB) and inefficient rock breaking. Generally, a larger amplitude yields a better oscillation effect. Conventional hydraulic oscillators rely on their inherent inertia to produce oscillating loads. However, the mass of the oscillating load provided by hydraulic oscillators is relatively small compared with the entire pipe string, resulting in limited oscillation amplitude that fails to effectively reduce friction and drag. To enhance the vibration effect and strength of the pipe string, in this article we propose the development of a novel hydraulic oscillation device that utilizes drilling robots for support. The relevant structure of the drilling robot has been designed, and a simulation wellbore experiment platform, based on the drilling robot, has been constructed. The simulation wellbore experiment based on different supporting conditions was completed. Through analysis of the collected experimental data, it has been observed that the axial and radial vibrations generated by the drilling robot are influenced by its supporting condition. The average acceleration amplitude and frequency of axial vibration without support are measured to be 0.37 m/s² and 8.2 Hz, respectively. In contrast, with supporting conditions, the average axial vibration acceleration amplitude increases to 0.63 m/s², and the frequency reaches 12.8 Hz. Consequently, the axial vibration intensity of the drilling robot is significantly higher when the drilling robot is supported. The average acceleration amplitude and frequency of radial vibration without support are 0.83 m/s² and 20.4 Hz, respectively. However, with supporting conditions, the average radial vibration acceleration amplitude drops to 0.43 m/s², and the frequency decreases to 12.2 Hz. The average axial vibration displacement amplitude of the supported drilling robot measures 50.2 mm, which is much greater than that of a typical hydraulic oscillator. Moreover, the WOB of the drilling robot with support is considerably higher compared with the unsupported drilling robot. By employing supporting conditions, the drilling robot can improve the transmission efficiency of drilling pressure and minimize the damage caused by radial vibration to downhole tools.

Study on corrosion of Cr-containing steel under different CO2 partial pressures at high temperatures

To achieve the goal of "carbon peak " and "carbon neutral", CO2 injection in oilfields has become a major trend, but it also comes with the risk of CO2 corrosion on the pipe strings, particularly under high temperature and pressure (HTHP). This study utilizes a laboratory-made HTHP reactor to conduct corrosion tests on three commonly used chromium-containing steels (13Cr, S13Cr, and 25Cr) in oil fields under conditions of 200 °C and a total pressure of 70 MPa, with CO2 partial pressures of 10 MPa, 25 MPa, and 45 MPa respectively. The corrosion components, phase structure and three-dimensional morphology of the specimens are analyzed by SEM/EDS and other microscopic characterization means. Additionally, the critical safety factor after the casing pitting corrosion is calculated. The results indicates that under experimental conditions, the uniform corrosion rate of 13Cr decreases with the increase of CO2 partial pressure, while the uniform corrosion rate of S13Cr and 25Cr initially decreases and then increases with the rise of CO2 partial pressure. Moreover, with the increase of CO2 partial pressure, the pitting corrosion rate of specimens decreases. Under the action of Cl− in the medium solution, the passivation film on the surface of Cr-containing steel is damaged. The severity of pitting corrosion among the materials follows the order: 25Cr > 13Cr > S13Cr. The main elements responsible for severe corrosion are oxygen (O) and sulfur (S). When the depth of the corrosion pit reaches 2.06 mm, the critical internal pressure safety factor of the casing is reached.

Evaluation of stresses on the surface of production columns equipped with sand filters when downing into a horizontal well

Relevance. The need to estimate the time of formation sand accumulation near the annulus of a horizontal well and the unit length of filter elements in the bottom of production strings and to determine the stresses on the surface of production strings equipped with sand filters when lowering into the well. Aim. Based on a study of the reasons for the continued flow of sand into wells equipped with anti-sand filters, to develop and propose measures related to the need to choose a reduction in the number of filters that provide the design flow rate of a horizontal well or a significant increase in the length of the filtering surface of the filters in order to reduce erosive wear of the wire winding. Objects. We are considering a well with a horizontal section, equipped with sand filters, the same size as the casing strings. It was assumed that the integrity of the surface of the filter elements would be preserved and the conditions for their destruction would be eliminated when lowering into the horizontal shaft. This presupposes the necessary efficient operation of the well throughout the entire operational period. The section of the first set of curvature and the forces arising during this are considered as wellas stability of a pipe string during possible stops. Centralizers are evenly located along the length of the column, then in some sections we will have a multi-span statically indeterminate beam, in each section of which a radial load acts. Methods. When studying the time of formation sand accumulation in the annular space of a horizontal well and a unit length of filter elements in the bottom of production strings, it is necessary at the first stage to determine the stresses on the surface of production strings equipped with sand filters when lowering into the well. Studying the assessment of the existence time of the transition period is of particular interest. This is, in other words, during what operational period there is a complete accumulation of formation sand in the annular space and the transition of formation drainage along the entire length of the horizontal wellbore to drainage of only zones adjacent to the filters. To calculate the fluid flow rate when the annular space of the horizontal well is completely filled with sand, the design values ​​of the AC4.8 formation parameters were used. The maximum value of depressions used in the calculations is assumed to be 1.5 MPa. Results. Consideration of situations that arise when filters are lowered into horizontal wells indicates that the outer surface of the filter elements is not protected from destruction as a result of contact stresses with the walls of the drilled wellbore. To protect against destruction and rubbing open gaps by clay-containing rocks, rigid centralizers should be installed along the edges of the filter elements, the maximum allowable distances between which should not exceed 4.0–4.5 m.

Numerical analysis of running resistance of a completion string with packers and sliding sleeves in horizontal wells

The installation of a completion string in small-diameter horizontal wells often presents challenges such as instability, bending, and high frictional resistance. To accurately estimate the running resistance during deployment and ensure safe descent to the bottom of the well, a three-dimensional numerical model has been developed incorporates real-time contact interaction between the completion string and the wellbore, while maintaining precision and field applicability. The analysis evaluates several factors, including buckling behavior, average and dynamics transient value of contact force, axial forces, and frictional forces. Results reveal that the upper pipe string exerting thrust on the lower pipe string causes bending and spiral buckling along with resulting contact with wellbore. Maximum hook load and maximum negative axial force occur at a inclination angle of 65°. Contact strength is more pronounced in inclined and horizontal section compared to vertical section. Leveraging extensive data, the study has yielded a quick prediction formula for quickly calculating the resistance experienced by a completion string of field area. The numerical results offer valuable insights into comprehending the resistance encountered during the descent of a completion string in horizontal wells, and provide robust theoretical support for predicting descent resistance.

Research on Pipe String Failure Based on Fluid–Structure Coupling Vibration of Pipe String During Instantaneous Shut-in

Research on Pipe String Failure Based on Fluid–Structure Coupling Vibration of Pipe String During Instantaneous Shut-in

Leakage monitoring of carbon dioxide injection well string using distributed optical fiber sensor

Whether the oil and gas fields in the Carbon Capture, Utilization, and Storage (CCUS) project use underground storage or energy supplementation to enhance oil recovery, they must be injected or monitored through the wellbore. Thus, the foundation and requirement for the safety of carbon dioxide (CO2) storage is the wellbore's integrity. When CO2 is dissolved in water, carbonic acid is created, and this acid strongly corrodes underground pipes. Therefore, the integrity issue with CO2 injection wells is more noticeable than with other wellbores. An annular pressure during gas injection is the primary symptom of gas injection string leakage in CO2 injection wells. This study aims to provide real-time pipe string monitoring using a distributed optical fiber temperature sensing system (DTS) and a distributed optical fiber acoustic sensing system (DAS). Variations in temperature and vibration are caused by annulus pressure relief or gas injection. Optical fiber logging, in contrast to traditional logging, has better performance indicators for optical fiber sensing apparatus. To adapt to complex wellbore conditions, it is necessary to enhance the temperature accuracy of DTS and the sensitivity and signal-to-noise ratio of DAS in CO2 drive injection wells based on the features of the gas injection string. To differentiate the leakage signal from the regular fluid flow signal, the energy calculation in the frequency band is done for DAS based on noise reduction, and the signal processing in the frequency band is done by the spectrum characteristics of the CO2 wellbore signal. The translation invariant wavelet algorithm is the primary denoising method for DTS, overcoming the shortcomings of traditional wavelet threshold algorithms such as excessive smoothing and the pseudo-Gibbs phenomenon. Furthermore, the depth correction during the optical cable lowering process is also examined in this paper. A CO2 gas injection well field experiment was conducted using this technology. A 1671m well was dug, and 1631m of optical cable were installed in the tubing. The tubing leakage position was successfully identified through gas injection, annulus pressure relief, and a comparison of DAS and DTS data. The field results demonstrate the accuracy with which the gas injection string integrity can be accurately monitored in real-time using distributed optical fiber sensing technology for CO2 injection wells.

Research on Accurate Detection Algorithm for the Cross-Section of Shale Gas Casing Deformation Pipe String Based on Laser Ranging

Under shear and non-uniform loads, the deformation of the section shape of a casing results in an irregular section, and the spatial continuity is poor. The change in the distance between the wall of the casing before and after stress is recorded to analyze the deformation of the casing, and the distance value is taken as the key characteristic of the casing. A large number of the key characteristic values of shale gas casing deformation can be obtained by using the circular traversal detection method. At the same time, this article focuses on the center deviation between the laser sensor axis and the pipe string axis, as well as on the disturbance problem during measurement. An eccentricity error correction algorithm is derived to correct the eccentricity error that occurs during the detection process, and then we use interpolation algorithms to draw cubic spline curves to improve detection accuracy. The test results show that the algorithm can effectively eliminate eccentricity errors in measurement and achieve the accurate measurement of deformation casing characteristic values, which can provide basic data for the study of a shale gas casing deformation mechanism.

Vibration characteristics and safety analysis of production string in high temperature, high pressure gas wells

During the production of high-temperature, high-pressure (HPHT) gas wells, the gas entering the production tubing column induces vibration, which in turn leads to changes in the mechanical properties and safety of the tubing column. A dynamic model of the production string in an HPHT gas well was established to study the dynamic characteristics of its production string. The additional axial force caused by the transient temperature change and the nonlinear contact collision between the production string and the casing were considered. The Newmark-β method was used to solve the problem by analyzing and comparing the flow-induced vibration characteristics of the production pipe string. In this study, a gas well in the southwest Sichuan Basin was used as the research object to study the effects of gas production, packer setting position, and string wall thickness on the dynamic characteristics of the string. The results show that in the gas production process, intense vibrations are generated in the transverse and longitudinal directions of the tubular column. After high-velocity gas flows through the production tubing column, the vibrations at the wellbore inclination and the top of the tubing column are more intense. With the rise of production and the downward movement of the packer setting position, the vibration displacement and frequency of the tubing column increase. In addition, as the column's wall thickness increases, the column's stiffness rises, which, in turn, reduces the vibration of the column. When the gas production increases from 60 × 104 m3/d to 150 × 104 m3/d, the maximum transverse vibration displacement of the production string will increase by 22.2%–39.3%, while the frequency will increase by 15.3%–54.3%. When the wall thickness of the pipe column reaches 9.53 mm and 10.92 mm, it can be employed to enhance the safety factor of the string and extend the fatigue life of the string. This study provides a theoretical framework for field string protection and production guidance.

Mud Cake Improver Mul-GX with Lubrication and Interface Enhancement Effect and Its Action Mechanism.

In view of the problems in which the solid content of drilling fluid increases in the middle and late stages of horizontal well drilling, the lubricity of mud cakes on the borehole wall decreases, and the friction of pipe string increases due to the gradual thickening of mud cakes, which leads to the sticking and the obvious decrease of cementing strength at the second interface, a mud cake improver Mul-GX with lubrication and interface enhancement effect was studied in this paper. Based on the hydration and filling mechanism, the lubricity of the mud cake was improved, its thickness was reduced, and its strength was improved through synergistic effects of solvated water film lubrication and buffering, hardening and crystallization of gelled substances, and filling and dispersion of elastic particles. The mud cake improver Mul-GX is composed of the metasilicate GX-ZQ, polymer copolymer GX-JB, and polymer GX-TX, and the mass ratio of each component was GX-ZQ: GX-JB: GX-TX = 15:1:0.5. The effect of Mul-GX was evaluated through the performance determination of the mud cake and interface cementing simulation experiments. In addition, the microscopic characterization by SEM and XRD were carried out to analyze the mechanism of Mul-GX. The experimental results showed that when Mul-GX was added to the water-based drilling fluid with the 1.0%-1.5% adding quantity, the mud cake lubricity improved by more than 60%, its thickness reduced by 53.9% on average, and its strength increased by 54.3% on average. At the same adding quantity, the interfacial bonding strength was 4.4 times more than the data before adding Mul-GX. All of the results showed that Mul-GX has obvious mud cake lubrication effect and interface enhancement effect.

Research on the Mechanical Properties and Structural Optimization of Pipe String Joint under Deep Well Fracturing Operation

In order to reduce the failure accidents caused by the insufficient strength of fracturing string joints, theoretical calculation and string design methods were adopted to conduct finite element calculations on commonly used long circular threads. The distribution laws of stress and contact pressure of long round threads were obtained, a non-standard special thread was designed, and a finite element model of the joint of the casing was established. Considering different make-up torques, tensile loads, and tensile torque loads within a certain range, the stress variation law of the special casing threaded joint under this design size was analyzed. Finally, the stress and contact pressure variation law on the threaded tooth was analyzed under different structures, working conditions, and wall thickness parameters. The thread strength and sealing function were compared under various parameters. The results showed that the smaller the wall thickness of the joints, the greater the contact pressure at the threaded tooth. Among them, the contact pressure of the external threaded tooth is too high, and is prone to the sticking phenomenon. The distribution of contact pressure in the middle section is relatively reasonable. Compared with the original structure, the new structure significantly reduces the contact pressure at the head and tail ends of the threaded connection, reducing the risk of sticking.

Incident during construction of an underwater passage by directional drilling

Relevance. This paper considers the issue of construction of underwater passages of trunk pipelines by the directional drilling method using concrete weight coated pipes. This issue is relevant, since at the present moment there is no standards and technical documentation regulating the calculation procedure of the minimum allowable elastic bend radius of a pipeline with concrete coating in a well. There are situations when design institutes made incorrect design decisions as a result, the pipe string got stuck during works. Those incidents led to unnecessary economic expenditures and a delay in the work implementation plan. Aim. To study the issues which related with the sticking of the pipe string during the construction of the underwater passage of the main pipeline by the method of directional drilling; calculate the minimum allowable elastic bend radius of a pipeline with concrete coating and the actual parameters of the pilot drillhole. Objects. An underwater passage of a trunk pipeline constructed by the method of directional drilling. Methods. Study of standards and technical documents on the construction of underwater crossings of main pipelines and an analysis of the incident in which a pipeline with concrete weight coating got stuck. Results. The authors substantiate the calculation of the minimum allowable elastic bend radius of a pipeline with a concrete coating based on the requirements of domestic standards and technical documentation. The authors have calculated this value by an analytical method, based on studies of the bending stiffness of concrete structures by foreign scientists, as well as actual parameters of the pilot drillhole. The obtained results of the studied values were analyzed and a conclusion was given about the causes of the incident associated with the sticking of the pipe string.

Development of All-electric Discharge Device for Working String

Most of the existing pipe string discharge devices in China are suitable for drilling operations, but some auxiliary devices for surface pipe string discharge in workover operations are not mature enough, and there are some problems such as inconvenient transportation, complex structure and large area. Based on the actual situation of small workover operation site, this paper puts forward the scheme of all-electric discharge device for well site operation pipe string, determines the structure function and work flow of the discharge device, carries out structural design for three parts of the lift, conveying device and pipe rack, and analyzes and calculates the structural parameters of the device. Through the static analysis of the main force components, the rationality of the device design is verified, and its structural strength is in line with the safe range.

Simulation of wellbore pipe flow in oil production engineering: Offshore concentric double-tube CO2-assisted superheated steam wellbore during SAGD process of heavy oil reservoirs

Heavy oil reservoirs are widely distributed around the world and play an important role in offshore oil and gas development. For heavy oil reservoirs, industrial productivity can only be obtained by effectively reducing the viscosity. In addition, by improving the steam injection pipe string, the production degree of the heavy oil reservoir can be effectively improved. In this paper, with the development of offshore heavy oil reservoirs as the background, the heat transfer characteristics of concentric double pipes are studied. Considering the influence of carbon dioxide on the superheated steam, a concentric double pipe flow model is established. The typical flow characteristics and the influence of carbon dioxide content are analyzed. The conclusions are as follows: (a) In the sea water section, the overall heat conduction rate of the concentric double pipe is reduced from 70.5 J/s (at 0 m) to 67.8978 J/s (at 120 m). In the formation section, the overall heat conduction rate of the concentric double pipe is reduced from 67.8978 J/s (at 120 m) to 61.5368 J/s (at 290 m). (b) For the integral joint tubing, the pressure of the mixed fluid of carbon dioxide and superheated steam in the integral joint tubing drops from 4.7 MPa (0 m) to 4.2399 MPa (290 m). (c) For the annular space, the pressure of the mixed fluid of carbon dioxide and superheated steam in the annular space drops from 4.7 MPa (0 m) to 4.3247 MPa (290 m).

Integrated technology for layered sand control and layered water injection

In order to solve the problem of water injection string failure caused by pipe creep and sand production in layered water injection wells, an integrated technology of layered sand control and layered water injection has been developed. A suspended large-radiuslayered mechanical sand control pipe column has been designed, providing sufficient design and usage space for the layered water injection pipe column. Developing a new type of anti-creep sealed packer can effectively improve the anti-creep performance of the water injection string and extend the validity period of the string. This technology integrates and optimizes layered water injection and sand control technology, large channel backwashing technology, integrated testing and allocation technology, and anti-creep technology of the pipe string. While effectively solving sand production in offshore water injection wells, it extends the service life of the water injection pipe string and reduces operating costs. Since 2018, this technology has been implemented in over 200 wells in Chengdao Oilfield, with a maximum of 6 layers for prevention and injection, a maximum well inclination of 48.8°, and a construction success rate of over 90%. It has achieved very good development results and economic benefits.

A new optimized method in wellbore to improve gas recovery in shale reservoirs

With the scale development of shale gas, the importance of selecting appropriate deliquification process has become increasingly evident in maintaining well productivity and improving shale gas recovery rate. At present, the preferred deliquification process are macro-control plate method and field experience method. The existing methods can only qualitatively select the deliquification process by considering limited influencing factors, resulting in poor process implementation. Based on the results of error analysis, the Gray model was optimized to calculate the pressure distribution in the shale gas wellbore and determine the applicable pressure limit. The W.Z.B. empirical model, which fully considers the influence of wellbore inclination, is used to calculate the gas-liquid carrying situation and determine the applicable liquid carrying limit. By analyzing the technical limits of five commonly used deliquification processes in the Changning shale gas field, namely, plunger lift, optimizing pipe string, gas lift, foam drainage, and intermittent production, a quantitative optimization method for deliquification processes was established. This method was then used to obtain the optimization chart for deliquification processes in shale gas wells. This method was applied in Well Ning 209-X, where the corresponding optimization chart for deliquification processes was drawn based on the production characteristics of the gas well. By quantitatively optimizing the deliquification processes and adjusting to suitable techniques, it effectively guided the production of the gas well and improved the gas field recovery rate.

STUDY OF THE DYNAMICS OF ASSOCIATED DRILL STRINGS INTERACTING WITH THE WELL WALL

The depth of exploration and production wells during the development of oil and gas fields can exceed 5-10 km, and the insufficient strength and reliability of the drill string often limits the possibility of further increasing labour productivity. In addition, accidents at wells lead to significant material costs. Therefore, the design and operation of drill strings, as well as the implementation of work to eliminate complications during drilling, should be carried out on the basis of a science-based approach, taking into account the latest advances in the field of drill string dynamics and technologies related to work to eliminate stuck problems. Unsteady vibrations of inhomogeneous distributed systems is a very complex problem in the mechanics of a deformable solid and the theory of vibrations. In connection with the rapid development of the extractive industries, solving this problem is of particular importance. This is due to ensuring the strength of drill string structures with increasing power and speed of drilling units and mechanisms. The study of the problem revealed a number of little-studied problems, which include issues of nonlinear interaction of the column with the surrounding soil, accompanied by various types of complications (sticking, pipe ruptures, etc.), wave and oscillatory processes in the elements of the drilling dynamic system (DDS), finding the boundaries of the interaction areas of the column with the walls of the well using low-cost techniques. The purpose of the work is theoretical research of wave and oscillatory processes in the pipes of the drilling assembly and the dynamics of associated drill strings interacting with the well wall. In this work, a homogeneous rod was used as a drill string model. The drill string consists of a drill pipe string (DPC) and a bottom drill string assembly (BDSA), which includes a bit, a downhole motor, wellbore forming elements: calibrators, centralizers, sections of drill collars (DC), the main purpose of which is to creating an axial load on the bit. The DPC consists of sections of drill pipes that are identical in their characteristics (type, outer diameter, wall thickness, joints used, etc.). Therefore, in general, the drill string is a heterogeneous structure.