No full-text available
To read the full-text of this research,
you can request a copy directly from the authors.
Mathematical modeling and experimental investigation of a rotary valve generating sinusoidal pressure signals based on fan-arc-straight orifice
Abstract
The continuous-wave mud pulse telemetry is currently one of the most advantageous methods for wireless downhole transmission. The rotary valve orifice of a continuous-wave mud pulser must be optimized to generate highly similar sinusoidal pressure waves for high-speed and reliable transmission. In this study, an improved fan-arc-straight-based valve orifice is designed based on a general fan-based valve orifice by analyzing the relationship between throttle area and relative rotation angle of the rotor/stator on the basis of thin-walled cutting edge differential pressure generation mechanism. Then, CFD simulation studies are investigated. It is indicated that the peak-to-peak value of the differential pressure is proportional to the square of the inlet flow; and with the increase of axial clearances between the stator and rotor, the peak-to-peak values of the differential pressure signals show a negative exponential decrease trend, while the correlation coefficients also decrease monotonously. Furthermore, surface hydraulic system experiments have also been implemented; and the actual 8Hz and 12Hz pressure waves with correlation coefficients greater than 0.99 are obtained compared with the corresponding sinusoidal signals. It is believed that the optimized valve can achieve highly similar sinusoidal pressure waves with acceptable amplitudes during practical operation to meet the field operation requirements.
... For example, the rotor is a core component of the CW signal generator in drilling mud [23]. The design of the valve hole structure and synchronized motor drive in the signal generator are of significant importance for generating high-quality pulse signals, improving the performance of the MPT system and achieving high-speed transmission of downhole information [24]. Additionally, erosion of the mud and friction between components can bring losses to system components. ...
Mastering real-time and accurate downhole information is crucial for ensuring drilling safety, improving drilling efficiency, and maximizing economic benefits. In recent years, logging while drilling (LWD) technologies, represented by mud pulse telemetry (MPT), achieved significant success. However, they still face challenges such as a large amount of downhole information conflicting with low information transmission rates, severe channel distortion, strong noise interference, and weak surface receiving signals. Therefore, this review collects and updates the papers, patents, and conference articles in the relevant field over the past ten years. Starting from the basic structure of communication systems, the downhole signal coding and modulation technologies of the MPT system are discussed. The attenuation reflection brought by the mud channel and various noise interferences in the system are described. The surface noise cancellation, channel equalization, synchronization, and decoding are studied in detail. By analyzing the theoretical principles, development breakthroughs, and relevant challenges that can improve the development of LWD technologies, this review aims to assist researchers in the field in obtaining the latest references and strategies.
Exploiting geothermal resources such as hot dry rocks (HDRs) requires directional drilling technology. Measurement-while-drilling (MWD) technology plays a crucial role in directional measurement. However, its high temperature and environment limit downhole measurement instruments in application. For this research, we designed an MWD system with a mechanical gravity tool face, and the fully mechanical structure was used to overcome the high-temperature constraints. The bias stabilization platform, gravity tool face coding method, and mud pulse generation structure were designed. The eccentric stable model and pulse generation structure model were established through numerical analysis, and a gravity tool face angle coding and identification method was also established. The experimental prototype testing system was built on theoretical analysis and hydrodynamics. The feasibility of the tool functions and the recognition algorithm were verified experimentally, with a maximum measurement error of 6° and an average measurement error of 2.6°. The average measurement error of the system in the well test is 6°, which verifies the reliability of the system.
The quality of pressure signals is intricately linked to the speed variation characteristics of the permanent magnet synchronous motor (PMSM) employed to drive the rotor of the continuous wave pulse generator. However, achieving precise control of PMSM is significantly challenged by complex and time-varying drilling operating conditions. A serial
n
ADRC (S
n
ADRC) is presented to increase the control motor's immunity and dynamic performance, where “
n
” indicates the number of sequential output stacking extended state observers (SOS-ESOs) equal to the highest order of the disturbance. Based on the deduced continuous wave pulse generator rotor model, first-order SOS-ESO is intended to detect the first-order disturbance, with the higher order SOS-ESO designed to anticipate the residual disturbances in order to accomplish real-time and precise hydraulic torque prediction. Moreover, the estimation performance of SOS-ESO is analyzed, and the intrinsic stability of S
n
ADRC with the speed loop control system is rigorously demonstrated using the Lyapunov theory. Additionally, SOS-ESO is employed in simulation to resist polynomial disturbances, and it is discovered that the
n
thorder SOS-ESO may successfully suppress complex disturbances up to (
n
-1) order. Finally, the control performance of S
n
ADRC is compared to that of classical control methods in both the simulation and experiment, and the results show that S
n
ADRC has excellent rapidity and stability in motor control, which opens up a wide range of possibilities for practical applications in control and engineering fields.
Low data rates, typically 1-3 bits/sec or less, are the norm in “mud pulse” Measurement-While-Drilling (MWD) systems. For example, “sirens” offering high carrier frequencies produce low-amplitude signals subject to severe attenuation; and strong signals from “positive pulsers” are slow since large forces are required to overcome mud inertia. Moreover, reflections, high pump noise, erosion and rapid power consumption affect all pulsers. This paper describes an integrated systems approach to high-data-rate telemetry. Source strength is enhanced using downhole constructive interference, and surface signal processing eliminates downward reflections and pump noise through “directional filters,” both drawing on wave-based methods. Hydraulic properties associated with torque, erosion, aerodynamic stability and turbine performance, and subtleties found in large-scale acoustic wave interactions, are studied using dynamic similarity. In particular, short and long wind tunnels are introduced with significantly reduced test times, cost and required labor. Experimental facilities, prototypes and signal processing methods are presented in detail.
High-speed downhole transmission technology plays an important role in measurement while drilling (MWD) and logging while drilling (LWD) systems, where the continuous wave mud pulse transmission method is currently the most advantageous method for wireless downhole transmission. To increase the production rate, transmission distance and testing intensity and to decrease the ground detected difficulty of continuous wave mud signals, the valve orifice must be optimized to satisfy the requirements for the continuous sinusoidal pressure output. In this study, an improved arc-fillet-line triangular valve orifice is designed based on a general line triangular valve orifice according to the relationships between the fluid differential pressure of a thin-walled cutting edge and the fluid flow area and between the correlation coefficient of the theoretical pressure difference and standard sinusoidal signal. The improved orifice is designed by calculating the variation between the flow area and relative rotation angle of the rotor to the stator through the established polar coordinate equations. The optimized valve structure is simple and easy to machine, and highly similar sinusoidal pressure wave signals can be achieved during practical operation to meet the requirements of the instrument design.
Wireless measure while drilling (MWD) transmits data by using mud pulse signal ; the ground decoding system collects the mud pulse signal and then decodes and displays the parameters under the down-hole according to the designed encoding rules and the correct detection and recognition of the ground decoding system towards the received mud pulse signal is one kind of the key technology of MWD. This paper introduces digit of Manchester encoding that transmits data and the format of the wireless transmission of data under the down-hole and develops a set of ground decoding systems. The ground decoding algorithm uses FIR (Finite impulse response) digital filtering to make de-noising on the mud pulse signal, then adopts the related base value modulating algorithm to eliminate the pump pulse base value of the denoised mud pulse signal, finally analyzes the mud pulse signal waveform shape of the selected Manchester encoding in three bits cycles, and applies the pattern similarity recognition algorithm to the mud pulse signal recognition. The field experiment results show that the developed device can make correctly extraction and recognition for the mud pulse signal with simple and practical decoding process and meet the requirements of engineering application.
Drilling fluid continuous wave (DFCW) technology is an advanced downhole information telemetry technology and has broad application prospects, and its generation, transmission and reception technology has been studied extensively. However, the research on the waveform characteristics of downhole DFCW is still insufficient. In this paper, the characteristic model for describing sinusoidal DFCW in deep wellbore is established by combining the Navier-Stokes equations, orifice throttling theory and Fourier transform method, and the effects of the frequency, wave speed, reflective distance and well depth on the waveform characteristics of DFCW are analyzed based on the proposed model. The research results show that: (1) well depth will influence the amplitude of the DFCW in low frequencies because of the slight compressibility of drilling fluid, (3) smaller reflection distance and larger wave velocity will lead to longer periods of the amplitude-frequencies curves of the DFCW because of the superposition of the pressure wave, (4) the peak value of DFCW is proportional to the wave velocity, but the reflection distance has little effect on the peak or trough of the DFCW amplitude, (5) the DFCW amplitude varies periodically with frequency. The research results can provide critical technical support for the development of downhole DFCW generator and the study of its working characteristics.
Technology of downhole data transmission based on drilling fluid continuous pressure waves is extensively applied to the drilling operation of oil/gas wells due to high transmission rate. For generation of the continuous pressure waves, this paper designs a signal generator with multi-row valve ports, and an optimizationmodel is established to preliminarily solve the valve ports distribution. In addition, a laboratory experiment is carried out to determine the relationship between flow and pressure of the drilling fluid flowing through the multi-row valve ports, and the flow coefficient and valve port exponent herein are adopted to modify the previous optimization result of the valve ports distribution. Ultimately, the pressure waves produced by the preliminary and modified optimization results are compared with sine wave. Results show that the multi-row valve port exponent and flow coefficient are experimentally measured to be 0.3 and 0.75, respectively, and based on them, the modified optimization result of the valve ports distribution is capable of generating a pressure wave that has a higher similarity with sine
wave. This is because that the correlation coefficient between them is as high as 0.9978, which is very close to 1. Research results indicate the optimization model for calculating the valve ports distribution is correct. Furthermore, the experimental data are reliable and can accurately reveal the flow and pressure characteristics of the multi-row valve ports.
High-speed downhole transmission technology is in high demand for measurement while drilling (MWD) and logging while drilling (LWD) systems which have had major roles in increasing the geo-steering and formation evaluation capacity of reach wells, difficult horizontal wells and branch wells as well as increasing drilling rates. This paper presents the conceptual design and performance of a novel continuous wave mud pulse generator with the goal of transmitting data using hydraulic pressure waves. The generator includes the rotary valve, drive shaft and bearings, rotary and static seals, motor and reducer, resolver, pressure balance structure and lower centralizer; all of these components are mounted within a rotary drill collar. In particular, the rotary valve is the key important part of the continuous wave mud pulse generator. Based on the concept of a sinusoidal signal output, an improved arc-fillet-line triangular valve orifice is designed according to the relationships between the fluid differential pressure of a thin-walled cutting edge and the fluid flow area calculated from the relative rotation angle of the rotor to the stator through the established polar coordinate equations. The highly similar sinusoidal pressure signals can be achieved by optimized valve structures, which were verified by computational fluid dynamics (CFD) simulations, where the valve flow pattern characteristics and the impact law between the gap of the stator/rotor and pressure waveform were also obtained. Moreover, the drive capability response curves of the motor driver unit with and without a load are precisely determined, and current ground hydraulic experiments indicate that the designed continuous wave mud pulse generator performs well as a whole. The generated real pressure waves exhibit clear spectrum structures with a distinctive characteristic signal.
Mud pulse generators have been widely used for the real-time transmission of valuable directional and formation data from downholes with depths of thousands of meters. There have been numerous studies on the design of mud pulse generators in which the pressure waves were typically nonsinusoidal. Sinusoidal waves provide improved long-distance data transmission and signal noise suppression compared with nonsinusoidal waves. Although sinusoidal pressure wave generators have been studied in the published literature, the influence of the risks of clogging on the design of the generator for producing sinusoidal pressure waves has rarely been considered. To generate sinusoidal pressure waves and to reduce the risks of clogging, a mathematical model for the design of a sinusoidal pressure wave generator is developed in this paper. The effects of the axial and radial clearances between the rotor and stator on the design of the generator are considered in the model. An optimum design method for the generator is provided by combining the developed model and a computational fluid dynamics analysis. Finally, an experimental platform was built and experiments at frequencies 2 Hz and 10 Hz were conducted to validate the design result. The simulation and experimental results show that the optimized pressure waves closely approximate sine waves. Therefore, the developed mathematical model and optimization approach can be used to design a sinusoidal pressure wave generator.
Mud pulse telemetry (MPT) is the leading real-time data transmission technology in the oil industry to deliver answers while drilling. New logging-while-drilling (LWD) tools produce increasing amounts of data that has to be transmitted to the surface. To avoid a compromise between rate of penetration (ROP) and log density, the real-time data rate has to increase. This is particularly true when demanding mud environments create demanding transmission conditions for MPT. As the well depth increases, it affects the mud density and mud plastic viscosity, making the situation even more challenging.
This paper describes evolutionary changes to a MPT system. The system uses a special training sequence (TS) that is regularly sent by a shear valve pulser. Surface controls detect the TS and use it to tune, automatically, adaptive filters. These filters respond to the current channel conditions, enabling reliable physical data rates of 10bit/s and greater. To avoid decreasing the decoding quality due to non-optimal filters that have been calculated during pressure/flow disturbed transmission, the system automatically tests the performance of all filter sets. Afterwards, the coefficients are saved into a database with additional information. This empowers the field service engineer to perform a quick look at the database and maintain high decoding quality.
Sophisticated changes to the TS and to the surface algorithms have significantly improved the automated detection rate of the TS search. Compared to offset runs in challenging fields, decoding quality and reliability have improved. The introduction of higher automation levels enables field personnel to deliver more answers to the operator, and provide multifaceted bottomhole assemblies with many LWD services. By eliminating the tradeoff between ROP and log density through higher data rates in MPT, the overall cost of drilling wells decreases without compromising safety.
The backflow occurred behind the rotor blades when the rotor rotated and the inlet velocity angle of the rotor varied with rotor's motion, which lead to the great change of the hydraulic torque on the rotary valve, and the dynamic performance of the rotary valve was influenced. A theoretical calculation model of the hydraulic torque on the rotary valve was established based on the theorem of momentum moment, and then the three-dimensional flow field inside the experimental prototype was simulated by CFD method, and the simulation analysis of several influence factors of the hydraulic torque on the rotary valve was made. The results show that the hydraulic torque on the rotary valve tends to open the rotary valve in the starting stage of the closure, and tends to close the rotary valve in other stages. The hydraulic torque can be changed mildly using the curved orifice, and the hydraulic torque can be decreased and the control performance of the motor can be improved by increasing the gap between the stator and rotor or increasing the number of the valve lobe or decreasing the thickness of the valve lobe.
Increasingly deep wellbores allow for quicker and more accurate transmission of data with the help of mud-pulse systems. In addition, telemetry systems are being improved to transmit real-time data quickly. This is done with wired pipe or a wait for the wireline data. Such advances allow for relevant economic benefits. This has made mud-pulse telemetry the most popular method of transmitting measurement-while-drilling and logging-while-drilling data. In fact, telemetry rates are now in the measure of 20 bits/sec at depths shallower than 20,000 ft and for depths more than 36,000 ft which has a value of over 3bits/sec.
Increasing water depth, total well depth, synthetic mud systems and increasing measurement complexity pose unique challenges for real-time data transmission via mud pulse telemetry. In deepwater environments, where the use of synthetic oil-based mud is prevalent, low water temperature significantly increases mud viscosity which reduces the signal strength at surface and makes detection of the signal more difficult. Noise within the mud channel further hinders transmission of downhole data. With rig rates approaching $350k per day and total well depths beginning to exceed 10700 m (35,000 ft), operators cannot afford to drill ahead without good quality real-time downhole data. On recent wells in deep water conditions in the Gulf of Mexico as many as seven different measurement while drilling/logging while drilling (MWD/LWD) tools have been run concurrently. Some of these tools may include the capability to produce real-time images. There is thus an increasing demand for higher data rates coupled with more reliable telemetry to transmit all this data to the surface in real-time. Recent advances in MWD tool design, signal strength prediction, and signal recovery on the surface, using advanced digital signal processing techniques, have made it possible to double telemetry data rates while also reducing error rates in the data received at the surface.
Offshore drilling has attracted more attention than ever before due to the increasing worldwide energy demand especially in China. High cost, long drilling cycles, and low rate of penetration (ROP) represent critical challenges for offshore drilling operations. The hydraulic pulse generator was specifically designed, based on China offshore drilling technologies and parameters, to overcome problems encountered during offshore drilling. Both laboratory and field tests were conducted to collect the characteristics of the hydraulic pulse generator. The relationships between flow rate and pressure amplitude, pressure loss and pulse frequency were obtained, which can be used to optimize operation parameters for hydraulic pulse jet drilling. Meanwhile a bottom hole assembly (BHA) for pulse jet drilling has been designed, combining the hydraulic pulse generator with the conventional BHA, positive displacement motor, and rotary steerable system (RSS) etc. Furthermore, the hydraulic pulse jet technique has been successfully applied in more than 10 offshore wells in China. The depth of the applied wells ranged from 2,000 m to 4,100 m with drilling bit diameters of 311 mm and 216 mm. The field application results showed that hydraulic pulse jet technique was feasible for various bit types and formations, and that ROP could be significantly increased, by more than 25%.
A numerical model and transmission characteristic analysis of DPSK (differential phase shift keying) pressure signals in mud
channels is introduced. With the control logic analysis of the rotary valve mud telemetry, a logical control signal is built
from a Gate function sequence according to the binary symbols of transmitted data and a phase-shift function is obtained by
integrating the logical control signal. A mathematical model of the DPSK pressure signal is built based on principles of communications
by modulating carrier phase with the phase-shift function and a numerical simulation of the pressure wave is implemented with
the mathematical model by MATLAB programming. Considering drillpipe pressure and drilling fluid temperature profile along
drillpipes, the drillpipe of a vertical well is divided into a number of sections. With water-based drilling fluids, the impacts
of travel distance, carrier frequency, drillpipe size, and drilling fluids on the signal transmission were studied by signal
transmission characteristic analysis for all the sections. Numerical calculation results indicate that the influences of the
viscosity of drilling fluids and volume fraction of gas in drilling fluids on the DPSK signal transmission are more notable
than the others and the signal will distort in waveform with differential attenuations of the signal frequent component.
The rotor parameter study of rotary valve mud pulser base on CFD
- Wang
Optimization design of rotary valve of continuous wave generator based on correlation coefficient
- Jia
Oil & gas drilling technology in China: past and present
- Su