Measurement While Drilling Research Articles

Reduction in Backup Tool Requirements: Risks vs. Benefits, a Probability Analysis

Summary A review of the use of measurement while drilling (MWD), logging while drilling (LWD), and directional drilling (DD) tools mobilized to offshore drilling units in the North Sea highlighted an opportunity to lower operational cost for the operator and reduce capital used for the oilfield services company. An objective was set to develop a risk-based probability model that would assess the positive and negative financial impacts of reducing, or perhaps entirely removing, backup tools in this historically risk-averse basin. The scope of the initial analysis was a drilling campaign on a single rig contracted by the operator (Rig A). This analysis was then extended to review scenarios in which several operations in close proximity would share backup tools. The last 3 years of MWD/LWD/DD tool reliability data from North Sea operations, recorded by the oilfield services company, were used as an input. To assess the probability of failure, a binomial model was developed to create a binomial distribution for each tool to calculate the probability of having zero to X failures for a selected tool or bottomhole assembly (BHA) for a given number of runs. Three binomial models were developed to study the effect of “easy,” “moderate,” and “challenging” drilling environments on tool reliability. A financial risk model was designed to balance the probability-weighted cost of failure for the operator against the lower costs resulting from reduced tool provision by the oilfield services company. To better estimate risks and financial impacts on the project, a sensitivity analysis was performed on the financial risk model using the three binomial models. As a result of the analysis, it was demonstrated that recent improvements in tool reliability support a reduction in the provision of backup MWD/LWD/DD drilling tools for the majority of North Sea drilling scenarios.

A Machine Learning Approach for Material Type Logging and Chemical Assaying from Autonomous Measure-While-Drilling (MWD) Data

Understanding the structure and mineralogical composition of a region is an essential step in mining, both during exploration (before mining) and in the mining process. During exploration, sparse but high-quality data are gathered to assess the overall orebody. During the mining process, boundary positions and material properties are refined as the mine progresses. This refinement is facilitated through drilling, material logging, and chemical assaying. Material type logging suffers from a high degree of variability due to factors such as the diversity in mineralization and geology, the subjective nature of human measurement even by experts, and human error in manually recording results. While laboratory-based chemical assaying is much more precise, it is time-consuming and costly and does not always capture or correlate boundary positions between all material types. This leads to significant challenges and financial implications for the industry, as the accuracy of production blasthole logging and assaying processes is essential for resource evaluation, planning, and execution of mine plans. To overcome these challenges, this work reports on a pilot study to automate the process of material logging and chemical assaying. A machine learning approach has been trained on features extracted from measurement-while-drilling (MWD) data, logged from autonomous drilling systems (ADS). MWD data facilitate the construction of profiles of physical drilling parameters as a function of hole depth. A hypothesis is formed to link these drilling parameters to the underlying mineral composition. The results of the pilot study discussed in this paper demonstrate the feasibility of this process, with correlation coefficients of up to 0.92 for chemical assays and 93% accuracy for material detection, depending on the material or assay type and their generalization across the different spatial regions.

Erosion wear characteristics of cemented carbide for mud pulser rotor

Mud pulser is the most commonly used Measurement While Drilling(MWD) instrument for downhole data transmission to the surface. The rotor of the key component of the mud pulser is made of cemented carbide material. Under the action of high speed mud erosion containing solid phase, the rotor will produce erosion wear and reduce the quality of signal transmission. To explore the erosion wear mechanism of rotor carbide in mud containing solid phase particles, the influences of different erosion angles and different erosion abrasive sizes on the erosion wear properties of cemented carbides were studied by taking quartz sand as erosion abrasive. By means of surface profilometer, scanning electron microscope (SEM) and energy spectrum analysis (EDS), the erosion wear mechanism of cemented carbide was revealed. The experimental results show that the erosion wear rate increases gradually with the increase of erosion angle. When the erosion angle is 90°, the maximum average erosion rate of WC-5Co, WC-6Co and WC-10Co cemented carbides is 2.39%, 2.42% and 3.22%, respectively. With the increase of the abrasive particle size, the erosion wear rate of the material increases first and then decreases. When 100–200 um, the maximum average erosion rates of WC-5Co, WC-6Co and WC-10Co are 1.84%, 1.98% and 2.48%, showing a significant “particle size effect”. At low erosion angle, the wear mechanism is furrow and cutting mark, while at high erosion angle, the wear mechanism is pit. The erosion wear mechanism of small particle size abrasives is that a large area of surface layer falls off in the erosion area. The erosion wear mechanism of large particle size abrasive is the material loss in the erosion pit in the erosion area.

An effective compression algorithm for real-time transmission data using predictive coding with mixed models of LSTM and XGBoost

In this paper, a compression and decompression algorithm is proposed for real-time transmission data by combining discrete wavelet decomposition and reconstruction, hybrid model prediction of long short-term memory (LSTM) and extreme gradient boosting (XGBoost), and the development of quantization sequences. The forward compression and reverse decompression are achieved by continuously acquiring the prediction error and data series with quantization error through the iterative shifting approach. To accurately forecast data series with quantization errors, three classes of data with specific distribution characteristics collected from the measurement-while-drilling (MWD) operation field are decomposed into approximate data and detailed data, which are then predicted by autoregressive integrated moving average (ARIMA), support vector regression (SVR), XGBoost, backpropagation neural network (BPNN), radial basis function neural network (RBFNN), and LSTM models. Particularly, the LSTM model and the XGBoost model are proven to be suitable strategies for working with approximate data and detailed data separately by comparing with conventional approaches in terms of the mean absolute error (MAE), root mean square error (RMSE), and coefficient of determination (R2) predictive indexes. Besides, experiment studies show that almost 50% compression performance can be reached under one in ten thousand distortions. It is verified that the proposed algorithm is appropriate and efficient for real-time data transmission applications with high performance.

Specifics of MWD Data Collection and Verification during Formation of Training Datasets

This paper presents a structured analysis in the area of measurement while drilling (MWD) data processing and verification methods, as well as describes the main nuances and certain specifics of “clean” data selection in order to build a “parent” training database for subsequent use in machine learning algorithms. The main purpose of the authors is to create a trainable machine learning algorithm, which, based on the available “clean” input data associated with specific conditions, could correlate, process and select parameters obtained from the drilling rig and use them for further estimation of various rock characteristics, prediction of optimal drilling and blasting parameters, and blasting results. The paper is a continuation of a series of publications devoted to the prospects of using MWD technology for the quality management of drilling and blasting operations at mining enterprises.

Schlumberger’s Drilling ECG Goes to the Heart of the Matter To Diagnose Abnormal Conditions in Real Time

The trading of technologies is nothing new for the upstream oil and gas and medical communities. The connection makes sense, particularly since both disciplines rely heavily on applied math for diagnoses. It should come as no surprise, then, that a popular paper at the 2021 Virtual SPE/IADC International Drilling Conference proposed a medically inspired approach to prevent catastrophic drilling system failures brought on by downhole shocks (SPE/IADC 204098). The paper describes a “drilling electrocardiogram” that diagnoses “arrhythmic drilling” similarly to how medical electrocardiograms diagnose dangerous vibration anomalies in heart patients. The approach classifies shock wave-forms acquired at 31,250 hertz (Hz) downhole. The shock signals are treated as drilling electrocardiograms (D-ECG) that are processed using clustering algorithms and merged with drilling incidents to identify in real time an arrhythmic signature pattern that can lead to catastrophic failures. A Revelation Justo Matheus, senior control engineer for Schlumberger and lead author of the paper, said that in studying field incidents in which rotary steerable system (RSS) bottomhole assemblies (BHA) had been severely damaged by shocks, the signature patterns reminded him of ECGs (Fig. 1). This led him to medical libraries, which in turn led to a revelation—that throughout the 3 decades that downhole vibration measurements while drilling (MWD) have been studied, only the analysis of the amplitude and root mean square (rms) values of shocks had been the focus. No one had considered frequency for diagnosing downhole shocks. It was this revelation that drove the concept of the D-ECG based on shock waveforms acquired at high frequency in real time to prevent failures of the BHA. What Is “Normal” and What Is Not? Drilling-generated shocks and vibrations affect rate of penetration, directional control, and wellbore quality, making them among the main causes of failures in drilling. “Shocks are present almost all the time,” said Matheus. “The challenge is in knowing which are normal and which are not.” RSS are equipped with measurement devices such as magnetometers, accelerometers, and shock and vibration sensors that obtain statistical information from which whirl, bit bounce, and stick/slip severity are inferred. Often, however, the derived statistics are not sufficient to distinguish between normal drilling vs. abnormal drilling for a location in the wellbore. Recent electronic advances enabled the development of high-resolution drilling dynamic data recorders, extending the sampling frequency from traditional 100 Hz to 1,600 Hz. However, most of these devices are for data recording only. There is no real-time communication with surface and no capability to inform about drilling conditions downhole.

Blastability and Ore Grade Assessment from Drill Monitoring for Open Pit Applications

Blasting performance is influenced by mechanical and structural properties of the rock, on one side, and blast design parameters on the other. This paper describes a new methodology to assess rock mass quality from drill-monitoring data to guide blasting in open pit operations. Principal component analysis has been used to combine measurement while drilling (MWD) information from two drill rigs; corrections of the MWD parameters to minimize external influences other than the rock mass have been applied. First, a Structural factor has been developed to classify the rock condition in three classes (massive, fractured and heavily fractured). From it, a structural block model has been developed to simplify the recognition of rock classes. Video recording of the inner wall of 256 blastholes has been used to calibrate the results obtained. Secondly, a combined strength-grade factor has been obtained based on the analysis of the rock type description and strength properties from geology reports, assaying of drilling chips (ore/waste identification) and 3D unmanned aerial vehicle reconstructions of the post-blast bench face. Data from 302 blastholes, comprised of 26 blasts, have been used for this analysis. From the results, four categories have been identified: soft-waste, hard-waste, transition zone and hard-ore. The model determines zones of soft and hard waste rock (schisted sandstone and limestone, respectively), and hard ore zones (siderite rock type). Finally, the structural block model has been combined with the strength-grade factor in an overall rock factor. This factor, exclusively obtained from drill monitoring data, can provide an automatic assessment of rock structure, strength, and waste/ore identification.

Numerical investigation on heat transfer rate from the outside environment into the electronic compartment of the measurement‐while‐drilling tools

AbstractWith the increase of drilling depth, a large number of high‐temperature wells with bottom hole temperatures of more than 150°C appear. However, conventional measurement‐while‐drilling (MWD) instruments are no longer suitable. Therefore, it is necessary to design a new MWD instrument suitable for high‐temperature downhole for a long time. Compared with other active refrigeration methods, a split‐Stirling cryocooler is the best choice. In this paper, a new active cooling system is designed, based on the split‐Stirling cryocooler. The heat transfer rate entering the instrument cabin of MWD from the external environment is calculated, and the effects of the heat transfer device, insulation material, circuit board, split‐Stirling cryocooler, and working condition on heat transfer rate are discussed. The results show that the thermal conductivity of insulation material has a great influence on heat transfer rate. The thermal conductivity of the insulation material filled with the gap in the cabin must be small enough. Meanwhile, the influence of the length of the circuit board is greater than the height and width. If conditions permit, the double‐layer circuit can be used. And the thermal power of the circuit board has no effect on the heat transfer rate entering the instrument cabin from outside.

SLURRY EROSION BEHAVIORS OF COPPER ALLOY BARREL OF MEASURE-MENT WHILE DRILLING

Measurement while drilling (MWD) has been widely used in petroleum drilling engineering because it can realize borehole trajectory monitoring and improve the drilling speed. However, the slurry erosion will deteriorate and shorten the life of MWD. A user-defined function (UDF) code was developed to calculate the particle properties (particle impact velocity, particle impact angle and particle impact number) and erosion depth to understand the erosion process. The results show that the Realizable κ-ε model can accurately predict the erosion profile and the erosion depth is consistent with the experiment results. Furthermore, high pressure will aggravate surface damage and expand the area of slurry erosion. It has been demonstrated that computational fluid dynamics (CFD) and experimental approach can be used to identify and explain the erosion mechanisms in different regions where the surface morphologies reveal four erosion patterns, namely, micro-cutting, cracks, pits and plastic deformation.

Experimental study on repeater-free acoustic telemetry for downhole operations

Measurement while drilling (MWD) enables real-time measurement of downhole conditions for directional drilling, but most commercial MWD telemetry techniques suffer from limited transmission speeds. Acoustic telemetry has the potential for significantly faster transmission speeds, but it has limited range due to drill string attenuation and noise. A common solution to this is to use acoustic repeaters, which incur high costs and require complex implementation. Instead of using repeaters, we utilized two carrier frequencies at the modes to transmit redundant data in combination with a lock-in amplifier (LIA) to extract the signals from the carriers. The extracted signals were then fused at the receiver to increase signal fidelity. An experimental setup was developed to transmit acoustic signals through a simulated drill string. The signals were first attenuated by the rubber section of the simulated drill string. The results show that the proposed system was able to achieve error-free transmission of packets at 64 bps up to 1.95 km without the use of a repeater which is orders of magnitude faster than current commercial MWD methods (mud-pulse and electromagnetic).

Simulating Drillstring Dynamics Motion and Post-Buckling State with Advanced Transient Dynamics Model

SummaryAs drilling sections become deeper and longer, transferring more weight downhole to improve rate of penetration is the primary concern for the operator. Drillstring dynamics and buckling are some primary limiters for drilling efficiency. Aggressive drilling parameters may lead to severe downhole dynamics, which leads to cutter breakage and tool damage. When axial compression exceeds a certain threshold, the drillstring buckles sinusoidally inside the wellbore first, followed by helical buckling. Buckling leads to accelerated joint wear, tool fatigue failures, and lower drilling efficiency. To better manage drillstring dynamics and buckling, we propose a method of simulating drillstring dynamics motion and postbuckling state using an advanced transient dynamics model.An analysis methodology was developed on the basis of the finite element transient dynamics model. The model captures the enriched physics of drillstring dynamics and loading: the large deformation of buckled drillstring, the strong nonlinearity of contact and friction forces, and the dynamically triggered instability caused by drilling rotation. Transient dynamics simulations are conducted for drillstring with the actual well trajectory and rotation speed. The weight on bit (WOB) is ramped up gradually, and the drillstring deformation is monitored to detect the onset of buckling or dynamics instability.To conduct the model validation, the buckling inception loads predicted by the model are compared against the analytical equation of critical buckling loads. A field extended reach drilling (ERD) job was simulated by the model. The downhole weight and torque data from the measurement-while-drilling (MWD) tool was used to validate the weight transfer prediction by the model. Most existing buckling theories use the analytical equations of critical buckling load, which were normally derived on the basis of the idealized assumptions, such as perfect wellbore shape and uniform tubular geometry. The proposed method simulates the drillstring behaviors in the field drilling conditions and aims to capture effects of wellbore friction and string rotation. The transient dynamics model is capable of simulating drillstring dynamics movement (whirling and snaking) and weight lockup under severe helical buckling. An automatic method is proposed to interpret the drillstring behaviors from the simulation results. Using the transient dynamics model, the procedure presented in this article can simulate the dynamics and buckling behaviors of drillstring and help mitigate associated risks in well-planning and execution phases.

Quantifying Global and Random Uncertainties in High Resolution Global Geomagnetic Field Models Used for Directional Drilling

SummaryTotal field strength, declination, and dip angle of the Earth's magnetic field, in conjunction with gravity, are used by magnetic-survey tools to determine a wellbore's location. Magnetic field values may be obtained from global models that, depending on the model, have a wide range of spatial resolution at the Earth's surface from large scale (3000 km) to small scale (28 km). The magnetic field varies continuously in both time and space, so no model can fully capture the complexity of all sources; hence, there are uncertainties associated with the values provided. The SPE Wellbore Positioning Technical Section/Industry Steering Committee on Wellbore Surveying Accuracy (ISCWSA) published their original measurement-while-drilling (MWD) error model in 2000. Such models and uncertainties define positional error ellipsoids along the wellbore, which assist the driller in achieving their geological target, in addition to aiding collision avoidance. With the recent update to Revision 5 of the ISCWSA error model, we have reassessed the uncertainties associated with our latest high-resolution global magnetic field model.We describe the derivation of location-specific global and random uncertainties for use with predicted geomagnetic values from high-resolution models within magnetic MWD survey-tool-error models. We propose a sophisticated approach to provide realistic values at different locations around the globe; for example, we determine separate errors for regions where the models have high spatial resolution from aeromagnetic data compared to regions where only satellite data are available.The combined uncertainties are freely available via a web service with which the user can also see how they vary with time. The use of the revised uncertainty values in the MWD-error model, in most cases, reduces the positional error ellipsoids and allows better use of the increased accuracy from recent improvements in geomagnetic modeling. This is demonstrated using the new uncertainty values in the MWD-error model for three standard ISCWSA well profiles. A fourth theoretical well offshore Brazil where the vertical magnetic field is weak shows that with drillstring interference correction relying on the more uncertain magnetic dip, the positional error ellipsoids can increase. This is clearly of concern for attaining geological targets and collision avoidance.

Efficient Removal of Magnetic Contamination From Drilling Fluids: The Effect on Directional Drilling

Abstract Magnetic debris in a drilling fluid have a significant influence on the ability of the drilling fluid to maintain its function. Down hole logging can suffer from poor signal to noise ratios. Directional drilling in areas close to the magnetic North Pole, such as in the Barents Sea, Northern Canada, or Russia, can suffer because of magnetic contamination in the drilling fluid. Magnetic particles in the drilling fluid introduce additional errors to the magnetic surveying compared to those normally included in the ellipsoid of uncertainty calculation. On many offshore drilling rigs, there are mounted ditch magnets to remove metallic swarf from the drilling fluid. These magnets normally only remove the coarser swarf. In this project, we use a combination of strong magnets and flow directors to significantly improve the performance of the ditch magnets. This combination, together with proper routines for cleaning the ditch magnets, significantly helps to clean the drilling fluid. Through the combined use of flow directors and ditch magnets, it was possible to extract more than five times as much magnetic contamination from the drilling fluid as normal compared with other proper ditch magnet systems. This is verified by comparing the ditch magnet efficiencies from two drilling rigs drilling extended reach drilling (ERD) wells in the North Sea area. In this paper, it is discussed how the accuracy of directional drilling and well position effected by various interferences can be improved by the use of a drilling fluid with minimal effect to the measurement while drilling (MWD) measurement.

Significant Surge and Swab Offshore Brazil Induced by Rig Heave during Drillpipe Connections

SummaryIn this paper, we describe measured and simulated downhole pressure variations (“surge and swab”) during drillpipe connections when drilling an ultradeepwater well offshore Brazil on Bacalhau (former Carcará) Field. Floating rig motion caused by waves and swell (“rig heave”) induces surge and swab when the drillstring is suspended in slips to make up or break a drillpipe connection and topside heave compensation is temporarily deactivated. This is a known issue in regions with harsh weather, such as the North Sea, where pressure oscillations of up to 20 bar have been reported during connections. Recorded downhole drilling data from Bacalhau Field reveals significant pressure oscillations downhole (in the same order of magnitude as in the North Sea) each time the drillstring was suspended in slips to make a connection in the subsalt 8½-in. section of the well. Mud losses were experienced around the same well depth, and they might have been caused by surge and swab.Measured surge and swab pressure variations have been reproduced in an advanced proprietary surge and swab simulator that considers rig heave, drillpipe elasticity, well friction, non-Newtonian drilling mud, well trajectory, and geometry. Moreover, findings in this paper suggest that surge and swab was in fact significantly higher than recorded by the measurement while drilling (MWD) tool. The true magnitude of surge and swab is not captured in the recorded MWD data due to low sampling frequency of the downhole pressure recording (one measurement every 6 seconds, a standard downhole pressure sampling rate used on many operations today).This work shows that surge and swab during drillpipe connections on floaters may challenge the available pressure window for some wells, even in regions with calm weather such as Brazil. Managed pressure drilling (MPD) is a technique that improves control of the downhole pressure. It is, however, not possible to compensate fast downhole pressure transients, such as heave-induced surge and swab, using MPD choke topside. This is due to the long distance between the choke and the bit, which translates into a time delay in the same order of magnitude as typical wave and heave periods. A downhole choke combined with continuous circulation is one of the potential solutions.Surge and swab during drillpipe connections can result in a loss or an influx and should be considered in the well planning phase when mud weight, section lengths, etc. are selected.

Optimized ANN model for predicting rock mass quality ahead of tunnel face using measure-while-drilling data

Rock mass quality assessment has a vital influence on the excavation of tunnels and caverns in rock mass. For this purpose, extensive field studies, including records of measure-while-drilling data and rock mass quality scores (RQS) from the observation reports of tunnel faces, have been conducted. In order to predict RQS, three optimized artificial neural network (ANN) models based on genetic algorithm (GA), particle swarm optimization (PSO), and imperialist competition algorithm (ICA) were developed. Six parameters of measure-while-drilling (MWD) data and their corresponding RQS constituted 1270 datasets, which were set as input and output of ANN, respectively. The traditional multiple linear regression (MLR), multiple nonlinear regression (MNR) statistical model, and ANN model were developed as comparative models. Comparison results reveal that PSO-ANN and ICA-ANN models are capable of predicting RQS with higher reliability than the MLR, MNR, ANN, and GA-ANN models. Results indicate that PSO-ANN and ICA-ANN models can be used to predict RQS; however, the PSO-ANN model has better performance.

Research on Improving Accuracy of MWD Based on Support Vector Classifier and K-Proximity Method

With the development of horizontal Wells and extended reach Wells in the field of oil and gas exploitation, it is of great significance to the development of MWD which can measure the drilling trajectory in real time. Therefore, in recent years, Measurement while drilling (MWD) has been widely recognized and rapidly developed in the field of precise target drilling. Accelerometers and fluxgates are related to well trajectory measurement in the MWD. The external environment and the processing and installation error of the sensor lead to some errors in the measured value. Deviation caused by environmental interference and installation error leads to the low control precision of drilling tool attitude. In view of the shortcomings of the current calibration methods and the time-consuming and complicated operation of the traditional tri-axis orthogonal inclinometer calibration, this paper proposes the attitude error calibration method of the MWD based on the support vector classifier and the K-proximity method. First, a neural network model is established based on the measured calibration results and the measurements errors. Then, the K-proximity method is used to further classify the drill tool attitude data, and a neural network model combining the K-proximity method is constructed. Secondly, the software and hardware experimental platform for on-line calibration of the slant meter while drilling is built by using the calibration frame and the geomagnetic sensor. Finally, the experimental results showed that the mean deviation of well inclination angle and tool face angle is controlled within ±0.2°, and the mean deviation of azimuth is controlled within ±0.5°, which verified that the algorithm can increase accurate of drilling tool attitude.

Theoretical Channel Model and Characteristics Analysis of EM-MWD in the Underground Coal Mine

The measurement while drilling (MWD) system in underground coal mine currently uses wire for signal transmission. However, it has shortcomings such as strict technical requirements for cable drill pipe processing and high cost of use. Electromagnetic measurement while drilling (EM-MWD) is a new technology has a high rate of information transmission with fast measurement speed and low cost and is not affected by the drilling media. Hence, it is necessary to investigate a reliable electromagnetic transmission channel which is suitable for underground coal mine. This study selects the excitation method through comparison and conducts theoretical research on this basis. Based on the classical electromagnetic theory, the equivalent transmission line method is adopted to calculate and analyze the channel characteristics, while the electrical properties of the coal seam and the surrounding rock are considered. The results demonstrate that the formation resistivity, drill pipe resistivity, and the emission frequency are the main factors affecting signal transmission. On the basis of the uniform equivalent transmission line model, the theoretical model is established by combining the segmented uniform transmission line theory. The layered equivalent transmission line model can be better used to evaluate the regional applicability of the EM-MWD system.

Research on Mud Pulse MWD Device for Mines

As the core accoutrement of directional drilling construction, the measurement while drilling (MWD) device can be divided into three types due to the different data transmission methods: wired, mud pulse and electromagnetic wave. This paper used the mud pulse method to develop a mud pulse MWD device for mines, and the working principle of the mud pulse signal transmission, the signal encoding method and the structure of the device were described. Experimental research showed that the mud pulse wireless MWD device had the advantages of long transmission distance and strong working stability. At the same time, the device was not restricted by the drill pipe during operation, which could be combined with sliding orientation and rotary feed, and had great promotion and application value.

Dynamic responses of a fluidic hammer with hydraulic-damping-device

Utilization of the rotary–percussive drilling tools can help to reduce friction along the drill string and improve drilling performance in hard rock formations. However, intrinsic vibration and shock loads may severely damage the bottom hole assembly (BHA) and measurement while drilling (MWD). This paper investigates the dynamic response of fluidic hammer with hydraulic-damping-device, a rotary–percussive drilling tool which can provide forward percussion while eliminating harmful backward impact collisions. Descriptive statistical methods are introduced to accurately estimate the required damping length (RDL) and maximize the actual stroke length. In order to evaluate the influence of hydraulic-damping-device on vibration elimination, this paper discusses the effect of principal operating and design parameters on the dynamic responses of the fluidic hammer. In particular, a parametric model is fitted, in which the probability that backward impact collision is sufficiently eliminated is restricted to follow the probability density function. According to this function, when the damping stroke equals 10 mm, it is better than 99.999% to fully eliminate the possibility of backward collision. The improved understanding of the dynamic responses and some optimization proposals of a fluidic hammer will lead to the system reliability enhancement and cost optimization of the drilling engineering by eliminating the harmful shock and reducing shock-related tool failures.

Noise cancellation for continuous wave mud pulse telemetry based on empirical mode decomposition and particle swarm optimization

Mud pulse telemetry (MPT) is the most widely implemented communication method in measurement while drilling (MWD) systems. However, the signal-to-noise ratio of received signals on surface in MPT systems is relatively low because of the various background noises the signals have been exposed to during the drilling process. Due to the reciprocating action of the mud pump, pump noise could be the most detrimental factor to the mud pulse signal. Hence, pump noise cancellation plays an important role in the mud pulse telemetry. This paper presents a novel approach for pump noise cancellation by making use of the optimal signal reconstruction based on the combination of the empirical mode decomposition (EMD) and the particle swarm optimization (PSO). The proposed method comprises the pump noise recovery and the pump noise subtraction. The pump noise recovery is implemented by EMD decomposing the pump noise into a series of subcomponents and by PSO searching for the optimal weights to reconstruct the pump noise. Then the pump noise is subtracted from the received signal. To validate the effectiveness of the proposed method, both simulation tests and field experiment were carried out. The noise cancellation results of the simulation tests showed a good agreement with the modulated signal. In the experiment, the downhole information data was successfully demodulated after the implementation of the EMD-PSO based noise cancellation method. Meanwhile, the proposed method could achieve a lower bit error rate than the pump noise filter method. The findings of this study indicate that the optimal signal reconstruction has a promising application in MPT systems in the future.