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Collecting multi-channel sensory signals is a feasible way to enhance performance in the diagnosis of mechanical equipment. In this article, a deep learning method combined with feature fusion on multi-channel sensory signals is proposed. First, a deep neural network (DNN) made up of auto-encoders is adopted to adaptively learn representative features from sensory signal and approximate non-linear relation between symptoms and fault modes. Then, Locality Preserving Projection (LPP) is utilized in the fusion of features extracted from multi-channel sensory signals. Finally, a novel diagnostic model based on multiple DNNs (MDNNs) and softmax is constructed with the input of fused deep features. The proposed method is verified in intelligent failure recognition for automobile final drive to evaluate its performance. A set of contrastive analyses of several intelligent models based on the Back-Propagation Neural Network (BPNN), Support Vector Machine (SVM) and the proposed deep architecture with single sensory signal and multi-channel sensory signals is implemented. The proposed deep architecture of feature extraction and feature fusion on multi-channel sensory signals can effectively recognize the fault patterns of final drive with the best diagnostic accuracy of 95.84%. The results confirm that the proposed method is more robust and effective than other comparative methods in the contrastive experiments.

Coiled tubing (CT) has been widely used for oil and gas exploitation, however corrosion of CT under high pressure and high temperature (HPHT) environment was often reported, also corrosion induced failures of CT welds were often observed to occur during service. Corrosion related behaviors of CT welds are not clear. Therefore, a study of the corrosion resistance of CT welds under HPHT environment is carried out. In order to efficiently evaluate the corrosion resistance of welds, some test samples were obtained by linear cutting out of a CT110 in service on the site. The water samples from gas field were used as the test reagent to simulate the actual corrosive medium. Based on the results of weight loss test under HPHT corrosive environment and tensile test under room conditions, the corrosion sensitivities of the welding seam and base material under various temperatures and partial pressures of CO2 as well as the mechanical properties of the corroded CT were compared and evaluated quantitatively, the corrosion morphologies and material products of the test samples were analyzed by scanning electron microscope (SEM). The test results showed that the corrosion rates of the welding seam in a HPHT caldron were 1.7, 2.0 and 1.2 times of the base metal’s when the total pressure is 4MPa, and the temperature is 30°C, 60°C and 90°C, respectively. The corrosion rates of the welding seam is 2.0, 2.1 and 2.0 times of the base metal’s when the partial pressure of CO2 is 0.1MPa, 0.2MPa and 0.3MPa, respectively. The yield strength of the weld seam after corrosion test was found to be reduced by 4.8% (the yield strength of the base metal was reduced by 4.0%) and its tensile strength was reduced by 8.2% (the base metal was reduced by 7.1%). This indicates that CT weld seam is more susceptible to corrosion than CT base material under service condition.

Impact load caused by adjacent heavy tamping construction has a significant effect on mechanical properties of the buried pipeline. Based on nonlinearly finite element method, a hammer-pipeline-soil coupling model was established and the process of heavy tamping construction was simulated. Not only the effects of the heavy tamping construction parameters but also the effects of the pipeline parameters on mechanical properties of the buried pipeline under eccentric impact were discussed. In addition, the effects of the eccentricity between hammer and buried pipeline were also taken into consideration. The results show that the impact force which buried pipeline bears decreases with the time during heavy tamping construction. And the impact force increases with the increasing of hammer height and tamping velocity, but decreases with the increasing of eccentricity, radius-thickness ratio, and buried depth. High stress area and equivalent plastic strain which appear at the left top half of the buried pipeline under eccentric impact increase with the decrease of eccentricity, inner pressure, and buried depth while they increase as hammer height, tamping velocity, and radius-thickness ratio increase.

Casings represent a very high proportion in OCTG (Oil Country Tubular Goods) and also influence the productive life of the wells. Studying the collapse strength of defective casing for steam injection wells can prevent casing collapse failure in advance, as well as improve life of defective casing and increase well production. Based on finite element analysis, the effect of pit shape, pit depth, pit circumferential spread, number of pit and circumferential spacing of pit on collapse strength is conducted, through which pit depth and pit circumferential spread are proven as the main controlling factors which affect the collapse strength of defective casing. A formula to calculate collapse strength of defective casing is obtained for steam injection wells by including the effect of temperature on the degradation of yield strength and compression stress function of a cylinder in the existing collapse strength formula. The formula is amended with results from numerical calculation and proven to be in good agreement with experimental data of collapse strength for defective casing. Therefore collapse strength can be accurately predicted using the proposed collapse strength formula for thermal recovery steam injection wells.

Erosion wear at the key point of a drill string is very severe in gas drilling. The investigation shows that failure of drill string is very serious in gas drilling. The probability of failure of the drill pipe and the drill collar is the highest in all the drill string, and the near placement of pin and box is often damaged. According to the investigation of drill string failure and erosion theory, the erosion model of drill string is established. The erosion rate at the key point of a drill string is solved using the Grant and Tabakoff formula. Different factors, such as gas injection volume, rate of penetration (ROP), cuttings' diameter, cuttings' shape factor, cuttings' number, and temperature of the annulus, are considered. The result shows that the erosion rate at the key point is more severe than that of other locations on the drill pipe. Because of higher peak stress for a drill string with eroded wear, there is a more serious effect on the residual strength of a drill string with eroded wear. Crack forms easily, due to severe erosive wear and deeper pits. Also, fracture failure of a drill string is caused by larger axial load and torque. In this paper, analysis of such influencing parameters as gas injection volume, ROP, cuttings' particle size, cuttings' shape factor, cuttings number and temperature of the annulus is conducted, among which gas injection volume, ROP and cuttings number are proven as the main controlling factors that affect the erosion wear at the key point of a drill pipe.

The service life of the casing is one of the technical problems affecting heavy oil recovery efficiency. Plastic limit analysis of the defective casing can effectively prevent casing failure and improve the comprehensive service life in high temperature and pressure thermal recovery wells. In this paper, the analysis of such influencing parameters as defect shape, defect depth, defect circumferential spread, defect number and defect distribution are conducted respectively and it is proven that defect depth and circumferential spread are the main controlling factor to the plastic limit load of defective casing. Furthermore, plastic limit load mathematical model of defective casing caused by the combination of high temperature and high steam injection pressure is presented through the classical formula of plastic limit load for ideal circular tube. The model is then amended by the numerical calculation results and proven to be in good agreement with the data gained from the defective casing blasting failure experiment. Hence, the presented mathematical model can accurately predict the plastic limit load of defective casing in thermal recovery wells.

Erosion of drill pipe is very severe in gas drilling. According to the erosion theory and actual condition, the erosion of drill pipe is investigated using laboratory experiment and CFD simulation technique. Different factors of gas drilling, such as drill pipe centralization, eccentricity of drill pipe, wellbore enlargement, gas injection volume, rate of penetration (ROP) and rotational speed of drill pipe, are considered. The results show that the local erosion rate of joint is more severe than that of the drill pipe body, and local erosion rate of drill pipe in horizontal well is larger than that one in vertical well. With the increase of the eccentricity of drill pipe, wellbore enlargement and ROP, the local peak erosion rate of drill pipe would increase. The gas injection volume and the rotational speed of drill pipe have very little on drill pipe erosion. The simulation results are in good agreement with experimental data.

Field experience has shown that inefficient transport of cuttings is a key factor for excessive torque & drag during gas drilling of horizontal well. Therefor, the focus on the transport of cuttings or the hole cleaning operation during gas drilling is essential. The cuttings tend to deposit themselves due to gravity's action, so forming a bed in the annular space between drill string and casing. If the cuttings bed isn't cleaned in time, it may cause the sticking accident, fluid flow interruption, drill string and casing erosion, finally it leads to the economic loss. Transport mechanism of cuttings during gas drilling has been studied based on gas and solid two-phase flow dynamics theory in different annular section of horizontal wellbore. The involved annular sections includes normal well, eccentric annular section formed by the drill string lying on the underground level of casing, diameter enlargement annular section. This paper presents a new tool for improving the cuttings transport efficiency during gas drilling. This tool is named cuttings falling-prevent joint (CFPJ) which has a split-flow nozzle. The structural parameters of split-flow nozzle, such as opening gradient, opening azimuth and nozzle linetype, which influence the CFPJ's sweeping and carrying capability, were studied using computational fluid dynamics technology. The study shows that changing CFPJ's structure parameters can adjust the radial, tangential and axial sweeping & carrying capability, and finally the recommended CFPJs can solve cuttings' falling problem in gas drilling horizontal well.

This paper discusses a new double-effect protector (DEP). The serious wear of casing and drill pipe brings huge economic losses in drilling. On the basis of the traditional technology, a new DEP is designed, to reduce the wear of casing and drill pipe. The DEP's volume, which can be worn, increases 14% than the traditional protector's. As design and optimization by CAE software, the maximum stress, which is caused by the contacting collision&friction, is greatly lowered. As design and optimization by using CFD software, the fluid pressure loss of the DEP's annulus space, is decreased 17.5% than the traditional protector's. A new composite has been synthesized firstly, and has excellent mechanical performance, for example, abrasion resistant performance at high temperature. By using the Nonlinear Drillstring System Dynamics Simulation and Torque & Drag forecasting software, the study has been completed, which is about installed number and position of DEPs, for reducing wear on casing and friction on drill string in the typical deep well, and then the scheme, that the DEP is reasonably mounted, is applied while drilling. This document describes the first application of the DEP in X301 on Southwest oilfield, Sichuan, China. From the practice, the DEP's average working life has been enhanced 200 hours. Because of the use of the DEP, the wear of casing and drill pipe is effectively reduced, the quality of wellbore is improved, and the drilling period is shortened. The DEP and matching technology can provide effective technical support for deep well drilling and post-mining.