A Method for Forecasting Failures of Sucker Rod-pumped Wells

An exact forecast of the failures of a sucker rod-pumped well in a production area means much for an oilfield’s operation budget, operational arrangement and production plan. In this paper, according to the characteristics of failed sucker rod-pumped well randomness and strong outburst, with the gray GM (1,1) forecast model and the Markov forecast model combined, gray GM (1,1) forecast model is utilized to handle the primary data of an oilfield, and Markov forecast model is utilized to calculate the state transfer probability of forecast value. Then, the gray Markov forecast model considering the influence of randomness factors is formed. Field results prove that the calculation precision of this method is higher and the practicability is greater.

Using the curve moment and the PSO-SVM method to diagnose downhole conditions of a sucker rod pumping unit

Downhole working conditions of sucker rod pumping wells are automatically identified on a computer from the analysis of dynamometer cards. In this process, extraction of feature parameters and pattern classification are two key steps. The dynamometer card is firstly divided into four parts which include different production information according to the ＂four point method＂ used in actual oilfield production, and then the moment invariants for pattern recognition are extracted. An improved support vector machine （SVM） method is used for pattern classification whose error penalty parameter C and kernel function parameter g are optimally chosen by the particle swarm optimization （PSO） algorithm. The simulation results show the method proposed in this paper has good classification results.

Fault diagnosis for down-hole conditions of sucker rod pumping systems based on the FBH-SC method

Dynamometer cards are commonly used to analyze down-hole working conditions of pumping systems in actual oil production. Nowadays, the traditional supervised learning methods heavily rely on the classification accuracy of the training samples. In order to reduce the errors of manual classification, an automatic clustering algorithm is proposed and applied to diagnose down-hole conditions of pumping systems. The spectral clustering （SC） is a new clustering algorithm, which is suitable for any data distribution. However, it is sensitive to initial cluster centers and scale parameters, and needs to predefine the cluster number. In order to overcome these shortcom- ings, we propose an automatic clustering algorithm, fast black hole-spectral clustering （FBH-SC）. The FBH algo- rithm is used to replace the K-mean method in SC, and a CritC index function is used as the target function to automatically choose the best scale parameter and clus- tering number in the clustering process. Different simulation experiments were designed to define the relationship among scale parameter, clustering number, CritC index value, and clustering accuracy. Finally, an example is given to validate the effectiveness of the proposed algorithm.

Approach to the Design Calculation of Sucker Rod Pumping Systems in Coalbed Methane Wells

The existing design of the pumping systems mainly focuses on the approximate computational formulae and procedures,which are developed based on the analytic approaches of conventional oil/gas fields.The calculation of polished rod loads usually just concerns about the static and inertial loads.And the computation of gearbox torque generally uses empirical formulae and correction factors.The above modeling procedures,if applied to the coalbed methane（CBM） wells,can not give the desired accuracy of the system design and its pertinent analysis.In this paper,based on the kinematic and dynamic analysis of the pumping system,the kinematic relation of polished rod is analyzed,and the variation of the total loads of polished rod is developed with the limits of CBM well conditions along the string.The gearbox torque calculation model is established by combining the counterbalance effect with the calculated dynamometer cards and torque factors.The application characteristics of this model are demonstrated by the example of ZH002-4 well in Qinshui basin.The interpretations of results show that the cranks of beam units should rotate in a counter clockwise direction viewed with the wellhead to the right.Compared with oil？gas fields,the dynamic and friction to polished rod load ratios are relatively high and the computation of polished rod loads should involve the static and inertial loads,as well as vibration and friction loads.And the dynamic load ratio decreases rapidly during the production.Besides,the total deformation of the string is small in CBM wells.As for balanced operation,the gearbox torque load usually has two approximately equal peaks and the magnitudes of instantaneous torque are just within 50% of unbalanced gearbox loadings.The proposed research improves efficiency of the pumping system,loads the pumping unit more uniformly,and provides the reasonable basis for selecting the units.

Effect of Produced Fluid on the Wear Behavior of Grade D Sucker Rod and N80 Type Tubing

Inuestigated wear tests of grade D sucker rod and N80 tubing with a produced liquid are the effect of the water cut of produced liquid on the wear rate and the wear coefficient of the friction pair. And presented here is a comparison of tribological performance of tubing/sucker rod with sprayed tubing/sucker rod and tubing/sprayed sucker rod. The results show that one of the main reasons for wear failure between the sucker rod and the tubing is a high water cut of the produced liquid. The wear rate increases greatly when the water cut ranges from 70% to 85%, and increases gradually when the water cut is less than 70% or more than 85%. The higher the water cut is, the greater the wear rate will be. SEM (scanning electron microscope) micrographs show that the worn surface of the tubing is smoother, with shallow grooves, when the water cut is 55%; when the water cut is 95%, there are broader and deeper grooves on the worn surface. The results also show that the wear rate of the sprayed wear-resistant coating of sucker rod/tubing is less than that of the unsprayed sucker rod/tubing.

Adaptive fault diagnosis of sucker rod pump systems based on optimal perceptron and simulation data

A highly precise and timely diagnosis technology can help effectively monitor and adjust the sucker rod production system(SRPS)used in oil wells to ensure a safe and efficient production.The current diagnosis method is pattern recognition of a dynamometer card(DC)based on feature extraction and perceptron.The premise of this method is that the training and target data have the same distribution.However,the training data are collected from a field SRPS with different system parameters designed to adapt to production conditions,which may significantly affect the diagnostic accuracy.To address this issue,in this study,an improved model of the sucker rod string(SRS)is derived by adding faultparameter dimensions,with which DCs under 16 working conditions could be generated.Subsequently an adaptive diagnosis method is proposed by taking simulated DCs generated near the working point of the target SRPS as training data.Meanwhile,to further improve the accuracy of the proposed method,the DC features are improved by relative normalization and using additional features of the DC position to increase the distance between different types of samples.The parameters of the perceptron are optimized to promote its discriminability.Finally,the accuracy and real-time performance of the proposed adaptive diagnosis method are validated using field data.

Multiple fault diagnosis of down-hole conditions of sucker-rod pumping wells based on Freeman chain code and DCA

It is important to achieve continuous, stable and efficient pumping well operation in actual oilfield operation. Down-hole pumping well working conditions can be monitored in real-time and a reasonable production scheme can be designed when computer diagnosis is used. However, it is difficult to make a comprehensive analysis to supply efficient technical guidance for operation of the pumping well with multiple faults of down-hole conditions, which cannot be effectively dealt with by the common methods. To solve this problem, a method based on designated component analysis （DCA） is used in this paper. Freeman chain code is used to represent the down-hole dynamometer card whose important characteristics are extracted to construct a designated mode set. A control chart is used as a basis for fault detection. The upper and lower control lines on the control chart are determined from standard samples in normal working conditions. In an incompletely orthogonal mode, the designated mode set could be divided into some subsets in which the modes are completely orthogonal. The observed data is projected into each designated mode to realize fault detection according to the upper and lower control lines. The examples show that the proposed method can effectively diagnose multiple faults of down-hole conditions.

Online Magnetic Flux Leakage Detection System for Sucker Rod Defects Based on LabVIEW Programming

Aiming at the detection of the sucker rod defects,a real-time detection system is designed using the non-destructive testing technology of magnetic flux leakage(MFL).An MFL measurement system consists of many parts,and this study focuses on the signal acquisition and processing system.First of all,this paper introduces the hardware part of the acquisition system in detail,including the selection of the Hall-effect sensor,the design of the signal conditioning circuit,and the working process of the single chip computer(SCM)control serial port.Based on LabVIEW,a graphical programming software,the software part of the acquisition system is written,including serial port parameter configuration,detection signal recognition,original signal filtering,real-time display,data storage and playback.Finally,an experimental platform for the MFL detection is set up,and the MFL measurement is carried out on the transverse and longitudinal defects of the sucker rod surface.The experimental result shows that the designed acquisition and processing system has good detection performance,simple design and high flexibility.

Novel sucker rod pumping system based on linear motor technology

Obtaining petroleum at the cost of electrical energy is a common problem in almost all oil fields, and it is mainly caused by low duty radio of induction motor used in beam pumping units. Traditional beam-pumping units have many intrinsic disadvantages such as low efficiency, complex transmission devices, poor flexibility, tremendous volume and weight in long stroke, etc.Therefore, a novel direct driven linear electromagnetic pumping unit (EMPU) has been developed by combining oil extraction technology with linear motor technology. The thrust of EMPU matches the changing of suspension center load to improve the system efficiency and cut down the consumption of energy. Based on previous experience, a small-scale prototype was developed and a simulation was conducted with it. Both theoretical analyses and experimental study showed that the problems exiting in beam pumping units can be solved with EMPU system, and this is a new method which can be used to solve high energy waste in oil fields.

Mechanical characteristic and failure mechanism of joint with composite sucker rod

Composite sucker rods are widely used in oil fields because of light weight,high strength,and corrosion resistance.Bonded technology becomes the primary connection method of composites.However,the joints with composite sucker rods are prone to debone and fracture.The connected characteristics are less considered,so the failure mechanism of the joint is still unclear.Based on the cohesive zone model(CZM)and the Johnson-Cook constitutive model,a novel full-scale numerical model of the joint with composite sucker rod was established,and verified by pull-out experiments.The mechanical properties and slip characteristics of the joint were studied,and the damaged procession of the joint was explored.The results showed that:a)the numerical model was in good agreement with the experimental results,and the error is within 5%;b)the von Mises stress,shear stress,and interface stress distributed symmetrically along the circumferential path increased gradually from the fixed end to the loading end;c)the first-bonded interface near the loading end was damaged at first,followed by debonding of the second-bonded interface,leading to the complete shear fracture of the epoxy,and resulted in the debonding of the joint with composite sucker rod,which can provide a theoretical basis for the structural design and optimization of the joint.

The real-time dynamic liquid level calculation method of the sucker rod well based on multi-view features fusion

In the production of the sucker rod well, the dynamic liquid level is important for the production efficiency and safety in the lifting process. It is influenced by multi-source data which need to be combined for the dynamic liquid level real-time calculation. In this paper, the multi-source data are regarded as the different views including the load of the sucker rod and liquid in the wellbore, the image of the dynamometer card and production dynamics parameters. These views can be fused by the multi-branch neural network with special fusion layer. With this method, the features of different views can be extracted by considering the difference of the modality and physical meaning between them. Then, the extraction results which are selected by multinomial sampling can be the input of the fusion layer.During the fusion process, the availability under different views determines whether the views are fused in the fusion layer or not. In this way, not only the correlation between the views can be considered, but also the missing data can be processed automatically. The results have shown that the load and production features fusion(the method proposed in this paper) performs best with the lowest mean absolute error(MAE) 39.63 m, followed by the features concatenation with MAE 42.47 m. They both performed better than only a single view and the lower MAE of the features fusion indicates that its generalization ability is stronger. In contrast, the image feature as a single view contributes little to the accuracy improvement after fused with other views with the highest MAE. When there is data missing in some view, compared with the features concatenation, the multi-view features fusion will not result in the unavailability of a large number of samples. When the missing rate is 10%, 30%, 50% and 80%, the method proposed in this paper can reduce MAE by 5.8, 7, 9.3 and 20.3 m respectively. In general, the multi-view features fusion method proposed in this paper can improve the accuracy obviously and process the missing data effectively, which helps provide technical support for real-time monitoring of the dynamic liquid level in oil fields.

多指标排序优选抽油井工作参数软件研发

针对原有抽油机井工作参数软件与采油生产实际结合不够紧密、使用不方便的问题,经过技术攻关研发出多指标排序优选抽油井工作参数软件。首先确立以产液量指标为主、井下效率指标为辅、安全指标可靠的优选抽油井工作参数的设计思路,其次是建立以产液量计算为核心的系统算法。应用工程计算和经验公式相结合的方法,通过抽油泵沉没压力使供液量与排液量建立联系,将与供液量接近的排液量作为产液量,进而计算出井下效率、悬点载荷和抽油杆负载率。对所有“泵径、冲程、冲次”组合的优势产液量和优势井下效率及其对应的指标和下泵深度以列表方式输出,对所有指标与井下效率的关系以曲线方式输出,经过排序对比即可挑选出各项指标均占优势且稳定可靠的抽油井工作参数组合,实现抽油井工作参数优化设计的目标。该软件自2017年应用以来年均指导调参130井次,平均单井增产原油63.54 t,提高井下效率3.2%,取得了显著的应用效果。

定向井抽油杆柱纵横扭耦合振动仿真研究

抽油杆柱是由接箍与抽油杆通过螺纹连接组成的细长杆柱。对抽油杆柱动力学行为的研究是预防抽油杆柱失效破坏,降低油井运行成本的基础。针对抽油杆柱的纵横扭耦合振动,提出杆管摩擦力产生的绕轴扭矩是扭转振动的激励这一观点。考虑摩擦力对杆柱纵横扭耦合振动的影响,建立了具有初弯曲的定向井抽油杆柱在顶端位移激励、底端载荷激励、弯曲井眼轨道激励与油管约束条件下的纵横扭耦合振动仿真模型。采用四阶龙格-库塔法实现了对仿真模型的求解和对杆柱动力学行为的仿真模拟。仿真结果表明:杆柱的纵横扭耦合振动对杆柱纵向、横向振动仿真结果均有影响,相对来说对纵向振动的影响并不明显;油井造斜段的杆管接触力大,杆柱受压段的杆管碰撞严重,因此油井的造斜段与杆柱的受压段为杆管偏磨的危险点;正常预紧情况下,杆柱的扭转振动不足以导致抽油杆柱脱扣,但当接箍螺纹预紧力降至杆柱的最大扭矩以下后,扭转振动即可能导致抽油杆柱脱扣。

抽油杆偏磨机理及防偏磨技术研究现状

在石油开采过程中,有杆泵是目前应用最广泛的人工举升方法之一。有杆采油系统在石油和天然气行业中被认为是一项成熟的技术,具有易于应用、使用成本低等优势,在世界范围内应用普遍。但在实际运行过程中,抽油杆与油管之间的偏磨问题较为严重,由此带来的经济损失较大。通过对抽油杆产生偏磨的原因进行分析,总结了五大类最新的防偏磨技术,并提出了现有技术的发展方向,以期对生产实践起到一定的指导作用。

等径空心防偏磨抽油杆使用性能分析

针对常规抽油杆偏磨断脱事故频发,扶正器加剧油管磨损等问题,定制了等径空心防偏磨抽油杆。使用数值模拟方法对等径空心防偏磨抽油杆的使用性能进行分析。建立等径空心防偏磨抽油杆上下冲程的受力分析模型,基于数值模拟方法得到等径空心防偏磨抽油杆在上下冲程中的受力变形情况,评定在新疆油田井筒环境中的使用性能。分析结果表明,在上下冲程中,等径空心防偏磨抽油杆与油管的接触分布都较为平均,抽油杆与油管之间的偏磨程度大大降低,进而显著降低抽油杆接箍断脱的风险。

抽油杆断裂原因

某油田抽油杆频繁发生断裂现象。采用宏观观察、化学成分分析、力学性能测试、金相检验、扫描电镜及能谱分析等方法分析了抽油杆断裂的原因。结果表明:该抽油杆的断裂性质为腐蚀疲劳断裂;采用深抽工艺后,抽油杆承受较大的拉伸载荷,增大了抽油杆的平均应力,缩短了抽油杆的疲劳寿命;油井中含有硫化氢,对抽油杆外壁产生腐蚀作用,导致抽油杆外壁产生腐蚀坑,腐蚀坑底部应力集中程度较大,在交变载荷作用下,腐蚀坑底部产生微裂纹,微裂纹不断扩展,最终导致抽油杆断裂。

抽油机光杆安装质量问题及对策研究

针对采油现场常见的游梁式抽油机光杆杆断失效模式,对光杆理论寿命与实际寿命进行了分析,就安装质量问题依据SY/T5643-2010《抽油杆维护和使用推荐作法》进行了阐述、分析,开展了光杆方卡子预紧力与载荷试验。现场实践预紧力与载荷试验证明了SY/T5643-2010《抽油杆维护和使用推荐作法》的正确性,针对光杆卡子预紧力缺失的情况,提出了指导性数据;针对现场安装质量提出了改进措施及建议。

抽油杆疲劳性能试验影响因素分析

随着各大油田进入开发中后期,抽油杆失效事故不断发生,不仅存在安全隐患,还严重影响油井正常运转,大幅提升采油成本。抽油杆失效的主要形式为疲劳断裂或腐蚀疲劳断裂。从试验机的夹持装置、试验频率、试样样式、试样表面状态以及试验机夹具同轴度5个方面,对抽油杆疲劳性能试验的影响因素进行分析。研制出三瓣式夹具和哑铃型试样,能有效避免应力集中的问题,大幅提高试验成功率。通过试验验证,证明了三瓣式夹具以及哑铃型试样的可行性,为准确高效检测抽油杆疲劳性能以及提高产品质量奠定基础。

H级抽油杆许用应力计算及疲劳寿命预测方法

为了有效使用H级抽油杆,对其许用应力计算方法和疲劳寿命预测方法进行了研究。在对H级抽油杆进行室内拉伸试验的基础上,计算了其抗拉强度与屈服强度的比值,根据该比值将H级抽油杆API最大许用应力计算系数由0.562 5修改为0.716 3;拟合建立了H级抽油杆的应力-疲劳曲线,折算了H级抽油杆在应力比为0.1条件下的极限疲劳应力;通过H级抽油杆在不同介质中和不同冲次下的疲劳测试,获得了含水率和冲次与抽油杆寿命的关系。研究的H级抽油杆许用应力计算及疲劳寿命预测方法,在长庆油田杏南作业区10口井进行了应用,结果表明,利用该方法对H级抽油杆进行优化设计可以改善其受力条件,充分发挥H级抽油杆的性能,使其满足现场生产对杆柱应力、寿命的需求。