The viscous resistance caused by the relative motion of plunger and pump barrel is an important factor in the dynamic analysis of the drainage and production mechanism during coalbed methane exploitation. Existing studies mostly focus on deep well (1000–3000 m) large-displacement pump (usually 80–300 m 3 /d), and the interstitial medium is mainly crude oil. Regression fitting is mainly carried out based on empirical formula or experimental simulation method, without considering the characteristics of shallower coalbed gas well (400–800 m) small-displacement pump (<10 m 3 /d). The variation of the clearance between plunger and barrel and the variation of viscous resistance between plunger and barrel are not revealed. Based on the Navier-Stokes equation and Newton's internal friction law, a mathematical model of the annular viscous resistance between the plunger and the pump barrel is established, and an analytical method is used to describe the influence of stroke times, annular clearance, and differential pressure between the upper and lower plungers on the viscous resistance. The results show that the plunger stroke is directly proportional to the variation range of viscous resistance, and low stroke is beneficial to reduce the viscous resistance. The effect of differential pressure between upper and lower plunger of rod pump on viscous resistance of small displacement coalbed gas well is significantly greater than that of plunger running speed. The annular clearance is directly proportional to the differential pressure between the upper and lower parts of the plunger, the inertia force of the plunger, and the shear force of the moving fluid. The annular viscous resistance model between plunger and pump barrel is helpful to improve the calculation accuracy of suspending point load of coalbed gas well pumping unit, analyze the working condition of coalbed gas drainage gas production process, and provide basis for the optimization design of coalbed gas well rod pump clearance.

Targeting the problem of a small amount of fluid accumulation in deep coal seam gas (CSG) wells during flowing production stage, the evaporation drainage method is proposed to discharge the liquid accumulation. Based on the Dalton evaporation model and wind speed function, a calculation model of evaporation drainage was established for deep CSG wells, which was verified by laboratory experiments. Taking a CSG well in the western Ordos Basin as an example to analyze the evaporation drainage capacity, the influence of temperature, daily gas production, bottomhole flowing pressure (BHFP), formation gas water saturation on the evaporation drainage capacity was investigated. The results show that the maximum evaporation water production is 2,533.8 kg/d at a bottomhole temperature of 80°C and a gas production rate of 30 × 103 m3/d. It is found that the temperature and pressure have a marked influence on the evaporation drainage. By improving the gas production and bottomhole temperature, and reducing the BHFP can effectively promote the evaporation drainage capacity. The initial moisture content of CSG in the reservoir are inversely proportional to the evaporation drainage capacity. By adjusting the BHFP and daily gas production, the evaporation drainage capacity can match the liquid production rate of the formation. Evaporation drainage can effectively extend the flowing production time of deep CSG wells and reduce the costs of production.

To study the corrosion characteristics of high-strength sucker rods in high-salinity well fluids under alternating stresses, a single-factor stress corrosion test was designed. The slow strain rate tensile test (SSRT) was carried out for four kinds of high-strength sucker rods under different Cl− and HCO3− concentrations and with different service strengths, and the variable stress corrosion cracking susceptibility was analyzed. The results show that the elongation loss and absorbed work loss of the H-grade ultra-high-strength 4330 sucker rod after stress corrosion are greater than those of both the high-strength 4142 sucker rod and the high-strength 20CrMoA sucker rod. The elongation and absorbed work loss of the 30CrMoA and 20CrMoA sucker rods are less affected by the changes in Cl− and HCO3−. With the increase in use strength, the elongation and absorbed work loss of the high-strength sucker rod increase. The change in the surface of the sucker rod during the corrosion process is inconsistent with the actual elongation of the sucker rod and the absorbed work loss. It can be concluded that the stress corrosion cracking susceptibility of the sucker rod is not necessarily related to the tensile strength of the sucker rod. The 4330 sucker rod is not suitable for applications in wells with a high concentration of Cl−, but it is suitable for operation in alkaline conditions where corrosive media such as HCO3− and Cl− coexist. Under highly corrosive and highly mineralized conditions, the 30CrMoA sucker rod is less susceptible to stress corrosion. The stress corrosion cracking susceptibility of the 20CrMoA sucker rod is lower than that of the 4142 sucker rod. In high-salinity well fluids, the higher the use strength, the higher the stress corrosion cracking susceptibility of the high-strength sucker rod is. The test results for the weight-loss-based corrosion rate and plastic loss may contradict the determination of the corrosion susceptibility of the material under working conditions.

In coal seam gas (CSG) coproduction wells, due to the different production pressures of CSG production layer at different depths, the interlayer interference in wellbore seriously affects the gas production of a coproduction well. To effectively suppress the interlayer interference of the wellbore, a wellbore pressure distribution method for a two-layer coproduction well is proposed. Based on the analysis of the factors influencing the flow pressure distribution in the wellbore of two-layer coproduction wells, a method of coproduction flow pressure adjustment by regulating the wellhead pressure and the depth of the dynamic fluid level was established in this paper. The results show that wellhead pressure can directly affect the production pressure of two layers. The variation in layer 1 output mainly affects the pressure difference between the wellhead pressure and the pressure at the depth of layer 1, which has little effect on the pressure difference between layer 1 and 2. An increase in gas production from layer 2 would not only cause a pressure increase in layer 1, but also result in a reduction of the production pressure at layer 2. The maximum pressure gradient of the gas section is 0.14 MPa/100 m, and the pressure gradient of the gas–liquid section is 0.53–1.0 MPa/100 m.

The gas phase accelerating beyond the liquid phase caused by gas-liquid slippage cannot be ignored in short horizontal pipelines with undulation and inflow, and there is no method to calculate it. Therefore, a pressure drop prediction model for variable liquid holdup was developed in this paper. The theoretical model calculation results were validated using computational fluid dynamics. The effectiveness of the pressure drop prediction model has been demonstrated. The various pressure drop, liquid holdup, and development length laws were then examined. The findings indicate that: the pressure drop in the developed section of stratified flow is not only the friction pressure drop but also the acceleration pressure drop; the length of the stratified flow development section and pipeline pressure drop are more easily affected by the flowrate than the liquid holdup in the pipe inlet. Using the relevant data from coalbed methane horizontal wells as an example, the L/D of the development section is approximately 40-85 when the inlet flowrate is 0.8-1 m/s, and the inlet liquid holdup is 0.3-0.5. The pressure drop characteristics in the gas-liquid stratified flow development section are obviously different from those in the stable section. The development of a pressure drop prediction model for the stratified flow development section lays the theoretical groundwork for the investigation of gas-liquid two-phase flow in horizontal pipelines with short or undulating and inflow conditions.

Rod pumping on offshore platform provides a solution to low efficient extraction of offshore heavy oil and the safety of working platform is the prerequisite for the implementation of this new technology. In this paper, a coupling dynamics model of rod pumping system and the jacket platform is established, and the dynamic characteristics of the pumping unit excitation, rod pumping system, and jacket platform is studied. Based on the analysis of the multi-body dynamics model, the three frequencies (pumping unit excitation, rod pumping system, jacket platform) are far apart, so the dynamic effect of rod pumping on the platform can be analyzed according to static load. Based on the limit working state and the cumulative damage theory of the structure, the safety evaluation standard for the increased load of the jacket platform is established. Under the extreme marine environment once in 50 years, the safety factor of the main structure of the platform is greater than 4, and the overall safety factor is 3% lower than that before the rod pumping operation. Offshore rod pumping has less influence on the jacket platform from analysis, and which lays a theoretical and safety foundation for offshore oil pumping.

Cleaning out the pulverized coal deposited at the bottom of a coalbed methane (CBM) well is key to achieving continuous CBM drainage and prolonging the workover period. In this study, Fluent is used in conjunction with the standard k-ε model and the Eulerian-Eulerian model to simulate and analyse jet erosion of deposited pulverized coal particles. The depth and width of the stable erosion pit that is formed by jet-impacting deposited pulverized coal under different conditions are determined and provide a theoretical basis for the cleanout of pulverized coal in the bottom of a CBM well. In this paper, the three parameters of the jet target distance, nozzle diameter and nozzle outlet flow velocity are selected to perform an orthogonal simulation. The change trends in the depth and width of the scouring pit with time are determined. The results show that jet impacting of deposited pulverized coal can be categorised into four stages, periods of rapid growth, stability, jet swing and dynamic stability. A sensitivity analysis shows that the nozzle outlet flow velocity has the strongest influence on the depth of the scouring pit among the selected parameters. The depth of the jet impact pit can reach the maximum depth at t = 3 s, while the width of the impact pit can reach the maximum after t = 7 s. This can provide key design parameters for CBM well pulverized coal impacting operation. It is of great significance for capacity damage control during CBM well workover operation.

为了提高修井作业的自动化程度,提出了"立式接替作业、吊卡不流转"的新型修井作业工艺.立式翻转猫道是该工艺的核心部件.分析了立式翻转猫道的结构组成,建立了简化的力学模型,求解得到液压缸驱动力变化规律,并通过SolidWorks Motion软件分析获得仿真曲线.理论解析与仿真分析结果一致,验证了理论解析的正确性.利用Adams软件对立式翻转猫道进行动力学仿真,得到了翻转运动规律.为立式翻转猫道设计和翻转运动控制提供了理论依据.

增强型地热系统(EGS)多层合采技术中,由于各储层进井压力差异显著,同井筒多储层合采作业中依然会出现较大的层间干扰现象,导致热产量较低且无法精确控制.以构造低产量多层位换热层合采作业为基础,结合井下解码器技术设计三管线控制六层位的EGS优化合采模型,通过管线与译码组合设计实现控制工质人流面积与压力来解决层间干扰与产量优化问题.结果表明:利用解码器技术控制第二层滑套,工质总产量达到最大值为977 m3/d,相对于无解码器工况下提高5.2％,通过该技术控制层位流量进行工质合采,可保证工质采收产量,同时可以避免由于单层流量大造成层间干扰等问题.

Traditional minor repair machines have low control efficiency and low automation. In order to improve the brake control efficiency of the oilfield minor repair machine, the oilfield minor repair machine brake control system based on wireless sensor network is designed. The front-end controller collects the data of the oilfield repair machine through the wireless sensor and realizes the communication between the sensor nodes and the data interaction with the communication node through the field bus inside the equipment. The server uploads the processed data through the 3G network, and the server receives the data from the front-end controller and saves it in the database. The remote-control center accesses the server through the Internet to view the front-end controller data. The brake control module uses the expert fuzzy PID control method to control the speed, oil pressure, and operating status of the oilfield minor repair machine and sends the data to the front-end control center to complete the oilfield minor repair remote-control machine by sending control instructions. Experimental results show that the system can meet the braking control requirements of oilfield minor repair machines, the output can quickly track input changes, the braking control effect is good, the dynamic deviation of the machine can be reduced, and the braking control efficiency can be improved.

For an accurate force prediction of BOP shearing drill pipe is of critical importance in reliable sealing of the wellhead in an emergency, based on the shear motion equation, the Treace yield criterion, sliding line field and wedge mechanics theory are applied to establish the prediction model of shearing force. The theoretical force is consistent with the simulation force in the novel shear rams simulated shearing CT90 tube process before the peak force and shear experiment verified the reliability of the numerical simulation. Further, the influences of the structural parameters of the rams on the maximum shearing force are investigated by the orthogonal test and range analysis method. The study shows that the maximum shearing force with the increase of the V-shape angle increases first and then decreases, decreases with the increase of the blade angle and the edge chamfer angle, and increases linearly with the increase of the blade mouth thickness; the optimal V-shape angle is around 75 degrees.

现阶段深部煤层的开发过程中,煤层埋藏深、温度高,开发初期伴生地层水携高温废热开采至地面造成了部分能源浪费.基于资源综合利用角度上,为了使深部煤层开发中携带的废热用于热泵技术热源,提出废井改造地热井以降低钻井成本,以此设立深部煤层地热开发的工艺及热泵技术适用条件,从经济性及安全性两方面去分析深部煤层地热开发的可行性,给出了利用热泵系统进行煤层伴生废热开发的条件,最终建立出相关热泵系统模型,通过具体的示例环境参数进行计算.得出鄂尔多斯东缘神府地区某区块深部煤层伴生废热的单井制热量可达14.8 kW,热泵系统的制热性能系数(COP)可达到4.33～7.31,同时,煤层气井出口混合产物温降将近10℃.表明煤层伴生废热开发在提高了井上采收作业安全性的同时拥有较好的采热开发环境,扩展了废热可利用的经济性,提出一种深部煤层综合性开发的新型模式.

纤维增强复合材料柔性管取代传统的碳素钢管是海洋油气选管的趋势.以热塑性纤维缠绕复合材料柔性管(RTPs)为研究对象,将弹塑性材料的本构关系与应力连续条件相结合,建立拉伸作用下任意增强层数RTPs的力学模型.在此基础上分析缠绕角、纤维增强层纤维含量、泊松比等参数对RTPs拉伸性能的影响,并开展拉伸试验进行验证.结果表明:纤维增强层的缠绕角是影响RTPs拉伸性能的主要因素,缠绕角度的降低显著提高了RTPs的纵向强度,缠绕角度小于±45°时纵向强度较高;增加纤维含量不能有效提高RTPs在有效应变范围内的整体抗拉强度,泊松比对RTPs的整体拉伸性能影响并不明显,试验结果与数值模拟结果吻合较好.

分析大斜度井段排采泵的泵筒3层流场及其液流携粉运移特性对提高排采泵的可靠性和保障煤系地层水平井和斜井的连续稳定排采具有重要意义.综合大斜度、低流速和低黏度等多因素耦合的作用,并结合大斜度泵低速液流携粉运移实验测试与分析结果,提出适用于大斜度井段排采泵低速流场的静止层、移动层与悬浮层3层流动模型,推导大斜度泵腔3层流场连续性方程、动量方程和扩散方程,建立水粉两相流动数学模型并依据数值求解和井场测试结果揭示大斜度泵分层流场低速液流携粉运移特性,为水平井和斜井的大斜度泵选型设计及其系统优化以及冲程和冲次等排采制度和煤粉防控措施制订提供依据.结果 表明,大斜度井段泵腔三相流场中,增大泵倾斜角和煤粉密度会增加悬浮层和移动层的压力梯度,其中泵倾斜角的影响尤为显著,移动层压力梯度受煤粉密度的影响相对较弱;增大水粉两相流煤粉体积分数时,移动层沿程压力损失始终增加,而悬浮层压力损失先是不断增加而后逐渐减弱;增大水粉两相流黏度会增加悬浮层和移动层的压力梯度,而增大液流携粉运移流量时,移动层沿程压力损失持续减小,且流量越大时压力损失减小的趋势越明显,而悬浮层的压力损失先是显著减小而后趋向平缓;大斜度井段柱塞伴随杆柱运动的过程中,大斜度泵入口处的水粉两相流煤粉体积分数随柱塞速度不断减小而逐渐增大,且速度波动对3层流场中悬浮层煤粉沉积的影响要小于其他2层.

针对连续油管作业过程中卡瓦闸板防喷器对其夹持时造成的划伤、缩颈并降低其使用寿命的问题,提出连续油管与卡瓦闸板之间摩擦阻力系数对其相互作用的影响.建立了卡瓦闸板夹持连续油管三维物理模型,基于弹塑性力学理论建立起其计算模型,以Ramberg-Osgood弹塑性模型为基础,采用数值模拟的手段分析了多种工况下不同摩擦阻力系数对连续油管最大Mises应力、轴向位移以及接触应力的影响.研究表明:适当增加摩擦阻力系数有利于减小连续油管上的应力集中,也有助于限制轴向位移避免划伤连续油管和造成卡瓦闸板崩齿,同时提高卡瓦闸板对连续油管的夹持效果.最终以屈服强度为指标,结合连续油管轴向位移量趋势变化给出摩擦阻力系数安全区间为0.4～0.6,旨在为连续油管安全作业提供参考.

在分析煤层气井小修作业特征的基础上,提出了基于气胎环形防喷器的简易小修不压井作业装置设计方案,设计了核心部件气胎环形防喷器和不压井修井作业工艺,对防喷器的关键部件胶芯进行了有限元分析.现场实验表明,该装置可以满足煤层气井小修不压井作业的要求,这对于减少煤层气井因修井作业导致的储层污染,实现稳产、高产,有重要意义.

Coalbed methane (CBM) wells are shorter in continuous effective production time and are maintained frequently in the process of exploitation, so it is quite important to study the adaptability of CBM production equipment. In this paper, the analytical hierarchy process and fuzzy comprehensive evaluation (AHP+FCE) method was adopted to analyze the main factors controlling the productivity of low-efficiency CBM well from three aspects, i.e., resource condition, output condition and development condition. Then, adaptability of the production equipment was evaluated. It is indicated by virtue of the AHP+FCE method that the productivity of CBM well is mainly affected by five indicators, including gas content, burial depth, permeability, pulverized coal output and production rate. The CBM production system and process can be optimized specifically according to these five main indicators. The adaptability of the commonly used CBM production equipment (e.g. “rod-pumping” equipment, progressive cavity pump (PCP), electric submersible pump (ESP) and jet pump) is analyzed from the aspects of pulverized coal output and production rate. The analysis conclusions provide the technical reference for selecting the production equipment of low-efficiency CBM wells.

综合低沉没度和大斜度等因素耦合作用的影响,推导泵阀阀球伴随弹簧运动和造斜段泵腔液流连续流动的微分方程,建立水平井造斜段泵阀随液流运动的数学模型,依据数值求解结果揭示低流速液流中泵阀伴随弹簧的运动特性.结果表明:低沉没度和大斜度等因素耦合作用下,增大冲程和冲次会提高泵阀阀球伴随弹簧运动的升程、速度和加速度,且增大冲程更有利于提高低流速液流入泵流速并使液流顺利进泵,下冲程中弹簧力与阀球重力的双重作用使得固定阀球伴随弹簧快速复位,这有利于顺利开启游动阀球和提高泵效;低流速液流中水平井泵阀开启瞬间的阀球加速度会出现短暂的周期性波动并在短时间内迅速变小,易引起阀球"抖动"现象并降低泵效,且增大冲程和冲次将缩短阀球加速度趋向平缓的时间.

The design and optimization of the hydrocyclone inlet are an effective way to improve the overall performance of the hydrocyclone. In this paper, a set of novel hydrocyclones are designed by changing single to multiple inlets and narrowing the inlet width. The effects of inlet size and number of inlet on the particle separation efficiency, cut-size, the velocity field and pressure characteristics are discussed based on the same feed flow rates, with computational fluid dynamics (CFD) and experimental methods. The governing equations are coupled using the SIMPLE algorithm, while the Reynolds stress model (RSM) is employed for hydrocyclone turbulent model due to anisotropic nature. Particle trajectories are simulated with discrete phase model (DPM) due to low volume fraction of solid particles in the mixed fluid. The simulated particle separation efficiencies and cut-size approximately agree with experimental data. The results show that it is changing single inlet to multiple inlets and narrowing the inlet width that produce positive effects on the growing of tangential velocity of the hydrocyclone, increasing the centrifugal force of the discrete phase, reducing the resistance buoyance, prolonging the residence time of particles, which reduce the effective size of the cut size and make the total separation efficiency increase by 4.31%.

In the stable production stage CBM wells have the characteristics of high gas production and low water production. The use of continuous velocity tube technology for drainage can achieve better drainage results. Accurate and rapid prediction of the pressure drop of velocity pipe string production in a coalbed methane well has become the key to the operation and management of velocity pipe technology. This paper uses the nonlinear mapping and prediction capabilities of the BP neural network to build a three-layer BP neural network to construct a velocity pipe string production pressure drop prediction model. The model is based on gas production, water production, bottom hole pressure, pipe string diameter, and well depth. The five factors are input, and the pressure drop of the pipe string is the output, which can quickly and accurately realize the pressure drop analysis and calculation of the speed pipe drainage. The analysis shows that it is feasible to use the BP neural network to calculate and analyse the pressure drop of the velocity string of coalbed methane wells.