Influence of Incomplete Soil Plugs on Bearing Capacities of Bucket Foundations in Clay

Due to the uneven seabed and heaving of soil during pumping,incomplete soil plugs may occur during the installation of bucket foundations,and the impacts on the bearing capacities of bucket foundations need to be evaluated.In this paper,the contact ratio(the ratio of the top diameter of the soil plug to the diameter of the bucket)and the soil plug ratio(the ratio of the soil heave height to the skirt height)are defined to describe the shape and size of the incomplete soil plug.Then,finite element models are established to investigate the bearing capacities of bucket foundations with incomplete soil plugs and the influences of the contact ratios,and the soil plug ratios on the bearing capacities are analyzed.The results show that the vertical bearing capacity of bucket foundations in homogeneous soil continuously improves with the increase of the contact ratio.However,in normally consolidated soil,the vertical bearing capacity barely changes when the contact ratio is smaller than 0.75,while the bearing capacity suddenly increases when the contact ratio increases to 1 due to the change of failure mode.The contact ratio hardly affects the horizontal bearing capacity of bucket foundations.Moreover,the moment bearing capacity improves with the increase of the contact ratio for small aspect ratios,but hardly varies with increasing contact ratio for aspect ratios larger than 0.5.Consequently,the reduction coefficient method is proposed based on this analysis to calculate the bearing capacities of bucket foundations considering the influence of incomplete soil plugs.The comparison results show that the proposed reduction coefficient method can be used to evaluate the influences of incomplete soil plug on the bearing capacities of bucket foundations.

A Gel-Based Solidification Technology for Large Fracture Plugging

Fault fractures usually have large openings and considerable extension. Accordingly, cross-linked gel materials aregenerally considered more suitable plugging agents than water-based gels because the latter often undergo contaminationvia formation water, which prevents them from being effective over long times. Hence, in this study, aset of oil-based composite gels based on waste grease and epoxy resin has been developed. These materials havebeen observed to possess high compressive strength and resistance to the aforementioned contamination, therebyleading to notable increase in plugging success rate. The compressive strength, thickening time, and resistance toformation water pollution of these gels have been evaluated indoors. The results show that the compressivestrength of the gel can reach 11 MPa;additionally, the related gelation time can be controlled to be more than3 h, thereby providing a safe construction time;Invasion of formation water has a small effect on the gel strengthand does not shorten the thickening time. All considered performance indicators of the oil-based gel confirm itssuitability as a plugging agent for fault fractures.

Dynamic plugging regulating strategy of pipeline robot based on reinforcement learning

Pipeline isolation plugging robot (PIPR) is an important tool in pipeline maintenance operation. During the plugging process, the violent vibration will occur by the flow field, which can cause serious damage to the pipeline and PIPR. In this paper, we propose a dynamic regulating strategy to reduce the plugging-induced vibration by regulating the spoiler angle and plugging velocity. Firstly, the dynamic plugging simulation and experiment are performed to study the flow field changes during dynamic plugging. And the pressure difference is proposed to evaluate the degree of flow field vibration. Secondly, the mathematical models of pressure difference with plugging states and spoiler angles are established based on the extreme learning machine (ELM) optimized by improved sparrow search algorithm (ISSA). Finally, a modified Q-learning algorithm based on simulated annealing is applied to determine the optimal strategy for the spoiler angle and plugging velocity in real time. The results show that the proposed method can reduce the plugging-induced vibration by 19.9% and 32.7% on average, compared with single-regulating methods. This study can effectively ensure the stability of the plugging process.

Effect of mechanical vibration process parameters on the cement plugs properties for abandoned wells

A high-quality plug of the abandoned wellbore is considered an essential technical aspect of the oil and gas well abandonment technology system. This paper presents a method of active mechanical excitation to enhance the quality of wellbore plug barriers. An indoor simulation platform is developed, and the effects of different combinations of vibration frequency, amplitude and duration on the properties of the wellbore plug cement material are investigated. It is observed that the optimal combination of excitation parameters occurs at a vibration frequency of 15 Hz, a vibration time of 6 min, and a vibration amplitude of 3 mm. Compared with the condition without the vibration process, the cementing strength, compressive strength, and tensile strength of wellbore cement plug with the optimal mechanical vibration process could increase by 51%, 38% and 20%, respectively, while the porosity decreases by 5%. As determined by scanning electron microscopy of the set cement's microstructure, mechanical vibration effectively eliminates internal porosity and improves the set cement's density. The optimal excitation parameters obtained from the test can guide the design of the vibration plugging tool. The designed vibration plugging tool is simulated in the near field. The cement plug cementation quality tester tests the vibrating and non-vibrating samples, and the cementation ratio is calculated. The test results show that the average cementation ratio of vibrating samples is 0.89375, and that of non-vibrating samples is 0.70625, and the cementation quality is improved by 27%. It is concluded that it not only provides essential data for the design of mechanical vibration plug apparatus, on-site vibration plugs, and the development of operational specifications for vibration plugs, but also provides solid engineering guidance.

Plugging behaviors of temporary plugging particles in hydraulic fractures

Using the visualized experimental device of temporary plugging in hydraulic fractures, the plugging behaviors of temporary plugging particles with different sizes and concentrations in hydraulic fractures were experimentally analyzed under the conditions of different carrier fluid displacements and viscosities. The results show that the greater the carrier fluid viscosity and displacement, the more difficult it is to form a plugging layer, and that the larger the size and concentration of the temporary plugging particle, the less difficult it is to form a plugging layer. When the ratio of particle size to fracture width is 0.45, the formation of the plugging layer is mainly controlled by the mass concentration of the temporary plugging particle and the viscosity of the carrier fluid, and a stable plugging layer cannot form if the mass concentration of the temporary plugging particle is less than 20 kg/m^(3)or the viscosity of the carrier fluid is greater than 3 mPa·s. When the ratio of particle size to fracture width is 0.60, the formation of the plugging layer is mainly controlled by the mass concentration of the temporary plugging particle, and a stable plugging layer cannot form if the mass concentration of the temporary plugging particle is less than 10 kg/m^(3). When the ratio of particle size to fracture width is 0.75, the formation of the plugging layer is basically not affected by other parameters, and a stable plugging layer can form within the experimental conditions. The formation process of plugging layer includes two stages and four modes. The main controlling factors affecting the formation mode are the ratio of particle size to fracture width, carrier fluid displacement and carrier fluid viscosity.

Numerical Analysis of Dynamical Effects Associated with a Plugging String in a Horizontal Well

The finite element method has been applied to simulate the dynamics of a water plugging string in a complex horizontal well of a low-permeability oilfield.The force associated with the pipe string and the packer has been determined under the sucking action of the oil well pump.Such analysis has been conducted for a real drilling well,taking into account the process of lifting,lowering,unblocking and water plugging.Comparison between field measured data and simulation data indicates that the model is reliable and accurate.The packer creep effect under different pressure differences has also been investigated in the framework of the same model.

Characteristics and Weldability of Resistance Plug Welding of Dissimilar Steels

TRIP980 high-strength steel plate/SPCC low-carbon steel plate were welded by RPW. The key factors such as size and material of filler were studied, and the structure, fusion ratio and mechanical properties of the RPW joint were analyzed. The experimental results show that the calculation formulas of the length and diameter of the filler were designed reasonably. Q235 as a filler for RPW of TRIP980 high-strength steel plate/SPCC low-carbon steel plate is suitable according to schaeffler organization chart. The deposited metal of RPW joint is in the shape of “spool”,and the base metal and cap of deposited metal are alternately combined. The deposited metal has the characteristics of “locking” as rivets, which is beneficial to the improvement of mechanical properties of RPW joint. The nugget of RPW joint is uniform without deviates. TRIP980 high-strength steel plate, SPCC low-carbon steel plate, and filler were metallurgically bonded in the RPW joint.

Complex fracture propagation model and plugging timing optimization for temporary plugging fracturing in naturally fractured shale

In this paper,a viscoelasticity-plastic damage constitutive equation for naturally fractured shale is deduced,coupling nonlinear tensile-shear mixed fracture mode.Dynamic perforation-erosion on fluid re-distribution among multi-clusters are considered as well.DFN-FEM(discrete fracture network combined with finite element method)was developed to simulate the multi-cluster complex fractures propagation within temporary plugging fracturing(TPF).Numerical results are matched with field injection and micro-seismic monitoring data.Based on geomechanical characteristics of Weiyuan deep shale gas reservoir in Sichuan Basin,SW China,a multi-cluster complex fractures propagation model is built for TPF.To study complex fractures propagation and the permeability-enhanced region evolution,intersecting and competition mechanisms between the fractures before and after TPF treatment are revealed.Simulation results show that:fracture from middle cluster is restricted by the fractures from side-clusters,and side-clusters plugging is benefit for multi fractures propagation in uniformity;optimized TPF timing should be delayed within a higher density or strike of natural fractures;Within a reservoir-featured natural fractures distribution,optimized TPF timing for most clustered method is 2/3 of total fluid injection time as the optimal plugging time under different clustering modes.

Experimental study of the temporary plugging capability of diverters to block hydraulic fractures in high-temperature geothermal reservoirs

The effective plugging of artificial fractures is key to the success of temporary plugging and diverting fracturing technology,which is one of the most promising ways to improve the heat recovery efficiency of hot dry rock.At present,how temporary plugging agents plug artificial fractures under high temperature remains unclear.In this paper,by establishing an improved experimental system for the evaluation of temporary plugging performance at high temperature,we clarified the effects of high temperature,injection rate,and fracture width on the pressure response and plugging efficiency of the fracture.The results revealed that the temporary plugging process of artificial fractures in hot dry rock can be divided into four main stages:the initial stage of temporary plugging,the bridging stage of the particles,the plugging formation stage,and the high-pressure dense plugging stage.As the temperature increases,the distribution distance of the temporary plugging agent,the number of pressure fluctuations,and the time required for crack plugging increases.Particularly,when the temperature increases by 100℃,the complete plugging time increases by 90.7%.

The Comparative Performance of Plug Preparation Using Different Fertilizer Sources and Concentrations

Plugs are crucial for initiating crop production in greenhouses, soil, and controlled environment agriculture (CEA). Vegetable, fruiting, ornamental, and other horticultural crops that utilize plugs for production have demonstrated superior transplant establishment rate, plant health, and total yield. The APS Laboratory for Sustainable Food at Florida Gulf Coast University investigated the quality of plugs grown based on different concentrations and fertigation sources using synthetic and organic sources. We carried out the growth of “Rex Butterhead” Lettuce (Latuca sativa) plugs with five different fertigation treatments, 1) full-strength synthetic starter fertilizer solution;2) half-strength synthetic starter fertilizer solution;3) full-strength organic starter fertilizer solution;4) half-strength organic starter fertilizer solution, and 5) no fertilizer for control. Fertilizer treatments were formulated following manufacturer recommendations. The seeds were sown in Oasis® Horticubes and saturated every day with the different fertilizer treatments. The plugs were cultivated for 15 days in a controlled environment until two leaves after the cotyledons had developed. After 15 days, we collected data which included wet weight (g), dry weight (g), leaf area (cm2), and chlorophyll concentration (mg/cm2). In addition, we derived data including the Leaf Area Index (LAI, cm2/cm2) and Specific Leaf Area (SLA, cm2/g). Descriptive statistics were used to describe the biomass data. A Tukey’s HSD test was carried out to understand the differences between the fertilizer sources. We determined there was a statistically significant difference (P = 7.34E−29) in the measured plug growth parameters due to the various fertigation sources. We found that all fertilizer treatments produced viable plugs except for the control treatment. Of all the treatments, we concluded the half-strength organic treatment produced the more vigorous plugs with the greatest wet weight (g) and largest total leaf area (cm2) which was statistically significantly different. Results from this study may inform growers about appropriate fertilizer options for plug production.

Effects of Nano-CaCO_(3)Addition on Properties of Corundum-based Dispersive Purging Plugs

In order to improve the properties of corundum based dispersive purging plugs,dispersive purging plug specimens were prepared using tabular corundum(1-0.15 and≤0.15 mm)as the aggregates,tabular corundum(≤0.044 mm)andα-Al_(2)O_(3)micropowder(d_(50)=0.6μm)as the matrix,Secar 71 cement as the binder,introducing different amounts of nano-CaCO_(3),casting into shapes,and firing at different temperatures(1200 or 1600℃)for 4 h.The effects of the nano-CaCO_(3) extra-addition(0,0.5%,1.0%,1.5%and 2.0%,by mass)on the consistency of the castables as well as the properties and microstructure of the dispersive purging plug specimens were studied.The results show that:(1)with the fixed water addition,the consistency of the corundum castables decreases as the nano-CaCO_(3)addition increases;(2)with the increasing nano-CaCO_(3)addition,the bulk density of the specimens fired at different temperatures for 4 h decreases,the apparent porosity,the cold strength and the hot modulus of rupture all increase,the gas permeability does not change significantly;(3)the specimens fired at 1600℃ for 4 h have obviously better cold comprehensive performance than those fired at 1200℃for 4 h;(4)when the nano-CaCO_(3)addition is 1.5%,the comprehensive performance of the specimen is the optimal.

Optimization of the Plugging Agent Dosage for High Temperature Salt Profile Control in Heavy Oil Reservoirs

After steam discharge in heavy oil reservoirs,the distribution of temperature,pressure,and permeability in different wells becomes irregular.Flow channels can easily be produced,which affect the sweep efficiency of the oil displacement.Previous studies have shown that the salting-out plugging method can effectively block these channels in high-temperature reservoirs,improve the suction profile,and increase oil production.In the present study,the optimal dosage of the plugging agent is determined taking into account connection transmissibility and inter-well volumes.Together with the connectivity model,a water flooding simulation model is introduced.Moreover,a non-gradient stochastic disturbance algorithm is used to obtain the optimal plugging agent dosage,which provides the basis for the high-temperature salting-out plugging agent adjustment in the field.

Fatigue Life Analysis of Coiled Tubing in Deep Well Jet Plugging Removal

The coiled tubing plugging has become the main means of plugging in gas Wells in Xinjiang. These Wells are deep and have high pressure, which can easily affect the fatigue life of the operating coiled tubing. In order to improve the life of coiled tubing in high-pressure gas Wells, this paper studies the plugging conditions of coiled tubing in high-pressure ultra-deep Wells. Firstly, the cross section deformation of coiled tubing under high internal pressure is analyzed. Secondly, the factors influencing the fatigue life of coiled tubing and the influence of surface damage on the fatigue life of coiled tubing were studied. Finally, the mechanism of furrow damage caused by coiled tubing and the main measures to reduce furrow damage are analyzed. The following suggestions are made to improve the life of coiled tubing: select the right material and the right size coiled tubing;Use appropriate measures to prevent premature coiled tubing failure and reduce operating costs.

Isolated Major Aortopulmonary Collateral Artery Causing Heart Failure: Transcatheter Occlusion of Mapcas Using Amplatzer Vascular Plugs and Amplatzer Piccolo Occluders

Major aortopulmonary collateral arteries (MAPCAs) are congenital vessels that arise from the aorta or its first-order branches and are distally connected to the pulmonary arterial vasculature, thereby providing pulmonary blood flow. MAPCAs are often associated with cyanotic congenital heart disease with decreased pulmonary blood flow. Isolated MAPCAs are rare in patients without congenital heart disease with structurally normal hearts. Sometimes, isolated congenital MAPCAs can occur without any lung disease. Isolated MAPCAs represent the occurrence of collaterals in the absence of underlying heart disease, which commonly presents as heart failure, recurrent respiratory tract infection, and pulmonary artery hypertension. We report a rare case of congestive heart failure in a 6-year-old patient with dual arterial supply to an otherwise normal right lung, with a normal bronchial tree, and a structurally normal heart. The patient was successfully managed by the closure of collaterals by Amplatzer vascular plugs II (AVPII) and Amplatzer Piccolo Occluders.

不同直插型基质对3种盆栽菊花生长的影响以及综合评价

为提高盆栽菊花(Chrysanthemum morifolium)扦插繁殖的成活率,提高菊花生产效率,以既有扦插基质又有营养基质的直插型基质代替传统栽培基质,设置了12种不同扦插基质,配合前期筛选的营养基质,扦插培养3种盆栽菊花‘辉煌’‘波尔多红’‘黄芙蓉’。测量其生长、生理以及光合指标,并利用主成分分析和隶属函数对不同直插型基质的盆栽菊花生长效果进行综合评价。结果表明:扦插基质为Z1(河沙)、Z2(珍珠岩)、Z3(蛭石)时,3个盆栽菊花品种的株高、茎粗、冠幅及花期等生长指标更具优势。‘辉煌’‘波尔多红’‘黄芙蓉’在Z2处理中的综合评价指数最高,分别为0.999、0.940、1.000,说明其育苗效果最好,可作为最佳直插型基质,其次为Z1、Z3处理。而扦插基质中,椰糠、稻壳和泥炭体积占比较大时,并不利于盆栽菊花的生长。

乳化沥青提高原油采收率研究进展

乳化沥青具有注入性能好、封堵强度高等优点,作为一种选择性堵剂在油田提高采收率领域比其他化学剂体系更具应用潜力。本文总结了国内乳化沥青堵水体系的开发历程及现场选择性堵水的应用效果。通过调研近年来国内外文献,概述了乳化沥青堵水的作用机理,一种是作为乳液的作用机理,主要是乳液颗粒被变形捕获产生贾敏效应和乳液液滴的机械滞留使水的流动阻力增大;另一种是其分散相也就是乳液破乳后沥青的作用机理,主要是沥青黏附在岩壁上起到的堵水作用。同时,总结了乳化沥青稳定的主要影响因素,包括温度、水相中的电解质浓度和pH值以及分散相中的沥青质,并且论述了各因素影响乳化沥青稳定性的作用机理。最后,详细叙述了乳化沥青应用于油田调剖堵水领域的最新研究进展,研究表明乳化沥青不仅具有优异的封堵效果,还具有独特的封堵选择性。此外,乳化沥青还能与CO_(2)吞吐、泡沫调驱组成复合增产技术进行现场应用,并且指出了乳化沥青应用于调剖堵水领域存在的问题与未来展望。

延迟成胶弹性硅酸凝胶堵水剂及其性能研究

针对现有硅酸凝胶堵水剂普遍存在成胶时间短、成胶后脆性大的问题,结合L油田油藏条件,通过考察活化剂类型及用量,弹性改善剂类型及用量,以及水玻璃用量对成胶时间和弹性模量的影响,得出了一种延迟成胶弹性硅酸凝胶堵水剂。其配方为:6%水玻璃+0.85%活化剂三元弱酸一铵GL-1+0.1%弹性改善剂正电胶,该配方在油藏温度65℃下,成胶强度达到E级的时间为72 h,成胶后的弹性模量为589.46 Pa。采用填砂管实验评价了堵水剂的注入性及封堵性,结果表明堵水剂在L油田中具有良好的注入性及封堵性,在渗透率为1168.06×10^(-3)~5061.57×10^(-3)μm^(2)的填砂管中,注入0.8 PV的最高注入压力仅有0.72 MPa,封堵率均>96%。该堵水剂可用于L油田的油井堵水。

基于坐封受力模型的暂堵球封堵效果影响因素与参数优化

暂堵球在射孔孔眼及压裂裂缝中的坐封状态影响其封堵稳定性,暂堵球封堵效果决定暂堵转向压裂技术的成败。通过建立暂堵球坐封受力计算模型,研究了压裂液排量、密度、暂堵球及孔眼参数对暂堵球坐封受力状态及其封堵效率的影响,实验模拟了不同射孔参数、压裂排量及暂堵球/压裂液性能对封堵效果的影响。结果表明:暂堵球受拖拽力、脱离力及持球力随压裂液排量的增加而增大,暂堵球更易坐封;压裂液及暂堵球密度对暂堵球坐封封堵效率影响不大;暂堵球粒径大于孔眼直径时,暂堵球坐封封堵效率随粒径增加而增大,当暂堵球直径小于孔眼直径时,暂堵球不容易坐封;射孔孔眼数增加影响暂堵球坐封封堵效率。实验评价暂堵球最佳直径为9.0 mm,最佳泵送排量大于4.0 m^(3)/min时,有助于提高暂堵球坐封成功率,增强暂堵压裂设计的可靠性。

改性聚乙醇酸暂堵剂研发及其在河南油田的应用

酸溶性暂堵剂对地层伤害较大,解堵较麻烦,油溶性暂堵剂不适合高含水的油层;河南油田低渗透油藏地层温度为50~120℃,注水驱油见水快,常规水溶性聚乙醇酸暂堵剂和聚乳酸暂堵剂水解温度大于80℃,不能完全满足低渗透油藏暂堵压裂的需求。结合颗粒类水溶性聚乙醇酸暂堵剂和聚乳酸暂堵剂的特性和暂堵原理,采用催化剂和抑制剂使聚乙醇酸和聚乳酸发生酯化反应,生成聚乙醇酸和聚乳酸融合物,再加入成核剂及结晶促进剂,可得到改性聚乙醇酸暂堵剂。经测试,改性聚乙醇酸暂堵剂在50~120℃温度下具有常规聚乙醇酸暂堵剂的溶解性能和暂堵强度;当改性聚乙醇酸暂堵剂的总用量占比达到18%、粗粒径与细粒径质量配比接近1:1时,其封堵强度大于40 MPa,暂堵性能良好。现场试验7井次,加入改性聚乙醇酸暂堵剂后,单井施工压力最高增加了6.1 MPa,日增油5.3 t,取得了明显的增油效果。

天然气井井筒解堵工作液的研究进展

通过文献调研,分析了各种井筒解堵工作液的解堵机理,综述了各类型常用井筒解堵工作液的应用进展及优缺点;介绍了有机解堵工作液、有机缓释微乳酸解堵工作液、复合型解堵工作液等新型解堵工作液的研究进展;分析了解堵工作液在制备与实际应用过程中存在的问题,并提出了未来解堵工作液的发展趋势。