Study of asphaltene dispersion and removal for high-asphaltene oil wells

Many wellbores are blocked by asphaltene deposits,which lead to production problems in the oilfield development process.In this paper,methods such as elemental analysis,and solvent extraction are adopted for the study of wellbore blockages.The content of organic matter in blockages is higher than 96% and asphaltene is the main component of the organic matter with n-heptane asphaltene content of 38%.Based on the above analyses,an agent for asphaltene dispersion and removal（named as SDJ） was developed.The performance of the SDJ agent was evaluated,and it was found that the dissolution rate of asphaltene can reach 2.9 mg.mL-1.min-1 at 60 oC.SDJ agent（1wt%） was added to crude oil with a colloid instability index greater than 0.9 can effectively inhibit asphaltene deposition in the wellbore.By the viscosity method,the dissolution amount of SDJ agent was calculated,and it was found that when the viscosity of the system is around 2,000 mPa.s（the common viscosity of crude oil）,the amount of SDJ agent added to the blockage was at least 96 g per 100 g blockages.Therefore,SDJ agent has promising application for dispersion and removal of asphaltene deposition in high-asphaltene wells.

Impact of Noise Barriers on Air-Pollution Dispersion

The impact of noise barriers on gaseous air-pollution dispersion was examined using the high-resolution CLMM (Charles University LES (Large Eddy Simulation) Microscale Model). The dispersion of a mixture of nitrogen oxides (denoted as NOx—a mix of NO and NO2) was computed, providing the simulation in which wind direction is approximately perpendicular to the noise barriers. The barriers were assumed to be straight and infinitely long, with a height of 3 m. Dispersion of NOx was modeled for situations with no noise barriers along the highway, barriers on both sides, and for a single barrier on the upwind and downwind sides of the highway. The modelling results are presented and discussed in relation to previous studies and the implications of the results are considered for pollution barriers along highways.

Boundary Conditions for Sturm-Liouville Equation with Transition Regions and Barriers or Wells

By means of expansions of rapidly in infinity decreasing functions in delta functions and their derivatives, we derive generalized boundary conditions of the Sturm-Liouville equation for transitions and barriers or wells between two asymptotic potentials for which the solutions are supposed as known. We call such expansions “moment series” because the coefficients are determined by moments of the function. An infinite system of boundary conditions is obtained and it is shown how by truncation it can be reduced to approximations of a different order (explicitly made up to third order). Reflection and refraction problems are considered with such approximations and also discrete bound states possible in nonsymmetric and symmetric potential wells are dealt with. This is applicable for large wavelengths compared with characteristic lengths of potential changes. In Appendices we represent the corresponding foundations of Generalized functions and apply them to barriers and wells and to transition functions. The Sturm-Liouville equation is not only interesting because some important second-order differential equations can be reduced to it but also because it is easier to demonstrates some details of the derivations for this one-dimensional equation than for the full three-dimensional vectorial equations of electrodynamics of media. The article continues a paper that was made long ago.

Quantum Supercurrent Transistors in Silicon Quantum Wells Confined by Superconductor Barriers

We present the findings of spin-dependent single-hole and pair-hole transport in plane and across the p-type high mobility silicon quantum wells (Si-QW), 2 nm, confined by the superconductor δ-barriers on the n-type Si (100) surface. The oscillations of the conductance in normal state and the zero-resistance supercurrent in superconductor state as a function of the top gate voltage are found to be correlated by on- and off-resonance tuning the two-dimensional levels of holes in Si-QW with the Fermi energy in the superconductor δ-barriers. The SIMS and STM studies have shown that the δ-barriers heavily doped with boron, 5 × 1021 cm–3, represent really alternating arrays of silicon empty and doped dots, with dimensions restricted to 2 nm. This concentration of boron seems to indicate that each doped dot located between empty dots contains two impurity atoms of boron. The EPR studies show that these boron pairs are the trigonal dipole centres, B+ - B–, that contain the pairs of holes, which result from the negative -U reconstruction of the shallow boron acceptors, 2B0 => B+ - B–. The electrical resistivity, magnetic susceptibility and specific heat measurements demonstrate that the high density of holes in the Si-QW (> 1011 cm–2) gives rise to the high temperature superconductor properties for the δ-barriers. The value of the superconductor energy gap obtained is in a good agreement with the data derived from the oscillations of the conductance in normal state and of the zero-resistance supercurrent in superconductor state as a function of the bias voltage. These oscillations appear to be correlated by on- and off-resonance tuning the two-dimensional subbands of holes with the Fermi energy in the superconductor δ-barriers. Finally, the proximity effect in the S-Si-QW-S structure is revealed by the findings of the quantization of the supercurrent and the multiple Andreev reflection (MAR) observed both across and along the Si-QW plane thereby identifying the spin transistor effect.

Influence of barrier thickness on the structural and optical properties of InGaN/GaN multiple quantum wells

The structural and optical properties of InGaN/GaN multiple quantum wells （MQWs） with different barrier thick-nesses are studied by means of high resolution X-ray diffraction （HRXRD）, a cross-sectional transmission electron mi-croscope （TEM）, and temperature-dependent photoluminescence （PL） measurements. HRXRD and cross-sectional TEM measurements show that the interfaces between wells and barriers are abrupt and the entire MQW region has good periodic- ity for all three samples. As the barrier thickness is increased, the temperature of the turning point from blueshift to redshift of the S-shaped temperature-dependent PL peak energy increases monotonously, which indicates that the localization po- tentials due to In-rich clusters is deeper. From the Arrhenius plot of the normalized integrated PL intensity, it is found that there are two kinds of nonradiative recombination processes accounting for the thermal quenching of photoluminescence, and the corresponding activation energy （or the localization potential） increases with the increase of the barrier thickness. The dependence on barrier thickness is attributed to the redistribution of In-rich clusters during the growth of barrier layers, i.e., clusters with lower In contents aggregate into clusters with higher In contents.

The critical rate of horizontal wells in bottom-water reservoirs with an impermeable barrier

Barrier impacts on water cut and critical rate of horizontal wells in bottom water-drive reservoirs have been recognized but not investigated quantitatively. Considering the existence of impermeable barriers in oil formations, this paper developed a horizontal well flow model and obtained mathematical equations for the critical rate when water cresting forms in bottom-water reservoirs. The result shows that the barrier increases the critical rate and delays water breakthrough. Further study of the barrier size and location shows that increases in the barrier size and the distance between the barrier and oil-water contact lead to higher critical rates. The critical rate gradually approaches a constant as the barrier size increases. The case study shows the method presented here can be used to predict the critical rate in a bottom-water reservoir and applied to investigate the water cresting behavior of horizontal wells.

Wave-vector filtering effect of the electric-magnetic barrier in HgTe quantum wells

Because of the helicity of electrons in HgTe quantum wells（QWs） with inverted band structures,the electrons cannot be confined by electric barriers since electrons can tunnel the barriers perfectly without backscattering in the HgTe QWs.This behavior is similar to Dirac electrons in graphene.In this paper,we propose a scheme to confine carriers in HgTe QWs using an electric-magnetic barrier.We calculate the transmission of carriers in 2-dimensional HgTe QWs and find that the wave-vector filtering effect of local magnetic fields can confine the carriers.The confining effect will have a potential application in nanodevices based on HgTe QWs.

Resin Plug Application on Subsea Wells as A Suspension Barrier

A subsea wellhead equipped with obsolete vertical Christmas tree needs to be suspended for subsea tree recovery and subsequently to be permanently abandoned. Due to obsolete Christmas tree design combined with tubing inaccessibility issue,conventional subsea intervention method for setting downhole mechanical plug barriers with a semisubmersible rig or a riserless light well intervention vessel is not feasible to suspend the well. Attempt was made to suspend the well from a riserless light well intervention vessel by setting tubing mechanical plugs in 2017,but the mandrel of the tree running tool (TRT) was sheared off accidently while landing the TRT&subsea intervention lubricator (SIL) on the subsea tree. Due to resin’s superior mechanical and rheological properties,resin was evaluated as a well suspension material to create a suspension barrier. Resin plug was deployed successfully from a dive support vessel (DSV) across the perforations to allow the tree removal at cost effective manner. Resin plugging demonstrates a new approach at well P&A area.

Dispersion Properties of NMR Relaxation for Crude Oil

Special requirements for design of tools used for wireline NMR logging and NMR logging while drilling and for interpretation model are demanded due to the dispersion properties of NMR relaxation for crude oil. NMR longitudinal relaxation time （T1） and transverse relaxation time （T2） of the dead oil samples with different viscosities were measured by NMR spectrometers with a Larmor frequency of 2 MHz and 23 MHz at five different temperatures respectively. The results showed that T~ was obviously dependent on the Larmor frequency of NMR spectrometer. The degree of T1 dispersion became stronger with the increasing crude oil viscosity, Larmor frequency and the viscosity/temperature ratio. T2 was independent of NMR spectrometer measuring frequency. It is suggested that the resonance frequency should be selected lower than 2 MHz when measuring T1 in logging while-drilling and that T1 dispersion should be corrected when Larmor frequency is higher than 2 MHz.

Comparative study of various methods for extraction of multi-quantum wells Schottky diode parameters

In this work,forward current voltage characteristics for multi-quantum wells Al_(0.33)Ga_(0.67)As Schottky diode were measured at temperature ranges from 100 to 300 K.The main parameters of this Schottky diode,such as the ideality factor,barrier height,series resistance and saturation current,have been extracted using both analytical and heuristics methods.Differential evolution(DE),particle swarm optimization(PSO)and artificial bee colony(ABC)have been chosen as candidate heuristics algorithms,while Cheung technic was selected as analytical extraction method.The obtained results show clearly the high performance of DE algorithms in terms of parameters accuracy,convergence speed and robustness.

System of Potential Barriers in Nanostructures

Nanoscale superlattice has been investigated theoretically. It has been shown that the deformation effects on the energy spectrum of nanoscale superlattice by changing the interatomic distances as well as varying the width and height of the potential barrier. The potential deformation has been estimated. It has been shown that for different edges of forbidden bands the deformation potential has different values. It has been also analyzed the dependence of the effective mass on energy. It has been determined that the effective mass crosses periodically the zero mark. It has been concluded that this phenomena contributes to the periodic change of the oscillation frequency de Haas-van Alphen effect.

油井水泥用抗分散聚合物的制备及其性能评价

【目的】研究调整井固井时因地层水侵入水泥浆的问题,通过加入抗分散聚合物提高油井水泥凝固前抗水侵能力。【方法】采用2-丙烯酰胺-2-甲基丙磺酸、丙烯酰胺、α-甲基丙烯酸、甲基丙烯酸十八酯为主要原料,十二烷基硫酸钠为稳定剂,过硫酸胺为引发剂,以水溶液自由基聚合法制备聚合物KSQ-Z;评价聚合物KSQ-Z的抗分散效果,并借助X射线衍射仪、扫描电子显微镜对掺入聚合物材料的水泥石进行微观测试,探究KSQ-Z抗分散机制。【结果】KSQ-Z是一种含酯基的聚合物;KSQ-Z掺量(质量分数,下同)的增加可明显提高水泥浆的抗分散性,其中掺量为1.2%时效果最好;同未水侵组相比,水灰质量比分别为0.46、0.48、0.50的实验组掺入质量分数为1.2%的KSQ-Z的水泥浆养护7 d后的抗压强度分别提高41.1%、26.2%和21.8%;聚合物KSQ-Z通过形成的网状结构增加水泥石稳定性,使水泥石更加致密。【结论】聚合物KSQ-Z可增强水泥浆的内聚力,避免地层水对水泥浆的稀释和离子流失的影响,从而显著提高固井用水泥的抗水侵性能。

煤层气井同心管气体射流排采特征分析

为解决煤层气井中有杆泵排采工艺存在的埋泵、卡泵及偏磨等问题,实现产气中后期降低井底流压、释放解吸气的目的,探索煤层气井中后期低产液量情况下的排采工艺至关重要。基于可压缩性的气体介质,考虑射流泵排采工艺的技术特点,分析了煤层气井井下同心管柱气体射流泵排液原理,计算管柱环空内气携液条件,建立了同心管气体射流泵喷嘴、喉管和扩散管等流动模型,考虑气体射流的音障,分析了不同喷喉组合下的携液特征。研究结果表明:初始注入气量、压力一定的情况下,喷嘴直径越小,射流速度越大,携液量越多;但喷嘴直径越小,所需的注入气量越小,气体的流速易超过临界流速导致流体特性发生改变;当产液量为3 m^(3)/d,注气压力为6 MPa,喷嘴直径为3.50、4.02、5.00 mm时,所需的注入气量分别为9338、11225、15023 m^(3)/d。气体射流泵排液机理、气体射流特征的研究结果可为同心管气体射流泵工艺设计和现场试验提供理论依据。

邻井气举辅助泡沫排水采气工艺起效时间探究

为了提升常规泡沫排水采气的效果,在对积液气井环空加注泡排剂的同时,使用邻井天然气对积液气井环空进行注气,即邻井气举辅助泡排新工艺。新工艺泡排剂起效时间决定关井时间和采气时率,对气井生产有重要的影响,目前行业内对此研究处于空白状态。在已有致密气井间歇泡排注剂后关井时间探究的基础上,依据注入泡排剂之后井口压力、气量和温度变化趋势来判定泡排剂下行时间和扩散时间,从而确定泡排剂的起效时间,并与常规泡排剂加注方式进行对比,分析了新工艺的优点及其原因。研究结果表明:①常规环空泡排注剂和邻井气举辅助泡沫排水采气工艺注剂后泡排剂的流动形态不一样,前者泡排剂呈“线状”,沿“静态”环空的油套管壁下行;后者泡排剂会以“液滴状”,在进入积液气井“动态”环空之后,随着邻井天然气迅速下行;②新工艺可以显著缩短泡排剂的起效时间,从8.2 h缩短至1.1 h,效率提高了86.6%,因借助注入的天然气对积液气井进行气举,排液效果更好,常规注剂不能复产的低产、低压气井借助新工艺可以正常恢复生产。为低产低压气井的排水采气提供了一种新思路,值得进一步推广应用。

针对交通环境减振的超表面型波屏障

针对轨道交通带来的环境振动问题,以表面波作为控制对象,通过在地表下周期浅埋填充管,设计了一种新式超表面型波屏障,并进行了系统的频散分析,传输特性仿真与实验测试,所得主要结论如下:由于填充管竖向共振与表面波间的强互相作用,表面波衰减域被打开,衰减域的作用频率及宽度与填充管的自振特性密切相关,可以通过材料与几何参数进行灵活调整;衰减域范围内,表面波得到了有效的控制,且随着周期数的增加,衰减域内减振效果逐渐提升,无论主、被动隔振,超表面型波屏障都可以起到良好的隔振效果;实验验证了超表面型波屏障减振的高效性,衰减域内平均插入损失可达9.8 dB,表面波向体波的模式转化是其主要作用机理;一定程度施工误差(≤10%)的引入不会影响衰减域内的减振效果,实验结果证明了超表面型波屏障减振具有高效性与鲁棒性;通过输入实测的地铁环境振动信号,超表面型波屏障应用于环境减振的可行性也得到了初步验证。超表面型波屏障具有减振高效稳定、设计灵活和施工便利的优势,在轨道交通环境减振领域具有良好的应用前景。

渤海JZ-X油田气顶窄油环油藏井位优化和挖潜策略

针对气顶底水窄油环油藏易气窜水锥、剩余油分布复杂的生产难题,在渤海矿区逐渐探索出利用水平井开发的井位优化与挖潜策略。基础井网阶段:水平井段垂直构造线穿多层来提高储量动用程度,并匹配智能滑套分采管柱以缓解层间矛盾;基础井网平行于流体界面,部署于油水界面之上1/3油柱高度避气控水。综合调整阶段:通过油藏数值模拟研究,油田开发进入中—后期,剩余油平面上主要富集于井间滞留区,纵向上后期水体能量驱动逐渐发挥主要作用,剩余油主要富集于油层上部。对比井间侧钻、气顶注气和屏障注水方案增油量指标,当前剩余油挖潜策略以井间侧钻与气顶注气为主。井间侧钻通过低产低效井平面侧钻至井间,纵向高部位部署挖潜剩余油,单井净增油量为3.4×10^(4)~4.2×10^(4)m^(3);气顶注气通过采气井转天然气回注,补充气顶能量,气驱水平井上部剩余油,提高原油采收率,预测净增油量为5.2×10^(4)m^(3)。

闭式注水油藏自分散型耐高温高盐调驱剂

南海东部高温高盐油藏闭式注水井无地面注水流程,常规调驱剂无法在地面混配后注入地层,且由于自分散性差,难以直接注入地层。以南海东部A油田为目标,从快速自分散和耐高温高盐两个角度出发,以2-丙烯酰胺-2-甲基丙磺酸(AMPS)含量为40%的耐温耐盐聚合物为基础,辅以多酚类复合交联剂、多支链醇聚醚类分散剂等,通过反应成胶、机械研磨,制得自分散型耐高温高盐调驱剂。采用激光粒度仪、电子显微镜、动态光散射仪等,对调驱剂的粒径、微观形貌和表面电性进行了表征,评价了调驱剂的自分散性能、注入性能和剖面调整性能,并在南海东部A油田X井组进行了现场应用。结果表明,自分散型耐高温高盐调驱剂呈球形,初始粒径D50(粒径中值)为1.09~11.63μm,通过调整配方、研磨条件或加热时间可调节调驱剂的粒径。调驱剂颗粒表面呈负电,Zeta电位值为-19.30~-26.1 mV。与常规油分散型颗粒调驱剂相比,该调驱剂自分散性好,遇水后能快速均匀分散,在注入水中的自分散率为90.0%,岩心注入压力仅为油分散型颗粒调驱剂的53.13%。调驱后,高渗透岩心的分流量由92.6%降至20.5%,低渗透岩心的分流量由7.4%增至79.5%,吸水剖面明显“反转”。现场实施效果良好,调驱剂施工爬坡压力为0.5 MPa,施工后最高日增油106 m3,阶段增油8900 m3。该调驱剂满足目标油田高温高盐条件,注入性好,增油效果明显,适合闭式注水油藏调驱。

隐患井井筒完整封堵方法研究与应用

随着油气田开发的深入,部分油气水井进入开发中后期,已无良好经济价值。对于需要永久性报废处理的废弃井,既要阻止地层流体在井内运移,也要防止油气沿井筒垂直运移到淡水层或地面。应保证井筒及套管环空同时有效封隔,形成井筒机械完整性以达到封堵目的。通常选择适当井段进行注水泥塞或坐封机械桥塞来阻止流体运移,而井筒外封堵采用锻铣再封堵工艺,但锻铣套管受诸多因素影响,速率低且风险高。本文探索另一种新工艺:射孔二次补注封堵,即对目的井段进行补射孔,建立局部连通,使用超细水泥浆二次固井形成完整水泥隔板,重新建立封堵井屏障。实际应用安全、高效、经济,获得满意效果,为隐患井治理提供新技术思路和经验。

气井油套环空远程监控系统设计

气井油套环空异常带压现象是严重影响安全生产的因素之一,该环空的状态监测能够为井筒完整性评估以及后续操作提供重要依据。针对气井油套环空异常带压的远程监控问题,开发了一套基于STM32的远程监控系统,该系统通过现场控制器和计算机上位机软件实现了对环空压力、温度和泄压流量的远程监测以及远程泄压控制,并建立了室内模拟试验验装置。通过理论计算与交叉试验,证实了该系统良好的准确性,为保障气井生产安全与井屏障完整性诊断工具研究提供了参考。

井下管柱渗漏导致注采气井A环空带压模拟分析研究

注采气井存在井下管柱渗漏导致A环空带压的现象,影响日常正常运行,测井工具可定位井下管柱漏点位置,但操作繁琐、成本高,有必要开展基于数值模拟的漏点参数诊断研究,定量化剖析环空带压规律。将A环空带压过程划分为气体渗漏、“气泡”膨胀、气柱聚并三个阶段,采用微元分析的思想,基于压力平衡、气液体积耦合等理论,创新建立了“气泡”膨胀阶段的数学模型。结合小孔模型形成A环空带压模拟方法,编制形成注采气井A环空带压计算模拟分析软件,通过参数假设、拟合对比可反向确定渗漏点的数量、深度、当量直径等参数。同时对渗漏点参数进行敏感性分析,研究表明渗漏点深度主要影响A环空的稳定带压值,渗漏点数量与当量直径主要影响A环空压力变化速率。现场注采气井实际运行中,若井下管柱在浅部产生多个大尺寸的渗漏点,A环空会快速产生较大的井口压力,应优先处理最上部渗漏点,避免环空压力过大导致井屏障失效。该研究为注采气井的管柱完整性评价提供了新的技术手段。