柔性管段对立管严重段塞流特性的影响

严重段塞流是深海混输立管面临的流动安全问题之一,开展混输立管严重段塞流研究对立管的流动安全及实际生产具有重要意义。在中国石油大学（北京）原立管系统实验装置及改造后的混合立管系统实验装置上进行的不同工况下的严重段塞流特性实验结果表明,柔性管严重段塞流特性不同于垂直管段。在立管总高度相等条件下,利用L型立管和混合立管的流型图、压力、周期和液塞等数据分析了柔性管的存在与否对立管严重段塞特性的影响。相对于L型立管,柔性管存在会在一定程度上缩小严重段塞流I的范围,同时使立管底部最大压力增大约15%～20%,严重段塞周期减小约12.09%,液塞长度减小约1.38%,液塞速度增加约2.93%。在立管总高度等几何参数一定的情况下,对柔性管跨度和长度变化对严重段塞流特性的影响进行了分析。结果表明,柔性管跨度对严重段塞流特性的影响较小;柔性管长度增加,会同时增大严重段塞流的周期和立管底部最大压力。     

Slug Water Alternating Gas Flow Processes Behavior in the Vicinity of Discontinuous Shales

Abstract

Gas injection is the second largest enhanced oil recovery process practiced in the world. To increase the macroscopic sweep efficiency, the gas is generally injected intermittently with water either simultaneously or as slugs. This mode of injection, called water alternating gas (WAG), is being widely used in the oil fields. This experimental and numerical study is aimed at understanding mechanisms of oil recovery following slug first-contact miscible WAG (FCMWAG) injection in the presence of discontinuous shales. A particular objective is to quantify the accuracy of numerical simulation when modeling slug FCMWAG displacements in these heterogeneous systems.

A series of well-characterized laboratory experiments in two-dimensional heterogeneous bead packs were carried out. Slug FCMWAG displacement experiments were performed in the porous media containing discontinuous shale. Slug injection was carried out at a WAG ratio of 1:1 with slug sizes of 5 and 50% PV. All experiments were then modeled using IMPES finite difference simulator without using history matching (all simulations used directly measured porous media properties as inputs) to quantify the accuracy of the simulation when modeling the slug FCMWAG displacements in a porous media with a discontinuous shale.

The large water slug (50% PV) displacement outperformed the 5% PV slug process because the large water slug injected ahead of solvent significantly reduced the extent of fingering and the bypassed oil around the shale barrier. Simulation of the slug WAG experiments showed good agreement for the oil recovery. However, a discrepancy in the physics of the fluid flow during the displacements, especially downstream and upstream of the shale barrier, was observed in the fluid cut curves. Simulation predicted less fingering and fewer breakdowns of the injected slugs.     

海底管道立管系统弯头部位静、动荷载分析

海底油气管道中流体的不稳定流动会诱发立管系统的振动,使立管系统弯头部位发生疲劳破坏,影响管道的使用寿命。基于段塞流特征参数的经验关系式和简化的段塞流运动模型,提出了一种分析立管弯头部位静、动荷载的计算方法。实例计算表明:弯头部位的动反力比静压力低2个数量级,实际分析时可忽略动反力的影响,认为段塞流对管道的冲击力近似等于管道所受到的静压力;流速对立管弯头部位的静、动荷载变化规律的影响极为明显。     

集气管线清管器旁通量计算模型探讨

在两相流管道中,使用旁通清管器可以吹扫积液段塞流,缓解末端液体处理器负荷。本文主要叙述了用于两相流管道旁通清管器的工作原理,在管道水力学基本理论基础上,针对长庆与壳牌合作区块的CB清管实例,用输气管道基本理论和流体力学孔口泄流理论对该管进行旁通量计算,通过比较、优选及校正,确定了苏里格气田集输管线旁通清管计算模型。模型的可靠性还有待进一步验证。     

A Review of Current Technologies for Severe Slugging Remediation

Abstract

One important problem expeienced in flexible risers is severe slugging phenomenon that typically occurs in the flowline-riser systems found on offshore floating production facilities. The flow and pressure oscillations due to severe slugging have several undesirable effects on the downstream topside facilities unless they are designed to accommodate them. However, designing the topside facilities to accept these transients may require large and expensive slug catchers with compression systems equipped with fast responding control systems. This may not be cost-effective and it may be more prudent to design the system to operate in a stable manner. While lowering production rates (slowing fluid velocity) can minimize severe slugging, operators are investigating alternatives that would allow for maximum production rates without the interruptions caused by slugs. This article references a combination of industrial experience and information from the literature to compile a list of methods of remediating the problems associated with severe slugging in pipeline-riser systems.     

气举法控制深水混合立管严重段塞流实验研究

利用深水混合立管系统模拟流动实验装置进行了严重段塞流的注气控制模拟实验,结果表明,在立管底部进行气举法控制可以减小流型图中不稳定流区域,并能明显减小管内压力大小和波动幅度,但过大的注气量会增大柔性管段的摩阻损失,使整个立管系统的压力增大,对流动反而不利。根据实验中管内压力随注气量增大的变化趋势的不同,将混合立管系统的气举控制过程分为4个阶段,不同控制阶段垂直立管内流型有所不同;注气控制不能完全消除深水混合立管系统中的不稳定流,但将垂直立管流型控制在段塞流与过渡流分界处时可达到较好的控制效果。     

气液混输管道管式段塞流捕集器设计原理及实践

段塞流是气液混输管道中一种常见的流型流态,对下游设备的压力波动影响极大。从段塞流的动力特性出发,分析了段塞流的物理特性和国外管式段塞流捕集器的结构特点和分离原理,建立了一套管式段塞流捕集器主要参数的设计计算数学模型,对主要设计参数进行了敏感性分析,得出规律性认识并给出设计案例。对研究管式段塞流捕集器的设计方法和优化凝析气田地面工艺流程有积极意义。     

降阻剂在多相管流中的作用机理

在多相管流中,加入降阻剂可有效地降低沿线的压降梯度,降阻剂黏度越大,减阻效果越好。降阻剂在低气体折算速度下的降阻效果比高气体折算速度下的好。未加降阻剂时,液体折算速度增大,导致液膜厚度增厚、段塞频率增大、管壁腐蚀速率加剧;加降阻剂之后,导致段塞频率减小、管壁腐蚀速率降低、液膜的有效厚度减小,但段塞迁移速度不变。     

国内外油气水多相管流技术的研究

地面油气水多相管流的研究经历了从经验、半经验关系式开始,到统一流动模型、瞬态模型和物理机理模型的发展过程。研究热点是:地形起伏多相管流的研究;油气水多相管流的研究;多相泵和多相流量计的研究;建立大型实验架,把这些在低压、小管径和低输量条件下得出的关系式加以适当修正后用到实际多相管路。筛选出一些较好的关系式,组合成一些适用范围广,精度高的组合关系式。     

稠油-水两相水平管流流型实验研究

以高粘度稠油和水为工质,将稠油和水先经搅拌罐混合,再由螺杆泵输送进入实验环道流程,在内径为25.4mm、长52m的水平钢质管道中,模拟了稠油油田现场情况。描述了实验流型,并命名了一种新的流型——Ew/o+D(Ew/o)/w间歇流流型,研究了稠油-水两相管流的压降及反相过程,重点探讨了混合流速对反相的影响。研究结果表明,随着混合流速的增大,反相有提前发生的趋势。在含水率为0.35-0.55时,混合流速的增大将直接引发反相。     

温西三区块空气驱提高采收率试验研究

温西三区因为油藏渗透率低,注水后期水驱效果变差和注入能力下降,导致开发效果变差,而空气驱技术针对低渗油藏采收率的提高有一定的效果。为此,本文在温西三油藏条件下进行空气驱岩心驱替试验,试验研究不同空气段塞大小(0.05 PV、0.1 PV、0.2 PV、0.3 PV、0.4 PV)对提高采收率的影响。结果表明,随着空气段塞的增加,提高采收率的幅度变大,且低渗管采收率提高幅度高于高渗管。当空气段塞为0.3 PV时,提高的采收率为6.25%,采收率提高幅度最为明显。     

浅层油藏稠油热水/CO2驱油效率实验模拟研究

新疆油田九_6区齐古组浅层稠油油藏已进入蒸汽开采中后期,油藏开采经历了蒸汽吞吐、加密调整、蒸汽驱过程,采出程度为37%。现阶段单一蒸汽驱效果明显下降,地层亏空严重,蒸汽热利用效率低,吸汽不均,波及程度差异大,油水流度比大,采收率低。热水复合CO_2驱油充分利用热水热效应和发挥CO_2溶解降黏等作用,是提高原油采收率的有效方法。因此,针对九_6区稠油开展不同混合方式热水/CO_2驱油模拟实验,分别研究了纯热水驱、热水与CO_2混注、热水与CO_2段塞的驱油效率。结果表明,纯热水驱累积驱油效率为49.19%,热水/CO_2混注累积驱油效率最大为71.25%,段塞驱累积驱油效率高达85.96%。同时,分析了驱出原油及岩心残余油组分变化。     

Numerical study of dispersed oil–water turbulent flow in horizontal tube

In this paper, the three-dimensional flow of two immiscible liquids in a horizontal pipe has been investigated numerically. The transient numerical simulations of two-phase dispersed flow in a pipe (of ID = 0.0024 m) have been carried out using commercial CFD package FLUENT 6.2 in conjunction with multiphase model. Oil–water system is selected as the two-phase system in this work. The k − ε model was used to describe the turbulence in continuous phase. The numerical results in terms of the phase distribution profiles and average in-situ hold-up are presented and discussed. The predicted results are seen to be in good agreement qualitatively as well as quantitatively with the previous experimental results available in the literature.     

Recovery of residual oil using the alkali/surfactant/polymer process: effect of alkali concentration

An experimental study was conducted to examine the effectiveness of sodium carbonate in alkali, surfactant and polymer combined slugs in recovering waterflood residual oil. The effects of sodium carbonate concentration on the slug viscosity, interfacial tension, and phase behavior were first examined. Core flood experiments were conducted with unfired linear Berea sandstone cores. The incremental oil recovery, oil cut, residual resistance factor, and chemical propagation were measured for each flood.A significant oil bank was formed for all combined slugs having sodium carbonate concentration ≥1 wt%. The incremental oil recovery, oil cut and the injectivity of the combined slugs greatly improved as sodium carbonate concentration was increased. The effect of sodium carbonate concentration on chemical propagation was dramatic for the synthetic surfactant; a slight delay in surfactant breakthrough and a much slower rate of surfactant propagation were observed at high sodium carbonate concentrations.The results obtained in the present study indicate that the residual oil was recovered by two mechanisms: low interfacial tension and wettability reversal. The former mechanism is dominant at sodium carbonate concentrations ≤1 wt%, whereas the latter plays an important role only at high sodium carbonate concentrations.     

CFD investigation on characteristics of heavy crude oil flow through a horizontal pipe

Transportation of heavy crude oil via pipelines possesses many technological issues that are inherently flow related. Accurate prediction of flow characteristics is an essential step for a reliable piping design of transporting the crude oil. A rheology-based Computational Fluid Dynamics (CFD) model of the Iraqi heavy crude oil flow through a horizontal pipe (1 m length of 3/4 in. inside diameter) was developed using the commercial software Ansys 15 Fluent. By using power law rheological model, the Iraqi heavy crude oil exhibits a non-Newtonian dilatant behavior over the examined shear rate range of 1–40 s⁻¹. The proposed axi-symmetric CFD model identifies velocity profile and generates values of friction factor, which are validated with experimental measurements. Additionally, wall shear stress and entrance length were numerically predicted and compared with well-established correlations from the literature for Non-Newtonian flow. Detailed results of the CFD model exhibited a reliable prediction of the characteristics of heavy crude oil flow.     

油气集输管线中气液两相团状流

针对油气集输管线中气液两相团状流的流动机理和特点,将每一段塞单元划分为带液层的气塞区和液塞区两个区域.对气塞区,采用分流模型建立了其水力计算模型;对液塞区,采用均流模型建立了其水力计算模型,并用实验数据关联了液塞区气液混合物的沿程阻力系数与雷诺数之间的相关式.通过气塞区和液塞区水力计算模型的结合,给出了团状流的水力计算模型.经大庆油田12井次实际生产数据检验,该水力计算模型所预测的压力梯度比传统的按流动状态所预测的压力梯度更符合实际值.     

高含水期油藏开发方式选择及最优方案设计

通过数值模拟,确定了M1油藏高含水期合理的开发方式,在此基础上,利用正交实验设计确定了各井组最优的气水交替注入方案。该方案不仅考虑了CO2注入量、CO2注入速率、水注入速率、CO2段塞数、气水段塞比等因素,还对首段塞与后续段塞比、CO2浓度、焖井时间等因素进行了优化。实验结果表明,首段塞与后续段塞比应在2∶1左右;注入CO2浓度不应低于90%;首段塞合理焖井天数在15 d左右,后续段塞合理焖井天数在7～8 d。将实验结果与水驱方式进行了对比,在开采后期气水交替注入的采油量有了明显的提高,而含水率低于水驱方式,因此CO2气水交替驱技术可以在M1油藏使用。     

Alkaline Surfactant Polymer Formulation for Carbonate Reservoirs

Abstract

This paper presents a systematic study to investigate the applicability of alkaline-surfactant-polymer (ASP) process as an enhanced oil recovery method to Saudi Arabian carbonate reservoirs. Several alkalis were first screened to test their compatibility with the injected sea water that has large quantities of divalent ions. Then surfactant-polymer, alkali-surfactant, and alkali-surfactant-polymer interactions at the reservoir temperature (90^○C) were investigated. Static adsorption of surfactant on reservoir carbonate rocks were also investigated at the same temperature. Interfacial tension (IFT) measurements were made between the slugs formulated and crude oil from the same reservoir. Two surfactants were tested, Triton X-102 and Ethoxylated sulfonate (Dodiflood B1083), and the polymer tested was FLOCON 4800C.

The results of the compatibility tests showed that the ASP slug has to be prepared using softened seawater and be protected by a pre- and after-flush softening seawater slugs. B1083 surfactant was found to be a promising candidate surfactant for the adverse conditions of the Saudi Arabian carbonate reservoir. A combination of NaHCO₃ and Na₂CO₃ was found to significantly reduce the adsorption level of B1083 surfactant on carbonate rock at low surfactant concentrations ( < 1% by wt.). This is very desirable for formulation of a cost-effective ASP slug.     

注聚过程中高分子聚合物的防窜研究

针对地层非均质性造成的注聚过程中聚合物窜流,研究了高分子聚合物溶液的驱油封窜性能.考察了聚合物黏度随温度变化的趋势,随着温度升高,聚合物黏度呈反“厂”字型降低.注入0.3 PV高浓度的高分子聚合物溶液段塞后,高渗透层相对出液量降低,低渗透层相对出液量明显增加.在后续水驱阶段,高分子聚合物溶液段塞注入压力变化趋势与常规分子聚合物溶液段塞基本一致,但相对分子质量越高,下降趋势越缓,有效时间越长,封堵效果越好.相对分子质量为1.8×10 7和2.0×107的聚合物溶液段塞对低渗透层的采收率比常规分子聚合物(1.4×107)溶液段塞的采收率分别高出9.05％和11.75％,组合段塞比常规段塞更高出19.64％.还讨论了高分子聚合物驱油机理.     

A mechanistic model of heat transfer for gas–liquid flow in vertical wellbore annuli

The most prominent aspect of multiphase flow is the variation in the physical distribution of the phases in the flow conduit known as the flow pattern. Several different flow patterns can exist under different flow conditions which have significant effects on liquid holdup, pressure gradient and heat transfer. Gas–liquid two-phase flow in an annulus can be found in a variety of practical situations. In high rate oil and gas production, it may be beneficial to flow fluids vertically through the annulus configuration between well tubing and casing. The flow patterns in annuli are different from pipe flow. There are both casing and tubing liquid films in slug flow and annular flow in the annulus. Multiphase heat transfer depends on the hydrodynamic behavior of the flow. There are very limited research results that can be found in the open literature for multiphase heat transfer in wellbore annuli. A mechanistic model of multiphase heat transfer is developed for different flow patterns of upward gas–liquid flow in vertical annuli. The required local flow parameters are predicted by use of the hydraulic model of steady-state multiphase flow in wellbore annuli recently developed by Yin et al. The modified heat-transfer model for single gas or liquid flow is verified by comparison with Manabe's experimental results. For different flow patterns, it is compared with modified unified Zhang et al. model based on representative diameters.