润湿性反转剂的微观渗流机理

为了研究润湿性反转剂对渗流过程的影响,对润湿性反转剂的微观渗流机理进行了研究。用接触角法和W ashburn法测定了固体表面的接触角,研究了润湿性反转剂对润湿性的影响;用界面张力仪测定了润湿性反转剂的油水界面张力,分析其降低油水界面张力的能力;并用微观刻蚀模型驱油试验研究了润湿性反转剂的微观渗流机理。试验结果表明:润湿性反转剂能改变表面的润湿性,使亲油表面变为亲水表面;润湿性反转剂有降低油水界面张力的能力,能使油水界面张力降低至10-1mN/m;润湿性反转剂使油膜剥离并形成油桥,使润湿性反转。该研究说明油水界面张力和润湿性都影响油水渗流特征,为进一步研究如何改善油水渗流过程奠定了基础。     

利用反向推理方法确定水驱特征曲线渗流方程

建立油水两相渗流特征与水驱特征曲线对应关系,揭示水驱特征曲线宏观规律中蕴含的微观渗流特征,一直是油藏工程长期性基础研究课题,目前已初步形成从油水相渗比值到水驱特征曲线的正向推理方法。但受现有油水相渗比值研究成果限制,已有水驱特征曲线的理论推导一直未能获得突破。为此,文中借鉴反向推理实现目标性较强的特点,提出了利用反向推理方法来确定水驱特征曲线渗流理论基础,并对推理过程中的关键数学逻辑式进行函数特征分析。结果表明,反向推理数学逻辑更加可行、严密,完全可实现油水渗流特征微分方程的求解,所得到的油水相渗比值关系式属超越方程,该结果也能完美地应用到正向数学逻辑推理中。将其应用于大庆南二、三开发区葡Ⅰ组油藏,从实际生产数据确定的油层油水渗流特征与实验测试得到的结果一致。这也为研究油藏水驱过程中实际油水渗流特征提供了新的思路与方法。     

基于Level Set有限元方法的微观水驱油数值模拟

在微观水驱油实验的基础上,建立了二维微观孔隙模型;引入Level Set数学方法,结合N-S方程,建立了微观两相渗流数学模型,借助有限元方法,进行水驱油两相数值模拟,研究微观水驱油动态特征。研究了孔喉非均质性、润湿非均质性、油水两相黏度以及驱替压差对驱油效果的影响;通过对模拟结果中孔隙内流体的波及效率、两相界面的运移速度以及优势渗流通道的分析发现,Level Set方法能很好地处理各因素下油水两相界面的拓扑变化,为微观水驱油机理的研究提供了一种新的技术方法。     

核磁共振技术在油水两相渗流特征研究中的应用

油水两相驱替实验主要从宏观角度描述渗流特征,但无法从微观层面对储层动用状况进行描述.为解决该问题,使用核磁共振技术从微观角度研究油水两相渗流特征,运用弛豫时间谱转换成喉道半径分布法和各喉道区间饱和度计算方法,研究饱和水状态下油驱水特征以及饱和油状态下水驱油特征,得出了不同驱替阶段油水在孔隙空间中的分布以及各喉道区间油相采出程度.该研究在一定程度上实现了对两相渗流机理较为全面的认识,对新区勘探和老油田开发技术调整具有重要意义.     

基于页岩油水两相渗流特性的油井产能模拟研究

页岩孔隙结构及固液相互作用复杂，其微观渗流特性加大了页岩油产能预测的难度。为准确评价体积压裂后多尺度孔隙结构发育的页岩油藏产能，基于页岩储层油水两相相渗计算方法和嵌入式离散裂缝模型，考虑页岩真实孔隙结构作用下的微观油水两相渗流特性，形成了考虑页岩体积压裂页岩油藏产能的数值模拟方法。基于页岩储层孔径分布计算油水相渗曲线，结合页岩油藏压裂/生产流程，开展了页岩油藏压裂液空间分布以及油井产能评价模拟分析。结果表明，不同孔径分布下的页岩油水两相相渗曲线存在差异，压裂液主要分布在压裂裂缝、与其相连的天然裂缝以及其周边基质中，在闷井过程中裂缝内压裂液逐渐渗吸进入基质并置换基质中原油，经体积压裂可实现改造区域的整体动用。研究结果可以从微观油水两相渗流特性与宏观产能评价角度为页岩油藏高效开发提供技术支撑。     

确定油藏油水渗流特征的新方法

在马克西莫夫-童宪章水驱特征曲线的基础上,将微分和物质平衡方程、Welge方程相结合,可得到马克西莫夫-童宪章水驱特征曲线对应的微观油水渗流特征方程,为利用油藏生产数据确定油水渗流特征提供新的方法。利用物性好的大庆油田南二三开发区葡Ⅰ组油藏生产数据,给出详细计算流程,其计算结果与水驱油实验结果基本一致,表明新方法可行。利用三塘湖油田牛圈湖特低渗油藏马62井区油水渗流特征进行验证,发现马62井区体积压裂后所表现出的油水渗流特征与相邻井区室内实验确定的结果相差较大,表明室内实验得到的油水渗流特征只反映了基岩的油水渗流特征,未能反映多孔介质油藏注水开发过程中的水驱油特征。     

异常渗流油藏油水两相渗流特征研究

异常渗流油藏往往因为或是流体性质异常、或是多孔介质异常、或是流动状况发生变化．从而造成流体渗流不符合达西渗流规律。通过室内试验．确立了异常渗流油藏油水两相渗流特征的研究方法,测试了其油水两相相对渗透率曲线,并由无因次采液(油)指数的变化规律和计算预测曲线研究了异常渗流油藏的油水两相渗流特征。     

特低渗透砂岩储层油水微观渗流通道与驱替特征实验研究——以鄂尔多斯盆地延长组为例

以鄂尔多斯盆地延长组2个典型的特低渗透砂岩储层为例,利用真实砂岩微观模型水驱油实验模拟注水开发过程,对水驱油过程中油水微观渗流通道类型和驱替特征进行了定性分析和定量表征.实验过程中共观察到粒间孔、溶蚀孔、粒间孔一溶蚀孔、微裂缝、微裂缝-孔隙和微孔6种主要的油水渗流通道,其差异性与沉积微相、孔隙和喉道的分选、连通情况及粘...     

岩心的核磁共振微成象及其应用

阐述了核磁共振微成象（ＮＭＲＩ）的方法原理，介绍了ＮＭＲＩ显示岩心内部结构、确定水油水分布状态、观测流体驱替过程、了解岩石中孔隙流体局部流动速度、研究微观渗流机理等方面的应用。图１０参１０     

相渗及核磁共振技术在高含水期储层渗流特征研究中的应用 ——以D油田密闭取心井明化镇组储层为例

老油田长期注水开发,在注入水的冲刷和水洗作用下,使得油田储层孔隙结构及填隙物含量均发生改变,必然造成储层渗流特征复杂多变.由于油水相渗实验结果主要从宏观角度反映储层渗流特征,无法从微观层面对储层情况进行描述,有必要将实验室油-水相渗和核磁共振两种实验方法相结合研究高含水期储层渗流特征,从宏观和微观角度出发,基于D油田密...     

Modeling Non-aqueous Phase Liquid Displacement Process

A pore-network model physically based on pore level multiphase flow was used to study the water-non-aqueous phase liquid (NAPL) displacement process, especially the effects of wettability, water-NAPL interfacial tension, the fraction of NAPL-wet pores, and initial water saturation on the displacement. The computed data show that with the wettability of the mineral surfaces changing from strongly water-wet to NAPL-wet, capillary pressure and the NAPL relative permeability gradually decrease, while water-NAPL interfacial tension has little effect on water relative permeability, but initial water saturation has a strong effect on water and NAPL relative permeabilities. The analytical results may help to understand the micro-structure displacement process of non-aqueous phase liquid and to provide the theoretical basis for controlling NAPL migration.     

The effect of wettability heterogeneity on capillary pressure and relative permeability

The effect of wettability on fluid flow properties in porous media has been extensively studied, and is still a subject of highly active investigation. Most of the work has focused on cores of homogeneous wettability. Little attention has been paid to wettability heterogeneity effects at the core or pore scale. In a previous paper, we reported on a series of centrifuge experiments performed to study the effect of wettability heterogeneity on capillary pressure. An experimental technique, named cyclic aging, was developed to create regions of different wetting in the same core sample. In this paper, the work is extended to study the effect of wettability heterogeneity on both capillary pressure and relative permeability curves using centrifuge, continuous injection and steady state techniques.The experimental procedure consists of three steps: (1) the core plug is fully saturated with brine and subsequently a drainage experiment is performed targeting an initial oil saturation S_oi, (2) after aging, oil is displaced by water to residual oil saturation S_or, and (3) oil is injected targeting higher initial oil saturation. In the secondary drainage experiment (step 3), oil first displaces water from the pores exposed to crude oil in primary drainage (step 1) and then enters fresh pores not exposed to crude oil before.In our previous study, it was found that wettability heterogeneity caused a step change in capillary pressure which correlated very well with the saturation at which wettability contrast was expected. However, the height of the step could not be explained by wettability contrast and/or water trapping alone. An experimental artifact caused by the centrifuge technique made the step higher than expected. The experimental artifact was the result of the nonuniform saturation profile developed across the core at the end of the centrifuge experiment. In this study, new techniques were used which resulted in a uniform saturation profile along the core sample during the primary drainage experiment. It was found that in this case the step in the capillary pressure is determined by wettability contrast and water trapping. It was also found that the relative permeability curve changes its characteristics when oil accesses the pores not previously exposed to crude oil.The results of this study show that (1) only the part of the pore space exposed to crude oil undergoes wettability changes on both core scale and pore scale, and (2) ignoring wettability heterogeneity can lead to large errors in the estimated two phase flow functions with important consequences with respect to fluid flow in porous media.     

MEMBRANE SEAL LEAKAGE IN NON‐FRACTURED CAPROCKS BY THE FORMATION OF OIL‐WET FLOW PATHS

Leakage through non‐fractured shaly caprock sequences is often envisioned as hydrocarbon percolation through water‐wet pore networks. Leakage by this process requires that the buoyancy of the hydrocarbon column overcomes the capillary entry pressure of the caprock pores. If it does not, then leakage through caprocks that are not hydrofractured depends on diffusion of hydrocarbons, which is an extremely slow process. As a result, the hydrocarbon residence time would be almost endless. We suggest a novel model for leakage through non‐fractured caprock shales. Two lines of laboratory‐based research motivate our suggestion. One of these addresses wettability alterations, while the other addresses pore‐scale fluid flow in the presence of capillary sealing. The latter approach has demonstrated that water can flow vertically through water‐wet oil reservoirs and further through caprocks, whereas the oil remains in the reservoir. This recognition is a consequence of the observation that residual water in the reservoir can be both continuous and mobile. We suggest that such flow of residual water through reservoirs and into caprocks can lead to the establishment of oil‐wet flow paths in membrane seals. This process takes place in a sequence of events that leads to wettability alterations in the seals. Such wettability alterations allow seals to leak by multiphase Darcy flow, which would hardly happen if the seals were water wet and with sufficiently small pore throats. One implication of this model is that capillary sealing will be effective only for a limited period of time. The model also predicts that residual oil saturation in the shales as a whole remains low, as the suggested flow paths only develop locally and develop narrow leakage pathways.     

井筒与油藏耦合数值模拟技术现状与发展趋势

从井流量方程、井筒内热多相管流计算、多段井模型和近井区域加密的扩展井模型等4个方面总结了井筒与油藏耦合数值模拟技术的研究进展,指出目前存在的主要问题包括:复杂结构井流量方程中参数取值误差很大,不能提供准确的源汇项;高含水阶段井筒内多相管流非常复杂,常用的计算流体力学模型误差很大;非等温井筒内流固耦合模拟机理认识不清楚,数值计算时间长;模拟多层合采时未考虑纵向非均质性,薄差油层的动用情况与实际不符。提出了基于多相管流计算的多段井模型与油藏耦合的数值模拟技术、扩展井模型与油藏耦合的数值模拟技术、考虑井筒出砂和结蜡等复杂现象的流固耦合数值模拟技术是未来的发展趋势。     

用数字岩心确定低渗透砂岩水锁临界值

探明水锁内在因素与损害程度之间的联系机制对水锁抑制措施的研发至关重要,但常规的水锁物理实验只能研究宏观水锁损害后的结果,而无法探讨其微观机理。为此,通过高分辨率微CT扫描构建了低渗透砂岩三维数字岩心,并建立了与之等价的孔隙网络模型,利用孔隙级流动模拟开展了由毛细管力控制的虚拟"自吸"实验,探讨了润湿性、含水饱和度、孔喉结构参数等微观内在因素与水锁损害程度的联系机制。结果表明:(1)润湿性从水湿依次过渡到气湿,水锁损害程度逐渐减轻,只要将强水湿毛细管环境转变为弱气湿,就能有效地减轻水锁损害,提高气井产能;(2)初始含水饱和度与束缚水饱和度之间差异越大,水锁损害越严重;(3)水锁损害程度与配位数呈负相关关系,而与孔喉比呈正相关关系;(4)在现有研究条件下,由中等尺寸喉道组成的地层更容易水锁。结论认为,存在一个临界喉道半径使得水锁最为严重。     

利用孔隙级网络模型研究油水两相流

从岩心薄片分析着手，利用模拟退火算法重建数字岩心；从所建数字岩心中提取对等的由形状简单的孔隙和孔喉组成的孔隙级网络模型。利用表面自由能平衡得到每个网络模型组成单元的毛细管入口压力，从而确定孔隙中流体的流动过程，即所有单元按毛细管入口压力从小到大的顺序进行驱替，入口压力越小的孔隙越先被驱替。由单相和多相时流量的不同可以求出油水两相的相对渗透率，而计算结果与实验结果的一致性则证明了模型是可以用来代表真实岩样的，可以作为一个平台更深入地研究流体在多孔介质中的流动。     

变启动压力梯度三维三相渗流数值模拟方法

建立了多相非达西渗流数学模型,构造了该模型的有限差分离散化方法;推演了模拟低渗透油藏非达西渗流的井-网格流动方程;基于原有黑油模拟器实现了这套模拟方法,使工程化模拟器具备了模拟低渗多相非达西流的能力;综合室内实验结果和矿场动态资料而得到的两相非达西渗流参数,使得模拟结果符合低渗透油藏的开发动态特征。通过对计算结果的分析,指出了基于不同流动规律预测开发指标的差别,提出了度量储层动用状况的启动系数概念,初步评价了注水开采渗透率为2×10^-3μm²油藏的井距适应性。     

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.     

生物酶改变岩石表面润湿性实验研究

根据岩石润湿性的衡量标准,用光学投影法测定岩石接触角,对生物酶改变岩石表面润湿性进行了实验研究,包括生物酶与岩石作用后岩石润湿性的变化、毛管力的变化以及粘附功的变化。实验结果表明,生物酶与岩石作用后,可以明显改变水驱油毛营力的大小,可以加速剩余油的流动,从而提高油藏的采收率。     

油藏岩石润湿性对气驱剩余油微观分布的影响机制

注气驱是目前油田进一步提高原油采收率的重要措施之一,油藏岩石润湿性对注气的效果有重要影响。基于三维孔隙级网络模型,运用孔隙级流动模拟方法,系统研究了6种不同润湿性油藏注气过程的油气水孔隙级分布和气驱效果。结果表明,水湿和MWS混合润湿(小孔隙为油湿)体系中的注气效果相对于另外4种润湿体系较差;这4种效果较好的润湿体系分别是油湿、中性润湿、MWL混合润湿(大孔隙为油湿)和部分润湿（其中30%孔隙水湿）体系。