Genesis of Micro Evolution and the Remaining Oil in the Reservoir

Due to the continuous water percolation and soaking during development of the oilfields, the dynamic balance of a reservoir is altered by the fluid; and the rock framework, pores and throats will be reformed and destroyed. The interaction between the fluid and the rock leads to a series of micro geological processes, such as clastation, denudation, dissolution and deposition, in the small spaces connected by pores or throats, which control the accumulation and distribution of the remaining oil. These micro geological processes are the essential factors for the evolution of the reservoirs during development. This evolution makes the recovery of the remaining oil more complex.

Study on Remaining Oil at High Water Cut Stage of the Offshore Strong Bottom Water Reservoir

C oilfield is a heavy oil field developed by horizontal wells and single sand body in Bohai oilfield. The edge and bottom water of the reservoir is active and the natural energy development mode is adopted. The comprehensive water cut of the oilfield was 95.3%, which had entered the stage of high water cut oil production. Some reservoirs were limited by crude oil viscosity and oil column height. Under the condition of existing development well pattern, some reserves were not produced or the degree of production was low, and the degree of well control was not high, so there is room for tapping the potential of remaining oil. This paper studied the rising law of water ridge of horizontal wells in bottom water reservoir by reservoir engineering method, and guided the infilling limit of horizontal wells in bottom water reservoir. At the same time, combined with the research results of fine reservoir description, the geological model was established, the numerical simulation was carried out, and the distribution law of remaining oil was analyzed. Through this study, we could understand the law of water flooding and remaining oil in the high water cut period of bottom water heavy oil reservoir, so as to provide guidance for the development strategy of this type of reservoir in the high water cut period.

Effects of microscopic pore structure heterogeneity on the distribution and morphology of remaining oil

Waterflooding experiments were performed using Micro-CT on four cores of different pore structures from Donghe sandstone reservoirs in the Tarim Basin. The water, oil and grains were accurately separated by the advanced image processing technology, the pore network model was established, and parameters such as the number of throats and the throat size distribution were calculated to characterize the microscopic heterogeneity of pore structure, the flow of oil phase during displacement, and the morphology and distribution of remaining oil after displacement. The cores with the same macroscopic porosity-permeability have great differences in microscopic heterogeneity of pore structure. Both macro porosity-permeability and micro heterogeneity of pore structure have an influence on the migration of oil phase and the morphology and distribution of remaining oil. When the heterogeneity is strong, the water phase will preferentially flow through the dominant paths and the remaining oil clusters will be formed in the small pores. The more the number of oil clusters(droplets) formed during displacement process, the smaller the average volume of cluster is, and the remaining oil is dominated by the cluster continuous phase with high saturation. The weaker the heterogeneity, the higher the pore sweep efficiency is, and the remaining oil clusters are mainly trapped in the form of non-continuous phase. The distribution and morphology of micro remaining oil are related to the absolute permeability, capillary number and micro-heterogeneity. So, the identification plate of microscopic residual oil continuity distribution established on this basis can describe the relationship between these three factors and distribution of remaining oil and identify the continuity of the remaining oil distribution accurately.

Visualization of Water Plugging Displacement with Foam/Gel Flooding in Internally Heterogeneous Reservoirs

During the displacement of water plugging with binary flooding in internally heterogeneous reservoirs,it is essential to understand the distributions of remaining oil as well as the oil displacement mechanisms at different stages.In this study,two types of internally heterogeneous systems,i.e.,vertical and horizontal wells are investigated experimentally through a microscopic approach.The results show that plugging agent types have a greater impact on oil recovery than well types,and foam injection can enhance oil recovery more effectively than gel injection.Additionally,the injection sequence of plugging agents significantly affects oil displacement efficiency.Injecting gel after foam is more beneficial.According to the present results,the main formation mechanisms of remaining oil in each displacement stage are influenced by:capillary force,viscous force,inertial force,shear force,microscopic fingering&channeling.

Remaining oil distribution in models with different heterogeneities after CO_(2) WAG injection:Visual research by nuclear magnetic resonance technique

Water alternating gas(WAG)injection is a widely used strategy for enhancing oil recovery(EOR)during gas flooding,and the mechanisms,operating parameters,and influencing factors of which have been extensively studied.However,with respect to its capacity in expanding macroscopic sweep volume under varying heterogeneities,the related results appear inadequate.In this research,three cores with different heterogeneities were used and flooded by the joint water and CO_(2) WAG,then the effects of heterogeneity on oil recovery were determined.More importantly,the cores after CO_(2) WAG injection were investigated using the nuclear magnetic resonance(NMR)technique for remaining oil distribution research,which could help us to understand the capacity of CO_(2) WAG in enlarging sweep volume at different heterogeneities.The results show that the presence of heterogeneity may largely weaken the effectiveness of water flooding,the more severe the heterogeneity,the worse the water flooding.The WAG injection of CO_(2) performs well in EOR after water flooding for all the cores with different heterogeneities;however,it could barely form a complete or full sweep throughout the low-permeability region,and un-swept bypassed regions remain.The homogeneous core is better developed by the injection of the joint water and CO_(2) WAG than the heterogeneous and fractured cases.

适用于哈拉哈塘高温高盐岩油藏表面活性剂的研制及应用

为了研制出适用于哈拉哈塘油藏条件的表面活性剂驱油剂,对该储层地层流体及岩石润湿性进行了测试,基于此,采用二甲胺、全氟丁酸、氯丙烯、丙烯酰胺、对苯乙烯磺酸钠等为主要原料,合成了一种耐高温高盐含氟两性离子型高分子表面活性剂(GPHQ-2),并对其表面活性、润湿性以及洗油效率等进行了室内评价。实验结果表明,150℃、25×10^(4)mg·L^(-1)矿化度老化后的GPHQ-2仍能有效降低油水界面张力,可使岩心表面实现润湿反转,洗油效率可达43.4%,远高于常规石油磺酸盐的洗油效率(5.6%);GPHQ-2具有很好的驱油效果,可在水驱阶段原油采收率基础上提高22.84%;现场应用结果表明,目标井采取注GPHQ-2表面活性剂吞吐驱油措施后,日产油量从4.9t提升到8.9t,增产效果明显,且持续有效。说明GPHQ-2表面活性剂满足哈拉哈塘油藏提高采收率需求,并可对该类油藏表面活性剂增产提供理论和实践指导。

近废弃油藏延长生命周期开发调整技术

针对近废弃油藏特高含水、优势通道发育、剩余油高度分散、非均质性强等主要矛盾,以双河油田北块Ⅱ(2油组)4—5层系为例,采用油藏精细地质建模、数值模拟方法和微观驱替实验方法,表征了聚合物驱后油藏剩余油分布特征。聚合物驱后宏观剩余油平面上注采非主流线、主流线弱势区及注采井距较大的边部区域剩余油饱和度较高,纵向上正韵律顶部剩余油富集;微观剩余油以半束缚态为主,依据剩余油分布特征提出了非均相复合驱变流线井网加密调整技术思路。通过井网变流线加密调整,形成交错式行列井网模式,流线方向转变30°以上,流线转向率达80%,促使剩余油有效动用。数值模拟预测该技术可提高采收率10.96%,新增可采储量70.61×10^(4) t,延长生命周期15 a,为聚合物驱后油藏大幅度提高采收率提供新的技术方法。

胜利油田油藏数值模拟技术新进展及发展方向

油藏数值模拟技术是油藏分析的重要手段,是油田开发人员编制开发方案、开展动态跟踪调整、进行提高油藏采收率研究等工作的有力工具。为明确胜利油田油藏数值模拟技术的未来发展方向,回顾了胜利油田60年以来油藏数值模拟应用技术和自主知识产权软件研发的发展历程,着重总结了“十三五”以来适配油田当前地质及开发特征的特高含水期精细油藏描述、低渗透油藏压驱开发、非均相复合驱、稠油油藏多元热复合驱、CO_(2)高压混相驱、页岩油大规模压裂整体开发等多个领域的数值模拟应用技术创新性进展;介绍了涵盖水驱、化学驱、微观、智能模拟等不同方向的多款胜利特色油藏数值模拟软件的研发及应用情况。最后指出在当前胜利油田的开发形势下,油藏数值模拟在精细程度、规模、效率和协作方式等方面面临着更大的挑战,油藏数值模拟需要进一步向一体化、并行化、智能化方向发展,为胜利油田开发提质增效提供技术支撑。

鄂尔多斯盆地超低渗油藏注采调整技术

超低渗油藏储层物性差、非均质性强、注采比高、地层压力保持水平低,部分油藏驱替方案构建难度大、注入水易于沿裂缝窜留,因而水驱波及体积小且采收率低。为了解决该难题,开展了长8段超低渗油藏注采调整政策综合研究。首先对单砂体的测井识别标志、叠置样式、侧向接触模式和见水见效特征进行精细刻画,裂缝、高渗带对水驱有双重作用。通过微观可视化仿真模型对不同孔隙结构下剩余油赋存模式进行研究,超低渗油藏剩余油分布模式主要有分散状及连片状形式,其分布受孔喉尺寸、并联结构、驱替压差、毛管力等因素影响。最终将研究结果应用于地质建模,指导油藏小层精细注采调整,确定了周期注水方式和周期,形成了超低渗油藏全生命周期精细注采技术。将该技术指导华庆、环江油田超低渗油藏注采调整1.5万次左右,采油速度平均增加0.2%、缓解油藏递减1.2%、年均累计增油5万t以上。

海上J油田自适应复合调驱技术研究与应用

针对海上J油田注入压力高、地层非均质性强、各层吸水不均、层间矛盾突出问题,设计了一种自适应复合调驱体系。确定了体系配方为8%自生气体系(生气剂亚硝酸钠与生气剂氯化铵质量比1.0∶1.1)+0.5%起泡剂+0.3%强化剂体系(聚合物+酚醛交联剂质量比1∶1),考察了体系的动静态性能。实验结果表明:该体系具有泡沫生成可控和成胶强度可控的“双控特点”,岩心实验结果表明该体系封堵率达到97.32%,采收率提高幅度高、中、低渗透率分别为19.59%、45.17%、57.83%,具有很好的调整吸水剖面性能。现场应用取得了很好的降水增油效果。该体系为海上油田水驱高效开发提供了技术支持,具有广阔应用前景。

渤海锦州南变质岩潜山油田储层分类及其剩余油分布规律

渤海锦州南油田为变质岩潜山油田,进入中高含水期,油井见水规律多样,剩余油分布复杂,稳油控水难度日益增大。根据取心、测井、薄片、生产动态等资料,采用三维物理模拟和数值模拟等方法,划分储层类型,讨论不同储层类型剩余油分布规律。结果表明:锦州南变质岩潜山油田分为背斜型、半背斜型及掀斜抬升型3类储层,受不同类型储层裂缝开度、密度、连通关系,以及油、水井距离等因素影响;背斜型储层采油井无水采油期长,剩余油主要富集基质系统和构造高部位裂缝系统,提高基质系统的渗吸作用,加强剩余油动用;半背斜型储层采油井存在优势见水方向,剩余油主要富集非优势见水方向的裂缝系统和基质系统,通过流场调控加强非优势见水方向的注水波及系数,提高剩余油动用;掀斜抬升型储层采油井易快速水淹,裂缝系统和基质系统剩余油大量富集,通过控制含水率上升提高剩余油动用。该结果对同类型潜山油田剩余油挖潜具有指导意义。

番禺油田群稠油油藏储集层构型特征及剩余油挖潜

针对番禺油田群稠油油藏采出程度低、隔夹层发育、剩余油预测难等问题,亟需提高储集层构型解剖和预测精度。利用地质、地震和测井资料,采用自然伽马回返率和大数据统计技术,识别储集层3级、4级和5级构型界面,研究各级次夹层的分布模式,定量表征储集层构型单元砂体内部结构以及夹层的展布形态,分析剩余油赋存模式及其主控因素,厘清构型界面对剩余油的控制作用。研究结果表明:储集层中发育的3级斜交型前积夹层能延缓流体垂向渗流,4级叠置型水平夹层能阻止流体垂向窜流;剩余油运移能量和方向主要受3级夹层、4级夹层及韵律差异控制。利用低产低效井侧钻10口调整井,初期总产量为680.00 m~3/d,侧钻后日产油量为侧钻前的5倍。

强边底水断块油藏剩余油二次富集规律及开发策略

强边底水油藏总体储量规模巨大,但一直面临采出程度低、开发效果不理想的难题。以沾化凹陷孤南油田152块油藏为例,通过油藏数值模拟和现场实践,开展了剩余油二次富集过程影响因素和开发策略研究。结果表明,强边底水油藏的流体属性、岩石储层物性以及地层属性等对剩余油二次富集过程的影响效果和程度不一,其中地层倾角、油层厚度、含油条带宽度、渗透率、地层水密度、岩石压缩系数、反韵律非均质性等是影响剩余油二次富集的有利因素。当油层渗透率小于500 mD,地层倾角小于35°,地层水密度小于1.3 g/cm^(3),油层厚度小于15 m,含油条带宽度小于400 m时,压缩系数、反韵律变化幅度、水侵速度(水动力梯度、孔隙流体压力变化幅度)等参数变化越大,油藏剩余油二次富集时间越短,油水二次运移速度越快,注采周期越短,水驱油效果越好,是加速剩余油二次富集和注采耦合驱油进程的主控因素。针对孤南152块和孤南2块的现场实践,提出了以缩放合理注采井距实施边外注水为主的人工调整剩余油二次加速富集策略,精准优化井位完善井网,提高单井储量控制,调整后单元日油能力从调整前的143 t提升至262.9 t,水驱控制程度达到91.1%,平均采收率由35.5%提高到46%,提高10.5个百分点,取得了良好的开发效果。

CO_(2)驱后水气交替注入驱替特征及剩余油启动机制

水气交替注入(WAG)是特低渗透油藏提高采收率的有效手段之一,但在CO_(2)连续气驱后实施WAG驱,仍然存在驱替特征模糊、剩余油启动机制不明确等问题。以海拉尔油田贝14区块为研究对象,借助Micro⁃CT研究WAG驱启动剩余油的微观作用机制,同时通过长岩心驱替实验研究CO_(2)驱后水气交替注入的驱替特征。Micro⁃CT实验结果表明:目标区块大孔隙的体积比例超过85%,在被CO_(2)全部动用后成为了气窜通道,采收率仅47.95%;CO_(2)驱后WAG驱不仅启动次级大孔隙中的剩余油,对中小孔隙的剩余油也有不同程度的动用。长岩心实验结果表明:在CO_(2)驱后开展WAG驱,水和气段塞需要交替注入一定量(0.40 PV左右)后采收率才能大幅度增加,气水比和段塞尺寸存在最优值,分别为1∶1和0.10 PV,该条件下WAG驱的采收率增幅主要由第3、4交替轮次所贡献,10轮次的水气交替注入可在CO_(2)驱的基础上提高采收率18.68百分点。研究成果可为特低渗透油藏CO_(2)驱后进一步提高采收率提供理论支撑。

中国首个长期弃置深水油田二次开发技术创新与实践

中国首个长期弃置的深水油田由于二次开发面临复杂的技术难题和较低的经济效益等问题,成为难以动用的边际油田。通过GGRP(地球物理-地质-油藏-生产)一体化技术研究与实践,盘活弃置油田,保障高产稳产。针对剩余油分布的不确定性、构造复杂、储层非均质及水下管汇限温等问题,克服了多项前沿技术难点。这些创新技术包括长期水驱关停油田的剩余油预测技术、复杂油藏的地质导向及精细描述技术、油藏管流耦合模型流动保障技术,成功指导了油田的二次开发,显著提升了油田的开发效果。结果表明:该油田初期产能跃居南海东部油田前三,实际含水上升趋势与方案设计基本一致,预计增加可采储量达259×10^(4)m^(3)。这一开拓性研究为长期弃置深水油田二次开发提供了宝贵的经验,该科技成果在同类油田的开发进程中有着广泛的应用前景。

储层非均质定量表征方法在礁灰岩油田开发中的应用

对南海流花 11 1油田储层层内、层间及平面非均质性进行了研究。在对储层非均质定量表征的方法中引入了储层非均质性综合指数概念 ,克服了以往研究工作中只应用单一因素表征储层非均质性的不足。利用该方法能够更准确反映储层的实际情况 ,进而研究储层非均质性对剩余油分布的控制作用 ,快速、直观地进行剩余油分布预测。在综合分析了油藏动、静态因素的基础上 ,根据对该油田储层非均质性研究成果 ,提出了剩余油潜力区 ,并在潜力区部署了侧钻井位。实际生产情况与非均质研究结果一致 ,取得了明显的效果。

礁灰岩油藏隔夹层控制的剩余油分布规律研究

珠江口盆地流花11-1油田是底水驱动的块状生物礁油藏,已处于油田开发中期,礁灰岩油藏内部的隔夹层是影响开发效果的因素之一,也是剩余油分布的主要控制因素。根据岩心、测井、地震、开发动态等资料,将该油田生物礁储集体中隔夹层划分为4类,分析隔夹层的成因及分布特征,揭示了隔夹层对剩余油分布的控制作用。在综合分析油藏动、静态因素的基础上,主要根据隔夹层的研究成果,指出了剩余油潜力区,并在潜力区部署了侧钻井位,实际生产与研究结果一致,取得了明显效果。

曲流河古河道储层构型精细解剖--以孤东油田七区西馆陶组为例

以胜利油区孤东油田七区西为例,在沉积微相研究的基础上,主要应用研究区岩心、测井,动态等资料,对曲流河古河道砂体进行了系统的储层层次构型精细解剖。在点坝定量分布模式的指导下,根据点坝砂体垂向上典型的正韵律、砂体厚度大以及紧邻废弃河道分布等特征,在研究区Ng522单层复合河道砂体内部识别出2个单一点坝。综合露头和现代沉积的研究成果、经验公式预测以及对子井分析,建立了研究区点坝内部构型定量模式,以单井上识别的泥质侧积层作为依据,点坝内部定量模式及动态监测结果作为指导,进行模式拟合,达到系统解剖点坝内部构型的目的。建立了点坝内部泥质侧积层控制的剩余油分布模式,提出了采用在点坝砂体中上部钻水平井的方式开采侧积层控制的剩余油。点坝构型解剖成果在研究区得到了较好的应用效果,而且对类似油田储层精细研究及剩余分布预测都有较好的借鉴作用。

辫状河储层构型分析

以羊三木油田羊三断块馆二上段为例,提出了辫状河砂体储层构型的研究方法,即基于辫状河露头及现代沉积原形模型,应用动、静态资料在井间识别单个心滩坝砂体,进行井间构型预测,建立构型三维展布模型。研究结果表明,辫状河心滩坝厚砂层内部存在次级界面,与界面伴生的夹层在心滩坝中心分布不稳定,剩余油往往富集于砂体顶部,而夹层在心滩坝两翼较为稳定,致使剩余油富集于被夹层分隔的某些相对均质段。

流花11-1油田礁灰岩油藏储层非均质性及剩余油分布规律

结合流花11-1油田的岩芯、测井、地震、开发动态等资料总结了礁灰岩油藏沉积、成岩及构造等因素造成的储层非均质特征,引入的储层非均质综合指数,可更快速、直观地揭示了剩余油的分布规律。分析了控制剩余油分布规律的地质因素和开发因素。根据储层非均质性的综合研究成果,指出了剩余油潜力区;在潜力区部署的侧钻井生产情况较好,研究成果得到了验证。该研究思路对类似油田储层非均质性的表征与剩余油分布的预测有较好的借鉴作用。