Effect of CO_(2)flooding in an oil reservoir with strong bottom-water drive in the Tahe Oilfield,Tarim Basin,Northwest China

The dissolution and diffusion of CO_(2)in oil and water and its displacement mechanism were investigated by laboratory experiment and numerical simulation for Block 9 in the Tahe oilfield,a sandstone oil reservoir with strong bottom-water drive in Tarim Basin,Northwest China.Such parameters were analyzed as solubility ratio of CO_(2)in oil,gas and water,interfacial tension,in-situ oil viscosity distribution,remaining oil saturation distribution,and oil compositions.The results show that CO_(2)flooding could control water coning and increase oil production.In the early stage of the injection process,CO_(2)expanded vertically due to gravity differentiation,and extended laterally under the action of strong bottom water in the intermediate and late stages.The CO_(2)got enriched and extended at the oil-water interface,forming a high interfacial tension zone,which inhibited the coning of bottom water to some extent.A miscible region with low interfacial tension formed at the gas injection front,which reduced the in-situ oil viscosity by about 50%.The numerical simulation results show that enhanced oil recovery(EOR)is estimated at 5.72%and the oil exchange ratio of CO_(2)is 0.17 t/t.

Evaluation of reservoir environment by chemical properties of reservoir water‒A case study of Chang 6 reservoir in Ansai oilfield,Ordos Basin,China

The Ordos Basin is the largest continental multi-energy mineral basin in China,which is rich in coal,oil and gas,and uranium resources.The exploitation of mineral resources is closely related to reservoir water.The chemical properties of reservoir water are very important for reservoir evaluation and are significant indicators of the sealing of reservoir oil and gas resources.Therefore,the caprock of the Chang 6 reservoir in the Yanchang Formation was evaluated.The authors tested and analyzed the chemical characteristics of water samples selected from 30 wells in the Chang 6 reservoir of Ansai Oilfield in the Ordos Basin.The results show that the Chang 6 reservoir water in Ansai Oilfield is dominated by calcium-chloride water type with a sodium chloride coefficient of generally less than 0.5.The chloride magnesium coefficients are between 33.7 and 925.5,most of which are greater than 200.The desulfurization coefficients range from 0.21 to 13.4,with an average of 2.227.The carbonate balance coefficients are mainly concentrated below 0.01,with an average of 0.008.The calcium and magnesium coefficients are between 0.08 and 0.003,with an average of 0.01.Combined with the characteristics of the four-corner layout of the reservoir water,the above results show that the graphics are basically consistent.The study indicates that the Chang 6 reservoir in Ansai Oilfield in the Ordos Basin is a favorable block for oil and gas storage with good sealing properties,great preservation conditions of oil and gas,and high pore connectivity.

A PRELIMINARY EVALUATION MODEL FOR RESERVOIR HYDROCARBON-GENERATING POTENTIAL ESTABLISHED BASED ON DISSOLVED HYDROCARBONS IN OILFIELD WATER

A large number of oilfield water samples were analyzed in this work. Research on the relationship between the concentrations and distribution of dissolved hydrocarbons suggested that the contents and composition of dissolved hydrocarbons varied with the hydrocarbon-generating potential of reservoirs. The concentrations of dissolved hydrocarbons were low in dry layers, water layers and gas-water layers, but high in gas reservoirs and oil reservoirs, especially in gas reservoirs with condensed oil. Series of carbon-number alkanes were usually absent in oilfield water from dry layers, water layers and gas-water layers but abundant in oilfield water from oil-water reservoirs, gas reservoirs and oil reservoirs, whose carbon numbers varied most widely in oil reservoirs and least in gas reservoirs. A preliminary evaluation model for reservoir hydrocarbon-generating potential was established based on the characteristics of dissolved hydrocarbons in oilfield water to assist hydrocarbon exploration.

Method of moderate water injection and its application in ultra-low permeability oil reservoirs of Yanchang Oilfield, NW China

To explore the method of improving development effect and solving the problem of water breakthrough and water out for ultralow permeability fractured reservoirs, an indoor evaluation method of dynamic imbibition for fracture-matrix system was established taking the Chang 8 reservoir in southern Yanchang Oilfield as a research target. Key factors for the imbibition effect were obtained, an imbibition's rate expression was obtained, a model considering the double effects of imbibition-displacement was built and optimal injection and production parameters for the research area were obtained as well. The results show that an optimum displacement rate that maximizes the oil displacement efficiency exists in the water displacing oil process, and the optimal displacing rate becomes smaller as the permeability decreases. The imbibition displacement efficiency increases as the reservoir quality index and water wettability index of rock become bigger. But the larger the initial water saturation or oil-water viscosity ratio is, the smaller the imbibition displacement efficiency is. The optimal injection-production ratio for the Chang 8 reservoir of southern Yanchang Oilfield is 0.95, and the predicted recovery is 17.2% when the water cut is 95%, it is 2.9% higher than the recovery of conventional injection-production ratio 1.2. By using the moderate water injection technique based on the double effects of imbibition-displacement mechanism, the water injection development effect for the ultra-low permeability fractured reservoirs can be improved significantly.

Geochemical Characteristics of Oilfield Waters fromthe Turpan Depression, Xinjiang and Their Petroleum Geological Significance

This paper, based on the fundamental inorganic chemical and organic geochemical characteristics of oilfield waters from the Turpan Depression, presents the contents of organic matter, the distribution of low-carbon fatty acids and the contents of aromatic hydrocarbons as well as their principal ultraviolet absorption spectral and fluorescence spectral characteristics in oilfield waters from different oil/gas-bearing areas. The oil/gas reservoirs in this depression are classified in terms of their conserving conditions. In addition, the paper also discusses the chemical characteristics of oilfield waters from different types of oil/gas reservoirs with an emphasis on the characteristics of their localization in the γ_Na/γCa-γNa/γ_Cl correction diagram. On this basis it is attempted to expound the fundamental geochemical characteristics of oilfield waters from the Turpan Depression and their geological significance.

Stable Production Technology for Horizontal Well Development in Shallow Water Delta Oilfield of Bohai Bay, China

BZ Oilfield is a medium-sized oilfield with shallow delta facies deposits in Bohai Bay of China,compared with fluvial and delta facies oilfields,there is no mature experience for reference of reservoir configuration,well pattern arrangement and development model in offshore oilfields in China.In view of the difficulty in describing the reservoir configuration of shallow water delta,the single distributary sand dam in shallow water delta is characterized by well-seismic combination and multi-attribute constraints.The mathematical mechanism model of pinch-out position of sand body is established,fine characterization of BZ shallow water delta reservoir is put forward.The horizontal well pattern arrangement type for shallow water delta reservoir is proposed and the method of well pattern optimization based on vertical displacement theory is put forward.A method of inversion of reservoir connectivity using production dynamic data by numerical well testing is proposed and a new method for optimizing water injection rate in water injection wells is proposed aiming at the difficulty of recognizing injection-production connectivity of shallow water delta reservoirs.The fine configuration of BZ shallow water delta reservoir based on distributary sand dam is proposed,which guides the recognition of remaining oil distribution law.By deploying adjustment wells,the water flooding coincidence degree of actual drilling is 86% compared with that of pre-drilling prediction,which indicates that the research results of reservoir configuration can effectively guide the understanding of oilfield geology.Through the theoretical well arrangement type of vertical displacement of single sand body in horizontal wells of shallow water delta reservoir,a high water flooding recovery rate of 35% is achieved in primary well pattern.The connectivity coefficients of injection-production boundary of shallow water delta reservoir configuration are calculated,and the water injection distribution coefficients are obtained by normalizing the directional coefficients.This paper presents a configuration method based on multi-attribute fusion under the constraints of sedimentary process.In this paper,a shallow water delta reservoir configuration method based on multi-attribute fusion constrained by sedimentary process is proposed,and the injection-production connectivity coefficient and injection well distribution coefficient of the configuration boundary are calculated.

Experimental study on surface-active polymer flooding for enhanced oil recovery: A case study of Daqing placanticline oilfield, NE China

Experiments on surface-active polymer flooding for enhanced oil recovery were carried out by detection analysis and modern physical simulation technique based on reservoirs and fluids in Daqing placanticline oilfield.The experimental results show that the surface-active polymer is different from other common polymers and polymer-surfactant systems in molecular aggregation,viscosity and flow capacity,and it has larger molecular coil size,higher viscosity and viscosifying capacity,and poorer mobility.The surface-active polymer solution has good performance of viscosity-increasing and viscosity retention,and has good performance of viscoelasticity and deformability to exert positive effects of viscosifying and viscoelastic properties.Surface-active polymer can change the chemical property of interface and reduce interfacial tension,making the reservoir rock turn water-wet,also it can emulsify the oil into relatively stable oil-in-water emulsion,and emulsification capacity is an important property to enhance oil washing efficiency under non-ultralow interfacial tension.The surface-active polymer flooding enlarges swept volume in two ways:Microscopically,the surface-active polymer has mobility control effect and can enter oil-bearing pores not swept by water to drive residual oil,and its mobility control effect has more contribution than oil washing capacity in enhancing oil recovery.Macroscopically,it has plugging capacity,and can emulsify and plug the dominant channels in layers with high permeability,forcing the injected fluid to enter the layer with medium or low permeability and low flow resistance,and thus enlarging swept volume.

Research on Composite Fracturing Technology in Qiaokou Oilfield, Dongpu Depression

Limited by serious heterogeneity both horizontally and vertically, water driving of low-permeability layers in Qiaokou oilfield appears to be very difficult. As the classⅠ layer reaches the stage of high water-content too early, the level of exploitation became worse with low-recovery. Regarding the serious heterogeneity and low recovery in layers class Ⅱand Ⅲ, composite fracturing technology suitable for this kind of reservoir was applied. Its basement was a lab study of indoor water driving efficiency and fracturing experiment. Perfect result has achieved by using the technology.

大庆油田油藏工程技术的创新发展与攻关方向

简要回顾了大庆油田开发65 a来油藏工程技术的进步历程,梳理了大庆油田立足油田开发实践创新形成的开发地质、数值模拟、水驱开发、化学驱油、油田开发规划编制方法5项综合研究体系;总结了在油藏工程领域创新发展的小层对比、精细储量计算、注水倍数对驱油效率的影响规律、全国第一条相渗透率曲线研制、小井距注水全过程开发试验、高含水期剩余油分布类型、高含水期稳油控水系统工程、聚合物黏弹性驱油理论和低酸值原油大幅度提高采收率的三元复合驱油理论10项行业领先的关键理论技术;提出了大庆油田持续开发面临的5大难题和需要进一步攻关的高含水区精细挖潜、天然气高效开发、CO_(2)驱油、微生物驱油、非常规油藏开发、地热能源开发、智能油田和高效优质驱油剂研制8项技术。研究成果为大庆油田可持续发展奠定了理论基础。

塔里木盆地塔河北部“过溶蚀残留型”断溶体发育特征及其成因

为了研究塔里木盆地塔河北部强剥蚀区海西早期古岩溶洞穴发育特征,用古地貌恢复、岩溶水系统分析、测井-岩心洞穴识别和地震属性刻画等方法进行了YQ5井区的洞穴类型样式识别、缝洞结构刻画和洞穴成因演化研究。研究结果表明:YQ5井区在塔河油田Ⅱ号和Ⅲ号古岩溶台地北部的地势平缓区,总体为多期次岩溶叠加改造后的残留地貌,主要发育幅差较小的溶峰洼地、溶丘洼地和溶丘平原,南部发育NE向展布的峰丛垄脊沟谷。与塔河油田主体区及斜坡区不同,YQ5井区地下和地表水系的流向与地貌趋势不一致,岩溶水系统遭受构造作用破坏,导致补给、径流和排泄的岩溶水循环过程不完整。YQ5井区主要发育暗河型洞穴和“过溶蚀残留型”断溶体。暗河型洞穴充填较为严重,洞穴的有效储集空间受到破坏,影响油气开发效果。岩溶台地的构造抬升造成区域侵蚀基准面的下降,顺走滑断裂的垂向侵蚀作用有利于“过溶蚀残留型”断溶体的持续发育和保存,油气开发效果好。“过溶蚀残留型”断溶体的发育主控因素为走滑断裂、地层剥蚀强度和负向地貌。与塔河古岩溶台地演化过程一致,YQ5井区的岩溶演化经历深切曲流期、岩溶改造期和下渗断溶期3个阶段。暗河型洞穴被持续改造破坏,断溶体则持续建造。

同位素注入剖面测井解释智能化批量处理技术的实现与应用

同位素注入剖面测井是水驱油田了解各小层吸水状况的主要监测手段,该测井方法在中国油田的年测井工作量在3万井次左右,在注水油藏动态监测中占主导地位。传统的同位素注水剖面测井结果依赖人工解释,工作效率低、工作量大且多解性强,容易受到不同分析员人为因素影响,已经无法满足日益增长的生产需求。运用大数据监测和机器学习等技术,解决了基础数据录入、原始数据解编、深度匹配、工具识别、曲线叠合、综合评价等关键环节技术难题,形成了智能化批量处理技术。通过在CIFLog测井解释平台上的集成运行,单井处理时间从30~60min缩短到30s,人工干预率低于12%,验证了该处理流程及算法的有效性。

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。

大庆油田X7地区低孔渗储层核磁共振测井可变T_(2)截止值确定方法

T_(2)截止值是计算核磁共振测井束缚水孔隙度、可动流体孔隙度和渗透率的关键参数。在岩心压汞资料与核磁共振测井资料的基础上,提出连续计算低孔隙度低渗透率(低孔渗)储层核磁共振测井T_(2)截止值的方法。用岩心对应深度的核磁共振测井T_(2)谱代替核磁共振实验T_(2)谱,用岩心压汞资料中的渗透率贡献确定束缚水所对应的进汞饱和度,此时剩余汞饱和度即为束缚水饱和度,结合T_(2)谱,通过插值算法得出岩心的T_(2)截止值;分析多块岩心T_(2)截止值在T_(2)谱上的分布规律,从而建立根据T_(2)谱形态连续计算可变T_(2)截止值的方法。在X7地区应用此方法实现核磁共振测井连续T_(2)截止值的计算,用计算出的T_(2)截止值进行孔隙度和渗透率等储层参数计算,明显提升了储层参数计算的精度。

薄层砂岩边底水油藏空气辅助内源微生物驱油技术

针对边底水油藏“双高阶段”零散分布剩余油如何有效动用、低成本高效微生物驱油体系如何研发、微生物驱效果评价及配套技术攻关等难题,建立微生物驱筛选图版并评价了油藏微生物驱的适应性;利用微生物分子生态学技术全面解析了油藏微生物群落结构,筛选了乳化效果好的采油功能菌株H3;通过对主要营养成分碳源、氮源、磷源的筛选,开展单因素实验和正交实验,确定了可实现原油乳化分散和抑制硫酸盐还原菌生长的复合粉激活体系;研究了底水油层“船底形”剩余油富集特征,形成了“微生物乳化+空气提效+稠化剂封堵”提高采收率驱油模式,明确了提高采收率幅度与注入菌体浓度、注入孔隙体积倍数正相关。将研究成果应用于准噶尔盆地陆梁油田薄层砂岩边底水油藏,实施“4注20采”微生物驱提高采收率矿场先导试验,注入微生物激活剂0.13倍孔隙体积,2017至2023年阶段增油5.6×104 t,采收率提高4.0个百分点,增油效果好的井主要分布在总菌浓度高、石油地质储量大、构造高部位、油层厚度大、底水薄、采出程度较高的区域。研究成果对丰富微生物驱提高采收率技术序列具有借鉴作用。

缝洞型油藏高压扩容注入动态模型及敏感性分析

高压扩容注水是缝洞型油藏提高采收率的有效方式之一。针对高压扩容注水注采过程认识不清的问题,提出了3类高压扩容注水模式,基于高压扩容注入动态模型,模拟不同敏感性参数对高压扩容注水和生产过程的影响,并结合哈拉哈塘缝洞型油藏矿场实例,分析了3类高压扩容注水模式。结果表明:高压扩容注水有远端低能型、渗流屏障型和近端小储集体型3类模式,3类高压扩容注水模式均可有效动用远端储集体,提高采出程度,渗流屏障型增油效果最优;近端储集体大小影响注水指示曲线拐点出现时间,远端储集体大小影响注水指示曲线出现拐点后的注水难易程度;注水过程的交换指数大于生产过程的交换指数,表明高压扩容注水有效;裂缝闭合压力越小,应力敏感系数越小,注水指示曲线出现拐点越早,累计产液量越高。

Ⅱ类广义气水混驱特征曲线的建立及应用

在Ⅱ类广义水驱特征曲线的基础上,引入了地下含气水率概念,类比建立了Ⅱ类广义气水混驱特征曲线。此类曲线对应的含气水变化规律数学模型在n、m取不同数值时,不仅可以转化为S型含气水变化规律,而且也可以转化为描述凸型、S-凸型、S-凹型、凹型等不同形态的含气水变化规律,丰富了气水混驱油藏开发效果评价方法。给出了Ⅱ类广义气水混驱特征曲线通式及其对应的含气水变化规律数学模型的求解方法,并分别评价了葡北油田三间房组油藏气水交替混相驱和锦州油田S31油藏气顶+边水混驱的开发效果,拟合精度较高,可供其他油藏开发借鉴。

春风油田沙湾组稠油油藏倾斜油水界面成因

春风油田新近系沙湾组一段稠油油藏油水关系复杂,运用传统油水界面观点难以解释,影响该油田勘探开发进程。以油水关系矛盾突出的P601-20区块为例,开展地震-地质综合研究及成藏动力学研究,结合油藏开发动态资料,分析春风油田沙湾组一段稠油油藏油水关系及其成因。研究认为:该油田油水关系复杂是由于油藏存在倾斜油水界面,其油藏类型仍然为构造-岩性油藏,并且存在边底水;储集层物性、断层、地层压力、构造运动等方面,形成倾斜油水界面的主要原因是构造运动导致油藏调整,原油稠化和地层构造平缓加剧了油水界面调整滞后,该油藏属于非稳态油气藏。

陆丰油田古近系低渗高温深层储层自源闭式强化注水技术研究与应用

受海上平台空间、作业成本、注水水源、施工工艺等条件限制,如何高效注水开发陆丰油田古近系低渗高温深层储层面临挑战。以陆丰油田古近系储层试验井为例,开展了注水可行性分析,优选了合适的水源层位和注入层;采用了同井自源类水层补充地层能量的自源闭式注水工艺,研发的配套配水器可满足调节扭矩≤5 N·m、耐压差35 MPa,测调仪器可满足耐温175℃、耐压60 MPa的性能要求,实现了海上平台深层一井多用、无须地面设备的注水新方式;采用了电缆传输的爆燃压裂工艺,实现快速、高效作业,措施的时间控制在14 h以内,时效提高10倍以上,火药密度超过6 kg/m;通过强溶缓速酸酸化复合增效。自源闭式强化注水技术已在陆丰油田试验井M10井取得成功应用,注水高效,受效井增产降水效果明显。本文研究成果有效拓展了注水技术在低渗、深层、高温储层中的应用,可为类似储层规模开发提供借鉴。

渤海特高孔渗储层控水防砂一体化完井技术

渤海BN油田的特高孔渗疏松砂岩油藏储层非均质性强,生产井出水、出砂问题严重,而现有各自独立设计实施的控水和防砂工艺存在设计实施繁琐、控水防砂效果差等问题。为此,在连续封隔体控水完井技术的基础上,根据地质工程一体化的思路,给出了优选连续封隔体颗粒粒径、设计ICD筛管控流强度及优化配置ICD筛管的方法,形成了适用于渤海特高孔渗储层的防砂控水一体化完井技术。BN油田3口井进行了控水防砂一体化完井技术试验,与邻井相比,单井无水采油期平均延长187 d,初期含水率远低于预期含水率,井口无砂时间明显增长,其中BN-D4H1井井口无砂时间长达889 d。现场试验结果表明,防砂控水一体化完井技术可以满足BN油田控水、防砂的双重需求。

流花D油田珠江组下段储层非均质性研究

油田储层非均质性分布规律的认识是深水油田产能指标设计的重要依据,因此是深水油田开发的关键影响因素之一。针对南海深水流花D油田珠江组下段储层展开层内、层间和平面非均质性分析,并结合沉积环境和成岩作用深入研究,厘清了油田内部非均质性分布认识。研究认为南海深水流花D油田隔层和夹层的分布是非均质性的重要影响因素,储层内发育隔层6套,夹层9~10套;此外,油田位于古陆架坡折带附近,沉积由三角洲前缘向浅海陆棚碳酸盐台地转变,在海侵的大背景下,水动力条件变换引起的沉积物变化是影响研究区储层非均质性的主控因素。