Quantitative characterization of deep fault-karst carbonate reservoirs: A case study of the Yuejin block in the Tahe oilfield

The Ordovician reservoirs in the Tahe oilfield are dominated by fractured-vuggy carbonate reservoirs, of which fault-karst reservoirs are a hot topic in recent years. Fault-karst reservoirs feature high production, large burial depth, and strong heterogeneity under the control of faulting and karstification. Based on geological, logging, and seismic data, this study classified the Ordovician fault-karst reservoirs in the Yuejin block of the Tahe oilfield into three types, namely karst-cave, dissolved-vug, and fractured types, and established the integrated identification criteria of the three types of reservoirs. This study characterized karst caves, dissolved vugs, and multi-scale faults through seismic wave impedance inversion and frequency-domain detection of multi-scale faults. 3D geological models of different types of reservoirs were built using the combined deterministic and stochastic methods and characterized the spatial distribution of multi-scale faults, karst caves, dissolved vugs, and physical property parameters of reservoir. This study established the method for the geological modeling of fault-karst reservoirs, achieved the quantitative characterization and revealed the heterogeneity of fault-karst reservoirs. The karst-cave and dissolved-vug types are high in porosity and act as reservoirs, while the fractured type is high in permeability and act as flow pathway. This study lays the foundation for the development index prediction, well emplacement, and efficient development of the fault-karst carbonate reservoirs.

Production evolution patterns and development stage division of waterflooding oilfields

The continuous growth of recoverable reserves in a waterflooding oilfield has a significant impact on the patterns of production evolution. A new production evolution model is established by improving the Weng Cycle model. With the new model, the statistical correspondence between the production decline stage and the reserve-production imbalance is clarified,and the correlation of water cut with the recovery percent of recoverable reserves is discussed, providing quantitative basis of reservoir engineering for dividing development stages of oilfield and defining mature oilfields. According to the statistics of oilfields in eastern China, the time point corresponding to the reserve-production balance coefficient dropping to less than 1dramatically is well correlated the beginning point of production decline, thus the time when the reserve-production balance coefficient drops dramatically can be taken as the initiation point of production decline stage. The research results show that the water cut and the recovery percent of recoverable reserves have a good statistical match in the high water cut stage, and it is more rational to take both the start point of production decline stage and the water cut of 90%(or the recovery percent of recoverable reserves of 80%) as the critical criteria for defining a mature oilfield. Five production evolution patterns can be summarized as follows: growth–peak plateau–stepped decline, growth–stepped stabilizing–stepped decline, growth–stepped stabilizing–rapid decline, growth–peak plateau–rapid decline, and growth–continuous decline.

Development technologies for Triassic Chang 7 shale oil in Ordos Basin: A case study of Qingcheng Oilfield, NW China

The reservoirs in the seventh member of the Triassic Yanchang Formation (Chang 7 Member) in the Qingcheng Oilfield of the Ordos Basin are characterized by thin sandbody, tight rocks, high heterogeneity, low formation pressure coefficient, and complex geomorphology. Through the efforts in the stages of exploration, appraisal, pilot testing and development, a series of key technologies have been formed, including “sweet spot” optimization, differentiated three-dimensional well deployment, fast drilling and completion of large-cluster horizontal well, intensively-staged volume fracturing in long horizontal well, and optimization of rational production system. Furthermore, a production organization mode represented by factory-like operations on loess platform has been implemented. Application of these technologies has enabled to significantly improve the single-well production of the Qingcheng Oilfield, reduce the investment cost, and realize a large-scale and beneficial development at a full cost below $55 per barrel. In 2022, the annual production of Chang 7 shale oil in the Ordos Basin reached 221×10^(4) t, accounting for 70% of the annual shale oil production of China. The practice of development technologies in the Qingcheng Oilfield provides valuable references for efficient development of continental shale oil.

Origin of gas condensate reservoir in Fuman Oilfield, Tarim Basin, NW China

To understand the reservoir property and hydrocarbon accumulation conditions of the Middle and Upper Ordovician intraplatform shoal between ultra-deep main strike-slip faults in Fuman Oilfield of the Tarim Basin, China, the main strike-slip faults in and around well FD1 in the basin were analyzed in terms of sedimentary facies, sequence stratigraphy, intraplatform shoal reservoir property, and oil and gas origins, based on drilling data. The Yingshan Formation intraplatform shoal between the main strike-slip faults is superimposed with low-order faults to form a new type of hydrocarbon play. Firstly, hydrocarbons generated from the Lower Cambrian Yuertusi Formation source rocks vertically migrated into the second member of Yingshan Formation through the main strike-slip faults, and then migrated laterally until they were accumulated. A small amount of oil from Well FD1 came from the Yuertusi Formation source rocks in the mature stage, and a large amount of gas originated from oil cracking in the ultra-deep reservoirs. Therefore, the secondary gas condensate reservoir in Well FD1 is characterized by high gas to oil ratio, dry gas (dryness coefficient being 0.970) and hybrid origin. This new type of hydrocarbon play characterized by intraplatform shoal and low-order fault suggests a prospect of continuous hydrocarbon-bearing area in Fuman Oilfield, which will expand the ultrap-deep oil and gas exploration in the oilfield.

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.

滨里海盆地东缘北特鲁瓦油田石炭系层序地层与沉积演化特征

根据三维地震、测井及钻井取心等资料,结合Vail的层序划分方案,在滨里海盆地东缘北特鲁瓦油田石炭系碳酸盐岩台地内识别出7个地震层序界面及7个钻井层序界面,并将KT-Ⅰ油层组划分为3个半三级层序,KT-Ⅱ油层组划分为3个三级层序。纵向上层序格架内沉积环境由开阔台地、局限台地至蒸发台地演化。根据研究区层序格架内的古地貌恢复及沉积演化研究,将研究区古地貌—沉积演化划分为3个阶段:台地初始隆坳分异期(SQ2-SQ3层序)、差异抬升与沉积分异定型期(SQ4层序)及继承发育期(SQ5-SQ7层序)。进一步分析认为,层序格架控制下的隆坳格局分异控制了白云岩亚类在平面上的分布,低部位以泥晶云岩—膏盐岩组合和泥晶云岩—泥晶灰岩组合为主,主要为潟湖相沉积;而高部位则以泥粉晶云岩、细粉晶云岩和残余颗粒泥晶云岩为主,发育云坪相及云化颗粒滩相沉积。结果表明,区内KT-Ⅰ油层组沉积期并非前人认为的西高东低剥蚀后沉降充填,而是继承性差异沉降的结果,古地理格局总体具有“东台西槽、北高南低”特征,其始终控制着有利相带和优质储集层的发育展布。这一认识对滨里海地区油气勘探开发战略选区具有重要的指导作用。

渤海C油田馆陶组储层堵塞实验评价研究

为了分析明确渤海C油田导管架期间预钻井的12口生产井,在组块安装后投产产量达不到配产目标的原因,针对有机质沉积、原油乳化堵塞、流体配伍性、钻完井液漏失与返排等潜在储层伤害因素,开展了储层堵塞实验评价研究。实验结果表明:1)免破胶无固相钻开液(EZFLOW)漏失量越高渗透率伤害程度越大,同时考虑钻完井液漏失时,天然岩心的渗透率伤害程度为37%,伤害程度中等;2)有机质沉积对储层伤害较为明显,注入0.4 PV原油后渗透率伤害程度达到98%,且随有机质沉积量的增加,储层伤害越大;3)油包水型乳状液(W/O型)驱替对岩心渗透率伤害程度高达75.01%,水包油型乳状液(O/W型)驱替对岩心渗透率伤害程度为25.21%,低含水层受原油乳化堵塞影响较明显。综合分析认为,渤海C油田12口预钻井低产原因为导管架预钻井后待组块安装期间关井静置过程中有机质沉积和原油乳化伤害。同时,渤海C油田12口预钻井目的层馆陶组储层物性因子较小,产液指数较低是导致低产的原因之一。研究结论为后续增产措施以及方案提供了依据。

准噶尔盆地永进油田侏罗系超深层致密砂岩储层成岩相识别及分布预测

深层致密砂岩储层非均质性强、分布规律复杂,地质甜点预测难度大。为实现高效勘探开发,如何准确识别与预测井间储层成岩相亟需深入研究。综合利用岩心、测井和三维地震资料,在准噶尔盆地永进油田侏罗系超深层储层成岩作用研究基础上,开展了成岩相识别及分布预测研究,认为储层成岩作用类型主要有压实作用、胶结作用及溶蚀与交代作用,可划分为强溶蚀+绿泥石包壳、中等溶蚀+自生高岭石、中等钙质胶结溶蚀、强钙质胶结及压实致密等5种成岩相。基于测井资料,利用岩石物理参数、物性参数对储层成岩相类型进行了综合识别,确定其垂向分布规律。研究发现强溶蚀+绿泥石包壳和中等溶蚀+自生高岭石这两种优势成岩相主要位于三角洲主干分流河道砂体内部,储层物性较好,是油层发育的主要部位。基于成岩相与地震纵波阻抗的对应关系分析,发现优势成岩相纵波阻抗相对较低,可通过纵波阻抗的数值分布特征预测优势成岩相分布。因此利用三维地震纵波阻抗反演成果开展了成岩相分布预测,根据纵波阻抗与不同类型成岩相对应关系落实了优势成岩相发育区。结果表明,优势成岩相主要位于研究区东北部的Y301—Y302井区以及西北部Y1井区,呈局部连片分布发育。储层成岩相识别可以为超深层地质甜点的分布预测研究提供重要依据。

大庆油田SEC储量折耗一体化评估模型

SEC储量是大庆油田有限责任公司经营决策的核心资产,是油气生产的物质基础。油气资产折耗和SEC储量相关,是完全成本中的重要构成部分,决定了油田经营效益。大庆油田进入双特高含水后期,开发对象变差导致增储能力变差、油气资产折耗上升,因此亟需开展SEC储量折耗一体化优化研究,使储量和折耗指标最优。结合折耗计算公式、ARPS递减模型和经济极限产量计算模型等公式,进行科学归纳和推导,建立了SEC储量折耗一体化增储模型,并且在量化分析各种影响因素的基础上,明确了储量和折耗的优化次序和参数,给油田开发经营提出建议。模型应用在大庆油田年度SEC储量评估中,使油田增储能力逐年提升,油气资产折耗得到有效控制。研究成果具有通用性和适应性,可以在国内其他油田推广应用。

大庆长垣油田水驱开发技术智能化实践与展望

数字化转型、智能化发展是老油田开发技术提档升级、提质增效的必要途径。全面总结了国内外油田开发技术智能化研究进展,介绍了人工智能技术在大庆长垣油田水驱开发中的应用进展及取得的重要成果,尤其强调了智能测井解释、智能井震结合储层预测、基于数据挖掘的注水优化调整以及措施井层智能优选等关键技术在提升油田开发效率、效果和经济效益方面的积极作用。通过技术创新,大庆长垣油田水驱自然递减率控制到7%以下,年含水上升值控制到0.2百分点以内,实现了特高含水后期油田的高水平、高质量开发。在此基础上,展望了水驱开发技术的智能化发展方向,指出应加快油气大语言模型的应用,加强实时动态监测技术的研发,并通过数字孪生模型、智能方案编制、注采智能优化等手段推动油田开发向更高水平的智能化转型。

基于超音速膨胀凝结的油田伴生气脱二氧化碳研究

油田伴生气通常含有大量的二氧化碳等酸性气体,为了提升油田伴生气质量,必须对天然气进行脱二氧化碳处理;将超音速旋流分离技术用于伴生气脱除二氧化碳是一条全新路径,但二氧化碳在超音速流动条件下的冷凝特性有待进一步明晰。建立二氧化碳在喷管中的相变过程数学模型,讨论二氧化碳超音速凝结流动特性,分析入口温度和压力对二氧化碳超音速凝结特性的影响规律。结果表明:二氧化碳在喷管喉部之后的扩张段发生凝结,生成大量的二氧化碳液滴;随着喷管入口温度增加,尽管凝结的二氧化碳液滴数量增加,但喷管出口和中轴线上的液相质量分数减小,凝结位置越靠近喷管出口;随着喷管入口压力增加,混合气体在喷管出口的压力和温度升高、速度减小,二氧化碳在喷管内凝结产生的液滴数量减少,喷管出口和中心轴线上的液相质量分数越大。

油田监测用密度可控同位素示踪微球的制备及应用

制备了用于油田监测的同位素示踪微球,分析了微球的形貌、抗压强度、热性能、耐溶剂性和加工性能,揭示了微球与同位素产率及加工性能的构效关系,提出了示踪微球密度计算方法。结果表明:示踪微球表面形貌主要为致密和松散两种,抗压强度的影响因素主要为黏合剂种类与加料方式;采用不同黏合剂制备的微球耐溶剂性差别较大,采用酚醛胺和聚酰胺制备的示踪微球抗压强度较高,耐热性较好;采用炭粉为原料获得的同位素产率较高;微球密度的调控可以通过一个经验系数来计算。

金属有机框架MIL-101(Fe)用于增强光催化降解含油污水中的原油

利用溶剂热法合成了一种稳定的金属有机框架(MOF)MIL-101(Fe),并作为一种新型光催化剂提高了油田废水中原油的降解性能。通过对反应条件的优化,确定了以下最佳参数:暗反应时间为30 min,光反应时间为30 min,p H值为5.5,催化剂量为150 mg/L,反应温度为303.15 K。在这些反应条件下,去除率达到了94.73%。本研究是铁基MOFs在油田废水光催化降解中的应用。MIL-101(Fe)在温和的酸性条件下表现出良好的稳定性,并且可以有效地循环利用。这些发现为利用MIL-101(Fe)作为一种很有前途的工业应用材料,通过光催化降解从受油污染的水中去除原油提供了有价值的见解。

普通稠油降黏复合驱技术研究与矿场试验

针对普通稠油油藏水驱采收率低且热采成本高、碳排放量大的问题,基于春光油田低温高盐储层的流体性质,优选了阴离子型降黏剂和耐盐聚合物,通过室内物理模拟实验,明确了热水驱、单一降黏剂驱、复合驱的降水增油机理;建立了降黏复合驱反应动力学方程,在CMG-STARS软件中开发了降黏复合驱数值模拟方法,并优化了春2单元普通稠油降黏复合驱井网、井距及注采方案。研究结果表明:降黏复合驱可以充分发挥驱替相增黏、被驱替相降黏的加和效应,具有体系用量少、碳排放低、提高采收率幅度大等优势;降黏复合驱适合五点法井网,注采井距应小于200 m,在增稠剂质量分数为0.25%、降黏剂质量分数为0.20%的条件下,最佳注入段塞量为0.5倍孔隙体积,注采比为1.05。矿场实践表明,特高含水后期(含水率96.0%)的油井实施降黏复合驱,含水率降幅达30%以上,日增油5 t/d。研究证实了该项技术矿场应用的可行性,可为改善普通稠油开发效果、实现工业减排提供借鉴。

大庆油田裸眼井测井技术进展与展望

为了提高大庆油田裸眼井测井技术支撑能力和研究成果领先水平,全面回顾了大庆油田测井采集系列及解释技术的创新发展历程,系统总结了特高含水期剩余油解释、火山岩等复杂岩性测井评价、碎屑岩储量参数解释、非常规油气“甜点”分类、缝洞型碳酸盐岩储层测井评价等油田勘探开发测井评价技术。在客观分析大庆油田勘探开发测井解释评价需求和面临瓶颈问题的基础上,结合当前油田测井评价对象规模小、物性差、埋藏深、地层结构复杂、非均质性强的特点。指明了测井解释评价核心技术主攻方向。围绕新阶段测井采集及解释评价技术体系完善与建立,对高分辨率和成像测井采集、后油藏时期和非常规测井解释评价、新一代智能解释技术体系等未来发展进行了展望。

塔河油田下寒武统烃源岩生排烃史差异演化及成藏效应

针对塔河奥陶系油藏多相态油气富集主控因素认识不清的问题,采用盆地模拟技术再现了塔河油田下寒武统烃源岩热演化史、生烃史及典型剖面油气运聚过程。研究表明:塔河地区下寒武统烃源岩从加里东早期进入成熟阶段,目前处于高成熟—湿气阶段,发育断续埋藏、持续埋藏和长期浅埋藏3种热演化模式,分别对应油气并举双峰型、油强气弱型、单峰型3种生烃模式。烃源岩热演化差异致使奥陶系油气发育多期充注、垂向疏导、侧向调整改造的演化历史,油气相态呈现轻质油藏—中质油藏—重质油藏的有序分布格局。塔河地区不同构造带下寒武统烃源岩热演化具有由北西向南东递增的趋势,与油气相态差异呈现明显的正相关性,体现出“源控”特征,喜山期控制了现今油气藏分布。研究发现,塔河油田盐下、托甫台生烃强度高,喜山期生烃总量相对较大,可作为下一步勘探开发的有利区。研究结果对塔河油田深层油气资源和目标评价有一定指导意义。

塔里木盆地塔河油田塔深5井震旦系原油地球化学特征及地质意义

塔深5(TS5)井于2021年完钻,井深9 017 m,是目前亚洲第一深井,同时也是塔里木盆地台盆区第一口在8 780~8 840 m的上震旦统白云岩段获得油气突破的钻井,也是继轮探1井寒武系盐下突破后,超深层白云岩领域的又一重大发现。为了探究其油气成因,分别对TS5井震旦系凝析油和上部奥陶系重质油,及其邻区寒武系挥发油和奥陶系凝析油进行了有机地球化学特征对比。结果表明,TS5井震旦系凝析油和白云岩储层氯仿抽提物的正构烷烃系列均分布完整,指示了其生烃母质形成于强还原环境;其与奥陶系正常油-超重质油和雅克拉地区凝析油总体具有相似的生物标志化合物和碳同位素分布特征,反映均具有相似的油源;其等效镜质体反射率(Rc)值为1.7%,成熟度高于奥陶系重质油、寒武系挥发油,与邻区凝析油相当,处于高成熟阶段。综合生物标志化合物和碳同位素证据,推测TS5井震旦系油气源来自下寒武统玉尔吐斯组,其与上覆玉尔吐斯组泥页岩构成良好的储盖组合,喜马拉雅晚期来自周边较低部位玉尔吐斯组生成的高成熟凝析油气,沿斜坡运移至震旦系白云岩构造圈闭内形成了一定规模的凝析气藏。TS5井震旦系油气突破,发现了新的含油气层系,丰富了超深层油气成藏过程,为塔里木盆地超深层勘探指明了新的探索方向。

长庆油田数智化油藏建设理论与实践

随着油气勘探认识和技术的不断进步,盆地边缘新层系非常规储层成为油气增储上产的重要领域,开采难度增加,工作量培增。然而,油田用工总量不增反降,如何提升油气藏研究的精细化水平,培育新质生产力,打造油田高质量发展新引擎,是油田急需解决的问题。长庆油田制定了“125”数智化油藏建设规划,通过数智化技术,助力资源勘探、油气开发和新能源3大主业的高质量发展。立足数智化油藏学科长远建设,结合地质研究、井位部署与随钻、产能建设、稳产提产等领域的数智化建设特点,总结出一套高效稳健的数智化油藏建设理论与方法,形成了“一体系四中台”基本建设思路,制定了勘探开发数智化整体解决方案。在该理论指导下,建成了数字油气藏研究与决策支持平台,有效推进了长庆油田的快速上产稳产,现已成为中国石油天然气集团有限公司的品牌产品,支撑着长庆油田向国际一流大油气田迈进。

大庆油田特高含水期原油开发规划技术发展现状与展望

开发规划在油田开采过程中发挥着重要的龙头指导作用,是油田企业在一定时期内制定的行动纲领和指南。开发规划技术水平的高低直接影响油田开发的效果和效益。在明确开发规划的基本内涵及与计划、战略的区别基础上,着重介绍了大庆油田发展的2类7项开发规划系列技术,包括开发规律及指标预测技术、技术经济政策界限确定技术、开发效果及潜力评价技术、规划编制及优化技术4项核心技术和可采储量及SEC储量评估技术、经济效益评价及决策支持技术、规划信息化技术3项支撑技术。通过分析当前油田开发规划技术发展存在的生产与技术难题,明确了3个发展方向以及3条实现路径。研究成果与认识对油田开发规划理论研究和实际应用具有重要的参考价值和借鉴意义。

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。