Formation damage mechanism and control strategy of the compound function of drilling fluid and fracturing fluid in shale reservoirs

For the analysis of the formation damage caused by the compound function of drilling fluid and fracturing fluid,the prediction method for dynamic invasion depth of drilling fluid is developed considering the fracture extension due to shale minerals erosion by oil-based drilling fluid.With the evaluation for the damage of natural and hydraulic fractures caused by mechanical properties weakening of shale fracture surface,fracture closure and rock powder blocking,the formation damage pattern is proposed with consideration of the compound effect of drilling fluid and fracturing fluid.The formation damage mechanism during drilling and completion process in shale reservoir is revealed,and the protection measures are raised.The drilling fluid can deeply invade into the shale formation through natural and induced fractures,erode shale minerals and weaken the mechanical properties of shale during the drilling process.In the process of hydraulic fracturing,the compound effect of drilling fluid and fracturing fluid further weakens the mechanical properties of shale,results in fracture closure and rock powder shedding,and thus induces stress-sensitive damage and solid blocking damage of natural/hydraulic fractures.The damage can yield significant conductivity decrease of fractures,and restrict the high and stable production of shale oil and gas wells.The measures of anti-collapse and anti-blocking to accelerate the drilling of reservoir section,forming chemical membrane to prevent the weakening of the mechanical properties of shale fracture surface,strengthening the plugging of shale fracture and reducing the invasion range of drilling fluid,optimizing fracturing fluid system to protect fracture conductivity are put forward for reservoir protection.

Multi-parameter quantitative assessment of 3D geological models for complex fault-block oil reservoirs

In the field of 3 D geologic modeling, researchers often pay more attention to modeling methods and workflows, but neglect the quantitative evaluation of models. If the evaluation is narrowed to the same reservoir type, the comparability and practicality of quantitative assessment will be emerging. The evaluation system should include three parts: data verification, geological understanding and process check. Data verification mainly involves testing the accuracy of local prediction with actual data, and geological understanding is to examine whether the global estimation honors geological principles and prior insights. Process check is also indispensable to avoid occasionality. To this end, we produced a set of assessment criteria, taking complex fault-block sandstone oil reservoir as an example. To be specific, thirteen characteristic parameters were totally selected, setting weights according to their rated importance, formulating three-level evaluation standards in a centesimal system for each characteristic parameter, and obtaining the final assessment based on the cumulative score. The results indicate that such evaluation can not only access the quality of the model objectively and comprehensively, but also identify the aspects in need of improvement through the deduction items.

Practice and theoretical and technical progress in exploration and development of Shunbei ultra-deep carbonate oil and gas field,Tarim Basin,NW China

In this review on the exploration and development process of the Shunbei ultra-deep carbonate oil and gas field in the Tarim Basin, the progress of exploration and development technologies during the National 13th Five-Year Plan of China has been summarized systematically, giving important guidance for the exploration and development of ultra-deep marine carbonate reservoirs in China and abroad. Through analyzing the primary geological factors of “hydrocarbon generation-reservoir formation-hydrocarbon accumulation” of ancient and superposed basin comprehensively and dynamically, we point out that because the Lower Cambrian Yuertusi Formation high-quality source rocks have been located in a low-temperature environment for a long time, they were capable of generating hydrocarbon continuously in late stage, providing ideal geological conditions for massive liquid hydrocarbon accumulation in ultra-deep layers. In addition, strike-slip faults developed in tectonically stable areas have strong control on reservoir formation and hydrocarbon accumulation in this region. With these understandings, the exploration focus shifted from the two paleo-uplifts located in the north and the south to the Shuntuoguole lower uplift located in between and achieved major hydrocarbon discoveries. Through continuing improvement of seismic exploration technologies for ultra-deep carbonates in desert, integrated technologies including seismic acquisition in ultra-deep carbonates,seismic imaging of strike-slip faults and the associated cavity-fracture systems, detailed structural interpretation of strike-slip faults, characterization and quantitative description of fault-controlled cavities and fractures, description of fault-controlled traps and target optimization have been established. Geology-engineering integration including well trajectory optimization,high efficiency drilling, completion and reservoir reformation technologies has provided important support for exploration and development of the Shunbei oil and gas field.

Fault-sand combination modes and hydrocarbon accumulation in Binhai fault nose of Qikou Sag, Bohai Bay Basin, East China

Based on seismic and logging data,taking the downthrow fault nose of Binhai fault in Qikou Sag as the object of study,we analyzed fault characteristics,sand body distribution,fault-sand combinations and hydrocarbon accumulation to reveal the hydrocarbon enrichment law in the fault-rich area of fault depression lake basin.The results show that the Binhai Cenozoic fault nose is characterized by east-west zoning,the main part of the western fault segment is simple in structure,whereas the broom-shaped faults in the eastern segment are complex in structure,including several groups of faults.The difference of fault evolution controls the spatial distribution of sand bodies.The sand bodies are in continuous large pieces in the downthrow fault trough belt along the Gangdong Fault in the middle segment of the fault nose,forming consequent fault-sand combination;whereas the fault activity period of the eastern part of the fault nose was later,and the sand bodies controlled by paleogeomorphology are distributed in multi-phase north-south finger-shaped pattern,forming vertical fault-sand combination pattern matching with the fault.The configuration between faults and sand bodies,and oil sources and caprocks determine the vertical conductivity,plane distribution and vertical distribution of oil and gas.Two oil and gas accumulation modes,i.e.single main fault hydrocarbon supply-fault sand consequent matching-oil accumulation in multi-layers stereoscopically and fault system transportation-fault sand vertical matching-oil accumulation in banded overlapping layers occur in the middle and eastern segments of the fault nose respectively,and they control the difference of oil and gas distribution and enrichment degree in the Binhai fault nose.

A study on accumulation and distribution of gas in southern Songliao Basin

A number of isolated fault sags in Late Jurassic--Early Cretaceous were developed in the early stage of southern Songliao Basin,and unified to a depression basin in the late stage.Therefore,multiple isolated lower petroliferous systems were formed with fault sags as source rocks.The source rocks of fault sags in Late Jurassic--Early Cretaceous were mainly described with gas generation as favorable source rocks,leading to the southern Songliao Basin rich in natural gas resources combined with organic gas resources in Nenjiang Formation.A number of tectonic movements in southern Songliao Basin led to the formation of abundant structural traps and complex fault systems,and controlled the distribution strata and positions of sources rocks in Late Jurassic--Early Cretaceous fault sags.The oil-gas reservoirs can be divided into two types,i.e.,primary and secondary ones.The primary oil-gas reservoirs were distributed in the fault sag strata and the bottom of overlying depression strata(lower Quan-1 Member).The oil-gas reservoir accumulation depended on the trap development situation and the distance from source rocks.The preservation conditions of oil-gas reservoirs depended on the degree of reconstruction in the late tectonism.The secondary oil-gas reservoirs were distribution in the Quantou Formation of depression strata,where oil and gas reservoir accumulation depended on three conditions,i.e.,trap development situation,deep gas sources and the fault to connect the shallow traps and deep gas sources.The southern Songliao Basin is rich in lower coal type gas,upper oil-gas and biogas resources,which are important resources in the future.

Study on Fault Lateral Sealing Based on SGR Method

Bozhong A Oilfield is located in the northeast of Huanghekou Sag in the Bohai Bay Basin, and is a complex fault block oilfield. The main oil bearing horizon is the lower Minghuazhen Member, belonging to shallow water delta sedimentation. For the rolling exploration and evaluation of adjacent fault blocks, this paper uses the mudstone smear method to analyze and accurately characterize the lithological contact relationship between the two walls of the fault. Based on the establishment of different reservoir docking modes on the two walls of the fault, the sealing parameters are calculated to evaluate the sealing ability of the fault, thereby evaluating its reservoir formation characteristics, and predicting the height of the oil column. The above methods provide geological basis for further rolling expansion and potential tapping in the study area and surrounding areas, and have guiding significance for exploration and rolling potential tapping in similar blocks in the Bohai Sea.

断块油藏高含水井关井后剩余油再动用运移规律微观模拟

基于微观可视化光刻玻璃模型,从微观角度定性、定量研究了断块油藏高含水井关井后剩余油再动用运移规律,并开展了影响因素分析。结果表明:水驱后关井期间剩余油再动用类型主要为滴状、柱状和簇状。关井期间剩余油会沿模型倾斜方向向高部位运移聚集,有利于后续水驱阶段进一步提高驱油效率。地层倾角的增大、原油黏度的减小有利于剩余油再动用;关井时间的增加有利于剩余油向高部位采出端接近聚集;后续水驱阶段注入速度的增大会增加波及面积。

复杂断块油藏井震联合建模数模一体化技术研究

【目的】为解决复杂断块油藏面临的油藏构造碎小、低序级断层数量多、准确识别难度大和油藏描述效率低等问题。【方法】充分应用地震资料、测井数据等储层信息,开展井震联合建模数模一体化技术研究,利用三维地震资料,结合现场生产动态响应情况开展断层精细解释、断裂系统精细刻画,准确落实低序级断层发育及组合方式,在精细地层对比研究的基础上,建立三维地质模型,利用数值模拟与模型互检,迭代修正更新模型,尽可能保证模型精准,以便厘清剩余油分布规律,指导后期开发。【结果】该技术在胜利油田复杂断块区D块、L块等多个区块先后进行了应用,结果显示,断点吻合率均达到100%,数模含水拟合率达到90%以上。【结论】该技术能够实现复杂断块构造的精细描述,对特高含水期自然断块剩余油潜力认识、提高老区采收率具有重要意义,对其他同类型油藏的剩余油挖潜具有指导意义和良好的推广价值。

基于运聚过程的断块内油气富集层位差异原因分析——以南堡M断块明化镇组为例

为了厘定南堡M断块明化镇组油气富集层位差异的原因,将油气成藏过程细分为油气进入圈闭、在圈闭中运移及在圈闭中聚集三个不同的运聚阶段,分析各阶段油气运聚的动力和阻力差异,结合断块内油气富集层位,明确了南堡M断块明化镇组不同小层油气富集程度差异的原因。研究表明:油气进入圈闭条件和聚集条件的差异是南堡M断块明化镇组油气富集层位差异的主要原因;造成油气进入圈闭和在圈闭中聚集条件差异的主要原因是各小层的输导断层和遮挡断层的断—储排驱压力差;断—储排驱压力差除了受断层断距、储层厚度的影响外,还与相邻地层的岩性组合有关。研究认识对于断块油藏精细滚动开发具有指导意义。

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。

苏北盆地陆相“断块型”页岩油地质特征及勘探实践

中国东部陆相断陷盆地群中-新生代发育多套巨厚的湖相富有机质页岩,蕴含丰厚的页岩油资源,但富有机质页岩普遍受断层切割,形成若干独立断块,与北美连续稳定分布的页岩地层条件存在较大差异,能否获得稳定的商业油流是勘探面临的首要问题。基于苏北盆地高邮凹陷古近系阜(阜宁组)二段页岩岩性、烃源岩品质、储层品质研究与综合评价,研究认为阜二段发育3套厚层有利层,具备“多层楼”立体勘探开发条件;基于阜二段有利层、断层和断块发育地质现状,提出水平井在同一断块内或跨断块、在同一或多个有利层长距离穿行的“断块型”页岩油勘探思路;根据断层断距与有利层厚度之间的配置关系,将“断块型”页岩油划分为“连续稳定”型、“微断层切割”型和“跨断块多甜点”型等3种勘探目标类型。通过勘探实践,证实3种勘探目标类型均可获得稳定的商业油流。研究成果丰富了中国陆相页岩油勘探领域和类型,对陆相断陷盆地页岩油勘探具有重要借鉴意义。

顺北一区超深断控油藏注天然气开发的可行性

顺北一区矿场天然气资源丰富、油藏压力高、顶部剩余油富集,具备注天然气混相驱的开发潜力。通过注气流体相态模拟实验和油藏数值模拟,从注气原油相态、混相条件、注气方式等方面,论证顺北一区注天然气混相驱开发的可行性。研究表明,注CH4原油具有饱和压力低、体积膨胀系数大、混相压力低等优势;注CH4最小混相压力约为46.80 MPa,注伴生气最小混相压力较注干气约降低4.00 MPa。回注天然气,80%以上的井组可实现混相驱替;气水交替注入可延缓气水突破时间,提高驱替相波及系数,补充地层能量和实现均衡驱替,模拟3年可提高采出程度11.2%。

田东油田开发调整潜力评价方法研究

针对田东油田油藏构造复杂、油水井地质条件及注采状况差异大、开发中后期措施潜力评价难等问题,文章依据油田经营及经济条件,采用技术与经济相结合的方法,研究了开发调整界限确定方法,并结合油田地质和开发动态实际,评价了开发调整潜力,为油田综合调整方案编制及开发调整提供依据。

断块油藏储层连通性分析和综合研究

P油田位于渤海湾渤南低凸起带上,在构造高部位走滑断裂带附近发育多条断层。经过多年的开发生产,目前油田构造高部位的主要问题是注采井网连通性差,生产动态反应与断层认识不相符。为了明确构造高部位断层分布模式,解决目前注采井网连通性差等问题,基于井网生产动态资料,结合对复杂走滑断裂带的新认识,利用数值模拟技术研究复杂断块油藏构造高部位储层的连通性,并与地震资料结合相互验证。研究结果表明:P油田走滑断层附近发育多组隐形断层,阻碍了注入水的推进,使得注水井端超压,生产井端亏压,导致油井端产油效果较差。研究结果可为P油田构造高部位后续调整井挖潜剩余油提供参考。

河口坝内部储层构型及剩余油分布特征——以大港油田枣南断块长轴缓坡辫状河三角洲为例

利用岩心、测井、地震及分析化验资料,综合层次分析、模式拟合及数值模拟等方法对河口坝内部储层构型模式进行研究,同时探讨了其内部夹层控制的剩余油分布特征。研究结果表明:受分流水道不同的沉积物卸载方式控制,河口坝内部夹层具有侧向叠置状及上拱状两种分布样式。侧向叠置状夹层样式在垂直物源方向呈一定倾角的侧向叠置状;上拱状夹层样式在垂直物源方向上呈多层隆升状。其中不同夹层分布样式的规模和方向存在较大差异。不同样式夹层剩余油富集方式存在差异。平行物源方向上,剩余油往往富集在夹层控制的注采不对应的前积体(增生体)内部,且其前端剩余油富集程度较高。垂直物源方向上,对侧向叠置状夹层样式来说,剩余油大量富集在坝主体内部夹层隔挡的侧积体内;对上拱样式来说,剩余油受水驱控制大量富集在拱状高部位。

复杂断块油藏三维地质模型多参数定量评价

在三维地质建模领域,研究人员更重视建模的方法和流程,而忽略了模型的定量评价。如果把评价范围缩小至同一油气藏类型,定量评价的可比性和实用性就会显现。研究认为,定量评价体系应包括资料验证、地质认识及过程检查这3个部分。资料验证主要是根据实际资料验证模型局部预测是否准确,地质认识主要是验证模型全局预测是否符合地质规律和前期认识,两者是从不同的角度对结果进行的定量验证,互为补充,是定量评价的重点;过程检查是为了避免偶然性。以复杂断块砂岩油藏为例,在征集业内专家意见的基础上,提炼并建立三维地质模型多参数定量评价标准,共选取13个特征参数,按重要性设置权重,按百分制确定各特征参数高、中、低三级评价标准,根据累积得分得出评价结论。评价结果表明,按此标准,既能客观、全面地评价模型质量,还能根据扣分项指出模型有待改进和提升的方面。

断层在高邮凹陷复杂断块区成藏中的作用

分析了苏北盆地高邮凹陷断裂的特征。统计发现,目前所发现的油藏(圈闭)均与断层有关,断层是复杂断块区构成圈闭的主要要素,断层在成藏中主要起封闭和聚集油气的作用。在不同结构的地层中断层的封闭能力不同,圈闭与断层的不同匹配关系对油气聚集有很大影响。

多层系油藏剩余油分布的精细数值模拟技术

针对东辛油田营 8块沙河街组地质构造复杂 ,开发历史长 ,合采合注井多 ,作业措施频繁 ,已进入特高含水期等特点与难点 ,采取了优选主力目标层 ,精细储量复算 ,优选模型区 ,优化网格 ,三维角点地质建模 ,分层系岩石流体物性控制 ,精细动态生产数据控制和精细历史拟合等数值模拟研究技术措施 ,分析了老区断块油藏特高含水期平面、纵向水淹状况和剩余油分布规律 ,确定了影响剩余油分布的主要因素 。

低渗油田注水能力下降原因分析及其对策研究

对注水井注水压力高、注水困难的原因进行了诊断,指出注入水中机械杂质含量严重超标、机杂粒径大,与低渗储层的孔隙喉道大小不匹配是导致储层孔隙堵塞的主要原因,近井地带石蜡的析出是导致储层孔隙堵塞的另一原因.针对此类堵塞,研究了解堵增注方案.通过方案的部署实施,该油田注水难的问题得到了有效解决,区块的开发效果得到了明显改善,提高了区块开发的效益,为同类型油藏的开发提供了借鉴模式.

高含水期复杂断块油藏剩余油分布及挖潜

高含水期陆相复杂断块层状油藏剩余油分布复杂 ,油藏模拟难度大。马 11复杂断块油藏在油藏精细描述基础上 ,利用动静态综合分析研究与密网格大规模数值模拟研究相结合 ,提高了剩余油研究精度和可信度 ;在此基础上 ,针对油藏剩余油分布特点并结合当前经济技术条件 ,部署实施了以调整井、调剖、堵水、油水井大修为主的剩余油挖潜方案 ,油藏含水上升率大幅度下降、采油速度上升、采收率提高了。