Numerical Simulation of Oil and Gas Two-Phase Flow in Deep Condensate Gas Reservoirs in Bohai Buried Hills

The BZ19-6 gas field is characterized by high temperature and high pressure (HTHP), high condensate content, little difference between the formation pressure and dew point pressure, and large amount of reverse condensate liquid. During the early stage of depletion development, the production gas-oil ratio (GOR) and production capacity remain relatively stable, which is inconsistent with the conventional reverse condensate seepage law. In view of the static and dynamic conflict in development and production, indoor high-temperature and high-pressure PVT experiment was carried out to reveal the mist-like condensation phenomenon of fluids in the BZ19-6 formation. And the seepage characteristics of condensate gas reservoirs with various degrees of depletion under the condition of HTHP were analyzed based on production performance. The change rule of fluid phase state was analyzed in response to the characterization difficulties of the seepage mechanism. The fluid state was described using the miscible mechanism. And the interphase permeability interpolation coefficient was introduced based on interfacial tension. By doing so, the accurate characterization of the “single-phase flow of condensate gas-near-miscible mist-like quasi single-phase flow-oil-gas two-phase flow” during the development process was achieved. Then the accurate fitting of key indicators for oilfield development was completed, and the distribution law of formation pressure and the law of condensate oil precipitation under different reservoir conditions are obtained. Based on research results, the regulation strategy of variable flow rate production was developed. Currently, the work system has been optimized for 11 wells, achieving a “zero increase” in the GOS of the gas field and an annual oil increase of 22,000 cubic meters.

A well test analysis model of generalized tube flow and seepage coupling

"Generalized mobility"is used to realize the unification of tube flow and seepage in form and the unification of commonly used linear and nonlinear flow laws in form,which makes it possible to use the same form of motion equations to construct unified governing equations for reservoirs of different scales in different regions.Firstly,by defining the generalized mobility under different flow conditions,the basic equation governing fluid flow in reservoir coupling generalized tube flow and seepage is established.Secondly,two typical well test analysis models for coupling tube flow and seepage flow are given,namely,pipe-shaped composite reservoir model and partially open cylindrical reservoir model.The log-log pressure draw-down type-curve of composite pipe-shaped reservoir model can show characteristics of two sets of linear flow.The log-log pressure drawdown plot of partially opened cylindrical reservoir model can show the characteristics of spherical flow and linear flow,as well as spherical flow and radial flow.The pressure build-up derivative curves of the two models basically coincide with their respective pressure drawdown derivative curves in the early stage,pulling down features in the late stage,and the shorter the production time is,the earlier the pulling down feature appears.Finally,the practicability and reliability of the models presented in this paper are verified by three application examples.

A review of development methods and EOR technologies for carbonate reservoirs

Carbonate reservoirs worldwide are complex in structure,diverse in form,and highly heterogeneous.Based on these characteristics,the reservoir stimulation technologies and fluid flow characteristics of carbonate reservoirs are briefly described in this study.The development methods and EOR technologies of carbonate reservoirs are systematically summarized,the relevant mechanisms are analyzed,and the application status of oil fields is catalogued.The challenges in the development of carbonate reservoirs are discussed,and future research directions are explored.In the current development processes of carbonate reservoirs,water flooding and gas flooding remain the primary means but are often prone to channeling problems.Chemical flooding is an effective method of tertiary oil recovery,but the harsh formation conditions require high-performance chemical agents.The application of emerging technologies can enhance the oil recovery efficiency and environmental friendliness to a certain extent,which is welcome in hard-to-recover areas such as heavy oil reservoirs,but the economic cost is often high.In future research on EOR technologies,flow field control and flow channel plugging will be the potential directions of traditional development methods,and the application of nanoparticles will revolutionize the chemical EOR methods.On the basis of diversified reservoir stimulation,combined with a variety of modern data processing schemes,multichannel EOR technologies are being developed to realize the systematic,intelligent,and cost-effective development of carbonate reservoirs.

Determination of microscopic waterflooding characteristics and influence factors in ultra-low permeability sandstone reservoir

Actual sandstone micromodel was used in this work to conduct the microscopic waterflooding experiment of ultra-low sandstone reservoir,since the inside seepage characteristics of microscopic waterflooding process of Chang 8 ultra-low permeability sandstone reservoir of Upper Triassic Yanchang formation in Huaqing region of the Ordos Basin,China is difficult to observe directly.Combined with physical property,casting thin sections,constant-rate mercury injection capillary pressure and nuclear magnetic resonance,the influence of reservoir property on the waterflooding characteristics in pores were analyzed and evaluated.Seepage paths of waterflooding characteristics were divided into four types:homogeneous seepage,reticular-homogeneous seepage,finger-reticular seepage and finger-like seepage,the waterflooding efficiency of which decreases in turn.More than 70%of residual oil occurs as flowing-around seepage and oil film.Physical property,pore structure and movable fluid characteristics are all controlled by digenesis and their impacts on waterflooding efficiency are in accordance.Generally,the pore throat radius size and distribution and movable fluid percentage are closely related to waterflooding law.

An Integrated Rock Typing Approach for Unraveling the Reservoir Heterogeneity of Tight Sands in the Whicher Range Field of Perth Basin, Western Australia

Tight gas sands in Whicher Range Field of Perth Basin show large heterogeneity in reservoir characteristics and production behavior related to depositional and diagenetic features. Diagenetic events (compaction and cementation) have severely affected the pore system. In order to investigate the petrophysical characteristics, reservoir sandstone facies were correlated with core porosity and permeability and their equivalent well log responses to describe hydraulic flow units and electrofacies, respectively. Thus, very tight, tight, and sub-tight sands were differentiated. To reveal the relationship between pore system properties and depositional and diagenetic characteristics in each sand type, reservoir rock types were extracted. The identified reservoir rock types are in fact a reflection of internal reservoir heterogeneity related to pore system properties. All reservoir rock types are characterized by a compacted fabric and cemented framework. But distribution and dominance of diagenetic products in each of them depend on primary depositional composition and texture. The results show that reservoir rock typing based on three aspects of reservoir sandstones (depositional properties, diagenetic features and petrophysical characteristics) is a suitable technique for depiction of reservoir heterogeneity, recognition of reservoir units and identifying factors controlling reservoir quality of tight sandstones. This methodology can be used for the other tight reservoirs.

抽蓄电站全库盆防渗水库渗流缺陷影响分析

针对抽蓄电站全库盆防渗水库土工膜缺陷导致水库渗流量产生变化的安全问题,结合陕西省某抽蓄电站水库库底土工膜防渗工程,采用单因素影响分析和多因素影响分析方法进行抽蓄电站全库盆防渗水库渗流缺陷影响分析。结果表明,水头大小、缺陷大小、缺陷个数均正向影响抽蓄水库渗流量,而缺陷位置与抽蓄水库渗流量的相关性不明显。其中缺陷大小是影响抽蓄水库渗流量的主要因素,其次为水头大小,再次为缺陷个数。

深层-超深层碳酸盐岩油气藏储层特征及渗流特征研究进展

深层-超深层碳酸盐岩油气资源因其储量丰富、潜力巨大,已成为全球能源供应的重要战略资源。然而,高温高压环境、复杂的孔喉结构,以及微观孔隙、宏观孔隙、溶蚀孔洞和裂缝等多介质的共存,使传统的勘探和开发技术难以应对其复杂性。随着勘探开发的深入,储层描述和渗流研究面临精确表征、复杂渗流实验和建模等难点。为此,详细阐述了深层-超深层碳酸盐岩储层的特征表征与渗流特征研究的最新进展和关键难点;系统总结了储层微观结构的精细刻画方法和基于人工智能的多属性地震表征技术;探讨了多尺度表征在复杂储层中的应用与成效,并梳理了当前储层识别与描述的主要技术路径及其发展趋势;重点汇总了高温高压条件下深层-超深层碳酸盐岩储层的渗流特性研究,涵盖了多尺度渗流理论和气-水两相渗流机理,并分析了国内外研究的实验数据和理论模型;讨论了渗流研究中面临的挑战与未来发展方向,为深层-超深层油气藏开发研究提供了重要参考。

地热储层岩体粗糙裂隙的热流耦合效应研究

为了解决地热开采涉及复杂的多物理场耦合问题,提高开采效率,本文针对开采过程中的渗流-传热问题以离散元软件3DEC构建岩体粗糙裂隙热-流耦合数值模型。考虑不同三维形貌特征的岩体裂隙,模拟水力开度为19.17μm在不同流速时的水-岩温度变化规律。结果表明:由于裂隙形貌的阻滞作用,粗糙面出水口温度下降较慢,出水口温度有所上升,模型达到稳态所需的时间随流速和对流换热系数的增大而减小。裂隙形貌对流体和岩体温度分布均有影响,粗糙裂隙面的冷锋形态和裂隙面的形貌密切相关。光滑裂隙热突破快于粗糙裂隙,增加裂隙面的粗糙度有助于延长热突破时间。粗糙裂隙面相对于光滑裂隙面的总热量提取率略有提升,流速和对流换热系数的增加显著提高总热量提取率。通过本文研究可以为地热能系统的设计提供重要参数和指导,能够提高地热能开发利用效率。

复兴地区高含黏土页岩凝析气藏渗吸排驱及液体渗流特征研究

复兴地区凉高山组为高含黏土页岩凝析气藏,体积压裂改造后闷井和返排期间易出现反凝析和液锁现象,影响开采效果。为准确了解高含黏土页岩凝析气藏的渗吸排驱和液体渗流特征,优化闷井转排驱时机,选取储层岩心,开展了气水渗吸排驱试验和三相渗吸排驱试验,采用核磁共振、恒压驱替相结合的方式,量化了渗吸排驱过程中压裂液的水锁伤害特征及凝析油的可流动特征;建立了液锁伤害表征方法,并模拟了矿场尺度闷井过程中的水锁特征。研究结果表明:该页岩储层压裂渗吸阶段岩心的渗吸采收率在50.22%~57.14%;渗吸液矿化度越低,返排率越低,水锁伤害率越高;油锁伤害率低于水锁伤害率;存在束缚水时,凝析油的临界可流动饱和度约可降低20%;若以闷井后解除近裂缝水锁伤害为目标,闷井时间以20~30 d为宜。研究结果为复兴地区高含黏土页岩凝析气藏高效开发提供了理论依据。

干湿循环作用下裂隙岩体渗流特性演化规律研究

为了研究水库消落带岩体的渗流特性,以乌东德库区白云岩为研究对象,开展干湿循环水-岩作用试验。基于单裂隙渗流试验研究了干湿循环作用下裂隙岩体渗流特性演化规律,采用理论分析方法研究了裂隙岩体各向异性渗透特性。研究结果表明:当围压恒定时,单裂隙渗流量随渗透水压力的增加线性增加;当渗透水压力恒定时,随着围压的增加渗流量呈指数函数关系递减;随着水-岩作用周期的增加,裂隙渗流量呈先骤减小后缓慢增大的变化规律。裂隙岩体渗透特性存在明显的各向异性特征,并且水-岩作用后主渗透系数和渗透张量减小,渗透椭圆半径增加,渗透主方向保持不变。

三峡水库已有洪水预报信息的不确定性分析

本研究主要分析2020-2022三峡水库现有场次入库洪水预报结果(来源于三峡梯调预报)和实测入库流量数据,从全年流量整体预报情况与场次洪水预报情况等多方面研究现有三峡入库洪水的预报精度及预报误差分布规律,为三峡水库的防洪调度提供参考指导。

致密砂岩压裂后的储层敏感性特征实验——以四川盆地JQ地区沙溪庙组8号砂体为例

随着油气勘探开发向非常规领域深入,压裂等储层改造措施的应用越来越广泛。为了深入认识储层特性,了解储层潜力,预测储层改造后敏感性特征变化,从而进行合理的储层保护措施,有必要开展储层岩心模拟改造后的敏感性实验,明确储层改造措施对储层敏感性特征的影响。基于钻井获取岩心,在薄片鉴定、X射线衍射、扫描电镜分析以及压汞测试实验等手段的基础上,开展不同压力、温度、流体化学性质等条件下的流动实验,以评估储层的敏感性特征。通过对比改造前后岩心敏感性实验结果的差异,分析储层改造措施对储层敏感性特征的影响。结果表明:①模拟储层改造后中侏罗统沙溪庙组8号砂体岩心出现网状裂缝,渗透率相比改造前平均提升167%。②改造之前的JQ地区沙溪庙组岩心具有中等偏弱速敏、强水敏、弱盐敏、弱碱敏、弱酸敏的特征;改造后,速敏、盐敏等敏感性特征没有改变,而水敏由强转弱,强水敏的样品比例由93%下降到17%。③综合分析改造后敏感性特征,改造后岩心的水敏程度较改造前下降,出现弱水敏和无水敏的结果,因此需要增加储层改造措施的影响范围,以此提升储层流体流动能力。

巴家咀水库混凝土防渗墙加固对坝体渗流特性的影响

目前少有防渗墙加固对坝体渗流特性的影响研究,湿陷性黄土地区病险土石坝采用混凝土防渗墙除险加固的报道更是鲜有。为了研究混凝土防渗墙在黄土高原深厚覆盖层湿陷性黄土地区病险土石坝除险加固中的适用性及防渗阻渗效果,本文以巴家咀水库土石坝为工程背景,采用有限元方法研究了上游马道处增设防渗墙后坝体的渗流特性,分析了防渗墙加固前后坝体浸润线高度、渗流量、渗透坡降等渗流特性。结果表明:与加固前相比,增设混凝土防渗墙后,河床断面浸润线高度显著降低,土石料渗透系数越大,降低程度越明显;防渗墙加固后坝体单宽渗流量有大幅度减小,最大减小幅度达64.2%,减小幅度随水库水位降低而增大;渗透系数越大,防渗墙加固后坝体单宽流量减小幅度越大,防渗墙控制坝体渗流量的效果越显著;防渗墙加固后坝体渗透坡降减小幅度随渗透系数减小而增大,渗透系数较小时,防渗墙加固对坝体渗透坡降的影响较为明显。增设防渗墙对坝体渗透稳定性起到了很好的提升效果,研究结果可为大厚度黄土地区土石坝除险加固及类似工程提供参考。

库水位涨落条件下挡墙坡体渗流特征数值模拟

为揭示库水位涨落条件对挡土墙坡体渗流特性的影响,基于饱和-非饱和渗流理论,采用有限元软件,分析库水位变化条件下挡土墙坡体的渗流特征。结果表明:库水位涨落的速率越大,墙后黏性土坡体比砂性土坡体的水位滞后于库水位的现象越明显;库水位骤升初期,近挡土墙坡体孔压等值线为斜率小于0的凹曲线,离挡土墙越近,孔压等值线的斜率绝对值越大,远离挡土墙,孔压等值线趋于直线;库水位骤变条件下,挡土墙墙后黏性坡体相比于砂性土坡体的孔压变化范围更小,当涨落速率为2 m/d时,挡土墙渗流时间最短,坡体孔压最快趋于稳定状态;库水位涨落条件下,挡土墙墙后附近浸润线呈曲线分布,远离挡土墙的浸润线呈直线分布,饱和渗透系数越小,浸润线曲线分布的范围增大约2倍。

桑涧水库大坝渗流数值模拟分析

文章以桑涧水库为例,由于测压管数据失真严重,利用Autobank设计软件对土石坝进行渗流稳定数值模拟分析计算,结果表明与大坝现状渗流异常现象相吻合,为解决大坝类似工程问题提供参考,也为大坝防渗加固提供依据。

武乡南区块深部煤层气储层特征及试采地质影响因素分析

深部煤层气行业依然处于初步地质研究和工程实践的起步探索阶段,为下步国内深部煤层气的开发提供依据,对武乡南区块进行储层特征及试采地质影响因素研究。结果表明,武乡南主采煤层3_(上)和15煤层,具有埋深较深、煤层含气量分布不均、煤厚变化较大、渗透性差、吸附性强以及地应力高的储层特征。在此地质条件下,武乡南区块采用水平井不固井完井和连油喷砂射孔压裂开发工艺,部分井实现较好产量,但整体表现平均单井产气量低。产气主要受地质储量、构造特征和渗流条件的影响。

超低渗致密油田气驱提高采收率化学机理研究

针对超低渗致密油藏开发难题,通过实验和数值模拟方法,系统探讨了气驱提高采收率的机理。研究结果表明,CO_(2)和N_(2)在岩心样本上的吸附量随压力增加而增加,在25℃、15 MPa的条件下,CO_(2)和N_(2)的吸附量分别达到1.5 mmol·g^(-1)和0.45 mmol·g^(-1),CO_(2)的吸附能力显著高于N_(2)。岩心流动实验显示,在2.5 MPa·m^(-1)的压力梯度下,CO_(2)的流速达到3.0 m·d^(-1),而N_(2)仅为1.2 m·d^(-1),证明了CO_(2)在致密介质中具有更高的传输效率。驱替效率分析揭示,在15 MPa、25℃条件下,CO_(2)的驱替采收率可达71.4%,而N_(2)为45.1%。技术经济评价显示,尽管高压CO_(2)注入成本较高,但其带来的增产油量收益最为显著,显示了其在经济效益上的优势。该研究为超低渗致密油藏的气驱提高采收率提供了重要的理论依据和实践指导,有助于提高开发效率和经济效益。

Transient flow model and pressure dynamic features of tree-shaped fractal reservoirs

A transient flow model of tree-shaped fractal reservoirs is built by embedding a fracture network simulated by a tree-shaped fractal network into a matrix system. The model can be solved using the Laplace conversion method. The dimensionless bottom hole pressure can be obtained using the Stehfest numerical inversion method. The bi-logarithmic type curves for the trce-shaped fractal reservoirs are thus obtained. The pressure transient responses under different fractal factors are discussed. The factors with a primary effect on the inter-porosity flow regime include the initial branch number N, the length ratio α, and the branch angle θ. The diameter ratio β has a significant effect on the fracture radial flow, the inter-porosity and the total system radial flow regimes. The total branch level M of the network mainly influences the total system radial flow regime. The model presented in this paper provides a new methodology for analyzing and predicting the pressure dynamic characteristics of naturally fractured reservoirs.

特高含水油藏剩余油分布特征与提高采收率新技术

渤海湾盆地胜利油区经过60多年开发,整装、断块油藏已处于特高含水开发阶段,含水率超过90%,稠油油藏进入高轮次吞吐开发阶段,整体采出程度不到40%,仍有大幅度提高采收率的潜力,需要攻关进一步提高采收率技术。针对整装油藏特高含水后期高耗水层带发育、低效水循环严重,断块油藏剩余油分布差异大、有效动用难度大,深层、薄层超稠油注汽难、热损失大,有碱复合驱油体系结垢严重,聚合物驱后油藏动态非均质性更强、剩余油更加分散以及特高含水后期套损井多、出砂加剧、精细分层注采要求高等难题,明确地质及剩余油分布特征,深化驱油机制认识,围绕整装油藏经济有效开发、断块油藏高效均衡开发、稠油油藏转方式开发、高温高盐油藏化学驱开发开展技术攻关,形成整装油藏精细流场调控技术、复杂断块油藏立体开发技术、稠油油藏热复合驱提高采收率技术、高温高盐油藏化学驱技术、特高含水期主导采油工程技术等特高含水油田提高采收率技术系列,开辟先导试验区,取得显著开发效果,实现工业化应用,支撑胜利油区持续稳产。

深厚覆盖层上土工膜防渗堆石坝渗流场影响因素分析

随着筑坝技术的发展,深厚覆盖层逐渐成为土石坝常选坝基方案,其中坝基渗流控制是需要解决的关键问题之一。采用有限元法,对深厚覆盖层上土工膜防渗堆石坝渗流场进行计算分析,重点研究悬挂式防渗墙深度、覆盖层深度和渗透性对坝基渗流特性的影响。结果表明:防渗墙深度、覆盖层深度和渗透性均显著影响坝基渗流特性;防渗墙深度变化或覆盖层深度变化下,大坝渗流量和相对防渗深度关系曲线基本重合,均呈现先线性缓慢减小后急剧下降的特点,防渗墙和覆盖层深度共同决定坝基渗控效果;采用悬挂式防渗设计时,为保证大坝渗流量控制率达到75%,相对防渗深度与覆盖层渗透系数之间呈强对数线性关系。研究成果可用于待建类似工程防渗墙深度的初拟或已建类似工程坝基覆盖层防渗效果的评价。