An approximate analytical model for unconventional reservoir considering variable matrix blocks and simultaneous matrix depletion

In regard to unconventional oil reservoirs,the transient dual-porosity and triple-porosity models have been adopted to describe the fluid flow in the complex fracture network.It has been proven to cause inaccurate production evaluations because of the absence of matrix-macrofracture communication.In addition,most of the existing models are solved analytically based on Laplace transform and numerical inversion.Hence,an approximate analytical solution is derived directly in real-time space considering variable matrix blocks and simultaneous matrix depletion.To simplify the derivation,the simultaneous matrix depletion is divided into two parts:one part feeding the macrofractures and the other part feeding the microfractures.Then,a series of partial differential equations(PDEs)describing the transient flow and boundary conditions are constructed and solved analytically by integration.Finally,a relationship between oil rate and production time in real-time space is obtained.The new model is verified against classical analytical models.When the microfracture system and matrix-macrofracture communication is neglected,the result of the new model agrees with those obtained with the dual-porosity and triple-porosity model,respectively.Certainly,the new model also has an excellent agreement with the numerical model.The model is then applied to two actual tight oil wells completed in western Canada sedimentary basin.After identifying the flow regime,the solution suitably matches the field production data,and the model parameters are determined.Through these output parameters,we can accurately forecast the production and even estimate the petrophysical properties.

Pre-stack-texture-based reservoir characteristics and seismic facies analysis

Seismic texture attributes are closely related to seismic facies and reservoir characteristics and are thus widely used in seismic data interpretation.However,information is mislaid in the stacking process when traditional texture attributes are extracted from poststack data,which is detrimental to complex reservoir description.In this study,pre-stack texture attributes are introduced,these attributes can not only capable of precisely depicting the lateral continuity of waveforms between different reflection points but also reflect amplitude versus offset,anisotropy,and heterogeneity in the medium.Due to its strong ability to represent stratigraphies,a pre-stack-data-based seismic facies analysis method is proposed using the selforganizing map algorithm.This method is tested on wide azimuth seismic data from China,and the advantages of pre-stack texture attributes in the description of stratum lateral changes are verified,in addition to the method＇s ability to reveal anisotropy and heterogeneity characteristics.The pre-stack texture classification results effectively distinguish different seismic reflection patterns,thereby providing reliable evidence for use in seismic facies analysis.

A Comprehensive Evaluation Method for Low-permeability Reservoirs

According to the geological characteristics and their influential factors of the low-permeability reservoirs, a comprehensive method for evaluation of low-permeability reservoirs is put forward. The method takes a matrix system as the basis, a fracture system as the focus and a stress field system as the restricted factor. It can objectively reflect not only the storage capability and seepage capability of low-permeability reservoirs, but also the effect on development as well. At the same time, it can predict the seepage characteristics at different development stages and provide a reasonable geological basis for the development of low-permeability reservoirs.

Integrated petrophysical log characterization for tight carbonate reservoir effectiveness: A case study from the Longgang area, Sichuan Basin, China

Ultra-low porosity and permeability, inhomogeneous fracture distribution, and complex storage space together make the effectiveness evaluation of tight carbonate reservoirs difficult. Aiming at the carbonate reservoirs of the Da＇anzhai Formation in the Longgang area of the Sichuan Basin, based on petrophysical experiments and logging response characteristics, we investigated the storage properties of matrix pores and the characteristics of fracture development to establish a method for the characterization of effectiveness of tight reservoirs. Mercury injection and nuclear magnetic resonance （NMR） experiments show that the conventional relationship between porosity and permeability cannot fully reflect the fluid flow behavior in tight matrix pores. Under reservoir conditions, the tight reservoirs still possess certain storage space and permeability, which are controlled by the characteristic structures of the matrix porosity. The degree of fracture development is crucial to the productivity and quality of tight reservoirs. By combining the fracture development similarity of the same type of reservoirs and the fracture development heterogeneity in the same block, a three-level classification method of fracture development was established on the basis of fracture porosity distribution and its cumulative features. According to the actual production data, based on the effectiveness analysis of the matrix pores and fast inversion of fracture parameters from dual laterolog data, we divided the effective reservoirs into three classes： Class I with developed fractures and pores, and high-intermediate productivity; Class II with moderately developed fractures and pores or of fractured type, and intermediate-low productivity; Class III with poorly developed fractures and matrix pores, and extremely low productivity. Accordingly log classification standards were set up. Production data shows that the classification of effective reservoirs is highly consistent with the reservoir productivity level, providing a new approach for the effectiveness evaluation of tight reservoirs.

Shape factor for regular and irregular matrix blocks in fractured porous media

Describing matrix–fracture interaction is one of the most important factors for modeling natural fractured reservoirs.A common approach for simulation of naturally fractured reservoirs is dual-porosity modeling where the degree of communication between the low-permeability medium(matrix)and high-permeability medium(fracture)is usually determined by a transfer function.Most of the proposed matrix–fracture functions depend on the geometry of the matrix and fractures that are lumped to a factor called shape factor.Unfortunately,there is no unique solution for calculating the shape factor even for symmetric cases.Conducting fine-scale modeling is a tool for calculating the shape factor and validating the current solutions in the literature.In this study,the shape factor is calculated based on the numerical simulation of fine-grid simulations for single-phase flow using finite element method.To the best of the author’s knowledge,this is the first study to calculate the shape factors for multidimensional irregular bodies in a systematic approach.Several models were used,and shape factors were calculated for both transient and pseudo-steady-state(PSS)cases,although in some cases they were not clarified and assumptions were not clear.The boundary condition dependency of the shape factor was also investigated,and the obtained results were compared with the results of other studies.Results show that some of the most popular formulas cannot capture the exact physics of matrix–fracture interaction.The obtained results also show that both PSS and transient approaches for describing matrix–fracture transfer lead to constant shape factors that are not unique and depend on the fracture pressure(boundary condition)and how it changes with time.

Pore-Fracture Distribution Heterogeneity of Shale Reservoirs Determined by using HPMI and LPN_(2 )GA Tests

The compressibility of shale matrix reflects the effects of reservoir lithology, material composition, pore structure and tectonic deformation. It is important to understand the factors that influence shale matrix compressibility(SMC) and their effects on pore size distribution(PSD) heterogeneity in order to evaluate the properties of unconventional reservoirs.In this study, the volumes of pores whose diameters were in the range 6–100 nm were corrected for SMC for 17 shale samples from basins in China using high-pressure mercury intrusion and low-temperature nitrogen gas adsorption analyses,in order to investigate the factors influencing the SMC values. In addition, the variations in fractal dimensions before and after pore volume correction were determined, using single and multifractal models to explain the effects of SMC on PSD heterogeneity. In this process, the applicability of each fractal model for characterizing PSD heterogeneity was determined using statistical analyses. The Menger and Sierpinski single fractal models, the thermodynamic fractal model and a multifractal model were all used in this study. The results showed the following. The matrix compression restricts the segmentation of the fractal dimension curves for the single fractal Menger and Sierpinski models, which leads to a uniformity of PSD heterogeneity for different pore diameters. However, matrix compression has only a weak influence on the results calculated using a thermodynamic model. The SMC clearly affects the multifractal value variations, showing that the fractal dimension values of shale samples under matrix compression are small. Overall PSD heterogeneity becomes small for pores with diameters below 100 nm and the SMC primarily affects the PSD heterogeneity of higher pore volume areas. The comparison of fractal curves before and after correction and the variance analysis indicate that the thermodynamic model is applicable to quantitatively characterize PSD heterogeneity of shale collected from this sampling area. The results show that PSD heterogeneity increases gradually as micro-pore volumes increase.

Salt-Lake Basin Bedrock Weathered Crust Gas Reservoir in the Altun Mountains Front of the Qaidam Basin,Western China

The bedrock weathered crust in front of the Altun Mountains in the Qaidam Basin,western China,is different from others because this is a salt-lake basin,where saline water fluid infiltrates and is deposited in the overlying strata.A large amount of gypsum infills the bedrock weathered crust,and this has changed the pore structure.Using core observation,polarized light microscopy,electron probe,physical property analysis and field emission scanning electron microscopy experiments,the characteristics of the weathered bedrock have been studied.There are cracks and a small number of dissolved pores in the interior of the weathered crust.Matrix micropores are widely developed,especially the various matrix cracks formed by tectonics and weathering,as well as the stress characteristics of small dissolved pores,and physical properties such as porosity and permeability.This‘dual structure’developed in the bedrock is important for guiding the exploration of the lake basin bedrock for natural gas.

胜利油田GF84区块CCUS气窜封堵技术及其应用

胜利油田GF84区块为低渗透油藏,采出程度较低,CO_(2)驱是提高该区块采收率的有效措施之一。在前期开发中注采井之间已形成明显的气窜通道,现阶段亟需进行气窜封堵,提高CO_(2)驱波及系数,实现均衡驱替。通过分析GF84区块气窜特征与开发矛盾,将气窜类型划分为“裂缝型气窜”和“基质型气窜”,并制定了“裂缝封堵”和“基质调剖”的治理策略。在明确气窜特征的基础上,通过室内实验研发了硅盐树脂堵剂、CO_(2)气溶性发泡剂和高温冻胶堵剂,并形成了“硅盐树脂裂缝封堵+CO_(2)气溶性发泡剂、高温冻胶基质调剖”化学封堵分级调控技术。结果表明,该技术在GF84区块成功应用4口井,其中硅盐树脂裂缝封堵2口井,CO_(2)气溶性发泡剂基质调剖2口井,措施有效率100%,有效期在0.5 a以上。研究成果可为低渗透油田CO_(2)驱开发提供技术支撑。

加强水库安全管理的对策建议

为对标高质量发展新要求,顺应新质生产力发展方向,确保水库大坝安全稳定运行,对我国水库大坝的主要特点进行了梳理概括,通过分析我国水库安全管理面临的新形势新任务,提出要综合运用法律、技术、经济等手段,坚持治水思路、问题导向、底线思维、预防为主、系统观念、创新发展。结合当前水库安全管理存在的主要问题,提出相关对策建议,包括坚持“安全第一”方针、完善法规制度标准、构建运行管理矩阵、压实管理责任、加强库容管理、加强安全监测、加强应急管理、加强队伍能力建设等,为下一步加强水库安全管理提供参考。

现代化水库运行管理矩阵体系分析与构建关键问题研究

为支撑行业重点任务建设,提高现代化水库运行管理矩阵的建设水平,通过文献查阅、实地考察和交流咨询等方法,绘制了以工程安全、设施设备、影响区、运行调度和管理监督5个关键环节为一体的现代化水库运行管理矩阵构建体系“一张图”。给出了现代化水库运行管理矩阵的整体架构、层次演进和各要素之间的相互关系,系统梳理了现代化水库运行管理矩阵提出的背景、内涵和要求,对“四全”、“四制(治)”、“四预”、“四管”和雨水情监测预报、工程安全风险感控、生产安全风险感控“三道防线”的对象进行了系统整合和扩展,分析了各概念之间的相互关系和关键技术问题。研究结果表明,构建现代化水库运行管理矩阵是科技和管理水平发展的必然要求。

深层裂缝性致密砂岩气藏基质-裂缝气体流动机理

为了探明深层裂缝性致密气藏的气体流动规律,研发了基质–裂缝系统气体流动物理模拟装置,建立了高温高压基质–裂缝系统气体流动物理模拟方法,模拟了不同温度和压力条件下气体从基质到天然裂缝及人工裂缝的流动过程,以及基质与裂缝之间的传质过程;对比分析了不同温度和压力条件下气体流动的差异性,明确了高温高压作用下应力和流态对气体流动规律的综合影响。模拟结果显示,储层压力和应力显著影响气体流量和岩石渗透率,温度变化对气体流量和渗透率的影响相对较小,含天然裂缝岩心受应力敏感和气体滑脱效应的影响显著。研究结果为深层裂缝性致密气藏的高效开发提供了理论依据。

构建现代化水库运行管理矩阵与发展水利新质生产力

加强水库安全管理具有极端重要性。分析了构建现代化水库运行管理矩阵、发展水利新质生产力对保障水库高水平安全的重大意义,从高科技、高效能、高质量三个维度阐释构建现代化水库运行管理矩阵与发展水利新质生产力的内在联系,提出强化“四全”管理、“四预”措施与信息技术深度融合等加快构建现代化水库运行管理矩阵、助力发展水利新质生产力的主要路径。

我国水库保险制度初探

水库是支撑水安全保障的重要基础设施,在一定条件下也可能成为造成淹没损失的重大风险源,特别是在近年来极端天气频发强发的背景下,水库的社会风险、经济风险、生态风险备受关注。保险作为对冲经济风险的重要手段,是水库管理手段的重要补充,对保障水库安全具有重要意义。根据我国水库实际特点和运行环境,从水库面临的不确定性和经济损失风险出发,结合水库风险事件“低频高损”、累积性、突发性、相关方多等特点,探讨保险制度在对冲水库风险中的适用性;梳理了国内外有关政策和实践经验,分析当前水库保险存在的主要瓶颈和问题,提出进一步推进水库保险制度的对策建议。研究认为,目前我国水库保险存在缺乏有效制度、费率量算科学性不足、相关方重视程度不足等问题,建议建立财政支持为主的多方参与保险体系,构建水库保险政策制度体系,开展费率厘定科学研究和示范应用,鼓励保险公司参与水库运行管护和应急抢险。

基于层次分析法的致密气藏储层分类定量评价——以新场气田蓬莱镇组气藏为例

储层评价是致密砂岩气藏开发的基础,评价结果的准确性直接影响气藏开发的潜力分析,评价方法的选择影响到开发指标预测的可靠性、开发调整部署的科学性。为解决致密砂岩气藏储层评价影响因素多、主控因素不明确、参数敏感性未知、评价指标未量化等问题,以川西新场气田蓬莱镇组气藏为例,运用层次分析法理论,建立定量分析模型,将复杂问题简单化、定性问题定量化。方法优选地球物理、测井解释和地质基础等参数为准则指标,通过构造判断矩阵、确定指标权重、一致性检验等步骤,建立定量评价模型,得到权值向量,再利用真实井进行验证分析可采储量和无阻流量均与评价值呈现较好的相关性,说明研究方法具有较好的可靠性,进一步明确了储层划分类型及标准。根据研究方法确定的气藏储层评价指标,可以深化同区致密砂岩气藏开发“甜点”认识,提升致密砂岩气藏储层预测及开发部署质量,为同类气藏高效开发提供借鉴。

碳酸盐岩储层酸蚀蚓孔物模实验研究进展

酸蚀蚓孔是碳酸盐岩储层基质酸化最典型、最基本的特征,其尺寸和形态对酸化效果有着重要影响,关于酸蚀蚓孔的物模研究对于碳酸盐岩储层基质酸化机理研究及现场施工设计具有重要指导意义。文章分别综述了线性流和径向流两种岩心流动实验研究的重要成果和最新进展,指出酸蚀蚓孔实时表征是线性流岩心流动实验研究的发展方向,针对渗透率、尺寸等岩心参数对酸蚀蚓孔发育的影响,应结合融合电测和示踪剂的蚓孔实时表征方法进行进一步研究。针对酸液突破岩心时孔隙体积倍数(PVBT)与岩心参数之间关系的认识,后续应进一步升级径向流岩心流动实验及表征设备,从而开展不同因素对酸蚀蚓孔发育影响的研究,重点解决酸蚀蚓孔从实验尺度升级到现场尺度问题。建议加强电测法室外模拟实验及现场应用研究,从而实现实验尺度和现场尺度酸蚀蚓孔的实时观测和表征。

不同渗透率储层超临界CO_(2)改造模拟研究

水力压裂是非常规能源开发中的一种高效储层改造方法,近年来超临界二氧化碳(S-CO_(2))被认为是一种很有前景的压裂液,相比于水基压裂液由于其具有更高的压裂能力而备受关注。但在基质渗透率(RMP)相对较高的储层岩石中,将超临界二氧化碳用于压裂会出现较高的滤失。本文通过离散裂缝网络(DFN)方法对考虑天然裂缝系统的不同储层进行了模拟,对用水压裂(WF)和用S-CO_(2)压裂(SCF)在不同岩石基质渗透率储层中的适用性及压裂能力进行了模拟研究。与常用的水基压裂液相比,在等同条件下S-CO_(2)的黏度和密度较低,更容易使储层岩石破裂并生成更为复杂的裂缝网络。但是在岩石基质渗透率相对较高的储层中,裂缝不断扩展会导致S-CO_(2)滤失量的不断加剧,严重影响裂缝流体压力的提升,并进一步影响到裂缝的扩展。数值模拟结果也呈现了压裂期间裂缝长度增长趋势出现近水平发展拐点,而这一现象恰恰反映流体滤失对裂缝扩展的影响。在这种情况下继续提高压裂液注入速度可以缩短压裂时间,从而有效降低滤失对压裂的影响。计算结果清楚地表明了岩石基质渗透率的重要性,这一结果可以直接用于S-CO_(2)压裂适用性及生产能力的理论指导。

通用型水库洪水全过程预演仿真模型构建技术

水库洪水全过程预演仿真模拟是水利工程防灾减灾领域的重要研究方向,模型是支撑预演仿真模拟的核心,也是构建现代化水库运行管理矩阵重要的支撑技术。从水库洪水灾害链演化过程出发,围绕上游洪水形成过程、库坝区洪水控制过程以及下游洪水演进过程三个阶段,从水库上游的水文产汇流模拟,坝址区域的水库洪水调度模拟、大坝安全性态综合模拟、溃坝过程模拟,以及水库下游的洪水演进模拟、致灾后果分析等角度出发,探讨了各环节的研究近况,梳理了当前各环节模型构建的主要技术和存在问题。围绕当前构建现代化水库运行管理矩阵中对洪水预演仿真模型的需求和建设现状,总结分析了目前平台模型构建运用过程中存在的模型整体性规划不足、缺乏模型和模拟标准、各模型衔接困难等问题。结合工程实践,从加强顶层设计、统一建设标准、模型计算微服务部署等方面提出平台模型构建建议,并对下一步研究进行了展望。

大柳塔煤矿地下水库水化学特征及来源解析

【目的】煤矿地下水库具有储存和净化矿井水的功能,深入理解水库水体的水化学特征及形成机制是大规模开发矿井水处理技术的重要前提。【方法】以神东大柳塔煤矿地下水库为对象,通过对水库进出水水样采集测试与分析,结合离子比值法、多元统计分析(包括相关性分析和主成分分析)和正矩阵分解模型等方法,分析了水库水体的水文地球化学特征及组分来源。【结果和结论】结果表明:(1)与水库进水水质相比,出水处水体的固体悬浮物(SS)、电导率(EC)、溶解性总固体(TDS)、Fe^(3+)、Mn^(2+)等重金属指标明显降低,且沿着水流方向上Na^(+)、Cl^(-)含量逐渐增加,Ca^(2+)、Mg^(2+)含量逐渐降低,水化学类型由进库的Cl·SO_(4)-Ca型向出库的Cl·SO_(4)-Na·Ca型和Cl·SO_(4)-Na型转变。(2)水库内垮落岩石主要为泥岩和砂岩,其矿物成分包括石英、正长石、钠长石、伊利石、高岭石、绿泥石、石膏和黄铁矿等,发生的水文地球化学作用主要包括矿物溶解(即岩盐、硅酸盐和石膏溶解)、阳离子交换、吸附和沉淀以及混合作用。(3)水库水体的水化学组分主要受矿物溶解和阳离子交换作用(F1)、离子的吸附和沉淀作用(F2)、不同水源的混合作用(F3) 3种因子控制,三者对水库水体离子质量浓度的平均贡献率分别为57.2%、22.0%和20.8%。(4) F1对Na^(+)、K^(+)、Ca^(2+)、Cl^(-)、SO_(4)^(2-)和HCO_(3)^(-)质量浓度的贡献率依次为86.9%、78.8%、79.2%、79.7%、74.0%、74.8%;F2对Fe^(3+)和Mn^(2+)质量浓度的贡献率分别为83.9%和70.3%;F3对Mg^(2+)质量浓度的贡献率为84.9%。研究成果为深入理解煤矿地下水库水质净化机理提供了理论支持,并为优化矿井水处理技术和实现水资源可持续利用提供了技术指导。

丹江口水库现代化运行管理矩阵构建实践

丹江口水库是南水北调中线工程重要水源地,为切实保障水库工程安全、供水安全和水质安全,依据水利部关于构建现代化水库运行管理矩阵有关技术要求,总结了丹江口水库运行管理现状,分析了新发展阶段丹江口水库支撑南水北调后续工程高质量发展仍然存在的问题与不足,在此基础上提出充分利用标准化管理和数字孪生汉江流域、数字孪生丹江口工程建设成果,推进监管全覆盖、掌握全要素、管控全天候、管理全周期“四全”管理,完善体制、健全机制、强化法治、落实责任制“四制(治)体系”,预报精准化、预警提前化、预演数字化、预案科学化“四预”措施,及时除险、定期体检、强化维护、保障安全“四管”工作等,提出全面构建丹江口水库现代化运行管理矩阵主要建设内容,并结合工程运行管理实践明确了矩阵建设主要工作。

维护南水北调中线水源工程“三个安全”实践与思考

丹江口水库是南水北调中线工程水源地,维护其工程安全、供水安全、水质安全至关重要。南水北调中线水源有限责任公司通过规划引领、风险防范、数字赋能、加强合作、强化管理等措施,有效开展了维护中线水源工程“三个安全”的实践。新形势下,中线水源工程维护“三个安全”存在诸多挑战,包括库区管理水平尚需提升、入库水量影响因素多、水质安全仍有风险隐患、多方协调管理边界交错、“天空地水工”一体化监测感知能力有待提升等。提出了一系列对策建议:加快构建现代化水库运行管理矩阵;精打细算做好供水计划,全力确保供水安全;不断提升监测感知能力,强化水质安全保障;促进各方形成齐抓共管合作机制;迭代优化数字孪生丹江口成果,以“智慧大脑”护航“三个安全”。