Integrated simulation and monitoring to analyze failure mechanism of the anti-dip layered slope with soft and hard rock interbedding

The significant difference between the mechanical properties of soft rock and hard rock results in the complexity of the failure mode of the anti-dip layered slope with soft and hard rock interbedding.In order to reveal the landslide mechanism,taking the north slope of Fushun West Open-pit Mine as an example,this paper analyzed the failure mechanism of different landslides with monitoring and field surveys,and simulated the evolution of landslides.The study indicated that when the green mudstone(hard rock)of the anti-dip slope contains siltized intercalations(soft rock),the existence of weak layers not only aggravates the toppling deformation of anti-dip layered slope with high dip,but also causes the shear failure of anti-dip layered slope with stable low dip.The shear failure including subsidence induced sliding and wedge failure mainly exists in the unloading zone of the slope.Its failure depth and failure time were far less than that of toppling failure.In terms of the development characteristics of deformation,toppling deformation has the long-term and progressive characteristics,but shear failure deformation has the abrupt and transient characteristics.This study has deepened the understanding of such slope landslide mechanism,and can provide reference for similar engineering.

Modification of rock mass rating system:Interbedding of strong and weak rock layers

Rock mass classification systems are the very important part for underground projects and rock mass rating(RMR) is one of the most commonly applied classification systems in numerous civil and mining projects. The type of rock mass consisting of an interbedding of strong and weak layers poses difficulties and uncertainties for determining the RMR. For this, the present paper uses the concept of rock bolt supporting factor(RSF) for modification of RMR system to be used in such rock mass types. The proposed method also demonstrates the importance of rock bolting practice in such rock masses. The geological parameters of the Shemshak Formation of the Alborz Tunnel in Iran are used as case examples for development of the theoretical approach.

Anisotropic creep behavior of soft-hard interbedded rock masses based on 3D printing and digital imaging correlation technology

Three-dimensional(3D)printing technology is increasingly used in experimental research of geotechnical engineering.Compared to other materials,3D layer-by-layer printing specimens are extremely similar to the inherent properties of natural layered rock masses.In this paper,soft-hard interbedded rock masses with different dip angles were prepared based on 3D printing(3DP)sand core technology.Uniaxial compression creep tests were conducted to investigate its anisotropic creep behavior based on digital imaging correlation(DIC)technology.The results show that the anisotropic creep behavior of the 3DP soft-hard interbedded rock mass is mainly affected by the dip angles of the weak interlayer when the stress is at low levels.As the stress level increases,the effect of creep stress on its creep anisotropy increases significantly,and the dip angle is no longer the main factor.The minimum value of the long-term strength and creep failure strength always appears in the weak interlayer within 30°–60°,which explains why the failure of the layered rock mass is controlled by the weak interlayer and generally emerges at 45°.The tests results are verified by comparing with theoretical and other published studies.The feasibility of the 3DP soft-hard interbedded rock mass provides broad prospects and application values for 3DP technology in future experimental research.

Theoretical study on stability evolution of soft and hard interbedded bedding reservoir slopes

Soft and hard interbedded bedding rock slopes,which is prone to failure,are widely distributed in the Three Gorges Reservoir,China.Limit equilibrium method(LEM)is commonly used to analyze the stability of bedding rock slopes that have a single failure plane.However,this method cannot accurately estimate the stability of soft and hard interbedded bedding reservoir slopes because the strength parameters of a soft and hard interbedded rock mass vary spatially along the bedding plane and deteriorate with time due to periodic fluctuations of reservoir level.A modified LEM is proposed to evaluate the stability evolution of soft and hard interbedded bedding reservoir slopes considering the spatial variation and temporal deterioration of shear strength parameters of rock masses and bedding planes.In the modified LEM,the S-curve model is used to define the spatial variation of shear strength parameters,and general deterioration equations of shear strength parameters with the increasing number of wettingdrying cycles(WDC)are proposed to describe the temporal deterioration.Also,this method is applied to evaluate the stability evolution of a soft and hard interbedded bedding reservoir slope,located at the Three Gorges Reservoir.The results show that neglecting the spatial variation and temporal deterioration of shear strength parameters may overestimate slope stability.Finally,the modified LEM provides useful guidance to reasonably evaluate the long-term stability of soft and hard interbedded bedding reservoir slopes in reservoir area.

Study on the Law of Hydraulic Fracture Propagation in Low Permeability Thin Interbed Reservoir

The third member of Weixinnanliu in the west of the South China Sea develops thin interbeds, and the vertical extension of fracturing fractures is excessive. Once the fractures extend vertically to the upper and lower aquifers, it is easy to cause water flooding of oil wells, and the effect after fracturing is not obvious. The present work aims to explore the longitudinal extension law of fractures in Low Permeability Thin Interbed Reservoir based on the finite element calculation platform. A three-dimensional expansion model of hydraulic fractures in the target reservoir was established, and the displacement, fracturing fluid viscosity, minimum horizontal principal stress difference, vertical stress, interlayer thickness, perforation point separation were studied. The interlayer distance and other factors affect the crack propagation law. The research results show that the thin interbed fractures have three forms: T-shaped fractures, through-layer fractures, and I-shaped fractures;for the target layer, the overlying stress is relatively large, and the minimum principal stress is along the horizontal direction. Vertical cracks;the farther the perforation point is or the greater the stress difference, the smaller the thickness of the interlayer required to control the fracture height;the stress difference is 3 MPa, and the distance between the perforation points exceeds 10 m, the thickness of the interlayer is required to be ≥4 m;In order to ensure that the width of the fracture in the middle spacer does not affect the placement of the proppant, it is recommended that the displacement be controlled within 3 m3/min and the viscosity of the fracturing fluid is 150 mPa·s;in addition, the thickness of the spacer required to control the fracture height is different due to different geological parameters. Different, different wells need targeted analysis.

砂泥互层储层条件下水力裂缝扩展实验研究

鄂尔多斯盆地某区块发育丰富砂岩和泥岩多薄互层的页岩油资源,该区块层理、裂缝发育,非均质性特征显著,压裂改造中裂缝的扩展机理不明确,体积压裂改造难度较大。针对该区块开展了室内真三轴水力压裂物理模拟实验,探究了层理、地应力、排量等因素对裂缝穿层扩展的影响。研究结果表明:500 mm×500 mm×500 mm的天然露头砂泥夹层型岩样水力裂缝形态主要以复杂缝为主,层理发育程度越高,水力裂缝越偏向于水平方向;水平应力差的增大可以增加水力裂缝垂向穿层能力;高排量可以提高分支缝的开启概率,增大形成复杂缝网的概率。

国家示范工程陆相湖盆夹层型页岩油高效开发技术

鄂尔多斯盆地长7地层发育一套典型的内陆坳陷淡水湖盆页岩油,资源潜力巨大,随着开发的深入,油藏进入稳产阶段,配套的油藏稳产技术政策和管理手段相对缺乏,无法满足生产需求。针对庆城油田管理人员少的特点,通过数字化建设,实现了线上资料录取、管线泄漏监控、设备运行线上监控、异常工况报警等功能,形成了页岩油智能化管理模式;针对长7储层致密、非均质性强、开发难度大的特点,通过应用二氧化碳前置压裂、精准分段酸化等工艺以及实施单井、平台、油藏差异化管理,推动了地质工程一体化和差异化精细管理;针对长7页岩油单井产量高、气量大的特点,创新大平台布站模式,通过橇装化、集成化、数智化,探索“油气水综合利用、全系统资源共享、多功能高效集成、全过程智能管控”的页岩油大平台至联合站一级布站地面建设模式。通过上述技术的推广应用,庆城油田长7页岩油各项生产参数逐渐向好,页岩油水平井自然递减由16.6%下降至15.9%;地层供液能力充足,流饱比基本保持稳定(1.0~1.2);单井产量较2022年实现了大幅提升;完全成本降低至51.33美元/桶,已经实现规模效益开发。探索、攻关形成的高效开发关键技术,助推庆城页岩油实现规模效益开发,也对我国陆相页岩油规模效益开发起到了良好的引领示范作用。

塔河油田T1-5H井泵送桥塞分段加砂压裂工艺

针对塔河油田泵送桥塞分段加砂压裂施工中存在泵送桥塞工具串易遇阻遇卡,缺乏相配的井下工具,含硫化氢、井控风险较高等问题,以T1-5H井为例,提出了井下工具泵送模拟技术,提高工具串在复合套管中的通过性;形成了人工井底地质深度回归结合连续油管探底的高精度校深方法,保证首段射孔位置精确;采用大通径全封堵桥塞,解决高压气井组下生产管柱的难题。应用表明,T1-5H井泵送桥塞分段加砂压裂完井工艺4段5簇,注入地层总液量3210.7 m^(3),累计产能提高2401.6 t,有效提高了储层动用程度。该工艺为西北工区砂泥岩薄互储层改造提供经验借鉴,为实现超深石炭系储层大规模开发奠定了技术基础。

一种薄互层条件下致密砂体展布地震综合预测的策略

松辽盆地北部上白垩统高台子油层发育典型的致密砂岩储层,属于三角洲前缘沉积环境,该套地层从上至下有三套主力砂层组,每套砂层组均为砂泥岩薄互层,单层砂岩厚度超薄,一般为2 m~3 m。寻找区域内砂体比高的砂层组并刻画砂组内部单砂体空间分布是致密油勘探开发的关键所在。而常规属性分析及地震反演储层预测效果差、精度低,为此提出了针对性的地震综合预测策略,除地震资料保真高分辨率处理和岩石物理分析外,主要包括砂层组级的多属性融合砂地比预测技术以及单砂体级的相控地质统计学反演技术。具体工作流程为:第一在地震属性归一化基础上,利用聚类分析方法将地震属性划分为三大类,每类挑选相关性最高的地震属性进行多元线性拟合,建立砂层组级的多属性融合砂地比预测模型;第二利用统计分析手段建立井点先验信息与砂地比对应关系,建立砂地比先验信息约束的单砂体级的相控地质统计学反演方法。松辽盆地北部某区块应用实例表明,综合预测策略在评价砂层组级的砂体发育情况、刻画砂层组内部薄砂体空间展布方面取得较好的效果,指导了水平井井组的部署方案优化设计。

松辽盆地北部青山口组夹层型页岩油形成地质条件及勘探潜力

松辽盆地北部青山口组是大庆油田重要的页岩产油层,主要发育泥纹型和夹层型2种类型的页岩油,其中泥纹型页岩油已经在Q9油层取得效益勘探,夹层型页岩油近2年也受到了广泛关注,部分探井取得较好效果,展现了一定的资源规模,是大庆油田增储建产的重要接替领域。基于钻井、测井、岩心和实验分析资料,通过对青山口组沉积相、砂体分布、储层宏微观特征和含油性的系统分析,明确了松辽盆地白垩系青山口组夹层型页岩油形成的地质条件及勘探潜力。结果表明:青山口组沉积时期,主要发育北部和西部物源,沉积微相类型主要为水下分流河道、河口坝、远砂坝、席状砂、浊积砂和砂质碎屑流,夹层砂岩在全区大面积分布,沿着物源方向逐渐减薄;夹层型页岩油砂岩储层主要发育粒间孔和溶蚀孔,有效孔隙度一般为6%~12%,页岩储层主要发育粒间孔、晶间孔、有机生烃缝等,砂岩和页岩均具有较好的储集能力;青山口组夹层型页岩油源储一体近距离运移立体成藏,砂岩、页岩普遍含油,在成熟烃源岩内为纯油区,大规模连续成藏;按照有效烃源岩范围、砂岩分布范围、储层特征、黏土矿物含量、油水关系等地质条件,综合划分了青山口组夹层型页岩油发育的有利区带,初步估算资源量潜力为25×10^(8) t,展现出良好的勘探前景。主要参数对比结果表明,齐家南和古龙西地区夹层砂岩相对较厚、源岩品质相对较好,是近期增储建产的现实区带。

软-硬互层岩体节理峰前循环剪切疲劳损伤机理研究

三峡库区频发微小地震下岩体节理循环剪切疲劳损伤对边坡动力稳定性具有重要影响。通过室内峰前循环剪切试验和PFC2D细观数值计算,研究了考虑一阶起伏角、含水率、剪切速率、剪切幅度、法向应力及循环剪切次数影响的软-硬互层岩体节理宏细观疲劳损伤机理。研究表明:①岩体节理剪切应力-剪切位移曲线历经初始非线性压剪变形、近似线弹性压剪变形、循环剪切疲劳损伤变形、应力缓升压剪变形、应力陡升压剪变形及应力脆性跌落压剪变形六个演化阶段。②岩体节理峰值(残余)剪切强度和疲劳剪切(法向)位移在相同一阶起伏角、含水率、剪切速率、剪切幅度或法向应力下随循环剪切次增多而分别降低和增大;且其在相同循环剪切次数下随一阶起伏角或法向应力变大而分别增大和降低,而随含水率、剪切速率或剪切幅度变大则分别降低和增大。③宏细观结果总体上吻合较好,且岩体节理细观剪切疲劳损伤裂纹数量随剪切位移变化呈前期微增-陡增、中期缓增及后期陡增-缓增-陡增的发展特征,而其随循环剪切次数变化则呈前期陡增和后期缓增的发展特征。④岩体节理宏细观剪切疲劳损伤典型演化过程可概述为压密-起裂破坏、循环错动-贯通破坏及分离-啃断破坏3个渐进性发展阶段,且宏细观剪切疲劳损伤裂纹近似呈“倒U形”密集分布于岩体节理附近。

岩性差异对裂缝穿层扩展的率相关断裂特征影响

薄互层致密砂岩储层由于层间岩性差异、纵向非均质性强等原因,导致主裂缝难以垂向扩展,提高裂缝扩展速率可有效促进裂缝穿层扩展。为研究裂缝穿层断裂过程中的率效应机制,采用人工预制水泥-砂岩试件进行了三点弯断裂试验,通过数字图像法监测了裂缝扩展至层间接触界面处时的断裂过程区(fracture process zone,FPZ)发育特征;基于断裂动力学理论,提出了考虑率效应的裂缝扩展路径预测模型。研究结果表明:低速扩展时裂缝形态曲折,FPZ呈现短、宽的现象,高速扩展时裂缝平直,FPZ呈现长、窄的特点;FPZ存在离散性,且存在相互吸引的特点,裂缝从低弹性模量岩石向高弹性模量岩石低速扩展时层间接触界面处会提前产生高应变区,导致裂缝扩展至层间接触界面处时沿层扩展,高速扩展无此现象;岩石抗拉强度与裂缝穿越单元体的平均抗拉强度呈正相关关系,低扩展速率裂缝优先沿微缺陷扩展,导致岩石抗拉强度降低,高扩展速率裂缝优先沿自相似方向扩展,穿过大量高强度单元导致岩石抗拉强度增加;裂缝与层间接触界面夹角越大,裂缝越容易穿层扩展,裂缝与层间接触界面夹角为30°时,夹角影响效果最大,夹角超过30°时影响效果逐渐下降。研究结果对水力压裂参数优化、增加水力裂缝高度、提高薄互层致密砂岩油气产量具有重要意义。

基于模型的薄互层地震反射滤波效应研究

薄层和薄互层油气藏的开发越来越受到重视,但由于地震资料对薄层的分辨能力有限,且传统的褶积模型无法模拟出薄层中复杂的波场传播现象,导致这类储层的地震预测难度较大。针对这一问题,本文以层状介质中的传递矩阵法为基础,发展了一种垂直入射时的反射率法,并运用该方法对多组典型的薄互层模型做正演模拟,然后对正演模拟的结果做频谱分析,研究薄互层对地震反射波的滤波效应。相较于层状介质中的传递矩阵法,垂直入射时的反射率法在更适用于纵波入射下的薄互层研究的同时,大大提升了反射率法正演的效率;而在频域对薄互层反射滤波效应做研究也在一定程度上解决了时域上分辨率不足的缺点。对于薄互层模型的频谱分析结果表明,垂直入射时的反射率法能较好地保留薄互层的层间信息,对根据该方法得出的正演结果做频谱分析,频谱曲线的幅值和陷波点的变化能反映出薄互层中互层数和砂泥比的变化情况,这对于油田后期的精细勘探阶段中薄储层空间展布规律及其性质的确定具有重要的意义。

单轴压缩条件下软硬互层类岩石的声发射特性与裂纹类型演化

为进一步揭示不同层理倾角的软硬互层岩在单轴压缩下的声发射特性和裂纹扩展规律,采用类岩石材料制备了软硬互层类岩石试样,基于搭载DS-5型声发射监测系统的RMT-150B型岩石力学试验系统,开展了不同层理倾角(0°、30°、45°、60°和90°)的软硬互层类岩石试样的单轴压缩试验,分析了层理倾角对岩样声发射特性、损伤演化和裂纹扩展的影响。结果表明:试样的声发射活动呈现明显的阶段性特征,且不同层理倾角下其分布特征具有明显差异,声发射特征参数表现出明显的层面效应,声发射累计振铃计数和累计能量随着层理倾角的增大先减小后增大;低频-超高幅信号的突然出现或占比增加可作为软硬互层类岩石试样的破坏前兆,低角度(0°、30°)试样表现为大尺度裂纹稳步扩展破坏,中角度(45°、60°)试样为大尺度裂纹突发失稳扩展破坏,高角度(90°)试样为小尺度裂纹突发失稳扩展破坏,60°层理倾角为试样破坏的最不利角度;试样的损伤累积过程同样具有明显的阶段性特征,在峰值应力前,试样的损伤累积主要集中在高速率损伤阶段,中等角度(45°、60°)的层理面加快了试样的损伤累积过程;不同层理倾角对软硬互层类岩石试样的拉剪裂纹演化的影响差异明显,水平层理面促进了拉剪裂纹的产生,层理倾角的逐渐增大促进了类岩石试样拉剪裂纹的发育,在层理面与岩石基体共同作用下,随着层理倾角的逐渐增大,类岩石试样的剪切裂纹占比先增大后减小,且剪切裂纹数目处于较高水平。研究结果对地下工程围岩结构的稳定性评估具有一定的参考作用。

苏里格砂泥薄互储层缝控压裂造缝机制及穿层判别准则

针对苏里格气田二叠系盒8段砂泥薄互储层压裂施工中裂缝穿层扩展判别与压裂效果评价存在的问题,建立考虑层间非均质性的砂泥薄互储层地质力学模型,开展水力裂缝穿层扩展实验,揭示砂泥薄互储层中人工裂缝的起裂-延伸-交互-穿层机制。基于非常规裂缝模型的数值模拟,阐明了裂缝在薄互层中的垂向起裂与扩展特征,构建了裂缝穿层的判别准则与压裂效果评价方法。研究表明:层间应力差是直接影响穿层压裂裂缝形态的主要地质因素,苏里格气田层间应力差异系数(ξ_(IL))小于0.40时,裂缝可突破隔层在目标砂岩层内扩展;0.40≤ξ_(IL)<0.45时,裂缝突破隔层但无法在目标砂层内有效扩展;ξ_(IL)≥0.45时,裂缝仅在射孔储层扩展,无法实现穿层扩展。提高压裂液黏度与排量能弥补能量损耗并突破隔层限制,苏里格气田压裂施工参数控制区域内采用高黏度(50~100mPa·s)压裂液、高排量(12~18 m^(3)/min)施工条件有利于裂缝穿层。

软硬互层型平缓反倾岩质斜坡采动变形破坏机理研究

为研究我国西南矿区软硬互层型平缓反倾岩质斜坡采动变形破坏机理,以我国贵州省都匀市某煤洞坡为例,采用数值模拟方法,分析采动诱发软硬互层型平缓反倾岩质斜坡的变形破坏特征,讨论采动对坡体的作用规律,研究单工况采动和留煤柱下重复采动对坡体的变形破坏机理。研究结果表明:靠近坡表工作面开采和留煤柱下重复采动对坡体的稳定性影响较大;采动裂隙首先集中于采空区两侧并向上发展,软硬夹层间产生离层裂隙的可能性一般较大;留煤柱可防止坡体沉陷破碎,但也可能加剧坡体稳定性下降。研究结果可为软硬互层型平缓反倾岩质斜坡地下开采时,有效预防诱发山体失稳等地质灾害提供理论参考。

华北东部晚古生代过渡相煤系地层低阻成因、控制因素与地质意义

华北东部晚古生代过渡相煤系地层中低阻层发育,明确其成因类型、控制因素以及地质意义,可以充分揭示其中所包含的地质信息,对于相关层系油气资源评价和勘探部署具有积极意义。本文以华北东部太原组和山西组中低阻层为研究对象,综合运用岩心、薄片、扫描电镜、碳氧同位素和测录井资料,围绕其成因类型、控制因素和地质意义开展研究。结果表明:华北东部晚古生代过渡相煤系低阻层主要发育在太1段和山2段,成因类型包括砂泥岩薄互层、高束缚水体积和发育导电矿物,沉积作用和成岩作用控制了低阻的形成;太1段低阻的成因为砂泥岩薄互层和高束缚水体积,潮汐作用导致的潮汐成因层理和微细孔隙发育促进了障壁海岸背景下太1段低阻的形成,山2段低阻的成因为菱铁矿的密集发育,稳定的覆水还原环境和沉积有机物的成岩演化共同控制了三角洲背景下山2段低阻的形成;太1段的低阻和高毛细管束缚水体积指示着潮坪沉积,说明太原组自下而上为一个海退的过程,是对早二叠世早期冈瓦纳冰川迅速扩张和全球海平面快速下降的响应,山2段的低阻和高光电吸收截面指数指示着三角洲前缘沉积,说明山西组由一期三角洲沉积组成。

Three-component seismic data in thin interbedded reservoir exploration

We present the first successful application of three-component seismic data to thin interbedded reservoir characterization in the Daqing placanticline of the LMD oilfield. The oilfield has reached the final high water cut stage and the principal problem is how to recognize the boundaries of sand layers that are thicker than 2 m. Conventional interpretation of single PP-wave seismic data results in multiple solutions, whereas the introduction of PS-wave enhances the reliability of interpretation. We analyze the gas reservoir characteristics by joint PP- and PS-waves, and use the amplitude and frequency decomposition attributes to delineate the gas reservoir boundaries because of the minimal effect of fl uids on S-wave. We perform joint inversion of PP- and PS-waves to obtain V P/V S, λρ, and μρ and map the lithology changes by using density, λρ, and μρ. The 3D–3C attribute λρ slices describe the sand layers distribution, while considering the well log data, and point to favorable region for tapping the remaining oil.

松南盆地情字外前缘砂页交互储层可压性评价

松南盆地情字外前缘砂页交互储层资源储量丰富,但储层孔渗较低,资源禀赋差,在采取改造措施前需要对其进行有效的可压性评价。通过对该区的岩心进行X射线衍射、三轴应力压缩等实验,以脆性系数、水平地应力差异系数、断裂韧性以及脆性矿物含量四种影响因素为基础,采用层次分析法确定各因素所占权重,构建了与储层具有较好匹配程度的可压性指数计算模型,综合波速各向异性分析、应力敏感性评价等实验结果,对储层的可压性进行综合评价。结果显示,情字外前缘砂页交互储层可压性指数计算结果为0.28,可压性中等,但水平层理及天然裂缝较为发育,目标层整体具有较大的改造潜力。应用该方法对H2-1井开展可压性评价,并根据评价结果对压裂方案进行优化,优化后微地震解释有效改造体积491.2×10^(4)m^(3)、平均日产油9 m^(3),应用效果显著,研究成果可为压裂施工技术路线的确定提供理论支撑。

海南福山油田流一段石英砂替代陶粒适应性评价及意义

页岩气、致密油气等非常规油气资源开发,关键在于提质增效降低成本。文章阐明了海南近海福山油田流一段薄互层致密砂岩采用本地石英砂替代陶粒作为主流支撑剂的低成本和优化裂缝导流能力的适应性特征;提供了海南本地20/40目石英砂和20/40目陶粒室内试验评价结果,在不同应力不同铺置浓度条件下, 20/40目石英砂和20/40目陶粒具有不同的导流能力;进一步揭示了地质参数相近两口开发井,在数值模拟优化试验基础上实施现场试验的结果:裂缝导流能力达到21D·cm,可满足流一段致密砂岩储层的导流需求;在35Mpa应力条件下, 10kg·m-2铺置浓度的20/40目石英砂可获得21D·cm以上的导流能力。现场试验表明,石英砂试验井压裂后前期基本可与陶粒试验井效果相同,随着开采时间延长,使用陶粒井的累计产油量和稳产有效期均超过使用本地石英砂开发井。因此,陶粒支撑剂经济效益更高,陶粒支撑剂值得继续长期和规模化使用。