Integrated wellbore-reservoir-geomechanics modeling for enhanced interpretation of distributed fiber-optic strain sensing data in hydraulicfracture analysis

Fiber-optic distributed strain sensing(FO-DSS)has been successful in monitoring strain changes along horizontal wellbores in hydraulically fractured reservoirs.However,the mechanism driving the various FO-DSS responses associated with near-wellbore hydraulic fracture properties is still unclear.To address this knowledge gap,we use coupled wellbore-reservoir-geomechanics simulations to study measured strain-change behavior and infer hydraulic fracture characteristics.The crossflow among fractures is captured through explicit modeling of the transient wellbore flow.In addition,local grid refinement is applied to accurately capture strain changes along the fiber.A Base Case model was designed with four fractures of varying properties,simulating strain change signals when the production well is shut-in for 10 d after 240 d of production and reopened for 2 d.Strain-pressure plots for different fracture clusters were used to gain insights into inferring fracture properties using DSS data.When comparing the model with and without the wellbore,distinct strain change signals were observed,emphasizing the importance of incorporating the wellbore in FO-DSS modeling.The effects of fracture spacing and matrix permeability on strain change signals were thoroughly investigated.The results of our numerical study can improve the understanding of the relation between DSS signals and fracture hydraulic properties,thus maximizing the value of the dataset for fracture diagnostics and characterization.

沉积微相对超深储层岩石力学性质的影响及其应用——以塔里木盆地库车坳陷BZ气田白垩系为例

为了优选塔里木盆地库车坳陷白垩系超深致密砂岩储层单井天然裂缝发育的甜点层段,利用露头、岩石薄片、成像测井等资料系统分析了BZ气田不同沉积微相的储层岩石力学性质差异,并结合相关露头中不同沉积微相的几何参数模型,提出了一种优化储层岩石力学参数模型的方法,提高了井筒周围(<200 m)天然裂缝预测精度。研究结果表明:(1)BZ气田白垩系巴什基奇克组三段不同沉积微相、相同微相不同位置的储层中,岩石组构和岩石组合(包括碎屑含量、杂基含量、粒度分选、砂地比和砂泥岩组合等)具有差异,从而影响了储层的泊松比和杨氏模量,不同微相储层具有不同的岩石力学参数。(2)不同沉积微相砂体的裂缝发育程度有所差异,扇三角洲前缘水下分支河道砂岩的裂缝最发育,比扇三角洲前缘支流间湾微相及扇三角洲平原分支河道微相更容易形成裂缝。(3)进一步根据露头中沉积微相几何参数,建立不同微相的三维模型,即可建立和优化井筒周围的沉积微相模型及岩石力学参数模型,并应用到井筒周围的裂缝预测中。

地质力学层定量划分方法及其超深层油气勘探开发应用

超深层油气高效勘探开发是当前全球能源地质研究关注的焦点,“地质力学层与油气勘探开发”是国际前沿研究领域,形成地质力学层的有效划分方法,对超深油气高效勘探和效益开发具有理论和实际意义。现今地应力状态影响天然裂缝有效性,裂缝发育分布影响岩石力学性质,而岩石力学性质又控制着现今地应力的分布,但当前“岩石力学层理论”不能完整涵盖三者之间耦合联系。为此,基于水平最小主应力、水平主应力差、弹性模量、现今地应力优势方位与天然裂缝走向的夹角、天然裂缝密度和应力集中系数等6种参数,构建储层地质力学层指标,形成一种地质力学层定量划分方法。基于塔里木盆地库车坳陷克拉苏构造带大北区块W井的实例分析,表明该井目的层白垩系巴什基奇克组垂向呈现强地质力学非均质性,储层地质力学层与气层发育段具有较好的对应关系。因此,借助地质力学层划分结果,可指导超深层油气甜点层段的优选。

珠江口盆地潜山储层地质力学及压裂参数优化研究

珠江口盆地珠一坳陷惠州27-1井区作为潜山油气储层,压裂层段厚度大、层数多、非均质性强、压裂改造难度大,对于人工裂缝的在潜山储层中的拓展延伸规律认识困难。针对此问题,首先建立动态参数测井解释模型,并与静态岩石力学数据协同校正,建立一维岩石力学剖面;结合深部成岩理论,建立三维地质力学模型,真实模拟研究区块成岩环境;最后基于三维地质力学模型,研究排量、液量、砂比、前置液占比、射孔层位厚度等参数对裂缝纵向和平面延伸规律的影响,优化压裂设计。结果表明:惠州27-1区块,杨氏模量平均值为45.47 GPa,最大水平主应力平均值为100.91 MPa,最小水平主应力平均值为80.98 MPa,泊松比平均值为0.30。排量6~7 m^(3)/min、液量600~700 m^(3)、砂比10%~15%、前置液比例50%~60%、射孔厚度8~11 m为最优施工参数,为现场施工提供指导意见。

地质力学参数智能预测技术进展与发展方向

随着人工智能技术在油气勘探领域应用的不断深入,地质力学参数预测从传统方法向智能化转型已成为必然趋势。本文系统归纳分析了机器学习算法在岩石力学参数直接与间接预测,地层孔隙压力钻前预测、随钻监测和钻后评估,一维地应力和三维地应力场预测中的应用现状,对比了不同预测任务下的机器学习模型、输入参数、样本数据量、输出参数以及模型预测性能。研究发现:相比于室内试验、现场测试和经验模型计算,机器学习算法在地质力学参数预测方面的准确性、时效性和适用性具有明显优势;集成模型、深度学习模型和物理约束神经网络模型凭借其准确性、鲁棒性、泛化能力和可解释性,已成为当前研究的热点和重点;但现有研究以一维地质力学参数的钻后预测为主,因而无法有效进行钻前和随钻三维地质力学参数预测。为了加快地质力学参数向智能化、数字化转型,本文提出了一种地质力学参数智能预测框架,该框架考虑地震、测井、录井等多源数据对地质力学参数预测的影响,通过数据+物理双驱动的机器学习模型进行三维地质力学参数的预测,并通过正钻井数据进行模型的实时更新,从而实现区域三维地质力学参数的钻前预测、随钻监测以及钻后评估。此外,分析了地质力学参数智能预测面临的关键技术难题:①实现非结构化数据类型的转换,降低数据集复杂度,确保数据的一致性和可比性;②开展多源数据融合研究,构建包括地震、测井、录井、室内试验、现场测试等方面的多源数据集,并进行数据处理、特征选择等工作;③加强机器学习模型研究以提升性能,采用集成模型提升预测精度,融入机理模型和领域知识提升模型鲁棒性和可解释性。

超深层断控碳酸盐岩油藏地质力学建模及其在开发中的应用

为提高超深断控碳酸盐岩油藏的开发效益,通过开展大尺寸岩样力学实验,揭示高角度—近直立断裂面变形与连通机理;基于高压注水提采的力学与流动耦合原理,通过地质力学建模,明确了断控碳酸盐岩油藏现今地应力场和断裂活动性分布规律;发现不同方位的断裂活动性以及不同部位的缝洞体连通性有明显差异,进而分析了不同井眼轨迹的开发效果,提出了地质工程一体化工作方法,科学指导井眼轨迹设计和注水方案优化。结果表明:①走滑断裂变形中的大尺度破碎体和高角度裂缝系统是影响储层品质的关键因素,高压注水一方面能够激活先存裂缝,一方面还能在先存裂缝基础上发生延伸扩展,甚至可以产生新的裂缝,促进了断控缝洞体在纵横向上的互相连通;②高压注水过程中断裂体内部发生力学与流动之间的耦合变化,渗流环境得到改善,通过循环举升,从而提高油气采收率;③根据断裂体形态、产状以及断裂面动态剪切变形连通性,可优选定向井最佳井点和井眼轨迹,并优化注水方案;④塔里木盆地断控油藏试验区通过高压注水,采收率提高5个百分点,该方法为超深断控型油藏高效开发提供了较好的理论依据和技术支撑。

煤巷围岩稳定性定量化评价及分类支护技术

目的为了建立晋城矿区煤巷围岩稳定性评价指标和定量化分类方法,方法在统计分析晋城矿区68组煤巷围岩强度、岩层结构发育程度、地应力数值的基础上,综合分析煤巷围岩稳定性影响因素,选取最大水平主应力、垂直主应力、顶板综合强度、巷帮煤体平均强度、顶板10 m范围内裂隙岩层厚度5个关键影响指标,提出顶板应力强度系数、巷帮应力强度系数、顶板松散性系数3个综合指标,通过K-means聚类算法,对煤巷顶板和巷帮进行定量化分类,结合成巷方式和煤柱尺寸,将晋城矿区煤巷围岩划分为5种稳定性类别和30种围岩类型。针对不同煤巷围岩稳定性类别,提出具体的支护形式和支护参数,并对不同类型围岩锚固方式、组合构件和护表构件进行精细化匹配。最后通过现场工业实践验证分类方法和支护方案的合理性。结果矿压监测结果表明,巷道掘进期间顶底板最大移近量78 mm,两帮最大移近量58 mm,回采期间巷道顶底板最大移近量260 mm,两帮最大移近量119 mm。结论晋城矿区煤巷围岩稳定性评价指标和定量化分类方法切实可行,分类支护方案合理。

页岩气老井重复压裂时机优化方法

基于多孔介质弹性理论、嵌入式离散裂缝模型及有限体积法,考虑页岩气微观渗流机制,建立适用于裂缝性页岩气储集层的渗流-地质力学全耦合模型,并提出了重复压裂时机优化方法,采用四川盆地涪陵页岩气井资料分析了重复压裂时机的影响因素。研究表明:受地层压力衰竭影响,最大水平主应力反转面积占总面积的百分比随时间的延长先增加后减小,且距人工裂缝越近的区域,应力反转面积百分比曲线出现峰值的时间越短,最终归零(恢复到初始状态)的时间也越短。重复压裂的最佳时间受基质渗透率、初始应力差、天然裂缝逼近角的影响:基质渗透率、初始应力差越大,应力反转面积百分比曲线出现峰值、恢复到初始状态的时间越短,采取重复压裂措施的时机越早。天然裂缝逼近角越大,裂缝附近越难发生应力反转、重复压裂最佳时间越早,人工裂缝末端以远区域越易发生应力反转、重复压裂最佳时间越晚。对于基质渗透率很小的储集层,其单井产能递减快,为保证经济性,可采取关井或注气补能等措施恢复应力,提前实施重复压裂。

基于三维地质力学的压力剖面钻前预测研究

为解决目前基于邻井测井资料评价得到的压力剖面与待钻井实际井轨迹上的结果不符等问题,提出基于三维地质力学的待钻井井眼轨迹上的压力剖面钻前预测方法。以地震解释的层位数据为基础,结合断层数据、钻井分层数据等构建三维地质模型。然后,利用已钻井测井数据,通过序贯高斯插值法获得三维岩石力学参数场,并且通过有限元数值模拟得到区域地应力以及压力系统,进而获得待钻井井眼轨迹上的压力剖面。研究结果表明:该方法预测精度较高,已钻井的孔隙压力预测值与实测值的误差为3.57%,地应力预测值与实测值误差为5.8%。现场2口井的预测层位与实钻层位吻合程度较高,预测的三压力剖面能够较好地解释实钻过程中出现的井下复杂问题。研究结果可为钻前地质工程设计、井身结构优化、井下复杂问题预防等提供较为可靠的数据参考。

基于地质工程一体化的裂缝性地层漏失压力预测

针对新探区裂缝性地层地质及工程资料严重缺乏,导致现有漏失压力计算模型有效性降低这一问题,文中提供了一套地质工程一体化裂缝性地层漏失压力预测方法,即在现有漏失压力计算模型的基础上,引入裂缝指数,结合钻井液漏失机理,制定漏失类型分类评价指标,形成裂缝性地层漏失压力三维建模方法。另外,建立了渤海A油田漏失层漏失类型分类评价指标,对A油田进行了三维漏失压力建模及预测,并在C-5井成功应用,钻井周期缩短15 d。应用结果表明,A油田的裂缝指数与漏点位置相关。文中方法综合利用地质、工程、地质力学数据,可为新探区提供可靠的漏失压力精细预测结果,有助于新探区的钻井优化设计和管理。

A gated recurrent unit model to predict Poisson’s ratio using deep learning

Static Poisson’s ratio(vs)is crucial for determining geomechanical properties in petroleum applications,namely sand production.Some models have been used to predict vs;however,the published models were limited to specific data ranges with an average absolute percentage relative error(AAPRE)of more than 10%.The published gated recurrent unit(GRU)models do not consider trend analysis to show physical behaviors.In this study,we aim to develop a GRU model using trend analysis and three inputs for predicting n s based on a broad range of data,n s(value of 0.1627-0.4492),bulk formation density(RHOB)(0.315-2.994 g/mL),compressional time(DTc)(44.43-186.9 μs/ft),and shear time(DTs)(72.9-341.2μ s/ft).The GRU model was evaluated using different approaches,including statistical error an-alyses.The GRU model showed the proper trends,and the model data ranges were wider than previous ones.The GRU model has the largest correlation coefficient(R)of 0.967 and the lowest AAPRE,average percent relative error(APRE),root mean square error(RMSE),and standard deviation(SD)of 3.228%,1.054%,4.389,and 0.013,respectively,compared to other models.The GRU model has a high accuracy for the different datasets:training,validation,testing,and the whole datasets with R and AAPRE values were 0.981 and 2.601%,0.966 and 3.274%,0.967 and 3.228%,and 0.977 and 2.861%,respectively.The group error analyses of all inputs show that the GRU model has less than 5% AAPRE for all input ranges,which is superior to other models that have different AAPRE values of more than 10% at various ranges of inputs.

基于三维地质建模的准噶尔盆地断层稳定性研究

地应力的分布特征及断层稳定性对复杂区域的水平井井位部署、钻井方位及水力压裂设计等方面至关重要。准噶尔盆地构造运动剧烈,地层特征较为复杂,需厘清地应力变化规律,判别断层稳定性,把控钻井风险,以提高钻井作业效率。该文以区域地质构造、地震等资料为基础,优选地应力计算模型,进行三维地质力学建模。通过模型计算,得出区域地应力大小和特征,判断区域特征为走滑断层控制过渡到正断层控制;基于模拟结果对三段重点层位进行研究,分析得到断层对地应力变化规律的影响。利用Coulomb破坏函数对研究区域内5条主干断层进行力学判别,分析得到F1和F3断层处于稳定状态,F2、F4和F5断层处于不稳定状态,这一判断结果有助于实现钻井风险的及时预警。该研究通过系统的地质力学建模和断层稳定性分析,为复杂区域相关工程研究提供了理论支持,可以有效地提高钻井作业效率。

Design,Development and Testing of the JTech Bolt for Use in Static,Quasi-Static and Dynamic Domains

Designing a rock reinforcement element requires knowledge of:geomechanical behaviour,interaction of the reinforcement element with rock mass and the element’s mechanistic response in static and dynamic environments.Using this knowledge the JTech bolt was developed and subjected to a thorough program to test,gather data and validate the bolt performance in varying domains.By conducting FE(finite element)modeling,the simulation reviews the JTech bolt design evaluating the effects of threadbar geometric variation,threadbar and nut engagement results under high stress,coating friction response and effects of thread tolerance extremes on the failure mode.These results determine safety factors,tolerances and quality management criteria.Once manufactured,in-situ system testing,laboratory and underground short encapsulation testing,resin mixing testing,double shear testing and dynamic testing at varying velocity and mass,determine the system’s capacity and effectiveness in static,quasi-static and dynamic mining environments.In this paper,the process and results are described.

地质力学模型实验中变形量测方法的应用研究

地质力学模型实验作为一种便捷高效、成本低廉的研究方法,不仅可以将工程的破坏过程直观地呈现出来,而且可以作为了解工程整体力学特征、破坏模式和稳定情况的重要研究手段,在各类岩土工程问题的研究中有着广泛应用。由于地质力学模型材料的变形模量较低,同等应力条件下应变极其敏感,因此模型实验中变形测量显得至关重要。为了提升地质力学模型实验中变形量测的便捷性和准确性,对目前地质力学模型中变形测量的主要方法进行总结分析。结果表明:目前对于模型变形量测的方法主要分为电测式测量方法、光学测量方法和机械式测量方法,其中电测式测量方法主要包括电阻式应变片法和位移计法,光学测量方法主要包括光纤类传感器法、数字图像相关法、光弹性贴片法和云纹干涉法,机械式测量方法主要包括百分表测量法和经纬仪观测法。通过对各种方法工作原理、主要应用案例及优缺点的阐述对比,得出不同方法的主要区别是测量范围和适用范围的差异,其中百分表测量法适用于测量小区域变形;测量内部变形可选择电阻式应变片法及光纤类传感器法;较大区域的变形可选择位移计法及光纤类传感器法;指定点位移可选择经纬仪观测法;全场观测可选择数字图像相关法、云纹干涉法以及光弹性贴片法。该成果可为相关地质力学模型实验的变形测量提供实验参考。

An Axionatics of Geomechanics

Taking the theory of mixture as a basic .framework, the paper merges the primesof rational mechanics irreivrsible thermodynamics and soil meehanics into an organicsystem and proposes an axiomatics of geomechanics .The theoretical system consistsof 5 basis laws and 8 constitutive principles .and it erects a bridge across the gapbetween the pure theory of mechanics and engineering practice .

亿欣煤业15号煤二盘区回采巷道支护技术研究

为了解决亿欣煤业15号煤二盘区工作面回采巷道顶板围岩裂隙发育,顶帮变形量大,现有支护无法满足安全生产的问题,通过煤岩基本物理力学参数测定、巷道围岩松动圈测试、地应力测试和围岩结构钻孔窥视掌握了15号煤二盘区围岩的各项地质力学参数,针对性的设计了工作面回采巷道顶板、煤柱侧巷帮、回采侧巷帮的支护方案。现场试验结果表明,采用该设计方案,巷道掘进后的变形量、顶板离层量和锚杆索轴力较小;在采动影响下回采巷道变形量增加,以底鼓变形为主,两帮移近变形次之,顶板下沉变形最小,锚杆索轴力和顶板离层增大,但均在其承载能力范围内,支护方案可满足15号煤二盘区工作面的正常生产要求,支护设计安全、有效。

基于四维动态地质力学的碳酸盐岩储气库承压能力分析

盖层动态密封性和断层动态密封性是储气库的主要评价指标,对储气库的安全运行具有重要意义。针对储气库盖层与断层静态评价体系的不足,以国内华北地区某碳酸盐岩型储气库为背景,结合测井资料开展岩石力学实验,建立岩石力学动静态参数转换模型和储气库四维地质力学模型,反演地质体初始应力场,开展储气库地质体承压能力分析,获得储气库在注采条件下的四维动态应力场信息(三维应力场在时间维度下的信息)。四维地质力学计算结果表明,当前上限压力(47 MPa)下盖层及断层破坏风险较低,当储气库上限压力提高到49 MPa时,盖层及断层仍然没有发生破坏,结合地面压缩机运行能力,确定储气库上限运行压力为49 MPa。四维动态应力场的建立为储气库的提压扩容提供了科学理论依据。

Geomechanics model test and numerical simulation of 2G-NPR bolt support effect in an active fault tunnel

Active faults are a common adverse geological phenomenon that can occur during tunnel excavation and has a very negative impact on the construction and operation of the tunnel.In this paper,the grade IV rock surrounding the cross-fault tunnel with poor geological conditions has been chosen for the study.The support capacity of 2^(nd) Generation-Negative Poisson’s Ratio(2G-NPR)bolt in an active fault tunnel has been carried out on the basis of relevant results obtained from the geomechanical model test and numerical investigations of failure model for existing unsupported fault tunnel.The investigation shows that surrounding rock of the tunnel is prone to shear deformation and crack formation along the fault,as a result,the rock mass on the upper part of the fault slips as a whole.Furthermore,small-scale deformation and loss of blocks are observed around the tunnel;however,the 2G-NPR bolt support is found to be helpful in keeping the overall tunnel intact without any damage and instability.Due to the blocking effect of fault,the stress of the surrounding rock on the upper and lower parts of the fault is significantly different,and the stress at the left shoulder of the tunnel is greater than that at the right shoulder.The asymmetrical arrangement of 2G-NPR bolts can effectively control the asymmetric deformation and instability of the surrounding rock.The present numerical scheme is in good agreement with the model test results,and can reasonably reflect the stress and displacement characteristics of the surrounding rock of the tunnel.In comparison to unsupported and ordinary PR(Poisson’s Ratio)bolt support,2G-NPR bolt can effectively limit the fault slip and control the stability of the surrounding rock of the fault tunnel.The research findings may serve as a guideline for the use of 2G-NPR bolts in fault tunnel support engineering.

Geology and geomechanics of hydraulic fracturing in the Marcellus shale gas play and their potential applications to the Fuling shale gas development

Geological characteristics,geomechanical behavior and hydraulic fracture propagation mechanism in the Marcellus shale gas play are analyzed and compared with China’s Fuling shale play.Successful experiences in hydraulic fracturing and shale gas development in the Marcellus shale gas play are summarized,which might be applicable in other shale plays.The main factors contributing to the successful development of the Marcellus shale gas play include adoption of advanced drilling and completion technologies,increases of hydraulic fracturing stages,proppant concentration and fluid injection volume.The geological and geomechanical mechanisms related to those technologies are analyzed,particularly the in-situ stress impacts on hydraulic fracturing.The minimum horizontal stress controls where the fractures are initiated,and the maximum horizontal stress dominates the direction of the hydraulic fracture propagation.Hydraulic fracturing performed in the shale reservoir normally has no stress barriers in most cases because the shale has a high minimum horizontal stress,inducing hydraulic fractures propagating beyond the reservoir zone,resulting in inefficient stimulation.This is a common problem in shale plays,and its mechanism is studied in the paper.It is also found that the on-azimuth well has a higher productivity than the off-azimuth well,because shear fractures are created in the off-azimuth well,causing main fractures to kink and increasing fracture tortuosity and friction.The Fuling shale gas play has a markedly higher minimum horizontal stress and much smaller horizontal stress difference.The high minimum horizontal stress causes a much higher formation breakdown pressure;therefore,hydraulic fracturing in the Fuling shale gas play needs a higher treatment pressure,which implies higher difficulty in fracture propagation.The small difference in the two horizontal stresses in the Fuling shale gas play generates shorter and more complex hydraulic fractures,because hydraulic fractures in this case are prone to curve to preexisting fractures.To overcome these difficulties,we recommend reducing well spacing and increasing proppant concentration to increase gas productivity for the Fuling shale gas development.

A geomechanics classification for the rating of railroad subgrade performance

The type of subgrade of a railroad foundation is vital to the overall performance of the track structure.With the train speed and tonnage increase,as well as environmental changes,the evaluation and influence of subgrade are even more paramount in the railroad track structure performance.A geomechanics classification for subgrade is proposed coupling the stiffness(resilient modulus)and permanent deformation behaviour evaluated by means of repeated triaxial loading tests.This classification covers from fine-to coarse-grained soils,grouped by UIC and ASTM.For this achievement,we first summarize the main models for estimating resilient modulus and permanent deformation,including the evaluation of their robustness and their sensitivity to mechanical and environmental parameters.This is followed by the procedure required to arrive at the geomechanical classification and rating,as well as a discussion of the influence of environmental factors.This work is the first attempt to obtain a new geomechanical classification that can be a useful tool in the evaluation and modelling of the foundation of railway structures.