Geomechanical effects of CO_2 storage in depleted gas reservoirs in the Netherlands:Inferences from feasibility studies and comparison with aquifer storage

In this paper,the geomechanical impact of large-scale carbon dioxide(CO_2) storage in depleted Dutch gas fields is compared with the impact of CO_2 storage in saline aquifers.The geomechanical behaviour of four potential CO_2 storage sites is examined using flow and geomechanical simulations.Many gas reservoirs in the Netherlands are found in fault blocks,one to a few kilometres wide,laterally bounded by sealing faults.Aquifer depletion or re-pressurization in the lateral direction is seldom an issue because of a lack of active aquifers.Reservoir pressure changes are therefore limited to a gas-bearing fault block,while the induced stress changes affect the gas reservoir and extend 1-3 km away into the surrounding rock.Arguments in favour of CO_2 storage in depleted gas fields are:proven seal quality,availability of field data,no record of seal integrity failure by fault reactivation from the seismically active producing Dutch gas fields,and the potential benefits of restoring the virgin formation pressure and stress state to geomechanical stability.On the other hand,CO_2 injection in saline aquifers causes pressure build-up that exceeds the virgin hydrostatic pressure.Stress perturbations resulting from pressure build-up affect large areas,extending tens of kilometres away from the injection wells.Induced stresses in top seals are.however,small and do not exceed a few tenths of megapascal for a pressure build-up of a few megapascals in the storage formation.Geomechanical effects on top seals are weak,but could be enhanced close to the injection zone by the thermal effects of injection.Uncertainties related to characterisation of large areas affected by pressure build-up are significant,and seal quality and continuity are more difficult to be demonstrated for aquifers than for depleted gas reservoirs that have held hydrocarbons for millions of years.     

油藏CO_2驱及封存过程中地化反应特征及埋存效率

油藏CO_2驱过程中,CO_2与地层水和岩石矿物发生化学反应,影响地层物性和CO_2的埋存形式。基于吉林油田某高温油藏的地层及流体性质,建立考虑地层水蒸发、水中CO_2溶解扩散、CO_2-地层水-岩石地化反应和孔渗关系的CO_2驱及埋存综合模拟模型,分析不同阶段的地化反应特征和CO_2埋存形式,研究CO_2注入方式对提高采收率和埋存效率的影响。结果表明:在CO_2驱油阶段,地化反应对储层孔隙度和渗透率产生一定影响,但对采收率的影响较小,CO_2主要以构造形式埋存于油藏内;在后续埋存阶段,气态CO_2通过地化反应不断转化为矿物形式,造成地层压力下降;水气交替注入方式可提高原油最终采收率和CO_2一次埋存效率,应为首选注入方式;对于其CO_2埋存量的不足,可在CO_2驱后注入一定的CO_2进行补充,同时起到维持地层压力的作用。     

Risk assessment of CO_2 injection processes and storage in carboniferous formations:a review

Over the last decades,people from almost all over the world have realized that it is necessary to quickly develop strategies for the control and reduction of greenhouse gases (GHG) emissions.Among various GHGs,carbon dioxide (CO2) is the most abundant GHG.Its underground storage involves less risk and lower levels of dangerousness.The paper briefly describes the most effective technologies available in the market for background processes to storage (capture and transport) CO2,as well as the more secure solu...     

Geomechanical analysis of the influence of CO_2 injection location on fault stability

Large amounts of carbon dioxide(CO_2) should be injected in deep saline formations to mitigate climate change,implying geomechanical challenges that require further understanding.Pressure build-up induced by CO_2 injection will decrease the effective stresses and may affect fault stability.Geomechanical effects of overpressure induced by CO_2 injection either in the hanging wall or in the foot wall on fault stability are investigated.CO_2 injection in the presence of a low-permeable fault induces pressurization of the storage formation between the injection well and the fault.The low permeability of the fault hinders fluid flow across it and leads to smaller overpressure on the other side of the fault.This variability in the fluid pressure distribution gives rise to differential total stress changes around the fault that reduce its stability.Despite a significant pressure build-up induced by the fault,caprock stability around the injection well is not compromised and thus,CO_2 leakage across the caprock is unlikely to happen.The decrease in fault stability is similar regardless of the side of the fault where CO_2 is injected.Simulation results show that fault core permeability has a significant effect on fault stability,becoming less affected for high-permeable faults.An appropriate pressure management will allow storing large quantities of CO_2 without inducing fault reactivation.     

Geomechanical response of overburden caused by CO_2 injection into a depleted oil reservoir

This study investigates the hydro-mechanical aspects of carbon dioxide(CO_2) injection into a depleted oil reservoir through the use of coupled multiphase fluid flow and geomechanical modeling.Both singlephase and multiphase fluid flow analyses coupled with geomechanics were carried out at the West Pearl Queen depleted oil reservoir site,and modeling results were compared with available measured data.The site geology and the material properties determined on the basis of available geophysical data were used in the analyses.Modeling results from the coupled multiphase fluid flow and geomechanical analyses show that computed fluid pressures match well with available measured data.The hydromechanical properties of the reservoir have a significant influence on computed fluid pressures and surface deformations.Hence,an accurate geologic characterization of the sequestration site and determination of engineering properties are important issues for the reliability of model predictions.The computed fluid pressure response is also significantly influenced by the relative permeability curves used in multiphase fluid flow models.While the multiphase fluid flow models provide more accurate fluid pressure response,single-phase fluid flow models can be used to obtain approximate solutions.The ground surface deformations obtained from single-phase fluid flow models coupled with geomechanics are slightly lower than those predicted by multiphase fluid flow models coupled with geomechanics.However,the advantage of a single-phase model is the simplicity.Limited field monitoring of subsurface fluid pressure and ground surface deformations during fluid injection can be used in calibrating coupled fluid flow and geomechanical models.The calibrated models can be used for investigating the performance of large-scale CO_2 storage in depleted oil reservoirs.     

Numerical modeling for rockbursts: A state-of-the-art review

As the depth of excavation increases,rockburst becomes one of the most serious geological hazards damaging equipment and facilities and even causing fatalities in mining and civil engineering.This has forced researchers worldwide to identify different methods to investigate rockburst-related problems.However,some problems,such as the mechanisms and the prediction of rockbursts,continue to be studied because rockburst is a very complicated phenomenon influenced by the uncertainty and complexity in geological conditions,in situ stresses,induced stresses,etc.Numerical modeling is a widely used method for investigating rockbursts.To date,great achievements have been made owing to the rapid development of information technology(IT)and computer equipment.Hence,it is necessary and meaningful to conduct a review of the current state of the studies for rockburst numerical modeling.In this paper,the categories and the origin of different numerical approaches employed in modeling rockbursts are reviewed and the current usage of various numerical modeling approaches is investigated by a literature research.Later,a state-of-the-art review is implemented to investigate the application of numerical modeling in the mechanism study,and prediction and prevention of rockbursts.The main achievements and problems are highlighted.Finally,this paper discusses the limitations and the future research of numerical modeling for rockbursts.An approach is proposed to provide researchers with a systematic and reasonable numerical modeling framework.     

Testing and modeling of rockfill materials:A review

The research development of rockfill materials(RFM) was investigated by a series of large-scale triaxial tests.It is observed that confining pressure and particle breakage play important roles in the mechanical property,dilatancy relation and constitutive model of RFM.In addition,it is observed that the conventional dilatancy relation and constitutive model are not suitable for RFM due to the complex mechanical behavior.Hence,it needs to propose a unified constitutive model of RFM,considering the statedependent and particle breakage behavior.     

Computational modeling of fracture in concrete: A review

This paper presents a review of fracture modeling of concrete. The complex material, such as concrete, has been widely used in construction industries and become trending issue in the last decades. Based on comprehensive literature review, there are two main approaches considered to-date of concrete fracture modeling, such as macroscopic and micromechanical models. The purpose of this review is to provide insight comparison from different techniques in modeling of fracture in concrete which are available. In the first section, an overview of fracture modeling in general is highlighted. Two different approaches both of macroscopic and micromechanical models will be reviewed. As heterogeneity of concrete material is major concern in micromechanical-based concrete modeling, one section will discuss this approach. Finally, the summary from all of reviewed techniques will be pointed out before the future perspective is given.     

Physical modeling of tunnels in soft ground: A review

Physical modeling has played an important role in studies related to excavation of tunnels in soft ground. A variety of modeling techniques have been developed by researchers all over the world to study ground response to tunneling. These techniques range from the two-dimensional trap door tests to the miniature tunnel boring machines that simulate the process of tunnel excavation and lining installation in a centrifuge. This paper presents a review of selected physical models that have been developed and used in soft ground tunneling research. Furthermore, this paper discusses some of the various approaches used to record soil deformation and failure mechanisms induced by tunneling. Experimental setups and sample results are presented for each technique as described by original authors. A summary of the advantages and disadvantages of each method is also presented.     

Geomechanical properties will constrain CO_2 injection into the lower Ordovician Rose Run sandstone deep saline reservoir,Appalachian Basin,Kentucky, USA

The Kentucky Geological Survey(KGS) 1 Hanson Aggregates stratigraphic research well, Carter County,Kentucky, USA, was drilled to a total depth of 1474 m as a field-scale test of potential CO_2 storage reservoir properties in the Central Appalachian Basin. Geomechanical properties of the Rose Run sandstone(upper Ordovician Knox group) were tested for its suitability as a storage reservoir. A 9.8-m thick section of the Rose Run was penetrated at 1000 m drilled depth and a whole-diameter core and rotary sidewall cores were taken. Average porosity and permeability measured in core plugs were 9.1%and 44.6 m D, respectively. Maximum vertical stress gradient calculated in the wellbore was 26 MPa/km.Wellbore fractures in dolomites underlying and overlying the Rose Run follow the contemporary N53 E Appalachian Basin stress field. The Rose Run elastic geomechanical properties were calibrated to values measured in core plugs to evaluate its fracturing risk as a CO_2 storage reservoir. Mean Young's modulus and Poisson's ratio values of the Rose Run were 45 GPa and 0.23, respectively, whereas Young's modulus and Poisson's ratio values were 77.1 GPa and 0.28, respectively, in the overlying Beekmantown dolomite,suggesting the Rose Run may fracture if overpressured during CO_2 injection but be confined by the Beekmantown. Triaxial compressive strength measured in core plugs found the Rose Run and Beekmantown fractured at mean axial stresses of 156.5 MPa and 282.2 MPa, respectively, confirming the Beekmantown as suitable for confining CO_2 injected into the Rose Run. A step-rate test was conducted in a mechanically-isolated 18.6-m interval bracketing the Rose Run. Static Rose Run reservoir pressure was9.3 MPa, and fracture gradient under injection was 13.6 MPa/km, suggesting step-rate testing before CO_2 injection, and subsequent pressure monitoring to ensure confinement. As the region around the KGS 1 Hanson Aggregates well is underpressured and adjacent to faulted Precambrian basement, further research is needed to evaluate its induced seismicity risk during CO_2 injection.     

A semi-automatic method for 3D modeling and visualizing complex geological bodies

Bulletin of Engineering Geology and the Environment - The technology of 3D geological modeling is a powerful tool for representing the geological structures and subsurface strata distribution,...     

花岗岩地质成因矿物成分文献综述

研究结果表明:花岗岩地质成因有三大类:①与物质来源结合;②与构造环境结合;③与大陆动力学结合,同时还存在按其他方法分类.花岗岩主要由长石、石英、云母等构成,不同种类花岗岩其矿物成分比例也不尽相同,可以通过电镜扫描、X衍射等实验得到含量.不同矿物成分其力学性质也不尽相同,目前花岗岩对矿物成分与力学性质之间关系的研究仍未成...     

Air pollution and terrain aerodynamics: A review of fluid modeling studies at the EPA fluid modeling facility

Recent fluid modeling studies conducted at the EPA Fluid Modeling Facility of flow and diffusion in complex terrain are reviewed. Ratios of the maximum concentration on a hill surface to the maximum concentration in the absence of the hill are estimated. This ratio may be regarded as a terrain amplification factor and is a function of hill aspect ratio (two-versus three-dimensional), hill slope, atmospheric stability, etc. For upwind sources, terrain amplification factors are typically 1 to 2 for neutral flow over two-dimensional hills and 2 to 4 for three-dimensional hills. Terrain amplification factors as large as 10 or 15 were found for low sources placed downwind of two-dimensional hills of moderate to large slope. For strongly stable flow over three-dimensional hills, it is more useful to compare maximum surface concentrations with those at the centerline of the plume in the absence of the hill. These concentrations have been shown to be essentially equal.     

Agent-based modeling in urban and architectural research: A brief literature review

Agent-based modeling (ABM) is an emerging modeling approach. In the past two decades, agent-based models have been increasingly adapted by social scientists, especially scientists in urban and geospatial studies, as an effective paradigm for framing the underlying problems of complex and dynamic processes. As a result, the literature of ABM research is growing rapidly, covering a diverse range of topics. This paper presents a systematic literature review of ABM research, and discusses both theoretical issues such as ABM definition and architecture, and practical issues such as ABM applications and development platforms. A comprehensive and up-to-date bibliography is presented.     

地层倾角对CO2地质封存的影响研究—以鄂尔多斯CCS工程为例

CO2地质储存是减少CO2向大气排放的有效手段。CO2在储层中的运移受地层的物理属性和空间展布形态的影响,本文以鄂尔多斯CO2地质封存示范场地石千峰组为研究对象,研究了地层产状倾斜对CO2地质储存的影响。结果表明,在定压注入时,地层倾角对CO2的空间分布、CO2的注入速率、CO2的空间运移距离、以及CO2的封存量等均呈现出规律性的影响;地层倾角越大,注入速率越小、横向运移距离越远,而其封存量小;地层倾角的增大不利于CO2地质封存。     

二氧化碳地质封存工程防灾监测中瑞雷波敏感性初步分析

瑞雷波勘察技术常用于地震场地土评价,且长波微动观测可以获得深部地层的信息,但其在CO2地质封存工程防灾监测中应用的可行性探讨还未见深入研究报道。基于一典型CO2封存场地地层模型,通过数值模拟的方式,分析了瑞雷波波速对储层弹性参数改变的敏感性。模拟分析表明,CO2储层弹性参数变化对瑞雷波波速的影响随频厚积变化而变化;研究发现CO2储层横波波速改变相对于层厚、纵波或密度的改变对面波波速影响较大;研究还发现当CO2储层薄且埋深大时,面波频散特性对储层弹性参数改变不敏感。研究初步认为,当前常规的瑞雷波勘察技术用于深部CO2封存工程防灾监测具有一定的技术难度。