A review of nuclear magnetic resonance(NMR) technology applied in the characterization of polymer gels for petroleum reservoir conformance control

Polymer gel systems have been widely applied to control excessive water and improve oil recovery(IOR)in petroleum reservoirs.They are usually divided into two main types,in-situ cross-linked polymer gels,and pre-formed polymer gels.In recent years,nuclear magnetic resonance(NMR) technology has been gradually applied to the research of polymer gel systems due to its unique analysis advantages.This paper is intent to review these works systematically.For in-situ cross-linked polymer gel systems,NMR can be used to characterize the chemical structure changes of the polymer,the cross-linker,and the auxiliary agent in the formulation of the polymer gel systems.Moreover,the gelation time and the gel strength of the in-situ cross-linked polymer gel systems can also be measured by NMR.For pre-formed polymer gels,NMR can be employed to detect the chemical structure of the designed products.Last,the NMR method can evaluate the plugging,water control,and oil improvement performance of the polymer gels in porous media without using dopants.This review can help readers build a more systematic understanding of the application of NMR technology in polymer gel systems for IOR and help re searchers to more deeply study the performance of polymer gel systems.

Relaxation study of cement based grouting material using nuclear magnetic resonance

Aiming at actual condition of poor effect of hole sealing for the reason of poor cement paste fluidity in the process of coal mine gas drainage,by adding a water reducing agent,cement paste for hole sealing was produced.The changes of initial distribution,weighted average values and total relaxation signal intensity of transverse relaxation time(T 2) of water in pure cement paste and water reducing agent added cement paste were studied with low field proton nuclear magnetic resonance(NMR).The results show that there are four peaks in T2 distribution curves of cement paste:the first peak is related to the bound water in flocculation,the second and the third peaks are related to the water in flocculation,water reducing agent makes it extending towards the long relaxation time,increasing its liquidity,and the fourth peak is related to the free water.By using weighted average values of T2 and total relaxation signal intensity,hydration process of cement pastes could be roughly divided into four stages:the initial period,reaction period,accelerated period and steady period.By analyzing the periods,it makes sure that the grouting process should be completed in the reaction period in the site,and the drainage process should be started in the steady period.The results have great guiding significance to the hole sealing and methane drainage.

Three dimensional structure prediction and proton nuclear magnetic resonance analysis of toxic pesticides in human blood plasma

The purpose of this study was to investigate the nuclear magnetic resonance （NMR） assignments of hydrolyzed products extracted from human blood plasma. The correlations between chemical, functional and structural prop- erties of highly toxic pesticides were investigated using the PreADME analysis. We observed that toxic pesticides possessed higher molecular weight and, more hydrogen bond donors and acceptors when compared with less toxic pesticides. The occurrence of functional groups and structural properties was analyzed using ~H-NMR. The ~H- NMR spectra of the phosphomethoxy class of pesticides were characterized by methyl resonances at 3.7-3.9 ppm （8） with the coupling constants of 11-16 Hz （Je-cns）. In phosphoethoxy pesticides, the methyl resonance was about 1.4 ppm （8） with the coupling constant of 10 Hz （Je-cH2） and the methylene resonances was 4.2-4.4 ppm （8） with the coupling constant of 0.8 Hz （Jp-cH3）, respectively. Our study shows that the values of four parameters such as chemical shift, coupling constant, integration and relaxation time correlated with the concentration of toxic pesticides, and can be used to characterise the proton groups in the molecular structures of toxic pesticides.

Study of Polymer Flooding in Heterogeneous Porous Media by Using Nuclear Magnetic Resonance

Polymer has been successfully used to enhance crude oil recovery at high water cut stage.However,the application of polymer flooding is limited by the heterogeneity of reservoir.In this work,the role of polymer flooding in heterogeneous reservoir was explored by nuclear magnetic resonance(NMR)spectroscopy.Parallel core displacement experiments were carried out to study polymer flooding in heterogeneous formation.The results showed that the polymer flooding area was related to permeability and pore connectivity.At the end of the water flooding stage,the residual oil was not evenly distributed in porous media.The percent crude oil recovery increased with the increase of pore diameter.Crude oil recovery from cores with larger pores was higher,and water broke through the highly permeable core first.After 0.3 PV polymer injection,the water mobility of the high permeability core decreased.Polymer injection showed a dual effect,an oil displacement effect and a traction effect.The oil displacement effect was responsible for driving out the crude oil in large pores,whereas the traction effect was responsible for driving out residual oil from small pores.After 1 PV polymer injection,the polymer solution channeled through the highly permeable core rapidly.The crude oil in large pores was washed out completely.The NMR water-phase spectrum line of the highly permeable core was much higher than that of the low permeable core.Under different core permeability and porosity,the NMR peak of the crude oil-phase spectrum line indicated that the polymer flooding is mainly effective on pores>40μm.

Comparison between computed tomography and magnetic resonance imaging in clinical diagnosis and treatment of tibial platform fractures

BACKGROUND Tibial plateau fracture is one of the common fracture types.It occurs mainly in teenagers and is usually caused by a fall.After the occurrence of fracture,knee swelling,pain,limited activity,etc.greatly affect the patient’s exercise habits and lifestyle.X-ray,computed tomography(CT)and magnetic resonance imaging(MRI)were used in this examination.X-rays are relatively new and easy to operate.However,there are some errors in the observation of fracture collapse and fracture displacement.In recent years,CT and MRI have been actively used to diagnose various types of clinical fractures.They have more diagnostic power than X-ray film.However,some scholars believe that CT is also prone to errors in clinical application.The volume effect leads to missed diagnosis and misdiagnosis in some cases,while the multidirection scanning of MRI technology can effectively overcome the shortcomings of CT.To facilitate the selection of clinical examination regimens,this study further observed the diagnostic ability of these two regimens in the diagnosis of tibial plateau fractures.AIM To explore the value of nuclear MRI and CT in the clinical diagnosis of tibial plateau fractures.METHODS A total of 120 patients with tibial plateau fractures admitted from September 2017 to August 2019 were included.All patients were examined by nuclear MRI and CT scanning.The results were sent to senior physicians in our hospital to complete the diagnosis.RESULTS Nuclear magnetic resonance showed the same effects as CT in four aspects:fracture displacement,bone defect,fracture site and fracture comminution.There was no significant difference in the score data(P>0.05).Nuclear magnetic resonance and CT tended to be consistent in the B3,C2 and C3 fracture diagnosis coincidence rate,combined injury detection rate and fracture detection rate.The diagnostic coincidence rate of type B1,B2 and C1 fractures and the accuracy rate of overall fracture classification indicated that the MRI technique was significantly better than that of CT(P>0.05).CONCLUSION MRI and CT have good diagnostic typing in the diagnosis of tibial plateau fractures,but MRI is more accurate and may be preferred.

Mammography combined with breast dynamic contrast-enhanced-magnetic resonance imaging for the diagnosis of early breast cancer

Objective The aim of this study was to investigate the application of mammography combined with breast dynamic contrast-enhanced magnetic resonance imaging(DCE-MRI) for the diagnosis of early breast cancer. Methods Mammography and DCE-MRI were performed for 120 patients with breast cancer(malignant, 102; benign; 18). Results The sensitivity of mammography for early diagnosis of breast cancer was 66.67%, specificity was 77.78%, and accuracy was 68.33%. The sensitivity of MRI for early diagnosis of breast cancer was 94.12%, specificity was 88.89%, and accuracy was 93.33%. However, the sensitivity of mammography combined with DCE-MRI volume imaging with enhanced water signal(VIEWS) scanning for early diagnosis of breast cancer was 97.06%, specificity was 94.44%, and accuracy was 96.67%. Conclusion Mammography combined with DCE-MRI increased the sensitivity, specificity, and accuracy of diagnosing early breast cancer.

Physics and mathematics of magnetic resonance imaging for nanomedicine:An overview

Magnetic resonance imaging(MRI), magnetic resonance angiography(MRA) and magnetic resonance spectroscopy(MRS) are fundamental concepts used in modern medicine to improve health care. These concepts are based on the principle of nuclear magnetic resonance(NMR). Over the years, various laboratories around the world have applied different numerical techniques based on the Bloch NMR equations to solve specific problems in physics, biology, chemistry, engineering and medicine. The ultimate goal of any physician is to obtain maximum physical, biophysical, chemical and biological information on any tissue or cell under examination. This goal can be achieved by solving the Bloch NMR flow equations analytically. In this review, we present the basic principle of NMR/MRI in a way that can be easily understood by any researcher who needs an NMR concept to solve a specific medical problems. After a very brief history of the subject, a second order, non homogeneous, time-dependent differential equation derived from the Bloch NMR equation is presented. This equation has the basic intrinsic properties of MRI, MRA and MRS that can be extracted by means of classical and quantum mechanics for possible application in nanomedicine.

Measuring Transverse Relaxation Time of Xenon Atoms Based on Single Beam of Laser in Nuclear Magnetic Resonance Gyroscope

Nuclear magnetic resonance gyroscope (NMRG) has the characteristics of high precision and miniaturization, and is one of the main applications of quantum technology in the field of navigation. The transverse relaxation time (T_(2)) of the xenon nuclear spin in the atomic cell of the NMRG directly affects the angular random walk of the gyro. Accurate and rapid measurement of T_(2) is conducive to further improvement of gyroscope. At present, for the measurement of T_(2), the schemes of two orthogonal lasers for pumping and detecting are usually used. By applying two fast-switching orthogonal static magnetic fields and a single beam of circularly polarized laser with corresponding wavelength to pump the atomic cell, the xenon nuclear macroscopic magnetic moment Larmor precession is generated. The cesium atoms parametric magnetometer in cell is formed to detect the free induction decay signal generated by nuclear spin precession of xenon atoms. The measurement of T_(2) by a single laser simplifies the measurement equipment compared with traditional method with two lasers. The experimental results show that the T_(2) of xenon atoms is more than 10 s, and the effects of temperature are studied, which lay the foundation for the subsequent improvement of gyro performance.

纳米氧化铝改性地面井固井水泥水化机制研究

随着地面井固井技术发展加快,工程现场对于地面井固井水泥浆的早期流动性及凝结性能有了更高的要求。为了提高固井工程注水泥作业的顶替效率,改善固井工程现场作业应用情况,提出了纳米氧化铝颗粒改性固井水泥的方法,利用核磁共振技术对质量分数为0、0.05%、0.10%、0.15%及0.20%的纳米氧化铝改性水泥浆(水灰比为0.44)在不同水化龄期的水化反应变化特征进行了研究,探究了纳米氧化铝改性水泥的水相分布、物理结合水总信号量变化、峰形指数及迁移速率。结果表明:纳米氧化铝改性水泥浆在水化阶段的T2图谱会出现3个弛豫峰,分别对应絮凝结构填充水(0.1~10 ms)、毛细水(10 ms)、自由水(800~1000 ms);其物理结合水总信号随纳米氧化铝质量分数增加而逐步减少,其中质量分数为0.20%的纳米氧化铝改性水泥浆信号量减少速率最快;峰形指数呈现先上升后下降的趋势,当水化反应进行至600 min时,质量分数为0.20%的改性水泥浆变化速率最快,弛豫峰向短弛豫方向移动速率加快;结合迁移速率将纳米氧化铝改性固井水泥水化反应阶段划分,其水化机制分别作用在4个水化时期:①初始水化期(5~60 min),水化速率未发生明显改变;②加速水化期(60~600 min),纳米氧化铝使水泥浆中物理结合水转化为化学结合水所经历时间变短,水化进程加快,达到促进水泥水化的效果;③稳定水化期(600~1200 min),水泥体系趋于稳定;④延缓水化期(1200~1800 min),物理结合水转化为化学结合水速率变慢,水泥水化进程减慢。研究结论得到,纳米氧化铝改性水泥浆水化时期可以划分为4个阶段,分别起到物理填充、加速、稳定、延缓的作用。在加速期,纳米氧化铝促进水泥的早期流动,有利于水泥浆的泵送及流动,在延缓期,纳米氧化铝延缓水泥的进一步水化进程,利于发展早期强度。其中,质量分数为0.20%的纳米氧化铝改性水泥浆对于水泥水化进程影响最大,促进填充水向结合水的转化,在加速水化期间对于水泥浆水化反应加速程度最大,以此作为依据对现场固井水泥的制备及应用提供指导。

基于NMR的非饱和土相对渗透系数快速预测新方法

非饱和土的渗透系数作为研究非饱和土中水分运移的重要参数,直接测量方法原理简明但试样尺寸较大,耗时较长;土-水特征曲线(SWCC)间接预测方法由于需要获取土-水特征曲线,同样较为耗时,工作量较大。为此,结合核磁共振(NMR)理论与渗流理论提出了不同孔径孔隙通道渗透系数与弛豫时间的关系,通过对不同大小孔隙通道渗透系数进行累加,提出了基于核磁共振的饱和/非饱和土渗透系数预测模型和快速预测方法。为验证模型的合理性,以湖南黏土为研究对象,进行了不同初始孔隙比试样脱湿、吸湿过程以及饱和状态下的95次核磁共振试验,获取相应的NMR曲线,采用瞬时剖面法获取不同初始孔隙比试样非饱和相对渗透系数,并与该模型预测值对比。研究发现:利用脱湿、吸湿过程不同含水率下NMR曲线以及饱和状态的NMR曲线均具有较好的预测效果,但基于饱和状态下试样的NMR曲线预测效果相对最好,测量成本和耗时也最小,因此建议采用饱和状态试样NMR曲线直接预测非饱和相对渗透系数。

震动载荷多次作用下烟煤孔裂隙结构演化特征试验研究

煤层开采过程中频繁采掘扰动或远场顶板周期性破断会产生多次的震动载荷,震动载荷对于煤样微观孔裂隙结构和宏观力学行为具有重要影响。为探索震动载荷下煤样孔裂隙结构演化特征,选取烟煤煤样,利用霍普金森压杆(SHPB)试验系统开展了多次震动载荷冲击煤样试验,借助低场核磁共振分析仪测试了每次冲击后煤样T_(2)谱,并通过核磁共振成像(MRI)分析了煤样孔裂隙分布及其损伤演化特征。结果表明,随着震动载荷作用次数增加,煤样峰值应力与动态弹性模量均呈现线性下降趋势,震动载荷冲击效应使得煤样承载和抵抗变形能力显著弱化,因此有必要对煤样孔裂隙演化特征展开深入分析。从T_(2)谱和MRI信息得出,震动载荷初次作用下煤样总体孔隙体积大幅增加,其中吸附孔体积增高达5.0倍,随着震动载荷持续作用,煤样微裂隙开始连通汇聚形成宏观裂纹,使得渗流孔之间连通性大幅提高,煤样总体孔隙率达到峰值,较煤样原始孔隙率提高约6倍。在煤样受震动载荷损伤、破坏的整个过程中,渗流孔的连通性逐渐提高与改善,其分形维数呈线性下降趋势。通过核磁共振成像揭示了震动载荷对煤样孔裂隙作用机制,结果表明煤样中部区域孔隙最先发育并逐步形成微裂隙,在后续震动波反射、拉伸作用下,损伤破坏区域向两侧逐渐演变直至贯通试样。

高倍数水驱砂岩中原油黏度、岩心润湿性时变规律核磁共振实验

根据模拟原油黏度与横向弛豫时间谱几何平均值的变化关系,建立了模拟原油黏度预测模型,并结合高倍数水驱核磁共振(NMR)实验实现了孔隙介质中模拟原油黏度的时变规律定量表征;基于核磁共振弛豫理论推导出新的NMR润湿性指数计算公式,结合砂岩岩心高倍数水驱实验,定量表征了水驱过程岩石润湿性的时变规律。研究表明:岩心中剩余油黏度与过水倍数正相关,过水倍数较低时剩余油黏度升高速度较快,过水倍数较高时剩余油黏度升高速度趋缓。剩余油黏度的变化与储层非均质性相关,储层均质性越强,剩余油中重质组分含量越高,黏度越高。注水后储层润湿性将发生改变,亲油储层向亲水储层转变,亲水储层则亲水性更强,且改变程度随过水倍数增加而增强。原油黏度的时变性与润湿性的时变性具有很高的关联性,原油的黏度变化不可忽略,考虑模拟原油黏度变化时计算得到NMR润湿性指数与测试Amott(自吸法)润湿性指数更具有一致性,更加符合储层润湿性时变规律。

超临界CO_(2)作用下无烟煤孔隙结构演化时间效应规律

CO_(2)地质封存技术是实现减排和废弃矿井资源再利用的有效技术之一,但煤层孔隙结构在CO_(2)注入后的变化具有时间效应,其演化规律将直接影响CO_(2)地质封存潜力。为了探索作用时间增加后煤层孔隙结构变化的真实情况,提高CO_(2)地质封存量计算精度,通过对重庆市南桐矿区无烟煤进行超临界CO_(2)吸附实验、低温氮气吸附实验、X射线衍射测试、核磁共振测试、扫描电镜测试等实验,研究了不同超临界CO_(2)作用时间对该区域内煤样孔隙结构的演化规律。研究结果表明:①超临界CO_(2)作用后煤样孔隙度的变化主要发生在7 d内,处理7 d后煤样孔隙度增加了3.20%,7~14 d内煤样孔隙度仅增加了0.05%;②随作用时间增加,煤样孔隙的比表面积增加但变化量逐渐减小,7 d内日均增长19.74%~24.50%,7~14 d内日均增长2.37%~4.60%,其变化规律近似呈对数函数关系;③超临界CO_(2)与煤产生的化学反应引起矿物质的溶解,增大了煤体的表面粗糙度,表征煤样粗糙度的分形维数随着作用时间的增加持续增大;④超临界CO_(2)作用后能有效改变煤样的孔隙度及表面形貌,为CO_(2)吸附提供了更多吸附点位,超临界CO_(2)对孔隙结构的改造效果在7 d内比较明显。结论认为,超临界CO_(2)作用下无烟煤孔隙结构的变化随作用时间增加最终会趋于稳定,研究结果可为无烟煤储层CO_(2)地质封存潜力评价提供理论指导。

连续波核磁共振实验中外扫描测量法的改进

本文对连续波核磁共振实验中外扫描法测横向弛豫时间误差的主要来源进行了分析,对系统误差的大小进行了定量估算.在此基础上,对外扫描法中横向弛豫时间的测量提出了相应的改进措施,通过计算确定了共振信号半高宽测量时共振信号应在的位置.结果表明,外扫描法测量中,通过x方向的相位调节把共振信号移到偏离中心适当距离的位置上来测量其半高宽,可有效降低非线性扫描电压引起的系统误差.此外,通过对误差大小及共振信号测量位置的计算,能加深学生对横向弛豫时间及外扫描测量法原理的理解.

在线核磁监测法优化裂缝性页岩油藏赋能渗吸吞吐工艺

赋能渗吸采油可以通过补充地层能量、置换等方式提高原油采收率,目前已成为页岩油藏开发的重要技术。设计合理的赋能渗吸工艺参数,可以更高效地开发页岩油藏。通过4轮次赋能渗吸吞吐实验,利用在线核磁技术分析纳米级原油微观运移特征,优化了裂缝性页岩油藏焖井时间、赋能时机、吞吐轮次等赋能渗吸工艺参数。实验结果表明,首次焖井时间控制在12~15 d即可,随着吞吐轮次的增加,焖井时间应相应减少;吞吐3轮次后对采收率的提升作用不明显,具有明显的有效轮次;压力下降至原始地层压力70%后,继续控压生产效果较差,需及时对地层进行补能,以保证页岩油井高效开发;赋能渗吸时不同液体注入量对采出油量有较大影响,注入量偏少,补充能量不充分,采出效果不佳;但由于储层渗透率极低,补充能量作用半径有限,补能流体量不能无限增加,一般达到压裂裂缝控制体积的0.4 PV左右即可。研究结果可为页岩油藏赋能渗吸工艺参数优选提供技术支撑。

基于核磁共振信号标定法的致密油藏渗吸实验研究

基于一种新的核磁共振信号标定法开展了致密砂岩岩样的油水渗吸实验,该方法可以根据回归模型将核磁信号总量换算为含油体积,相较常规方法计算更方便、更准确。研究发现渗吸过程可划分为过渡渗吸和稳定渗吸2个阶段,低黏度煤油渗吸样品最佳渗吸时间集中在68 h左右,高黏度致密油渗吸样品最佳渗吸时间集中在188 h左右。渗吸时间充足的情况下,煤油和致密油的最终换油率相差不大,但如果渗吸时间较短,则黏度越大换油率越低。同层位、同黏度的样品具有相似的渗吸动态特征;同层位、高黏油的样品达到稳定渗吸阶段无因次渗吸时间相较低黏油更短。以半径0.5µm作为大、小孔隙的分界线,煤油渗吸样品中半径小于0.5µm的孔隙渗吸换油贡献率平均为83.93%,占据主导地位,原油动用率平均为23.54%;半径大于0.5µm的孔隙渗吸换油贡献率平均为16.07%,相对较少,原油的动用率平均为8.50%,普遍较低,容易形成水锁。致密油渗吸样品在所有孔隙中的渗吸换油贡献率则相对均衡,半径小于0.5µm的孔隙原油动用率平均为14.82%,相对较低;而半径大于0.5µm的孔隙原油动用率平均为29.82%,在焖井过程中普遍会得到有效动用。

六种香精化合物核磁共振法纯度定值

建立了核磁共振氢谱法(1HNMR)测定6种香精化合物(香豆素、香兰素、甲基香兰素、乙基香兰素、麦芽酚、乙基麦芽酚)纯度的定值方法。选择合适的溶剂、内标,通过测定样品的定量信号的纵向弛豫时间(T 1)来计算准确定量所需的理论弛豫时间(D 1),比较样品在不同弛豫时间下测得的实际纯度来对D 1进行优化的数据,实验结果显示两种D 1优化方法结果一致。分析样品中每个合适的定量信号所得到的定值结果并找到定值结果差异的原因。最终6种样品的纯度结果分别为99.79%、99.80%、99.78%、99.82%、99.86%、99.53%,扩展不确定度(k=2)分别为0.16%、0.10%、0.22%、0.18%、0.14%、0.14%。其不仅适用于香豆素等香精化合物的含量测定,在弛豫时间及定量峰的确定方面也适用于其他化合物,以确保更精确的定值。

冬虫夏草成分分析技术进展

综述了冬虫夏草成分分析技术进展。冬虫夏草成分分析技术主要包括色谱及其联用技术、光谱技术、核磁共振波谱技术等。色谱及其联用技术操作简单、分离效果好、效率高、易于自动化,广泛用于冬虫夏草核苷类、多糖类和甾醇类等成分的分离分析中;光谱技术分析速度快,检出限低、灵敏度高,能够精准实现冬虫夏草多糖类、氨基酸和重金属的定性定量分析;核磁共振波谱技术常用于辨别复杂混合物的化学性质,具有高重现性、非选择性、非破坏性等特点,能对冬虫夏草多种成分进行同步分析。提高冬虫夏草成分分析灵敏度与精确度,降低其检出限,研发出更多的新型分析技术与多技术联用将会是未来发展的重点方向。

相邻骨科植入物的磁共振射频致热耦合效应作用机理

该文研究了1.5 T/3.0 T磁共振(magnetic resonance imaging,MRI)环境下2个相邻的骨科植入物的射频场相互耦合对射频致热的作用。当患者佩戴多个相邻的植入物时,这些植入物之间的相互作用可能会增加射频致热。采用骨板和骨钉作为例子,通过基于惠更斯原理的数值模拟计算并提取热点位置的入射和散射电场向量的振幅和方向,以分析其他相邻植入物的影响。结果表明,不仅入射场的存在会导致强耦合效应,强散射场也会起作用,通过惠更斯源可以得到器械之间产生的一阶和二阶散射场,如果在一定区域内,一阶和二阶电场项相互叠加,则双植入物系统的射频致热风险会增加。

高温对不同粒径花岗岩剪切特性影响研究

在干热岩水力压裂过程中,高温会弱化热储岩体裂隙壁面强度从而表现出裂隙错动的行为特征,而这种弱化现象与黏聚力和内摩擦角的热变特性相关,因此,了解花岗岩在高温下的力学特性对于干热岩开发过程中热储岩体的稳定性评价具有重要意义。在不同高温条件下进行了粗、细颗粒花岗岩变角剪切试验(45°、55°、65°),分析了高温对不同粒径花岗岩黏聚力和内摩擦角的影响,结合扫描电镜与低场核磁共振试验,进一步研究了热力耦合作用对花岗岩微裂纹与孔隙结构演化规律的影响。研究结果表明:花岗岩的黏聚力随温度升高呈现先增加后降低的趋势,内摩擦角变化规律受温度影响较小,300℃为花岗岩黏聚力发生转化的阈值温度。在温度阈值前,粗颗粒花岗岩黏聚力增幅约为细颗粒花岗岩的5.73倍,温度强化效应对粗颗粒花岗岩影响更为显著。随着温度的升高,花岗岩微裂纹形式由晶内裂纹向沿晶裂纹发展。核磁共振T2谱曲线存在多个间断性峰值,温度升高使粗颗粒花岗岩大孔隙受到压实作用,导致弛豫效应减弱,而热力耦合作用对细颗粒花岗岩大孔隙发展影响有限。该研究结果有望为干热岩热储岩体稳定性评价提供参考。