基于CYT资料的储层岩石特性参数定量预测

介绍了空间源直接探矿仪(CYT)岩性探测原理,探讨了用探测资料预测储层岩石特性参数的可行性.利用天然低频电磁波作场源,获取地下不同深度岩性综合能量值,经计算机处理来预测储层岩石特性参数;导出了预测孔隙喉道平均半径、毛细管迂曲度、孔隙度和渗透率的理论模型.2个现场验证实例对比分析表明,用CYT资料预测储层岩石特性参数是可行的,储层岩石特性参数预测符合率总体为75.8%,误差为24.2%,预测误差达到24.2%的主要原因是实例井探测层段的地层倾角较大.     

电阻率测井原理在饱和度测量中的应用

针对在实验室条件下测量岩石孔隙内的含水饱和度分布受测量方法和精度的限制,而CT、核磁图像等方法具有实验费用高、不适合频繁使用等特点,比较了电阻率测井原理及实验测量结果,发现在一定浓度范围内,溶液电阻值与离子浓度呈线性关系;油藏条件下,岩石电阻值与探针间距离呈线性关系,岩石内的含水饱和度值可以由测量的岩石电阻值计算得到.研究认为:为提高测量精度,实验前必须进行溶液浓度与电阻值关系和CT图像饱和度值与电阻值关系的两项校正.进行了平板模型的驱替实验,证实了这种方法能清晰反映出不同阶段的平面含水变化情况;相对于其他测量方法而言,该方法具有方便易行、安全等优点而适合实验室条件下使用.     

Seepage-stress coupling constitutive model of anisotropic soft rock

To provide a seepage-stress coupling constitutive model that can directly describe the seepage-stress coupling relationship, a series of one-dimensional seepage-stress coupling tests on two kinds of soft rock (argillaceous siltstone and brown mudstone) were performed by using an MTS-815.02 tri-axial rock mechanics test system, with which the stress—strain curves according to the seepage variation were obtained. Based on the experimental results and by employing Hooke’s law, the formulation of the coefficient of strain-dependent permeability was presented and introduced to establish a coupling model. In addition, the mathematical expression and the incremental formulation for coupling model were advanced, in which five parameters that can be respectively determined by using the experimental results were included. The calculated results show that the proposed coupling model is capable of simulating the stress—strain relationship with considering the seepage-stress coupling in the nonlinear elastic stage of two kinds of soft rock. Foundation item: Projects(50378069, 50639090) supported by the National Natural Science Foundation of China; Project(50639090) supported by the Joint Fund of Yalong River Hydropower Development, China     

Failure mode and strength anisotropic characteristic of stratified rock mass under uniaxial compressive situation

A stratified rock mass model was founded by FLAC^3D. The failure mode and anisotropic characteristic of strength for stratified rock mass were analyzed. The analysis results show that the numerical simulation can visually reflect the failure modes of rock samples under different inclination angles β of structural plane. The stiffness of rock sample before peak strength changes in the compressive procedure. With the increase of β, the compressive strength σ _c of rock sample decreases firstly and then increases; when β is in the range of 20°–30° and 80°–90°, σ _c has the largest sensitivity to β; while β falls in the range of 30°–70°, σ _c varies little. When ϕ _j <β<90° (β _j is friction angle of structure plane), the results obtained from numerical simulation and theoretical analysis are in almost the same values; while β⩽ ϕ _j or β=90°, they are in great different values. The results obtained from theoretical analysis are obvious larger than those from numerical simulation; and the results from numerical simulation can reflect the difference of compressive strength of rock samples for the two situations of β⩾ ϕ _j and β=90°, which is in more accordance with the real situation. Foundation item: Project (50099620) supported by the National Natural Science Foundation of China     

Dynamic fracture behavior of rock under impact load using the caustics method

We studied the dynamic fracture mechanical behavior of rock under different impact rates. The fracture experiment was a three-point bending beam subjected to different impact loads monitored using the reflected caustics method. The mechanical parameters for fracture of the three-point bending beam specimen under impact load are analyzed. The mechanism of crack propagation is discussed. Experimental results show that the dynamic stress intensity factor increases before crack initiation. When the dynamic stress intensity factor reaches its maximum value the crack starts to develop. After crack initiation the dynamic stress intensity factor decreases rapidly and oscillates. As the impact rate increases the cracks initiate earlier, the maximum value of crack growth velocity becomes smaller and the values of dynamic stress intensity factor also vary less during crack propagation. The results provide a theoretical basis for the study of rock dynamic fracture.     

胶结物对东营凹陷储层砂岩弹性特征的影响

储层岩石的地震弹性属性是进行油气储层勘探及动态监测的基础。系统选取东营凹陷古近系各层段砂岩样品250块（以沙河街组为主）,在模拟储层条件下利用脉冲穿透法测试样品的纵、横波速度。样品在纵波速度一泊松比交汇图中表现出两种主要变化趋势,分别对应泥质与钙质胶结物的影响;在每个变化趋势中随泥质含量与钙质胶结物含量的增加,岩石结构从颗粒所构成的骨架支撑逐渐表现为基质支撑,弹性波能量的传播也从通过颗粒接触边界转变为通过岩石基质传播,这是使砂岩样品测试结果表现出两种截然不同变化趋势的主要原因,为利用岩石物理特性从地震资料中提取岩石结构、沉积与成岩特征的信息提供了依据。     

岩石节理多层结构模型研究

为了研究节理细观形态对其宏观力学性状的影响,据岩石节理分形特点,将节理面分解为不同层次细观结构面,节理破坏拟为粗糙度分层渐进破坏的过程,基于Plesha本构建立了岩石节理多层结构模型.模型将粗糙度定义为等效起伏角,力学响应发生在最底层（基本面）,结构面受力性状由下层结构面平均化得到,基本面破坏后,其上层结构面转化为基本面.模型考虑了弹性变形、滑动变形、磨损、剪断、压碎、分离等作用机理,能模拟剪胀、应变软化等现象,能考虑单调及循环剪切效应.采用ABAQUS的用户子程序UEL进行了模型验证与参数分析.计算表明：峰值剪切应力随着结构层次的增加而增大;在结构层次不变时,等效峰值摩擦系数随法向应力的增大而减小;剪切应力终值由基本摩擦角控制;剪应力 位移曲线形态取决于粗糙度结构特性;模型中刚度系数对剪切性状影响很小.     

胜利油气区下古生界碳酸盐岩储层可动水录井分析方法探讨

胜利油区下古生界碳酸盐岩油气层评价同碎屑岩储层相比,具有非均质程度高、储集空间类型和形态复杂的特点,储层评价难度大,在一定程度上影响到完井方案、试油方案、开发方案的确定。通过气测录井重烃组分百分含量、岩石热解色谱录井、罐顶气轻烃分析苯含量参数、核磁共振录井可动流体饱和度及含油饱和度参数可有效识别可动水,且具有较好的应用效果。     

不同角度单裂隙对类岩石加卸载强度影响的试验研究

天然岩体内部存在大量裂隙,严重削弱了岩体的强度和稳定性,含不同裂隙的岩体在加载和卸载条件下其力学特性有显著区别.为研究含不同角度(裂隙面与水平方向夹角)裂隙的岩体在加卸载时的力学特性,根据相似三定理,制备了含有五组不同角度裂隙(0°、30°、45°、75°、90°)的完整类岩石试件,对每组试件分别进行了单轴和三轴循环加卸载试验,研究裂隙倾角和加卸载对其峰值强度的影响.结果表明:随裂隙角度的增大,单轴峰值强度显著增加,弹性模量增大、而泊松比随角度增加呈现降低趋势;不同倾角的岩石循环加卸载强度随角度增加而增大;三轴峰值强度随裂隙倾角的增加而增大,但围压对裂隙试件强度影响明显,在三轴循环加卸载环境下,强度会随裂隙倾角增加而明显增大.     

基于SEM的干湿循环蚀变花岗岩分形特征与力学特性演化规律

分形维数是对岩石裂隙、破碎程度和损伤等细观特征的定量描述,岩石的细观结构往往会对宏观强度特征产生较大的影响。为了研究干湿循环侵水对蚀变花岗岩细观特征的影响,基于电镜扫描(SEM)试验,得到了经历不同干湿循环次数的蚀变花岗岩的细观图像,并通过盒维数法计算得到各岩样的分形维数,建立基于分形维数的细观损伤演化方程;其次,通过室内单轴抗压强度和抗拉强度试验,获得不同干湿循环次数下蚀变花岗岩的力学特性。通过试验数据,得到了干湿循环次数及分形维数分别与岩石强度特性和弹性参数的关系。研究表明:岩石干湿循环次数的增加在宏观上表现为抗拉强度、单轴抗压强度以及弹性模量的减小;在细观上表现为分形维数的增大;泊松比不受此影响。分形维数将岩石细观特征量化、建立了细观和宏观的联系。研究结果可为衡量蚀变花岗岩强度特性的指标提供依据。