苏里格气田二叠系盒_8段储集层的成岩作用及孔隙演化

鄂尔多斯盆地北部内蒙古自治区鄂多克旗—乌审旗一带 ,长庆油田公司的天然气勘探取得了重大突破 ,发现了苏里格气田 ,含气面积约 6 0 0 0km2 。圈闭类型为岩性圈闭气藏 ,下石盒子组为主要目的层 ,储集岩为一套中、粗粒砂岩 ,储集空间以各类次生孔隙为主。成岩作用对储层的影响有利有弊 ,压实与胶结作用使原生孔隙几乎丧失贻尽 ,溶蚀作用所形成的次生孔隙改善了砂岩储层的孔渗性。砂岩储集层埋深在 2 85 0～ 310 0m时 ,最有利于次生孔隙的形成。成功地预测次生孔隙发育区 ,将是寻找高产富集区的关键。

水饱和边坡夹层热-孔隙水-力耦合作用模型及应用

为了研究温度对水饱和边坡夹层力学参数的影响,将水饱和边坡夹层视为固-液两相的线弹性体,建立了水饱和边坡夹层热-孔隙水-力耦合作用的力学模型,并推导了其耦合控制方程;采用物理相似模拟的方法,建立了与边坡原型相似的试验模型,研究温度引起的边坡夹层力学参数的变化特征;通过比较分析理论计算结果与模型试验结果,验证了所建立的耦合力学模型的适用性。研究结果表明:孔隙水压力系数和热压力系数是引起水饱和边坡夹层孔隙水压力增加的关键控制因素;孔隙水压力系数取决于孔隙排水压缩特性和固相介质压缩特性,这两者差值越大,孔隙水压力系数越大;孔隙水热膨胀系数和孔隙体积热膨胀系数是影响热压力系数的主要因素,这两者差值越大,热压力系数也越大;边坡夹层孔隙水压力随温度升高呈现出先缓慢增加而后急剧增加的变化特征,而黏聚力和抗剪强度随温度升高而缓慢降低,且孔隙水压力的理论计算结果与试验测试结果吻合良好。因此,水饱和边坡夹层热-孔隙水-力耦合作用的力学模型能较好地反映孔隙水压力在加热升温过程中的变化特征,为科学地预测和控制类似边坡工程的稳定性提供了参考。

孔隙水压力作用下三级边坡稳定性的上限

根据极限分析上限原理,建立了孔隙水压力作用下三级边坡的对数螺旋线破坏机制,并对其稳定性进行了分析。计算了其外部重力做功功率、孔隙水压力做功功率以及内部能量耗散功率方程,将孔隙水压力作用下三级边坡临界高度的求解转化为非线性规划的数学问题。分析了孔隙水压力作用下土体强度参数对三级边坡稳定性的影响。

孔隙水压力作用下的分层边坡稳定性上限分析

针对传统边坡稳定性分析时将边坡土层视为均匀土层分析的局限性及边坡土体的稳定性由内摩擦角φ及忽视粘聚力c0决定,而忽视诸如地震力及孔隙水压力等外部因素影响的问题,在传统边坡稳定性分析的基础上,将边坡划分为三个部分两个不同的土层,同时考虑孔隙水压力对边坡稳定性的影响,采用极限分析上限定理,计算各外力功率及速度间断线上的内能耗散功率,并通过约束条件运用MATLAB优化计算出边坡的临界高度.

细颗粒泥沙吸附铜离子后表面孔隙变化的实验研究

细颗粒泥沙的表面形貌十分丰富,研究其表面的复杂结构对泥沙的吸附、输移具有重要的理论意义。本文通过镶嵌制样观察泥沙颗粒的孔隙结构,采用物理化学吸附仪对重金属离子吸附后的实验沙进行孔径分布分析与孔隙特征变化研究。结果表明细颗粒泥沙为多孔性固体,微孔与中孔是吸附作用的重要因素。铜离子在吸附量由低到高的过程,首先聚集在孔隙入口处,再逐渐填满孔隙内部空间。伴随这一过程,泥沙的形貌特征也发生了相应的改变。

断陷盆地油气成藏作用面及其石油地质意义——以济阳坳陷东营凹陷为例

在含油气盆地不同级别、不同类型、不同作用形式的界面中,石油地质研究中关注最多的是与含烃流体生、排、运、聚有关的不同新生流体的作用界面。在对断陷盆地生排烃、超压、次生孔隙发育、耗水等界面定义、特征及作用方式分析的基础上,以济阳坳陷东营凹陷为例,提出了断陷盆地成藏作用面的概念,初步定义为盆地新生流体运动过程、能量形式及其相互耦合的作用面,是生排烃、超压、次生孔隙发育、耗水4种界面耦合作用的结果,既是流体作用转换面、不同类型储集空间分界面,也是流体不同类型能量转换面和油藏类型分布转换面。成藏作用面通过对断陷盆地不同类型流体势能分布及叠加的控制作用,影响了不同类型油藏分布特征,因此通过对不同类型流体作用面的识别、研究和评价,能够有效预测油藏类型、分布样式,进而有效预测盆地油藏的丰富程度,对于盆地评价具有重要意义。

考虑孔隙水压力的深埋隧道掌子面支护力上限分析

基于极限分析上限定理,建立了平动与转动相结合的深埋隧道掌子面破坏机制,通过对外力功率、孔隙水压力及内能耗散功率的计算,获得了该破坏模式下掌子面支护力上限解,并将掌子面支护力最优上限解转化为非线性规划的数学问题,借助MATLAB分析工具,分析了h/d值及不同深埋隧道内摩擦角φ对支护力上限解和掌子面稳定性的影响。

降雨型泥石流对沟床侵蚀的水力学机理

为解决降雨型泥石流对沟床的侵蚀和重塑机理,以水文学为基础,在科学表征泥石流流深的前提下,借助水力学理论,分析了沟床在泥石流流动剪切和渗流水压耦合作用下的侵蚀机理,研究了泥石流流动剪应力、沟床基质孔压、泥石流静压及沟床自重作用的计算方法,给出了沟床侵蚀临界深度表达;借助算例阐明了流域降雨特征、沟道几何参数以及泥石流性质对泥石流流态及侵蚀力的影响规律,展示了沟道侵蚀曲线和侵蚀量的计算方法.结果表明:(1)泥石流侵蚀能力随沟床基质埋深的增加而下降,并在临界深度处消失;(2)不同降雨条件、沟谷特征和泥石流性质下的临界侵蚀深度因流深流速的差异而不同,越利于流深流速增大的流域沟道条件则越利于侵蚀的进行.

饱和土动力问题求解的隐-隐格式交替解法

研究饱和土受地震这样的非高频动力荷载作用时,采用固相位移和孔压为基本未知量的u-p形式的方程相对比较简单。对这一方程的求解采用无条件稳定的隐—隐式交替解法有很多的优点。在Zienkiewicz提出的无条件稳定的隐-隐格式高效算法的基础上,结合Bazzi等提出的ρ-方法,建立了一种新的无条件稳定的隐—隐格式交替解法。文章详细地证明了这种方法的无条件稳定性,并将其应用于求解饱和一维土柱模型。数值算例表明,此方法能更有效地减少位移和孔压时程曲线的振荡。

深厚饱和软土场地中透镜体对上部结构地震响应的影响

工程场地中透镜体对地震动具有明显的影响,且饱和场地与相应干土场地的地震响应具有明显的差别,而目前对于深厚饱和软土场地中透镜体对地震响应的影响还鲜有研究。采用有限元-间接边界元耦合法,建立饱和场地中非线性土-结构动力相互作用模型,对深厚饱和软土场地中透镜体的宽度、厚度和埋深对上部结构动力响应的影响进行了系统地分析,并着重讨论了土骨架-孔隙水耦合作用的影响。研究表明,深厚饱和软土场地中的透镜体可能会明显改变上部结构的动力响应;透镜体的宽度、厚度和埋深对上部结构动力响应有不同程度的影响,且与干土场地中规律存在明显差异;土骨架-孔隙水耦合作用对上部结构动力响应的影响显著。

金湖凹陷阜二段碎屑岩储层成岩演化定量分析

通过微观薄片图像分析、流体包裹体分析与储层物性实验相结合的手段,获取原始孔隙度、现今孔隙度、胶结物量、交代物量、填隙物量、溶蚀量、成岩期次、成岩温度等多种数据,并运用数据统计分析将面孔率转化为孔隙度,结合成岩作用与成岩阶段分析,定量研究了金湖凹陷阜二段碎屑岩储层的成岩演化过程。研究认为金湖凹陷阜二段碎屑岩储层成岩过程较为复杂,胶结作用强烈,早晚两期胶结共造成了平均25.2%的孔隙损失,压实作用也造成了近15%的孔隙损失,溶蚀作用则提高了15.2%的孔隙度,成岩阶段整体上进入中成岩A期,部分达到中成岩B期,而储层在进入中成岩A期时,演化方向分为两支,一支主要发育胶结作用成为差储层,另一支则经历了溶蚀、压实、晚期胶结作用后进入中成岩B期,但仍可成为低渗透的有效储层。

多次孔隙水压作用下沥青混合料性能演化试验

为研究沥青混合料在水-力共同作用下的性能演化过程,在实验室内制备了3种不同沥青含量(3.5%、4.5%、5.5%)的SBS改性沥青混合料试件,利用沥青混合料水敏感性试验(MIST)进行不同次数(500次~7000次)孔隙水压作用的湿度处理,通过湿度处理后试件的物理指标(体积、毛体积密度)来表征沥青混合料的内部结构变化。利用间接拉伸试验(IDT)测得的不同孔隙水压作用次数下的ITS以及TSR来表征沥青混合料力学性能的演化过程。结果发现:随着孔隙水压作用次数的增加,试件内部结构发生了变化,导致试件体积先增大、后减小,毛体积密度有微小的下降。ITS以及TSR结果表明,试件力学性能先降低、后上升。在对不同MIST作用次数湿度处理后试件的含水率进行测量后发现:500次孔隙水压循环是试件由不饱和状态向饱和状态转变的临界作用次数。小于500次作用时,试件未饱和,MIST循环产生孔隙水压较大,因此力学性能不断降低;大于500次作用时,试件已饱和,温度作用取代孔隙水压作用成为主要影响,导致力学性能上升。因此,对于孔隙率为4%左右的小型密级配沥青混合料试件,推荐采用500次MIST循环作为湿度处理来进行沥青混合料的抗水损害能力的评价。

Formative mechanism of preferential solution flow during dump leaching

Preferential flow is a rapid movement of solution through pores caused by coarse ores. Macropore is the main factor for the preferential flow. Macropore can be defined from three aspects. Segregation of the ores during dumping was studied according to particle kinematics. Small ores become smaller under the effect of acid and weathering. Clay in the rainwater from the hillside precipitates in the dump. Segregation and fine ores are the main causes in macropore. The permeability in coarse ores is better than that in fine ores. The mechanism in the preferential flows was studied combining the fast conducting effect of the macropore. Experimental result shows that, at certain application rate, fine ore area is saturated while large volume of solution flows laterally to the coarse ore area and leaks out quickly through the macropores. Thus the mechanism of preferential solution flows is further illustrated.

Coal-gas interaction： implications of changes in texture and porosity

Transient sorption and desorption of helium and carbon dioxide in Upper Freeport coal powder and lumps were analyzed. Differences in texture and porosity between the powder and lumps may affect the transport and interaction of the penetrant and coal. In this work, we address macroscopic and mesoscopic structural differences between powdered and non-powdered coals that influence the rates of the gas transport kinetics and changes in coal texture （swelling, shrinkage, and changes in the pore structure and interconnectivity） and the reciprocal free-phase pressure decay （relaxation）. Com- parison of the multi-exponential relaxation time constants as a function of pressure, for CO2 and inert gas （helium）, allows us to postulate several mechanisms responsible for observed pressure decay patterns.

Quantitative research of diagenesis:its effect on pore evolution of the Fuyu oil reservoir in the north Qijia region

From observing cores of 18 wells,identifying 175 ordinary thin sections and 61 thin casting sections,energy spectrum analyses of 37 samples,homogenization temperature measurement of fluid inclusions of 11 samples,we determine the types of diagenesis and pores of the Fuyu oil reservoir in the north Qijia region.We classified the pores and measured their plane porosity using CIA 2000,the software of rock image analysis,calculated the effect of different kinds of diagenesis on porosity,studied the controlling actions of diagenesis to pore evolution quantitatively,combined with burial history,thermal history and their diagenetic environments.Our results show that mechanical compaction and carbonate cementation are the major destructive diagenesed,developed during early diagenesis stages.The reduction in porosity by mechanical compaction and carbonate cementation are about 25% and 8%,while the destructive intensity of siliceous cementation and clay mineral cementation is relatively much smaller,i.e.,the reduction of porosity is about 2% and 0.2% Dissolution is constructive diagenesis,the increment of porosity is about 6%.There are four diagenesis evolution stages,during which the porosity reduced from 30%～38% to 2%～20%.Mechanical compaction and early cementation are the main diageneses in the early diagenesis stages,when porosity was reduced to 2%～10%.Dissolution is the main diagenesis of an A I substage of the middle diagenesis stage,when porosity increased 1%～8%.The dissolution of the A Ⅱ substage of the middle diagenesis stage affected by late cementation,raised porosity 1%～5%.The porosity varied slightly during the middle stage B.

Wave-induced seepage and its possible contribution to the formation of pockmarks in the Huanghe(Yellow) River delta

Wave-induced seepage and its possible contribution to the formation of pockmarks in the Huanghe(Yellow) River delta were investigated experimentally and numerically. Laboratory experiments were carried out to explore the response of a layered silty seabed with various saturation conditions under cyclic wave loads,in which the pore pressure and seepage-related phenomena were particularly monitored. Numerical models to simulate wave-induced seepage in the seabed were presented and evaluated,then applied to the Huanghe River delta. The experimental results show that the excess pore pressure decreases more rapidly at the surface layer,while the seepage-related phenomena are more pronounced when large cyclic loads are applied and the underlying layer is less saturated. The proposed numerical models were verified by comparing with the experiments. The calculated seepage depth agreed well with the depth of the pockmarks in the Huanghe River delta. The experimental and numerical results and the existing insitu investigations indicate that the wave-induced seepage may be a direct cause of the pockmarks in the Huanghe River delta. Extreme storm waves and the dual-layered structure of hard surface layer and weak underlying layer are essential external and internal factors,respectively. Wave- or current-induced scour and transport are possible contributors to the reformation of pockmarks at a later stage.

Mechanical property of calcareous sand under action of compaction

Calcareous sand is a kind of special medium which is composed of calcium carbonate and other difficult soluble carbonate substances. Because of its rich in inner pore space and easy crashed,the mechanical property is very different from conventional quartz sand. Based on the compaction test and direct shear test of calcareous sand,by means of data fitting,the coupling relationship between compaction density and mechanical property under different water contents was obtained; meanwhile,the shear strength expression was built on the basis of the relationship between water content and dry density.

Environmental effects induced by excavation

Based on 3D Biot’s consolidation theory and nonlinear Duncan-Chang’s model, a 3D FEM (finite element method) program is developed considering the coupling of groundwater seepage and soil skeleton deformation during excavation. The comparison between the analysis result considering the variation of water head difference and that without considering it shows that the porewater pressure distribution of the former is distinctly different from that of the latter and that the foundation pit de- formations of the former are larger than those of the latter, so that the result without considering the variation of water head dif- ference is unreliable. The distribution rules of soil horizontal and vertical displacements around the pit and excess porewater pressure are analyzed in detail in time and space, which is very significant for guiding underground engineering construction and ensuring environment safety around the pit.

Diagenesis and porosity evolution of sandstone reservoirs in the East II part of Sulige gas field, Ordos Basin

It is becoming an important controlling factor of gas exploration and exploitation in the east part of Sulige gas field in the Ordos Basin where the reservoir of main gas formations is tight sandstones. Employing experimental methods of slice identification, casting slice, scan electron microscope, and X-ray diffrac- tions, we studied the characteristics of petrology and diagenesis on reservoirs in Shanl section of Shanxi formation and He8 section of Shihezi formation of the Permian system in the East II part of Sulige gas field. The results include： （1） the main sandstones in these areas are dominated by lithic sandstone and litbic silicarenite with low grade of maturity; （2） the diagenesis of sandstone in these areas mainly include compaction, cementation, corrosion and alteration. Conclusions are as follows： （1） the diagenetic stage reached period B of the middle diagenetic stage; （2） the early diagenetic compaction is one of the main factors to decreasing porosity; （3） the secondary pores formed by corrosion in acidity medium con- ditions in period A of the middle diagenetic stage can distinctly ameliorate the poor reservoir capability of sandstone and, （4） cementation in period B of the middle diagenetic stage is the most important factor leading; to poor physical property of sandstone reservoirs.

Determination of consolidation behaviour of clay slurries

The main objective of this study was to determine the consolidation behaviour of clay slurries.A finegrained clay with high consistency limits(W_L = 180%,w_P= 120%) was investigated using conventional oedometer and bench-top centrifuge tests.Results indicated that the slurry had an apparent preconsolidation(due to initial conditions,electrochemical interactions,tortuous drainage,and thixotropic strength) from e = 5.7 to e = 5.5 followed by virgin compression.Likewise,the low hydraulic conductivity(10^(-10)-10^(-12) m/s) was due to low porosity(small pore throats) and high tortuosity(long flow paths).Unlike consolidation of soils,the c_v and m_v decreased with increasing σ' but increased with increasing e and k.The data from the two tests correlated well in the range of σ' = 10-65 kPa,e = 5.5-3.86,k= 1.7 × 10^(-10)-5×10^(-11) m/s,F_c = 1-40 MN.New equations were developed to correlate the consolidation parameters(e,σ',k) with F_c.The deviation of k beyond 40 MN(e = 4.65) was due to deviation from the initial straight line portion of the settlement curve in the centrifuge test.