胶东乳山金矿床成矿过程:周期性压力波动诱发的流体不混溶

位于胶东东部苏鲁地体内的乳山金矿曾是我国单脉金储量最大的矿床,其主矿脉为一具有复杂内部结构的富金石英脉,形成于包含周期性流体活动的增量增长过程。该矿床成矿流体演化、精细成矿过程和金沉淀机制仍缺乏有效制约。本研究在详细结构构造观察基础上,在代表单次成矿流体活动的同一石英层内识别出分别代表三个连续成矿阶段的三类黄铁矿,开展激光剥蚀-电感耦合等离子质谱原位微量元素测试。结果显示不同阶段黄铁矿微量元素成分基本一致,Co、Ni、As等元素因成矿流体间歇性压力波动而周期性地以不同含量进入黄铁矿,形成这些元素的韵律成分环带。Au等其他微量元素在不同阶段黄铁矿内均匀分布,其分布行为受压力波动影响较小。间歇性压力波动和由此引发的周期性流体不混溶使乳白色粗粒石英和黄铁矿、烟灰色中细粒他形石英和黄铁矿依次大规模沉淀,金银碲化物、银金矿、自然金和方铅矿、闪锌矿、黄铜矿等硫化物随后在愈加富Au、Ag、Te、Pb、Zn和Cu等的流体中近于同时沉淀。在此过程中成矿流体虽整体表现为还原性,但其还原性随着压力波动而不断递减氧化性持续增加;流体碲逸度早期保持稳定,后期则大幅上升。金以可见金形式充填先成黄铁矿裂隙或沿黄铁矿边缘分布,周期性流体压力波动引发的间歇性流体不混溶导致H2S、CO2和CH4等气体大规模逸出,金硫络合物失稳分解,金被吸附至黄铁矿内水力致裂形成的裂隙面发生沉淀。排除了先成黄铁矿内不可见金再活化为可见金的可能性,认为周期性流体压力波动引起的流体不混溶是引发乳山金矿床可见金高效沉淀的关键机制。

Research on Mechanism of Airshooting

The composition and ultimate principle of airshooting experimental system were expounded, and the mechanism of airshooting was emphatically discussed on the basis of experiments. The results indicate that the fracture of medium under airshooting resultes from both shock action of air spray and quasi static dilatation of high pressure air. The action of air spray leads to the initial fracture of the wall of borehole and arouses stress wave to propagate in the medium. The quasi static dilatation of high pressure air results in the propagation of initial fractures and produces shear fracture in the medium along the free boundary. Along the direction of minimum burden, the superposition of quasi static and dynamic stress fields can prompt the propagation of cracks. The superposition of the reflected wave, which comes from multiple free surfaces, will result in the fracture of medium also if multiple free boundaries exist.

Influence of Separated Vortex on Aerodynamic Noise of an Airfoil Blade

In order to clarify the mechanism by which aerodynamic noise is generated from separated flow around an airfoil blade,the relation between the attack angle and the aerodynamic noise of the blade was analyzed using a wind tunnel experiment and a CFD code.In the case of rear surface separation,the separated vortex which has a large-scale structure in the direction of the blade chord is transformed into a structure that concentrates at the trailing edge with an increase in the attack angle.The aerodynamic noise level then becomes small according to the vortex scale in the blade chord.When the flow is separated at the leading edge,a separated vortex of low pressure is formed at the vicinity of the trailing edge.The pressure fluctuations on the blade surface at the vicinity of the trailing edge become large due to the vortex in the wake.It is considered that the aerodynamic noise level increases when the flow is separated at the leading edge because the separated vortex is causing the fluctuations due to wake vortex shedding.

水平井分段多簇压裂过程储层动应力响应规律分析

水平井分段多簇压裂技术现有研究主要围绕稳定流体压力作用展开,波动流体压力激励下的储层动应力响应规律尚不清晰。为此,考虑动力因素影响,建立了多簇压裂过程波动流体压力激励下储层应力响应规律仿真模型,分析了簇间距、簇数量及波动流体压力变化频率对储层应力响应规律的影响。研究表明,簇间距、簇数量及流体压力变化频率对于储层内诱导应力场影响明显:随着簇间距的提高有效应力扰动区域先减小后增大,而随着簇数量及流体压力波动频率的提高有效应力扰动区域逐渐减小。上述研究结果可以为水平井分段多簇压裂的施工方案设计提供理论指导。