Controls on reservoir quality of Lower Cretaceous tight sandstones in the Laiyang Sag,Jiaolai Basin,Eastern China: Integrated sedimentologic,diagenetic and microfracturing data

The Jiaolai Basin (Fig. 1) is an under-explored rift basin that has produced minor oil from Lower Cretaceous lacustrine deltaic sandstones. The reservoir quality is highly heterogeneous and is an important exploratory unknown in the basin. This study investigates how reservoir porosity and permeability vary with diagenetic minerals and burial history, particularly the effects of fracturing on the diagenesis and reservoir deliverability. The Laiyang sandstones are tight reservoirs with low porosity and permeability (Φ < 10% and K < 1 mD). Spatial variations in detrital supply and burial history significantly affected the diagenetic alterations during burial. In the western Laiyang Sag, the rocks are primarily feldspathic litharenites that underwent progressive burial, and thus, the primary porosity was partially to completely eliminated as a result of significant mechanical compaction of ductile grains. In contrast, in the eastern Laiyang Sag, the rocks are lithic arkoses that were uplifted to the surface and extensively eroded, which resulted in less porosity reduction by compaction. The tectonic uplift could promote leaching by meteoric water and the dissolution of remaining feldspars and calcite cement. Relatively high-quality reservoirs are preferentially developed in distributary channel and mouth-bar sandstones with chlorite rims on detrital quartz grains, which are also the locations of aqueous fluid flow that produced secondary porosity. The fold-related fractures are primarily developed in the silt–sandstones of Longwangzhuang and Shuinan members in the eastern Laiyang Sag. Quartz is the most prevalent fracture filling mineral in the Laiyang sandstones, and most of the small-aperture fractures are completely sealed, whereas the large-aperture fractures in a given set may be only partially sealed. The greatest fracture density is in the silt–sandstones containing more brittle minerals such as calcite and quartz cement. The wide apertures are crucial to preservation of the fracture porosity, and the great variation in the distribution of fracture-filling cements presents an opportunity for targeting fractures that contribute to fluid flow.     

含硬包体试样破裂孕育过程中应变场的变化特征

在含硬包体的混凝土试样，双轴加压的破裂孕育过程中，观测自由面的应变场，随着应力增加，高应变区逐步形成，应变梯度增大，主破裂前，有的高应变区应变量与应变梯度均减小，有的则增加，主破裂发生应变及其梯度相对都较低的一个高应变梯度区，应变场区内不同测点，其应变随应力及时间的变化而形态不同，临皮裂前，距破裂带和包体近的测点应图像复杂，有的反向加速增大，有的同向加速增大，有的显著减小；而远处测点，变化迟缓且不     

郯庐断裂带（莒县招贤～宿迁晓店段）变形产物中的微观粘滑与蠕滑标志

通过对郯庐断裂带莒县招贤～宿迁晓店段断裂变形产物进行定向采集、原态固结，对其进行显微观测，结合宏观和实验岩石学资料分析，归纳出反映该活动断裂段运动特性的微观粘滑与蠕滑标志，并对有关问题进行了讨论     

关于地电阻率短临机制与应用的研究

在地震预报研究中，中长期预报的研究固然需要，但更有实际意义的应是短临预报的探索。但至今对短临预报问题的解决取得进展甚少。本文根据断裂力学观点，分析研究了大量的实测资料，发现地电阻率的突变与地下介质的破裂存在着一定联系。统计结果表明，一旦有台站出现突变，未来一个月内将有６０％以上可能，在其周围附近发生地震。因此，地电阻率的加减速变化所引起的地电突变是有可能作为震兆予以考虑。这些变化特征，不但在云南地