鄂尔多斯盆地红河油田长8油藏天然裂缝特征及其对开发的影响

鄂尔多斯盆地红河油田长8油藏是典型的致密砂岩油藏,其储层物性差,天然裂缝发育,实践证明,断层、裂缝的发育程度对红河油田油气富集和高效开发具有重要作用。针对红河油田长8储层裂缝的特征、类型、成因进行精细刻画,阐明储层裂缝形成机理和分布规律;通过系统分析长8储层裂缝与油气富集之间的关系,厘清储层裂缝对红河油田长8油藏开发动用的影响。研究表明,红河油田长8储层裂缝发育,但有效性较差;天然裂缝是长8储层的主要储集空间和渗流通道,是控制油井产能的关键因素,也是油藏注水开发效果的重要影响因素。其中,断层端部、断层上盘和断层之间的裂缝发育区是高产有利区。

Research on stability of a slope due to underground mining

This paper will present a detailed analysis of the deformation mechanism and stability assessment of the slope through field investigations, numerical modeling and measurements. Field investigation indicated that three thin coal seams encountered large mined-out area at one side and free surface of hill slope at the other side, which lead to the caving of roof strata movement, ground movement and crown crack along the preferred orientations of joints. The three-dimensional numeri- cal modeling study on the case demonstrated that the plasticity failure occurred gradually along with the extension of mined-out area in depth. When the depth of mining reached the verge defined by the seismic prospecting method, a large mount of tension failure occurred on the crown of the slope. The factor of safety was 1.36 calculated by the shear strength reduction technique, which indicated the slope was in stable state. The measurement showed that the residual deformation occurred before 1998 and became stable subsequently, which indicated that the residual deformation almost finished and the slope is in stable state.

Underground mining of thick coal seams

This paper reviews underground mining methods for total thickness of a thick coal seam in single lift （TI＇rCSSL）. Review shows the required engineering for extraction of thick seams needs to be fitted with thickness of the seam, behavior of rock-mass and surrounding stress conditions for efficient mining. Variants of TI＇rCSSL are able to extract a maximum 10-12 m thickness only. An improvement in bending moment of the overlying coal band in longwall top coal caving （LTCC） provides better under-winning opportunity for the roof coal band. An acceptable limit of 25 MPa compressive strength of coal for the success of LTCC may be increased under favorable geo-technical conditions. Bord and pillar in India adopted induced caving of roof coal band for single lift depillaring of total thickness （SLDTr） of a compe- tent thick coal seam developed along floor. Case studies are given to arrest the adverse effects of extrac- tion height on pillars.

Fractured zone height of longwall mining and its effects on the overburden aquifers

As mining depth becomes deeper and deeper,the possibility of undermining overburden aquifers is increasing.It is very important for coal miners to undertake studies on the height of fractured zone during longwall mining and the effects of longwall mining on the underground water while mining under surface water bodies and underground aquifers.In order to study this problem,piezometers for monitoring underground water levels were installed above the longwall panels in an American coalmine.Large amounts of pre-mining,during mining and post-mining monitoring data were collected.Based on the data,the heights of fractured zones were obtained and the effects of longwall mining on the underground water were studied.The results demonstrate that when the piezometer monitoring wells had an interburden thickness of less than 72.7 m,the groundwater level decreased immediately to immeasurable levels and the wells went dry after undermining the face of longwall.The height of the fractured zone is 72.7-85.3 m in the geological and mining conditions.The results also show that the calculated values of fractured zones by the empirical formulae used in China are smaller than the actual results.Therefore,it is not always safe to use them for analyses while mining under water bodies.

Water Security Situation in Haihe River Basin after South-to-North Water Transfer Project

The over-exploitation of water resources in the Haihe River Basin （HRB） has now become a serious problem. This is clearly evidenced by the fact that many local rivers and lakes are drying up and the total amount of over-exploited groundwater has reached over 1000×10^8m^3. It is important to note that the exploitation of water resources in HRB was reasonable before 1979. After 1980, however, over-exploitation happened with an annual average amount of 40×10^8m^3. Both the dry season and rapid economic growth in HRB took place at the same time. Therefore, the over-exploitation of water in HRB was actually the negative result of the conjunction of a continuous dry season and rapid economic growth. So the over-exploitation would not be as serious as it is today if either of the above two stopped. After the first stage of south-to-north water transfer project, the water shortage problem in HRB could be eased for the following reasons： firstly, water transfer project will bring to the Basin 60x108m3 water resources; secondly, a wet season will come back eventually according to natural law of climate variability; finally, its agricultural and industrial use and total water consumption all have decreased from the peak value, so that the groundwater table will raise certainly and ecological water in rivers and lakes that were dried-up will be partly restored. In the future, the main problem of water resources security in HRB will include water pollution, operation risk of the south-to-north water transfer project, groundwater pollution and engineering geological hazards that may be brought by groundwater rise. The proposed countermeasures are as follows： keeping strengthening water demand management, raising water price as well as subsidies for the low- income family and improving other water related policies, preventing and dealing with water pollution seriously and getting fully prepared for the operation of south-to-north water transfer project.

三维点云数据微地形特征量的提取及应用研究

针对一般地形特征量无法有效识别微地形特征量和小型地质灾害隐患的问题,在讨论不同常用地形特征量的基础上,提出了适用于激光雷达三维点云数据的微地形特征量的选取及其计算方法。微地形特征量分别选取地上开度、地下开度和坡度,配合特征值比,突出了与地质灾害具有高度非线性相关的地形凹凸特征,其高维度信息量可直接作为机器学习算法地形特征量的输入,降维下的特征量也可以在二维可视化下最大限度地保留地形的凹凸特征。研究结果表明,二维可视化后开度和坡度的融合可以清晰表达微地形的凹凸特征,特征值比可突出表达微地形凹凸变化的方向性特征。这些特征量对微地形条件下不同尺度地质灾害隐患的识别提供地形特征的有效数据支持。