Lithofacies paleogeography mapping and reservoir prediction in tight sandstone strata: A case study from central Sichuan Basin,China

Sand-rich tight sandstone reservoirs are potential areas for oil and gas exploration. However, the high ratio of sandstone thickness to that of the strata in the formation poses many challenges and uncertainties to traditional lithofacies paleogeography mapping. Therefore, the prediction of reservoir sweet spots has remained problematic in the field of petroleum exploration. This study provides new insight into resolving this problem, based on the analyses of depositional characteristics of a typical modern sand-rich formation in a shallow braided river delta of the central Sichuan Basin, China. The varieties of sand-rich strata in the braided river delta environment include primary braided channels, secondary distributary channels and the distribution of sediments is controlled by the successive superposed strata deposited in paleogeomorphic valleys. The primary distributary channels have stronger hydrodynamic forces with higher proportions of coarse sand deposits than the secondary distributary channels. Therefore, lithofacies paleogeography mapping is controlled by the geomorphology, valley locations, and the migration of channels. We reconstructed the paleogeomorphology and valley systems that existed prior to the deposition of the Xujiahe Formation. Following this, rock-electro identification model for coarse skeletal sand bodies was constructed based on coring data. The results suggest that skeletal sand bodies in primary distributary channels occur mainly in the valleys and low-lying areas, whereas secondary distributary channels and fine deposits generally occur in the highland areas. The thickness distribution of skeletal sand bodies and lithofacies paleogeography map indicate a positive correlation in primary distributary channels and reservoir thickness. A significant correlation exists between different sedimentary facies and petrophysical properties. In addition, the degree of reservoir development in different sedimentary facies indicates that the mapping method reliably predicts the distribution of sweet spots. The application and understanding of the mapping method provide a reference for exploring tight sandstone reservoirs on a regional basis.     

Notes on laboratory rearing of juvenile spiny lobsters,jasus edwardsii (hutton) (crustacea: Decapoda: Palinuridae)

Post‐puerulus specimens of Jasus edwardsii (Hutton) have been successfully reared in the laboratory from the puerulus stage for periods of up to 12 months. The spiny lobsters were reared in concrete‐asbestos tanks measuring 2.4m × 37cm × 23cm. The tanks were supplied with a continuous flow of sea water and provided with constant aeration. Empty shells of paua (Haliotis iris Martyn) and rocks from the intertidal zone provided cover within the tanks.

Fresh mussel (Mytilus sp.) was preferred to all other foods tried in feeding experiments. The animals were fed every second day on opened mussels, and occasionally on fresh fish. The juveniles “grazed” actively on the calcareous algae (Corallina officinalis L.) present on the rocks.

The animals were extremely sensitive to pollution. To reduce pollution risks all sediments were removed from each tank, as the interstices between them were found to harbour uneaten food particles. Any uneaten foods were siphoned out every second day and each tank was thoroughly cleaned every six to eight weeks.

From a total of over 3,300 animals collected since November 1965, over 800 are presently being reared in the laboratory and various aspects of their ecology studied. The first step in raising larger adult sizes from juvenile stages in the laboratory is clearly possible.     

三江平原沼泽湿地植被净初级生产力空间变化特征分析

基于EOS/MODIS卫星2000～2005年的MOD17A3数据集,分析21世纪初三江平原沼泽湿地植被净初级生产力(NPP)时间变化和空间分异特征及其与气候因子(气温和降水)的关系,并采用空间分析方法,分析道路、河流、居民点等因子对沼泽湿地生产力的影响.结果表明,三江平原沼泽湿地生产力(C)的变化范围为92.2～675 g/(m2·a),平均值为374.2 g/(m2·a).沼泽湿地生产力主要受三江平原综合水热条件控制,其与气温和降水显著复相关,复相关系数为0.49(n=6,p<0.05).低生产力沼泽湿地主要分布在三江平原西、北部地区,高生产力沼泽湿地主要分布在东、南部地区.河流在0～8 km的范围内对三江平原沼泽湿地生产力有一定促进作用,但影响不显著.居民点扩建,道路修筑等人类活动影响沼泽湿地分布,并导致沼泽湿地生产力下降,其有效影响范围分别是0～6 km区域和0～8 km区域.     

空间分辨率对总初级生产力模拟结果差异的影响

利用模型分析气候变化对陆地生态系统功能的影响,是当前全球变化生态学的研究热点,然而模型模拟不确定性来源之一就是空间异质性的问题。空间异质性是尺度的函数,基于气象和遥感数据驱动的生态系统过程模型（BEPS模型）,分别模拟2003-2005年中国生态系统通量观测与研究网络（ChinaFLUX）长白山站、千烟洲站、海北站及当雄站在1 km和8 km空间分辨率下的总初级生产力（GPP）的时间动态变化,并结合土地覆盖类型及叶面积指数(LAI)的差异,探讨两种空间分辨率输入数据对GPP模拟结果的影响。结果表明：① 差异性主要是由于8 km范围内混合像元导致LAI的不同,4个站点月均差异值分别为0.85、1.60、0.13及0.04;② 两种空间分辨率均能较好地反映各站点GPP的季节动态变化,与GPP观测值的相关性R²为0.79~0.97 (1 km)、0.69~0.97(8 km),月均差异值为11.46~29.65 gC/m²/month (1 km)、11.87~24.81 gC/m²/month (8 km);③ 4个通量站点在两种空间分辨率下的GPP月均差异值分别为14.43,12.05,4.79,3.22 gC/m²/month,不同空间分辨率的模拟结果在森林站的差异大于草地站,且生长季的差异大于非生长季。因此,模型在模拟大尺度、长时间序列GPP时,为了提高模型模拟效率,适度降低空间分辨率是可行的,但应尽量减小低空间分辨率对于森林生态系统以及生长季GPP模拟上的误差。     

无线传感器网络和遥感技术结合监测煤矿环境地质

针对矿区环境地质监测面临的主要问题,本文探讨了结合无线传感器网络技术和遥感技术对矿区进行环境地质监测的方案,并针对该方案面临的问题与难点,提出了运用这两种技术在矿区建立植被净初值生产力(NPP)动态模型来实时监测矿区的环境地质状况的设想。     

Effects of reduced salt concentrations on plant communities in the River Werra (Germany)

The reduction and equalization of the salt concentrations in the River Werra have resulted in a gradual recovery of the aquatic flora. Spatial high-resolution macrophyte mappings document the spread of the aquatic vascular plants in the middle and lower River Werra. Simultaneously, the plankton blooms have declined. Changes in the composition of the algal communities including diatoms also indicated lower salinity. In addition to the salinity, high nutrient concentrations, waste water discharges and structural degradation are important stressors in the River Werra as shown by e.g. low species richness of vascular plants and the common occurrence of pollution tolerant diatoms. From the existing data it is clear that an encompassing improvement of the ecological conditions in the River Werra can only be achieved by further restoration measures considering all stressors.     

基于广义的炮偏移方法实现地表多次波和一次波联合成像

多次波是地下反射层的多次波反射,也蕴含了地下反射界面的信息,因此并不是绝对地只能被当做噪音来处理.为实现对地下构造的准确成像,本文基于广义概念上的炮偏移成像算法,对常规一次波偏移方法从用于向下延拓的上、下行场以及成像条件方面进行了改进,将同时含有表层多次波的炮记录与脉冲震源之和作为下行延拓的震源波场,将同时含有表层多次...     

武汉天河机场低能见度现象的气候特征分析

用5年滑动平均方法并用最小二乘法建立方程式,计算太阳辐射气候倾向率及日照气候倾向反映太阳辐射的45a变化趋势,用小波分析方法分析太阳总辐射的周期变化规律。结果表明,太原地区的年日照时数减少,年总辐射量呈显著减少趋势,有11a的周期变化,在1981年左右有突变。初步统计能见度低于10km次数在逐年增多。     

Seasonal variation of microzooplankton (20–200 μm) and its possible implications on the vertical carbon flux in the western Bay of Bengal

Stratification (throughout the year) and low solar radiation (during monsoon periods) have caused low chlorophyll a and primary production (seasonal average 13–18 mg m⁻² and 242–265 mg C m⁻² d⁻¹, respectively) in the western Bay of Bengal (BoB). The microzooplankton (MZP) community of BoB was numerically dominated by heterotrophic dinoflagellates (HDS) followed by ciliates (CTS). The highest MZP abundance (average 665±226×10⁴ m⁻²), biomass (average 260±145 mg C m⁻²) and species diversity (Shannon weaver index 2.8±0.42 for CTS and 2.6±0.35 for HDS) have occurred during the spring intermonsoon (SIM). This might be due to high abundance of smaller phytoplankton in the western BoB during SIM as a consequence of intense stratification and nitrate limitation (nitracline at 60 m depth). The strong stratification during SIM was biologically evidenced by intense blooms of Trichodesmium erythraeum and frequent Synechococcus–HDS associations. The high abundance of smaller phytoplankton favors microbial food webs where photosynthetic carbon is channeled to higher trophic levels through MZP. This causes less efficient transfer of primary organic carbon to higher trophic levels than through the traditional food web. The microbial food web dominant in the western BoB during SIM might be responsible for the lowest mesozooplankton biomass observed (average 223 mg C m⁻²). The long residence time of the organic carbon in the surface waters due to the active herbivorous pathways of the microbial food web could be a causative factor for the low vertical flux of biogenic carbon during SIM.     

Measuring spatial accessibility to primary care in rural areas: Improving the effectiveness of the two-step floating catchment area method

Quantifying spatial accessibility in relation to the provision of rural health services has proven difficult. This article critically appraises the two-step floating catchment area (2SFCA) method, a recent solution for measuring primary care service accessibility across rural areas of Victoria, Australia. The 2SFCA method is demonstrated to have two fundamental shortcomings – specifically the use of only one catchment size for all populations, and secondly the assumption that proximity is undifferentiated within a catchment (especially problematic when the catchment is large). Despite its advantages over simple population-to-provider ratios, the 2SFCA method needs to be used with caution.