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Feeding rate is an important factor influencing the carbon and nitrogen input and greenhouse gas emission from aquaculture systems. However, the quantitative relationship between feeding rates and GHG emissions is still poorly understood. In this study, we conducted a laboratory-scale experiment to examine the impact of feeding rate (0%, 2%, 4%, 6%, and 8%) on the CH4 and N2O emissions from a pond rice-fish co-culture system. The results showed that the total amount of CH4 emission did not significantly differ when the feeding rate was no more than 6%, but increased more than four times when the feeding rate reach to 8%. The amount of N2O emission showed a linearly increasing trend with the feeding rate. The emission factors of CH4 and N2O was significantly higher for 8% feeding rate than other feeding rates. The variation of CH4 emission was primarily attributed to the ratio of mcrA/pmoA in the sediment and the contents of biological oxygen demand (COD) and dissolved oxygen (DO) in the water; and the variation of N2O was primarily affected by the available nitrogen in the water and sediment and the content of DO in the water. The overall emission of CH4 and N2O showed an exponential relationship with feeding rate. The total yields of fish and rice did not continuously increase when the feeding rate exceeded 4%. The lowest emission intensity per unit yield was reached at the feeding rate of 2.99%. These results can provide a reference for the determination of low-carbon feeding strategy for pond rice-fish co-culture system. [ABSTRACT FROM AUTHOR]

Exchange of nitrogen and phosphorus across sediment-water interface plays an important role in the management of nutrient recycling in the aquaculture pond. In this study, a plot experiment was conducted to study the effect of rice-catfish/shrimp co-culture on the micro-profile of oxygen (O2), pH and nutrient exchange across sediment-water interface in the intensive culture ponds. The results showed that rice-catfish co-culture increased the concentration and penetrating depth of O2, but decreased the pH value across the sediment-water interface, compared with catfish monoculture. Additional rice cultivation significantly reduced the flux rates of ammonium (NH4+) and nitrate (NO3−) across sediment-water interface in the catfish and shrimp ponds. The flux rates of NO2− and soluble phosphorus (PO43−) showed no significant difference between rice-catfish/shrimp co-culture ponds and catfish/shrimp monoculture ponds. Rice only affected the dissolved inorganic nitrogen and phosphorus fractions in the sediment. The concentrations of NH4+ were significantly lower in the sediment of co-culture ponds than in the monoculture ponds. Additional rice cultivation also significantly reduced the content and percentage of dissolved inorganic phosphorus in the sediment of catfish ponds. Keywords: sediment-water interface, rice-fish co-culture, eutrophication, nitrogen and phosphorus recycling, aquaculture

As several major new gas discoveries have been made recently in the Lower Cambrian Longwangmiao Fm reservoirs in the Leshan-Longnǚsi Palaeohigh of the Sichuan Basin, a super-huge gas reservoir group with multiple gas pay zones vertically and cluster reservoirs laterally is unfolding in the east segment of the palaeohigh. Study shows that the large-scale enrichment and accumulation of natural gas benefits from the good reservoir-forming conditions, including: (1) multiple sets of source rocks vertically, among which, the high-quality Lower Paleozoic source rocks are widespread, and have a hydrocarbon kitchen at the structural high of the Palaeohigh, providing favorable conditions for gas accumulation near the source; (2) three sets of good-quality reservoirs, namely, the porous-vuggy dolomite reservoirs of mound-shoal facies in the 2nd and 4th members of the Sinian Dengying Fm as well as the porous dolomite reservoirs of arene-shoal facies in the Lower Cambrian Longwangmiao Fm, are thick and wide in distribution; (3) structural, lithological and compound traps developed in the setting of large nose-like uplift provide favorable space for hydrocarbon accumulation. It is concluded that the inheritance development of the Palaeohigh and its favorable timing configuration with source rock evolution are critical factors for the extensive enrichment of gas in the Lower Cambrian Longwangmiao Fm reservoirs. The structural high of the Palaeohigh is the favorable area for gas accumulation. The inherited structural, stratigraphic and lithological traps are the favorable sites for gas enrichment. The areas where present structures and ancient structures overlap are the sweet-spots of gas accumulation.

The large gas province of platform margin reefs and shoals of the Permian-Triassic ChangxingFormation-Feixianguan Formation in the Sichuan Basin is studied as an example to describe the forming conditions and geological characteristics of large strip-like gas provinces of platform margin reefs and shoals. The Sichuan Basin experienced cratonic rifting and basement faulting during the Late Permian. Within a widespread regional ramp, a paleogeomorphology pattern of “three highs and three depressions” were formed. The three negative relieves are, respectively, Chengkou-E'xi trough, Kaijiang-Liangping trough, and Nanchong-Mianyang intraplatform depression, and the three topographic highs are Fengjie-Zhenba platform flat, Shizhu-Yilong platform flat, and Suining-Moxi platform flat. In the transitional areas between platform flats and troughs, large-scale platform margin reef-shoal complexes were developed under high energy environment. Diagenetic processes, such as early stage dissolution, seepage-reflux dolomitization and burial dissolution, contributed to porosity improvement in high-quality dolomite reservoirs along platform margins. High mature source rocks and faults developed within the platform margin reef-shoal complexes, forming better hydrocarbon accumulation conditions than those of intraplatform reefs and shoals. Therefore, the distribution of platform margins controlled that of gas accumulation zones. Paleogeography background of large platform, extensive dolomitization and solution in reef-shoal reservoirs, good underlying and lateral adjacent source rocks, strip assemblages of lithological, structural, and litho-structural oil and gas traps are the four basic elements that determine the formation and distribution of large strip-like gas provinces. The configuration of the four elements in the studied area shows promising exploration prospects of large platform margin oil and gas provinces. 摘要: 以四川盆地二叠系—三叠系长兴组—飞仙关组台缘带礁滩大气区为例 阐述了台缘礁滩体带状大气区形成条件与地质特征。四川盆地晚二叠世经历了克拉通内裂陷作用和基底断裂活动 在区域大缓坡背景下 形成了以城口—鄂西海、开江—梁平海槽及南充—绵阳台内洼地3个负向单元以及奉节—镇巴台坪、石柱—仪陇台坪、遂宁—磨溪台坪3个古地貌高点为特征的“三隆三凹”的古地理格局 台坪向海槽过渡的高能带环境发育大型台缘带礁滩体 经历早期溶蚀、回流渗透白云石化与埋藏溶蚀等建设性成岩作用 形成了沿台缘带分布的优质白云岩储集层 台缘带礁滩体具有良好烃源条件 断层发育 油气成藏条件明显优于台内礁滩体 台缘带控制天然气富集 即大型台缘古地理背景、规模白云岩溶蚀礁滩储集层、良好的下生与侧向气源条件和带状集群展布的岩性、构造及构造-岩性复合3类圈闭“四要素”有机配置决定带状大气区的形成与分布 展示了台缘带礁滩大油气区的良好勘探前景。图7表3参12 关键词台缘带 礁滩大气区 成藏条件 白云岩储集层 基底断裂 四川盆地-图分类号P618.130.2; TE122 文献标识码A Key words: platform margin, large reef-shoal gas province, hydrocarbon accumulation condition, dolomite reservoir, basement faulting, Sichuan Basin

Using the Guang'an and Hechuan reservoirs as a basis, reservoir-forming conditions and mechanisms have been studied in the central Sichuan Basin. Reservoirs in the Xujiahe Formation form as extensive patch-like accumulations. The gentle structural setting and the sandwich-type source-reservoir-cap association provide a fundamental basis for gas accumulation across a large area. Gas-generating intensity is horizontally variable, and the heterogeneity of reservoirs is laterally strong, which makes it difficult to form a large connected area of reservoir, but favorable for forming patch-like reservoirs in a large area. The uplifting of the Sichuan Basin since the end of Cretaceous has caused hydrocarbon expulsion and gas reservoir-forming to take place on a large scale, and the effective storage space left after the diagenesis and tectonic action is a “patch” type rather than “sheet” type, which causes commercial gas reservoirs to be “extensive patch-like accumulations” rather than “extensive continuous gas accumulations”. Gas accumulation in the Xujiahe Formation reservoir is determined jointly by source kitchen, major sand body, structural setting, and fractures. Further research on source kitchen should be conducted to find co-developed areas of sandbodies, fractures, and high-intensity gas generation. The evaluation and research of sedimentary sandbodies in Members I, III and V should be intensified. 摘要: 以广安、合川等典型气藏解剖研究为基础，对川中地区天然气成藏条件与机理等进行研究。川中须家河组天然气为“大范围斑块式”成藏：平缓构造背景和生储盖组合“三明治”结构为大面积成藏提供了基础，但源灶生气强度平面分布不均衡和储集层横向非均质性决定不能大面积连片式成藏，而是大范围斑块式成藏；白垩纪末期以来的整体抬升是一次重要的卸载排烃、成藏事件，成藏是大范围的，成岩和构造作用以后保留下来的有效储集空间是“斑块状”而非“席状”分布的，决定经济性的天然气成藏是“大范围斑块状”而非“大面积连片式”的。须家河组天然气成藏具有源控性，天然气富集主要受气源灶、主砂体、构造背景和裂缝发育的联合控制，应细化气源灶研究，在高生气强度区内，寻找主砂体和裂缝共生发育带。此外，加强与须家河组一、三、五段源岩同期沉积砂体的评价研究，应有新气藏发现。 Key words: extensive patch-like accumulation, extensive continuous gas accumulation, economic gas accumulation, natural gas, Xujiahe Formation, central Sichuan Basin

Based on distribution of oil and gas in the world, the connotation and characteristics of “continuous” petroleum reservoirs are elaborated in this paper. “Continuous” petroleum reservoirs refer to unconventional trap reservoirs existing in a large-scale unconventional reservoir system, and the distribution of oil and gas is continuous. The main geological characteristics of “continuous” petroleum reservoirs are as follows: located in the center and slope of a basin, large-scale distribution and rich locally; mainly of large-scale unconventional reservoirs; traps have no clear boundaries; mainly of self-generating and self-preserving; mainly of primary migration; accumulated by diffusion and buoyancy is limited; non-Darcy flow; poor oil-water differentiation and different saturation; oil, water and gas coexist and have no common interface and pressure system; resources abundance is low and reserves are calculated by well-control region; the mining technologies are special and tailored techniques are required. In this paper are discussed the cause of deep-water “sandy debris flow” and a few examples on “continuous” reservoirs, the shallow-water delta low or ultra-low porosity and permeability reservoirs, coal-bed methane and shale-cracked reservoirs and so on. Key words: “continuous” petroleum reservoirs, unconventional trap reservoir, sandy debris flow, FORSPAN resources assessment model

The comprehensive analysis of geological setting, accumulation condition, trapping mechanism and distribution regularity of oil-gas of the Upper Triassic in Sichuan Basin reveals that the gas accumulation in Xujiahe Formation is a layered lithologic giant gas province. Coal source rocks in layers expelled hydrocarbon evaporatively. Under the setting of the episodic fold-thrusting and compression in the boundary orogen, multi-sources charged quickly and formed a coarse deltaic environment with a large-scale delta plain and a small-scale delta front. In gentle structures, Darcy and non-Darcy flow mechanisms coexist because of the limited buoyancy of low permeability sandstone, thus forming the coexisting oil-gas-water system. This paper classifies the diagenetic facies quantitatively using compaction percentage, cementation percentage and corrosion percentage, and defines eight diagenetic subfacies and twenty diagenetic microfacies. Besides, the origin of diagenetic facies is analyzed by using Ro and formation water parameter. This kind of giant gas province originated mainly from stable large-scale continental depressions, gentle foreland slopes and paralic facies in central China. It is characterized by large-area layered distribution, no obvious trap and cap formation, large-scale resource, low-abundance reserves, and difficult to exploit. Key words: coal source rock, layered giant gas province, layered evaporative hydrocarbon expulsion, differential entrapment, unconventional trap, “continuous” gas reservoirs

Enhanced-efficiency nitrogen fertilizer (EENF) is a recommend nitrogen fertilizer for rice production because of its advantage on improving nitrogen use efficiency. However, its efficacy on CH4, the dominant greenhouse gas, emission from rice fields showed great variation under field conditions. And the factors influencing its efficacy are still unclear. We synthesized the results of 46 field studies and analyzed the impact of product type, rice variety, and primary agronomic measures (rice cropping system, nitrogen (N) application rate, and water management options) on the effectiveness of EENF on the CH4 emission and rice yield. Overall, EENF, including inhibitors (IS) and slow/control-released fertilizer (S/CRF), significantly reduced CH4 emission by 16.2% and increased rice yield by 7.3%, resulting in a significant reduction in yield-scaled CH4 by 21.7%, compared with conventional N fertilizer. Nitrapyrin, DMPP (3,4-dimethylpyrazole phosphate), and HQ (Hydroquinone) + Nitrapyrin showed relative higher efficacy on the mitigation of CH4 emission than other EENF products; and HQ showed relative lower efficacy on rice yield than other EENF products. The reduction in CH4 emission response of hybrid rice varieties to IS and S/CRF was greater than that of inbred rice varieties. IS significantly reduced the CH4 emission and increased the rice yield under all three rice cropping systems, and showed the highest efficacy in the late rice season of double rice cropping system. Whereas, S/CRF did not significantly reduce the CH4 emission from rice seasons of single rice cropping system and rice-upland crops rotation system. IS did not reduce the CH4 emission when N application rate less than 100 kg ha−1, and S/CRF did not affect the CH4 emission when N application rate less than 100 kg ha−1 or above 200 kg ha−1. Continuous flooding was unfavorable for IS and S/CRF to mitigate CH4 emission and enhance rice yield. These results emphasized the necessary to link EENF products with rice varieties and agronomic practices to assess their efficacy on CH4 emissions and rice yield. [ABSTRACT FROM AUTHOR]

Frequency dynamics is one of the most important measures of an electrical power system status. To better understand power system dynamics, an accurately measured wide-area frequency is needed. The concept of building an Internet-based real-time GPS-synchronized wide-area frequency monitoring network (FNET) was proposed in 2000 by Qiu et al., and this concept has been realized. The FNET system consists of frequency disturbance recorders and an information management system. The FNET has made the synchronized observations of the entire U.S. power network possible with very little cost for the first time. This paper summarizes the implementation of the FNET system and shows some preliminary observations and analyses of the data that have been collected from the FNET. Index Terms--Frequency disturbance recorder (FDR), frequency monitoring network (FNET), global positioning system (GPS), phasor measurement unit (PMU), power system measurement, wide-area measurement.