From Cycles to Sequences:Sequence Stratigraphy and Relative Sea Level Change for the Late Cambrian of the North China Platform

In the Late Cambrian, the North China Platform was a typical carbonate ramp platform. The Upper Cambrian of the northern part of the North China Platform is famous for the development of bioherm limestones and storm calcirudites and can be divided from bottom to top into the Gushan, Changshan and Fengshan formations. In this set of strata, the deep-ramp mudstone and marls and the shallow-ramp packstones and grainstones constitute many carbonate meter-scale cycles of subtidal type. More tidal-flat dolomites are developed in the Upper Cambrian of the southern margin of the North China platform, in which limestone and dolomite beds also constitute many carbonate meter-scale cycles of the peritidal type. These cycles are marked by a variety of litho-facies successions. There are regularly vertical stacking patterns of meter-scale cycles in long-term third-order sequences, which is the key to discerning such sequences. Third- order sequence is marked by a particular sedimentary-facies succession that is the result of the environment-changing process of deepening and shoaling, which is genetically related to third-order sea level changes. Furthermore, four third- order sequences can be grouped in the Upper Cambrian of the North China Platform. The main features of these four third -order sequences in the northern part of the platform can be summarized as follows: firstly, sequence-boundaries are characterized by drowning unconformities; secondly, the sedimentary-facies succession is generally constituted by one from deep-ramp facies to shallow-ramp facies; thirdly, a succession of “CS (?)+HST” (i.e., “condensed section and high- stand system”) forms these four third-order sequences. The chief features for the third-order sequences in the southern part of the North China Platform comprises: more dolomites are developed in the HSTs of third-order sequences and also developed more carbonate meter-scale cycles of peritidal types; the sedimentary-facies succession of the third-order sequences is marked by “shallow ramp-tidal flat”; the sequence boundaries are characterized by exposure punctuated surfaces. According to the changes for the third-order sequences from the north to the south, a regular sequence- stratigraphic framework can be established. From cycles to sequences, the study of sequence stratigraphy from litho-facies successions to sedimentary-facies successions exposes that as follows: meter-scale cycles that are used as the basic working unit actually are litho-facies successions formed by the mechanism of a punctuated aggradational cycle, and third -order sequences that are constituted by regularly vertical stacking patterns of meter-scale cycles are marked by sedimentary-facies successions. On the basis of the changing curve of water depth at each section, the curve of the relative third-order sea level changes in the late Cambrian of the North China Platform can be integrated qualitatively from changing curve of water depth. The correlation of Late Cambrian long-term sea level changes between North China and North America demonstrates that there are not only similarities but also differences, reflecting control of long-term sea level changes both by global eustacy and by regional factors.

Overview on Routes for Development of China's Petroleum Refining Technology

China has formed a complete and packaged system of domestic petroleum refining industry. Till 2020 the demand for petroleum products in China will record a sharp growth. However, China is currently confronted with a shortage of oil resources, unsatisfactory quality of petroleum products, a widening gap between demand and supply of steam cracking feedstocks, and a stern situation in environmental protection.In this context the petroleum refiners of China, while taking into account the actual conditions, should seek for the way of deep processing to produce transportation fuels and chemical feedstocks that can hardly be replaced by other energy forms, continue to bring into full play FCC process as core process for making finished oil products, speed up the development of hydrocracking to achieve integration between refining and chemical production, adopt measures that can combine feedstock pre-treatment, novel FCC technologies and after-treatment of products to improve the quality of finished products, as well as realize the recycling of wastewater and control over air pollution caused by SOx to accelerate the development of petroleum processing industry in China.

Accelerating the Development of Hydrogenation Process and Technology in China

The crude oils processed at refineries worldwide are becom ing heavier with the contents of sulfur and heavy metals increasing since the 1990s. The environmental regulations promulgated by the governments of many countries are tight ening and there is an urgent need which calls the refiners'attention to adopt clean production processes and make clean fuels.

Thoughts on Structure Adjustment of China‘s Refining Industry and Recommendations on Improving Economy of Scale

By the end of 1998 China boasted 220 refineries with a totalcrude processing capacity of 262 Mt/a. The average refinerysize at that time was 1.194 Mt/a. Refineries with processingcapacity exceeding 5.0 Mt/a accounted for only 21.26%,while the capacity of single refining units were also smallthat could not conform with the economy of scale. China'srefining industry is faced with a tough task of structureadjustment.