Geological conditions of natural gas accumulation and new exploration areas in the Mesoproterozoic to Lower Paleozoic of Ordos Basin, NW China

Based on field outcrop investigation,interpretation and analysis of drilling and seismic data,and consulting on a large number of previous research results,the characteristics of ancient marine hydrocarbon source rocks,favorable reservoir facies belts,hydrocarbon migration direction and reservoir-forming law in the Ordos Basin have been studied from the viewpoints of North China Craton breakup and Qilian-Qinling oceanic basin opening and closing.Four main results are obtained:(1)Controlled by deep-water shelf-rift,there are three suites of source rocks in the Ordos Basin and its periphery:Mesoproterozoic,Lower Cambrian and Middle-Upper Ordovician.(2)Controlled by littoral environment,paleo-uplift and platform margin,four types of reservoirs are developed in the area:Mesoproterozoic-Lower Cambrian littoral shallow sea quartz sandstone,Middle-Upper Cambrian–Ordovician weathering crust and dolomitized reservoir,and Ordovician L-shape platform margin reef and beach bodies.(3)Reservoir-forming assemblages vary greatly in the study area,with"upper generation and lower storage"as the main pattern in the platform,followed by"self-generation and self-storage".There are both"upper generation and lower storage"and"self-generation and self-storage"in the platform margin zone.In addition,in the case of communication between deep-large faults and the Changchengian system paleo-rift trough,there may also exist a"lower generation and upper reservoir"combination between the platform and the margin.(4)There are four new exploration fields including Qingyang paleo-uplift pre-Carboniferous weathering crust,L-shape platform margin zone in southwestern margin of the basin,Ordovician subsalt assemblage in central and eastern parts of the basin,and Mesoproterozoic–Cambrian.Among them,pre-Carboniferous weathering crust and L-shape platform margin facies zone are more realistic replacement areas,and Ordovician subsalt assemblage and the Proterozoic-Cambrian have certain potential and are worth exploring.

Real-time Risk-averse Dispatch of an Integrated Electricity and Natural Gas System via Condi-tional Value-at-risk-based Lookup-table Ap-proximate Dynamic Programming

The real-time risk-averse dispatch problem of an integrated electricity and natural gas system(IEGS)is studied in this paper.It is formulated as a real-time conditional value-at-risk(CVaR)-based risk-averse dis-patch model in the Markov decision process framework.Because of its stochasticity,nonconvexity and nonlinearity,the model is difficult to analyze by traditional algorithms in an acceptable time.To address this non-deterministic polynomial-hard problem,a CVaR-based lookup-table approximate dynamic programming(CVaR-ADP)algo-rithm is proposed,and the risk-averse dispatch problem is decoupled into a series of tractable subproblems.The line pack is used as the state variable to describe the impact of one period’s decision on the future.This facilitates the reduction of load shedding and wind power curtailment.Through the proposed method,real-time decisions can be made according to the current information,while the value functions can be used to overview the whole opti-mization horizon to balance the current cost and future risk loss.Numerical simulations indicate that the pro-posed method can effectively measure and control the risk costs in extreme scenarios.Moreover,the decisions can be made within 10 s,which meets the requirement of the real-time dispatch of an IEGS.Index Terms—Integrated electricity and natural gas system,approximate dynamic programming,real-time dispatch,risk-averse,conditional value-at-risk.

Geological and Geophysical Conditions for Potential Natural Gas Hydrate Resources in Southern South China Sea Waters

The water depth in Nansha（南沙） waters,which is located in the southern South China Sea,varies from 200 to 2 500 m,with a deep-water（500 m） area of 500 000 km2.In this region,there are many depositional basins with various structural features,prone to the accumulation of organic material.The temperature and pressure conditions in the deep-water environment are suitable for the preservation of gas hydrate.At several sites,we have recognized bottom-simulating reflectors（BSRs） from seismic data.Regional geology analyses show that the Nansha waters may have abundant gas hy-drate prospects,especially in localities such as the Nansha trough and other deep-water basins of the central Nansha waters.

吉拉克凝析气集中处理站再生气工艺流程的改造

吉拉克凝析气集中处理站的脱水工艺系统中,三叠系凝析气采用分子筛吸附脱水,其再生气由于在再生时带走了大量水分,虽然经过空冷器与水冷器进行降温分离后,又一次经过再生气压缩机增压脱水,仍不能满足水露点标准,被迫放空烧掉,造成了巨大的能源浪费和环境污染。改造后的工艺充分合理利用三叠系制冷系统的冷量对再生气进行制冷,满足外输气的质量标准,挽回了损失。

Simulation of performance of intermediate fluid vaporizer under wide operation conditions

The intermediate fluid vaporizer(IFV)is a typical vaporizer of liquefied natural gas(LNG),which in general consists of three shell-and-tube heat exchangers(an evaporator,a condenser,and a thermolator).LNG is heated by seawater and the intermediate fluid in these heat exchangers.A one-dimensional heat transfer model for IFV is established in this paper in order to investigate the influences of structure and operation parameters on the heat transfer performance.In the rated condition,it is suggested to reduce tube diameters appropriately to get a large total heat transfer coefficient and increase the tube number to ensure the sufficient heat transfer area.According to simulation results,although the IFV capacity is much larger than the simplified-IFV(SIFV)capacity,the mode of SIFV could be recommended in some low-load cases as well.In some cases at high loads exceeding the capacity of a single IFV,it is better to add an AAV or an SCV operating to the IFV than just to increase the mass flow rate of seawater in the IFV in LNG receiving terminals.

Numerical Study of Heat Transfer Characteristic for Subcooled Falling Film outside the Shaped Tubes under Rolling Motion

The heat transfer performance of spiral wound heat exchanger used in the floating liquefied natural gas(FLNG)may be significantly affected by the sloshing conditions.In this paper,a three-dimensional numerical model combined with the dynamic mesh technology is conducted to study subcooled falling film heat transfer under static and sloshing conditions.The three-dimensional velocity distribution of the liquid film on the shell side is observed.The effects of cross-section shape of heat exchange tubes,Reynolds numbers and sloshing parameters on heat transfer characteristics are analyzed.The results indicate that the heat transfer performance of the egg-shaped tube is superior to that of the elliptical and circular tube under both static and sloshing conditions due to significant heat transfer improvement in the lower half of the tube.The heat transfer coefficients of three different kinds of tubes decrease under sloshing conditions.When the rolling amplitude is 6°,the average heat transfer coefficients of the circular tube,elliptical tube and egg-shaped tube are reduced by 2.1%,3.7%and 4.9%respectively.Under the current sloshing parameters,increasing the rolling amplitude,the heat transfer coefficients of three different tubes are slightly increased,while the sloshing period has little effect on heat transfer.The egg-shaped tube and elliptical tube are greatly affected by sloshing motion at the low Reynolds number,while the effect is relatively small at the high Reynolds number.