Characteristics and Origin of Yacheng Gas Field in Qiongdongnan Basin,South China Sea

The Yacheng gas field lies in the foot wall of the No. 1 fault, the boundary fault between the Yinggehai and Qiongdongnan basins. An overpressured system developed in the Meishan Formation near the No. 1 fault in the gas field and in the adjacent Yinggehai basin. Away from this fault into the Qiongdongnan basin, the overpressure diminishes. Below 3 600 m in the gas field, an obvious thermal anomaly occurs. The gases show obvious compositional heterogeneities which reflect reservoir filling process and origin of the gas field. The gas field was charged from both the Qiongdongnan and the Yinggehai basins but mainly from the former. Hydrocarbons sourced from the Qiongdongnan basin have relatively low maturities while hydrocarbons from the Yinggehai basin have relatively high maturities.

Adaptability Study of Intelligent Well Systems in East China Sea Oil Field

Intelligent well system is the well that has a set of equipment fixed in the down hole including sensing devices, data transmission system and operating devices for information acquiring, data gathering and decision analysis. By this remote control process, the smart well system can ultimately optimize well deliverability; it is used more and more often in oil fields with its stability and control technique. At present, the main intelligent well systems in the worm include SCRAMS, Direct Hydraulic, Digital Hydraulic that belongs to WellDynamics Company, InForce and InCharge that belongs to Baker Oil Tools Company, RMC that belongs to Schlumberger Company. This paper compares different types of systems and their characteristics, recommending the InCharge system as the intelligent well system for East China Sea Oil Field according to its geological and reservoir conditions.

A new algorithm based on the background field for red tide monitoring in the East China Sea

Remote sensing has been proven to be an effective means of monitoring red tides. The spectral information is an important basis for establishing a model to monitor red tides. The spectral curves of red tide events are analyzed and compared with multiyear monthly averaged spectral curves based on MODIS data from July 2002 to June 2012, as well as spectral differences at the same location during red tide presence and absence. A red tide monitoring algorithm is developed based on the background field to extract the red tide information of the East China Sea （ECS）. With the application of the algorithm in the ECS, the results reveal that the developed model can effectively determine the location of red tides, with good correspondence to the results from an official bulletin. This demonstrates that the algorithm can effectively extract the red tide information.

Stratigraphic Sequence and Sedimentary Systems in the Middle-Southern Continental Slope of the East China Sea from Seismic Reflection Data: Exploration Prospects of Gas Hydrate

Many evidences for gas hydrate bearing sediments had been found in the continental slope of the East China Sea,such as bottom simulating reflections(BSRs),undersea gas springs,pyrite associated with methane leakage,mud diapirs/mud volcanos,bottom-water methane anomalies and so on.In this study,six key stratigraphic interfaces including T_0(seafloor),T_1(LGM,23 kyr B.P.),T_2(2.58 Myr),T_3(5.33 Myr),T_4(11.02 Myr)and T_5(16.12 Myr)were identified,and then five third-order sequences of SQIII1 to SQIII5 were divided.However,T5 in southern continental slope is not found,which shows that the middle-northern Okinawa Trough had begun to rift in the early Miocene,earlier than the southern segment.Four system tracts including lowstand systems tract(LST),transgressive systems tract(TST),highstand systems tract(HST)and falling stage systems tract(FSST)are further divided.The marine erosion interface of 11.02 Myr and regressive unconformity interface of 23 kyr B.P.indicate two large-scale sea level drop events in the research area.Seven typical seismic facies identified in the continental slope are continental shelf-edge deltas,littoral fluvial-delta plains,incised channels or submarine canyons,slope fans,submarine fans or coastal sandbars,littoral-neritic finegrained sediments,mud volcanos and some other geological bodies respectively.The minimum water depth for hydrate occurrence in the Okinawa Trough is 630 m,and the thickness of gas hydrate stability zone in continental slope is between 0 and 590 m.The calculated bottom boundary of hydrate stability zone is slightly deeper than BSRs on the seismic sections.The re-depositional turbidite sand bodies,such as canyon channels,slope fans and submarine fans developed in Quaternary strata,are the predominant hydrate reservoirs.According to developing process,the dynamic accumulation of hydrate systems can be divided into three evolutionary stages including canyon erosion and hydrate stability zone migration stage,sediments destabilizing and methane leakage stage,and channel filling and hydrate re-occurrence stage.

Typhoon-induced wind waves in the northern East China Sea during two typhoon events:the impact of wind field and wave-current interaction

We examined the influences of the wind fi eld and wave-current interaction(WCI)on the numerical simulation results of typhoon-induced wind waves in the northern East China Sea(NECS)using the coupled Simulating Waves Nearshore+Advanced Circulation(SWAN+ADCIRC)model.The simulations were performed during two typhoon events(Lekima and Muifa),and two widely used reanalysis wind fields,the Climate Forecast System Version 2(CFSv2)from the National Centers for Environmental Prediction(NCEP)and the fifth-generation European Centre for Medium-Range Weather Forecasts(ECMWF)Reanalysis(ERA5),were compared.The results indicate that the ERA5 and CFSv2 wind fields both reliably reproduced the wind variations measured by in-situ buoys,and the accuracy of the winds from ERA5 were generally better than those from CFSv2 because CFSv2 tended to overestimate the wind speed and the simulated significant wave height(SWH),particularly the peak SWH.The WCI effects between the two wind field simulations were similar;these effects enhanced the SWH throughout the nearshore NECS during both typhoons but suppressed the SWH on the right side of the Typhoon Muifa track in the deep and off shore sea areas.In summary,variations in the water depth and current propagation direction dominate the modulation of wave height.

A three-dimentional model of the northeast East China Sea, with application to the M2 current field

A simple three-dimensional tidal model is used to examine the M2 tidal current distribution in a northeastern part of the East China Sea, especially the vertical variation of the current in the region. Computed M2 current is compared with observations available and found to be in good agreement.Main features of the calculating method in this study are: (1) Vertical variation of the tidal current is taken as a funetion of the depth-mean velocity: (2) the method is applicable to a variety of the vertical eddy viscosities; (3) it has a fine vertical resolution, especially near the sea bootom. So, this method not only enables us to get a steady state solution easily but also depicts effects of the friction on the vertical variation of the current much better.

Distribution and Characteristics of Hazardous Geological Features in the Marine Coastal and Offshore Areas of Zhejiang Province, East China Sea

Newly acquired high-resolution shallow seismic profiles(7069 km in length) in the coastal and offshore areas of Zhejiang Province, East China Sea, China, have revealed eight marine hazardous geological features: shallow gas, sand ridges, erosion ditches, scarps, irregular bedrock features, underwater shoals, buried paleo-channels, and submarine deltas. Based on the seismic profiles, we have constructed a marine geological map of these hazardous features. Shallow gas accumulations are common and occur mainly in two separate nearshore regions that cover 4613 and 3382 km^2 respectively. There are also scattered shallow gas accumulations in the offshore area, typically accompanied by paleo-channels that occur mainly in the middle of the study area. Sand ridges, erosion ditches, scarps, and irregular bedrock features are found mainly in the northeast of the study area in association with each other. In the southeastern part of the study area, the sand ridges have a linear form and trend NW–SE, representing the western part of the linear sand ridges in the East China Sea. The maximum slope gradient is 1?, which suggests that this area is prone to landslides. These hazardous marine geological features are important to marine and engineering activities in this region.

Derivation of sea surface current field from sequential satellite images of the East China Sea

A series of NOAA AVHRR data over the East China Sea were collected from the ground station of the Second Institute of Oceanography, Hangzhou, China. Three methods, including a functional analytic method (FAM), a maximum cross correlation (MCC)'method and a correlation relaxation (C - R) method, are applied to derive the sea surface current field from sequential satellite images in the area of the East China Sea. Several preprocessing steps, such as geometric correction, SST determination, image projection, image navigation and grey value normalization as well as land and cloud mask are performed. The results from the three methods reflect the general current system in this area reasonably.

Differential interformational velocity analysis as an effective direct hydrocarbon indicator under velocity reversal conditions,an example from the anomalously high temperature and over-pressured DF1-1 Gas Field in the Yinggehai Basin,South China Sea

In the DF1-1 Gas Field in the Yinggehai Basin, South China Sea, the velocity-depth plot and velocity spectra show significant variations from a linear trend, exhibiting a distinct reversal phenomenon. Velocity parameters derived from velocity spectral analysis of the seismic data and sonic logs indicate that the interval velocity reverses below 2,100 m (2.2 s two-way time (TWT)) in the DF1-1 Gas Field. Some direct hydrocarbon indicators (DHIs) models developed for the shallow strata cannot be simply applied to the moderately to deeply buried strata for direct exploration target recognition because the velocity reversal has caused the middle-deep gas reservoirs to exhibit a moderate or weak seismic amplitude. The hydrocarbon indicator method of “Differential Interformational Velocity Analysis (DIVA)” with the aid of other hydrocarbon indicating techniques was employed to effectively identify DHIs in the middle-deep strata under velocity inversion. The result has shown that the DIVA technique can be effectively used as a DHI in both the shallow and the middle-deep strata in the study area with the shallow strata characterized by Type I DIVA anomaly and the middle-deep strata characterized by the Type II DIVA anomaly.

Start of Production at the Ya 13-1 Gas Field in South China Sea

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Abrupt changes of radiolarian fauna at 600 and 120 ka B. P. in the southern South China Sea and their paleoceanographic implications

Abrupt changes in radiolarian composition are discovered over the last 600 and 120 ka B. P. based on quantitative analyses of radiolarians in ~ 17957 - 2 of the southern South China Sea. The distinct changes at 600 ka B. P. could correspond to the onset of the 100 ka cycle during the glacial and interglacial periods. This abrupt change in the 100 ka cyclicity at 600 ka B. P. occurred also in the magnetic susceptibility signal that is obtained from and paleosol sequences of the China Loss Plateau. The larger amplitude and stronger cyclicity in the susceptibility signal after 600 ka B. P. reflect the prominent change in the intensity of the monsoon, induced by an enhancement of the momsoon circula- tion. Stronger seasonality during the glacial period in the South China Sea, resulted from strengthening of winter monsoon, might lead to the changes in the radiolarian composition at 600 and 120 ka B. P. It can be suggested that only species adapted to a broader temperature range might have been able to live in this environment. Therefore, the abrupt changes in radiolarian composition at 600 and 120 ka B. P. could be attributed to the stronger so differences between summer and winter that were caused by the striking change in the intensity of the monsoon circulation.

Modeling underwater transport of oil spilled from deepwater area in the South China Sea

Based on a Lagrangian integral technique and Lagrangian particle-tracking technique,a numerical model was developed to simulate the underwater transport of oil from a deepwater spill. This model comprises two submodels: a plume dynamics model and an advection-diffusion model. The former is used to simulate the stages dominated by the initial jet momentum and plume buoyancy of the spilled oil,while the latter is used to simulate the stage dominated by the ambient current and turbulence. The model validity was verified through comparisons of the model predictions with experimental data from several laboratory flume experiments and a field experiment. To demonstrate the capability of the model further,it was applied to the simulation of a hypothetical oil spill occurring at the seabed of a deepwater oil/gas field in the South China Sea. The results of the simulation would be useful for contingency planning with regard to the emergency response to an underwater oil spill.

An Installation System of Deepwater Risers by An S-Lay Vessel

Along with the consumption increase of the petroleum products, more countries have transferred their attentions to the offshore fields, especially the deepwater oil and gas reserves. For deepwater exploitation, the risers must be installed to act as the conduits connecting surface platforms to subsea facilities. In this paper, the typical risers sorted by different classes are introduced, and the correspondent installation methods are presented. By investigating the recent projects performed in the deepwater hot spots, and combining the challenges of HYSY20 l for riser installation, a lifting device developed for assisting riser installation is proposed and detailed to satisfy the installation of deepwater risers in the LW3-1 Gas Field of 1500 m in the South China Sea. Tests on both the functions and performances of such a new system exhibit the satisfaction of meeting all challenging requirements of HYSY201 for application to riser installation in waters up to a depth of 3000 m in the South China Sea.

东海海域海表温度场的EOF分析

本文利用EOF分析方法,分析了东海26.5°N^33.5°N,122.5°E^129.5°E范围内自1984-2003年的年平均海表温度,结果显示出代表厄尔尼诺和黑潮、对马暖流、伸入黄海的高盐暖水舌的各种空间模态和时间演变情况。

基于井眼清洁效果的大位移井钻井参数与钻井液性能优化方法研究与实践

针对东海油气田大位移井在钻井过程中易形成岩屑床,井眼清洁困难,导致摩阻扭矩大甚至频繁出现憋泵憋扭矩等复杂的问题,提出了一种基于井眼清洁效果的钻井参数设计和钻井液性能优化方法。首先,分析大位移井井眼清洁的主要影响因素,使用VIRTUALMUD软件对影响大位移井井眼清洁性能的钻井液排量、机械钻速等工程参数和钻井液6转3转读数等钻井液参数进行优化设计。然后,通过优选合适的基础油、乳化剂和重晶石等方法对现场使用的油基钻井液进行性能改进。在大位移井A井应用优化后的钻井参数及钻井液体系,井眼清洁效果好,钻井液携岩效率高,在作业过程中未发生憋钻卡钻等复杂情况,起下钻顺利。现场应用情况表明,该方法具有较好的可行性和有效性,对于提高钻井效率和降低钻井成本具有重要意义。

东海B气田基底潜山地质模式初探

近年来,越来越多的潜山型油气藏被发现,由于埋深大、钻井少,导致研究难度较高。本文以渤海B气田为例,探讨仅有一口井钻遇基底潜山时,应如何利用地质思维合理猜测并建立潜山地质模式,为后续预测有利储层和部署井位提供重要依据。

CNOOC Discovers Deepwater Gas Field in South China Sea

China National Offshore Oil Corporation (CNOOC) andHusky Oil China Limited have made a new deepwater gasdiscovery,Liuhua (LH) 34-2,which is the second deepwatergas discovery in the Pearl River Mouth Basin in the easternSouth China Sea following Liwan (LW) 3-1 in this area.CNOOC Limited said on December 9th,2009.The Liuhua 34-2-1 well has ability of producing 55 millioncubic feet of natural gas per day.

反渗透钻井液在东海高压井的优化与应用

随着油气田开发的进行,钻井井深不断增大,深部钻遇异常高压地层风险逐渐升高。为平衡地层压力,需要提高钻井液密度,而水基钻井液在高密度时容易出现泥浆增稠,泥饼质量变差,滤失量增大等问题。本文通过优选包被剂及加量、降滤失剂加量,对高密度下反渗透钻井液性能进行优化调整,使其抗温性能达到150℃,2.00 g/cm3密度条件流型良好,高温高压滤失量低于10.0 mL,以适应东海高压井钻井需求。现场应用结果显示,优化后的反渗透钻井液性能稳定,井壁稳定性良好,起下钻总体顺利,同时气测活跃,储层保护效果好,圆满完成了探勘开发目标,具有巨大的推广应用前景。

东海大型底栖生物次级生产力研究(英文)

根据2000年秋季和2001年春季在东海23个大面站进行的大型底栖生物定量采集样品资料,利用Brey’s(1990)的经验公式对调查海区进行了大型底栖生物栖息密度、生物量、次级生产力和P/B值的研究和计算.结果表明,该海域大型底栖生物平均栖息密度在秋季为87m-2,远低于春季的138m-2,而平均生物量以去灰干重计,秋季为1.40gm-2,高于春季的1.25gm-2;年平均次级生产力以去灰干重计,为1.62gm-2a-1,远低于渤海和南黄海.研究表明,大型底栖生物生物量和次级生产力受水温和水深的影响.平均P/B值在研究海域为1.41a-1,高于渤海和黄海,表明在东海大型底栖生物中个体小而代谢快、生活史短的种在大型底栖生物中占的比重要大于渤海和南黄海,P/B值随水温升高而升高.

中国东部及南海西部陆缘CO_2气藏形成机理

以我国东部及南海西部陆缘众多CO2气藏为依据,分析了气藏中气体组分、同位素组成及分布特征,指出该地区从北至南分布着一巨型北东向岩浆 幔源无机成因CO2气藏带,莺歌海盆地中具有壳幔混源特征,其形成机理与欧亚板块和太平洋板块碰撞俯冲带所形成的构造 岩浆作用有关;靠近俯冲带,热源体以火山岩体、基性玄武岩为主,远离俯冲带则以泥底辟热流体为主;超壳断裂是幔源气和热源的输运通道。