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

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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.

Characteristics of carbon isotopic composition of alkane gas in large gas fields in China

Exploration and development of large gas fields is an important way for a country to rapidly develop its natural gas industry.From 1991 to 2020,China discovered 68 new large gas fields,boosting its annual gas output to 1925×108m3in 2020,making it the fourth largest gas-producing country in the world.Based on 1696 molecular components and carbon isotopic composition data of alkane gas in 70 large gas fields in China,the characteristics of carbon isotopic composition of alkane gas in large gas fields in China were obtained.The lightest and average values ofδ^(13)C_(1),δ13C2,δ13C3andδ13C4become heavier with increasing carbon number,while the heaviest values ofδ^(13)C_(1),δ13C2,δ13C3andδ13C4become lighter with increasing carbon number.Theδ^(13)C_(1)values of large gas fields in China range from-71.2‰to-11.4‰(specifically,from-71.2‰to-56.4‰for bacterial gas,from-54.4‰to-21.6‰for oil-related gas,from-49.3‰to-18.9‰for coal-derived gas,and from-35.6‰to-11.4‰for abiogenic gas).Based on these data,theδ^(13)C_(1)chart of large gas fields in China was plotted.Moreover,theδ^(13)C_(1)values of natural gas in China range from-107.1‰to-8.9‰,specifically,from-1071%o to-55.1‰for bacterial gas,from-54.4‰to-21.6‰for oil-related gas,from-49.3‰to-13.3‰for coal-derived gas,and from-36.2‰to-8.9‰for abiogenic gas.Based on these data,theδ^(13)C_(1)chart of natural gas in China was plotted.

North slope transition zone of Songnan-Baodao sag in Qiongdongnan Basin and its control on medium and large gas fields,South China Sea

Based on analysis of newly collected 3D seismic and drilled well data,the geological structure and fault system of Baodao sag have been systematically examined to figure out characteristics of the transition fault terrace belt and its control on the formation of natural gas reservoirs.The research results show that the Baodao sag has the northern fault terrace belt,central depression belt and southern slope belt developed,among them,the northern fault terrace belt consists of multiple transition fault terrace belts such as Baodao B,A and C from west to east which control the source rocks,traps,reservoirs,oil and gas migration and hydrocarbon enrichment in the Baodao sag.The activity of the main fault of the transition belt in the sedimentary period of Yacheng Formation in the Early Oligocene controlled the hydrocarbon generation kitchen and hydrocarbon generation potential.From west to east,getting closer to the provenance,the transition belt increased in activity strength,thickness of source rock and scale of delta,and had multiple hydrocarbon generation depressions developed.The main fault had local compression under the background of tension and torsion,giving rise to composite traps under the background of large nose structure,and the Baodao A and Baodao C traps to the east are larger than Baodao B trap.Multiple fault terraces controlled the material source input from the uplift area to form large delta sand bodies,and the synthetic transition belt of the west and middle sections and the gentle slope of the east section of the F12 fault in the Baodao A transition belt controlled the input of two major material sources,giving rise to a number of delta lobes in the west and east branches.The large structural ridge formed under the control of the main fault close to the hydrocarbon generation center allows efficient migration and accumulation of oil and gas.The combination mode and active time of the main faults matched well with the natural gas charging period,resulting in the hydrocarbon gas enrichment.Baodao A transition belt is adjacent to Baodao 27,25 and 21 lows,where large braided river delta deposits supplied by Shenhu uplift provenance develop,and it is characterized by large structural ridges allowing high efficient hydrocarbon accumulation,parallel combination of main faults and early cessation of faulting activity,so it is a favorable area for hydrocarbon gas accumulation.Thick high-quality gas reservoirs have been revealed through drilling,leading to the discovery of the first large-scale gas field in Baodo 21-1 of Baodao sag.This discovery also confirms that the north transition zone of Songnan-Baodao sag has good reservoir forming conditions,and the transition fault terrace belt has great exploration potential eastward.

Characteristics and accumulation mechanisms of the Dongfang 13-1 high temperature and overpressured gas field in the Yinggehai Basin, the South China Sea

The Dongfang 13-1 is located in the diapiric structure belt of the Yinggehai Basin. The formation pressure of its main gas res- ervoir in the Miocene Huangliu Formation is up to 54.6 MPa （pressure coefficient=l.91） and the temperature is as high as 143°C （geothermal gradient 4.36°C/100 m）, indicating that it is a typical high-temperature and overpressured gas reservoir. The natural gas is interpreted to be coal-type gas derived from the Miocene mature source rocks containing type Ⅱ2-Ⅲ kero- gens as evidenced by high dryness index of up to 0.98 and heavy carbon isotopes, i.e., the δ13C2 ranging from -30.76%o to -37.52%o and δ13C2 ranging from -25.02%o to -25.62%o. The high temperature and overpressured Miocene petroleum system is related mainly to diapir in the Yinggehai Basin and contains more pore water in the overpressured reservoirs due to under- compaction process. The experimental and calculated results show that the solubility of natural gas in formation water is as high as 10.5 m3/m3 under the temperature and pressure conditions of the Sanya Formation, indicating that at least part of the gas may migrate in the form of water-soluble phase. Meanwhile, the abundant gas source in the Basin makes it possible for the rapid saturation of natural gas in formation water and exsolution of soluble gas. Therefore, the main elements controlling formation of the Dongfang 13-1 gas pool include that （1） the diapir activities and accompanying changes in temperature and pressure accelerate the water-soluble gas exsolution and release a lot of free gas; （2） submarine fan fine sandstone in the Huangliu Formation provides good gas-water segregation and accumulation space; and （3） the overlying overpressured mud rocks act as effective caps. The accumulation mechanism reveals that the high temperatural and high pressure structure belt near the diapir structures has a good potential for large and medium-sized gas field exploration.

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.

Munc13-1、Munc18-1对锰染毒SH-SY5Y细胞中多巴胺分泌障碍的影响

[背景]慢性锰中毒诱发神经递质分泌障碍一直是其造成机体损伤的重要原因之一,但锰致神经递质分泌障碍的机制目前并不清楚。[目的]探究突触前膜胞内蛋白13-1(Munc13-1)与突触融合蛋白结合蛋白18-1(Munc18-1)对氯化锰(MnCl_(2))致人神经母细胞瘤细胞(SH-SY5Y细胞)多巴胺(DA)分泌障碍的影响。[方法]建立MnCl_(2)诱导SH-SY5Y细胞模型,根据MTT法测细胞存活率,实验分组为对照组和低、中、高浓度染锰组(0、100、200、400μmol·L^(−1)MnCl_(2)),处理24 h。用酶联免疫吸附试验试剂盒测定培养基中DA分泌量。通过实时荧光定量PCR检测细胞突触融合蛋白-1(Syntaxin-1)mRNA表达水平。提取细胞总蛋白,采用Western blotting检测Munc13-1、Munc18-1以及Syntaxin-1蛋白表达水平。并对MnCl_(2)染毒浓度和DA分泌量与Munc13-1、Munc18-1蛋白表达量之间做Pearson相关性分析。[结果]与对照组比较,随着锰染毒浓度的增加,细胞存活率逐渐下降,中、高浓度染锰组差异具有统计学意义(P<0.05);各锰染毒组细胞培养液中DA浓度随锰浓度增加呈下降趋势,与对照组和低浓度染锰组比,中、高浓度染锰组差异具有统计学意义(P<0.05);Syntaxin-1的表达量在mRNA和蛋白层次上,在各组间变化不明显,差异不具有统计学意义(P>0.05)。与对照组比较,Munc13-1的蛋白表达量随染锰浓度增加而依次下降,Munc18-1的蛋白表达量依次上升(P<0.05),其中与低浓度染锰组相比,高浓度染锰组Munc13-1和中、高浓度染锰组Munc18-1蛋白变化有统计学意义(P<0.05),与中浓度染锰组比,高浓度染锰组Munc18-1蛋白变化有统计学意义(P<0.05)。相关性分析显示,MnCl_(2)染毒浓度与Munc13-1蛋白表达呈负相关(r=-0.898,P<0.05),与Munc18-1蛋白表达呈正相关(r=0.678,P<0.05);DA浓度与Munc13-1蛋白表达呈正相关(r=0.932,P<0.05),与Munc18-1蛋白表达呈负相关(r=-0.817,P<0.05)。[结论]锰染毒SH-SY5Y细胞致DA的分泌抑制,与其上调Munc18-1和下调Munc13-1蛋白的表达水平有关,这可能是锰致神经损伤的原因之一。

The Great Pretenders Among the ULX Class

The recent discoveries of pulsed X-ray emission from three ultraluminous X-ray （ULX） sources have finally enabled us to recognize a subclass within the ULX class： the great pretenders, neutron stars （NSs） that appear to emit X-ray radiation at isotropic luminosities Lx = 7 × 10^39 erg s-1 _ 1 ×10^41 erg s-i only because their emissions are strongly beamed toward our direction and our sight lines are offset by only a few degrees from their magnetic-dipole axes. The three known pretenders appear to be stronger emitters than the presumed black holes of the ULX class, such as Holmberg II ＆ IX X-1, IC10 X-1 and NGC 300 X-1. For these three NSs, we have adopted a single reasonable assumption, that their brightest observed outbursts unfold at the Eddington rate, and we have calculated both their propeller states and their surface magnetic-field magnitudes. We find that the results are not at all different from those recently obtained for the Magellanic Be/X-ray pulsars： the three NSs reveal modest magnetic fields of about 0.3-0.4TG and beamed propeller-line X-ray luminosities of 1036 - 1037 erg s-1, substantially below the Eddington limit.