地球多层圈有机—无机相互作用的资源效应

地球内部不同层圈相互作用过程中的物质循环和能量传递对浅层盆地内部多种类型资源的形成及富集具有显著影响。深部地质作用过程与浅部资源效应这一核心科学问题备受关注,其中在深部流体/熔体物质传输影响下的有机—无机相互作用及资源效应是关键所在。梳理了地球多层圈有机—无机相互作用对盆内多种资源的影响机理。在深部流体/熔体活动背景下,有机—无机相互作用主要通过形成利于富有机质烃源岩发育的沉积环境、提供促进生烃的物质能量、产生改造储层性质的流体环境和影响油气组分的聚集效果的方式控制油气资源的形成和聚集;深部流体携带地球深部的气体组分(CH_(4)、H_(2)、CO_(2)等)和热能进入盆地促使了天然氢气和地热资源潜力的形成;深部物质为铀矿提供铀源,富铀流体在生物作用和含烃流体作用下形成砂岩型铀矿;深部流体活动对煤矿资源的形成和变质也产生了较大影响。未来针对地球多层圈有机—无机相互作用的研究应当突破盆地限制,在地球系统的背景下围绕层圈物质和能量传输、盆内与盆外一体化展开。重点对非生物烷烃气成因、工业聚集和天然富(含)氢气藏的成因、富集、潜在勘探区评价、地质储存开展深入研究,助力推进中国能源转型和绿色发展。

深层海相凝析油气藏成因机制与富集主控因素——以塔里木盆地顺北4号断裂带为例

塔里木盆地顺北地区4号断裂带发育典型凝析油气藏,凝析油气成因机制与富集主控因素不明制约了勘探向外围的拓展。基于有机地球化学特征与区域地质背景综合分析,明确了顺北4号断裂带凝析油气成因机制与富集主控因素,主要取得以下3点认识:(1)顺北4号断裂带发育原生的凝析油气藏,凝析油气藏的形成主要受到有机质差异演化,多期成藏以及次生作用影响。(2)顺北4号断裂带凝析油气藏整体次生作用较弱,但是中段和南段所经历的次生作用相对强于北段;次生作用包括原油裂解作用、气侵作用以及TSR作用。(3)顺北4号断裂带北段凝析油气藏富集程度明显高于中段和南段;凝析油气富集高产主要受到输导条件以及储层规模控制,断裂活动强度越大,输导条件越好,储层规模越大,膏盐岩越薄也越有利于油气沿走滑断裂向上运移,从而导致油气高产富集。

The first extra-large helium-rich gas field identified in a tight sandstone of the Dongsheng Gas Field,Ordos Basin,China

Helium gas is a scarce but important strategic resource,which is usually associated with natural gas.Presently,only one extra-large helium-rich gas field has been found in China:the Hetianhe Gas Field in the Tarim Basin.This paper reports a new example,the Dongsheng Gas Field(DGF)in the Ordos Basin.In this study,92 natural gas samples from the DGF were analyzed for helium content and isotope composition using isotope mass spectrometry.The natural gas samples were found to have an average helium content of 0.133%,with 65(70.7%)of the samples having a helium content of 0.1%or more.Based on the proven natural gas reserves of the DGF,the proven geological helium reserves were calculated to be 1.96×10^(8)m^(3),suggesting that it represents the first extra-large helium-rich natural gas reservoir to be hosted in tight sandstone in China.The ^(3)He/^(4)He ratios of 5 natural gas samples from the DGF are within the range of 3.03×10^(−8)–3.44×10^(−8).Therefore,the helium in the gas field is thought to be of typical crustal origin and to have formed in the granitic basement that is rich in uranium and thorium.The accumulation of helium-rich natural gas was controlled by regional tectonic activities.Activity along the fault connecting the reservoir with the basement caused release of the helium gas,which entered the overlying strata along the fault and accumulated with conventional hydrocarbon gas.Based on the structural background and the distribution of helium source rocks in the Ordos Basin,the main helium source rocks with high exploration potential are located in deep strata within the north and middle parts of the basin.

Source and distribution of mercury in natural gas of major petroliferous basins in China

Based on the analysis of the natural gas samples of 146 wells from four major petroliferous basins of China,the source and distribution of mercury in natural gas in major petroliferous basins of China were identified.Studies have shown that the mercury concentration of natural gas in petroliferous basins of China varies widely,ranging from 0.01 to 4050μg/m^3.The gas well with the highest mercury concentration is in the Xushen gas field in the Songliao Basin.The mercury concentration in the craton basin is relatively low,and the secondary gas reservoir in the Tarim Basin has the lowest mercury concentration.In the rift basin,due to the presence of deep faults which cut the basement and mixing effects of deep fluids,the mercury concentration in natural gas may be abnormally high,e.g.the Xushen gas field in the Songliao Basin.In relatively stable basins where deep and large faults do not develop,mercury is primarily of organic origin.In rift basins where deep fluids are mixed with gas reservoirs,mercury in natural gas may mainly come from the deep fluids and is characterized by abnormally high mercury concentration and R/Ra values.

Characteristics and geochemical implications of light hydrocarbons from ultra-deep Ordovician oils in the North Shuntuoguole area, Tarim Basin

The ultra-deep Ordovician reservoirs in North Shuntuoguole Oilfield(or Shunbei Oilfield)of Sinopec have achieved annual production of one million ton,and the oil&gas in different faults show different physical properties and fluid phases.In this study,the 28 oil samples from the ultra-deep Ordovician were analyzed using whole oil chromatography.The heptane and isoheptane values of the oil samples were in the range of 29.79%‒46.86%and 1.01%-3.06%,respectively,indicating the oils are high mature.The maturity that calculated based on light hydrocarbon values was higher than which calculated by using aromatic hydrocarbon parameters,suggesting the light hydrocarbon maturity mostly reflects the maturity of the late charged hydrocarbon.The 2M-/3M-C5 and 2M-/3M-C_(6) ratios varied in the ranges of 1.41‒1.81 and 0.79-1.09,respectively,and the iC_(5)/nC_(5) and 3M-C_(5)/nC_(6) ratios were 0.31‒0.90 and 0.16-0.37,respectively,indicating that ultra-deep Ordovician reservoirs have not experienced biodegradation.The Mango parameter K_(1) of the oil samples ranges 0.96‒1.01 except for the oil from Well SB4,which suggests that most of the reservoirs have not suffered thermochemical sulfur reduction(TSR).Meanwhile,the oils have not experienced evaporative fractionation since the toluene/nC_(7) and nC_(7)/MCC_(6) ratios range from 0.10-0.38 and 1.50‒1.80,respectively.The close correlation between P_(3) and P_(2)+N_(2) and between P_(2) and N_(2)/P_(3) indicates that the oils from different faults have the same origin.According to the characteristics of LHs rich in n-alkane,as well as other biomarkers,such as aryl isoprenoids,and aromatic hydrocarbon parameters,the oil originated from the source rock of Lower Cambrian Yu’ertusi Formation.Meanwhile,the source rocks in different fault zones slightly differed in organic facies.