基于自然伽马能谱测井的氦气资源评价方法——以塔里木盆地古城地区为例

Quantifying the helium generation based on natural gamma-ray spectrometry data:Gucheng area,Tarim Basin

塔里木盆地是我国天然气勘探开发的主战场,其中不乏具有工业开采价值的氦气藏,但对其氦气生成潜力的研究仍处于空白阶段。据此,对塔里木盆地古城地区奥陶系的岩石样品展开测试,生氦潜量呈现出泥岩>泥质灰岩>高铀白云岩>白云岩>灰岩的特征。基于自然伽马能谱测井资料,提出了一套氦气资源评价流程和方法。以古城地区15口钻井为例进行实际案例研究,结果表明:古城地区奥陶系地层的生氦潜量为1.50×10^(-10)cm^(3)/g,氦气生成量为13.91 km^(3)。生氦潜量最高最广的区域位于古城14井区域,其次为古城12井区域。却尔却克组泥岩生氦潜量为1.45×10^(-10)cm^(3)/g,生氦量占比为83.5%,是研究区生氦的主力层位,但是估算的天然气中氦气含量约为0.033%,低于工业开采标准。原因在于富含有机质的泥岩大量生烃,大大稀释了氦气的浓度,因此在对油气烃源岩进行氦资源评价时应该保持谨慎。基于自然伽马能谱测井的氦气资源评价方法的提出有助于含油气盆地中氦气资源评价工作的开展,为我国氦气资源勘探调查研究提供新的思路和方法。

Tarim Basin is an important natural gas exploitation basin in China and there are also many helium gas pools with industrial extraction value.However,the research on helium generation potential in this area is still in a blank stage.The helium production of rocks per unit time and per unit mass from the Ordovician in the Gucheng area are as follow:mudstone>muddy limestone>high-uranium dolomite>dolomite>limestone.Based on the natural gamma spectroscopy logging data,a set of helium resource evaluation procedure and method are proposed.We take 10 drilling wells from the Gucheng area as a case study.The results show that the helium generation rate of Ordovician strata in the Gucheng area is 1.5×10^(-10) cm^(3)/g,and the helium generation is 13.91 km^(3).The area of high helium generation rate is located in the Well Gucheng 14 zone,followed by the Well Gucheng 12 zone.Wherein,the helium generation rate of mudstone in the Queerqueke Formation is the highest,accounting for 83.5%of the total helium generation,which indicate that Queerqueke Formation is the main source of helium.But it is estimated that the helium content in natural gas is about 0.033%,which is lower than the industrial mining standard.The reason is that the organic matter-rich mudstone produced a large num-ber of hydrocarbons that dramatically diluted the concentration of helium.Therefore,caution should be exercised when evaluating helium resources on hydrocarbon source rocks.The establishment of helium evaluation method based on natural gamma spectroscopy data promotes the development of helium estimation in petroliferous basins and provides new ideas for the exploration and survey of helium resources in China.