低矿化度地层水地层油气水层识别研究

RECOGNITION OF OIL ,GAS AND WATER LAYERS IN THE STRATUM CONTAINING LOW SALINITY FORMATION WATER

低矿化度地层水地层是指地层水矿化度与泥浆矿化度相差不大 ,基本在一个数量级。低矿化度地层水地层的油气水层 ,用常规测井解释方法计算的含水饱和度大小难以识别出储层中的油气水层 ,由于油气层 (特别是新疆准南地区 )凝聚有一定数量的天然气 ,天然气对声波、密度、中子测井产生不同的影响。当地层含气饱和度较高时 ,有低中子、低密度、高时差及高电阻率特征明显 ;而含气饱和度较低时 ,气层特征不明显 ,往往被人忽视。所应用的判别流体性质充分地利用了三孔隙度测井 (即中子、密度、声波 )、电阻率测井 (侧向 )在水层的共性和在油气层的各向异性特征 ;利用补偿中子、补偿声波、补偿密度和电阻率测井的交互运算 ,利用计算机技术对这些信息进行放大 ,足以提高三孔隙度和电阻率曲线的分辨能力 ,直观地显示出油气水层。其测井解释符合率达到了 95%以上。

The stratum containing low salinity formation water means that formation water salinity is near to mud salinity,their difference being about an order of magnitude.The oil ,gas and water layers in the stratum containing low salinity formation water are difficult to be recognized according to the water saturation values calculated by use of the traditional log interpretation methods,because a certain quantity of natural gas which coagulated in the oil and gas bearing formations(especially in the south part of Zhunge′er Basin,Xinjiang Province)can exert different influences upon the acoustic,density and neutron loggings.When the gas saturation in formation is high,the characters of low neutron,low density,high interval transit time and high resistance are obvious;while the gas saturation is low,these characters of gas bearing formation are not obvious so as to be often ignored.In order to recognize the fluid properties,the generality of three porosity(i.e.neutron,density and acoustic)loggings and resistivity logging (laterolog) in water formations and the anisotropism of them in oil and gas formations should be fully utilized;through an interactive operation by use of the compensated neutron,compensated acoustic,compensated density and resistivity loggings and a magnification of these informations by use of computer technique,it is enough to raise the resolution capabilities of the three porosity and resistivity curves to audio visually indicate the oil ,gas and water layers.The coincidence rate of the log interpretation by these methods is up to 95%.