复杂气层识别技术研究

RESEARCH ON THE TECHNIQUE OF IDENTIFYING THE COMPLEX GAS BEARING FORMATION

复杂气层是指在现有测井技术条件下，用常规解释方法难以识别的气层。这些气层往往由于受传统解释方法的限制而未能被正确地识别，如泥质细砂、粉砂岩等常被误认为是泥岩层或干层。复杂气层识别技术的主要原理是只要地层中含有一定数量的天然气，就必然对声波、密度、中子测井产生一定的影响。当地层含气饱和度较高时，气层的低密度、低中子、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，往往被人们忽视。该方法充分利用了三孔隙度即中子、密度和声波曲线在水层的共性和在气层的各向异性特征；利用弹性模量、合成纵波时差、声波密度中子的斜率、声阻抗４个物理量的交互运算，利用计算机技术对这些信息进行放大，足以提高三孔隙度曲线的分辨能力，直观地显示出气层。

The complex gas bearing formations in Yinggehai Qiongdongnan Basin refer to what are difficult to be identified by conventional interpretation methods under present logging techniques.Restricted by the conventional interpretation techniques,such as the shaly fine sand and siltstone are usually recognized as mudstone or dry formation.The principle of this technique is that so long as some amount of natural gas is contained in this formation,there must have a certain effect on the results of acoustic,density and neutron logging.Formations with relatively high gas saturation,present distinct characters of low density,low neutron value,high interual transit time and high resistivity.Formations,with relatively low gas saturation,however,do not present those characters obviously,and so are often ignored by people.In this technique,the generality of three kinds of porosity (from neutron,density and interval transit curves,respectively) in water layers and the anisotropism in gas bearing formations are taken fully into account.Resolution capability of these three kinds of porosity curves can be improved by use of the multiple computation of elasticity modulus,synthetic interval compressional transit time,slopes from interval transit time,density and neutron curves and acoustic impedance,and those information amplified through computer.As a result,the gas bearing formations can be shown in a direct way.