综合录井参数在欠平衡井气层解释评价中的应用

Application of comprehensive mud logging parameters in interpretation & evaluation of the under-balanced well gas layers

深层天然气井欠平衡钻井过程中,由于先钻开的气层气体不断地进入钻井液中,使后续钻开的气层在气测录井曲线上显示微弱,无法根据常规气测录井方法进行解释评价。针对这一情况,阐述并验证了钻井液出口密度、温度的变化与深层气井储集层的关系;通过对气测录井甲烷、全烃和测井有效孔隙度的研究分析,分别建立了甲烷含量差值、甲烷与全烃比值和测井有效孔隙度的解释评价图板和标准。实际应用结果表明,在深层气井欠平衡钻井过程中,利用两图板可有效解释评价储集层。

During drilling into the under-balanced deep gas wells, as the gas from pre-drilled gas layers continuously flows in- to the drilling fluid,which makes the subsequently drilled gas layers show weak on gas logging curves,the interpreta- tion & evaluation can not be made according to the conven- tional gas logging methods.In view of this situation,the paper expounds and proves the relations between the chan- ges of drilling fluid outlet density and temperature and deep gas well reservoirs.Through making a study and analysis of gas logging methane,total hydrocarbon and well logging ac- tual porosity,the interpretation & evaluation charts and criteria for methane content difference,the ratio of methane to total hydrocarbon and the well logging actual porosity are set up respectively.The applied results show that during drilling into the under-balanced deep gas wells,both charts can be used to interpret and evaluate reservoirs effectively.