欠平衡钻井条件下气体采集与解释评价

Gas acquisition and interpretation & evaluation under under-balanced drilling

从欠平衡钻井的工艺原理和施工流程角度出发,阐述了欠平衡钻井对气测录井的影响。对比实验结果表明,在欠平衡钻井条件下,从振动筛脱出的气体不仅可以反映地下气层的组分特征,而且有利于实时录井分析和解释评价。结合YS1井资料,提出了利用钻时判别储集层物性,以气测值、气体流量的变化来衡量地层含气量的高低,参考套管压力、立管压力和钻井液参数的变化并观察钻井液槽面变化及火炬的燃烧情况,来综合识别和评价气层的方法。该方法经测试验证是有效的。

From the points of technical principles and construction flow diagram,the paper expounds the effects of under-balanced drilling on gas logging.Comparative results from experiments indicated that under the condition of under-balanced drilling,the trapped gases from shaker screen not only reflected components characteristics of the underground gas but also helped real-time mud logging analysis,interpretation and evaluation.Combining with well YS1 data,the paper puts forward the comprehensive discriminating and evaluating method of judging the reservoir physical properties with the drilling time,determining the gas concentration of the formation with gas logging values and the gas flow rate,by observing the variation of drilling parameters and the change of the mud ditch surface and the state of the torch combustion.The tested results proved this method is efficient.