莺琼盆地勘探钻井速度问题及解决方法

THE PROBLEM OF DRILLING VELOCITY OF EXPLORATION IN YINGQIONG BASIN AND THE METHOD FOR ITS SOLUTION

莺琼盆地具有巨大的天然气资源,除现有的几个已投产大气田外,其勘探程度还比较低。由于莺琼盆地探井较少,很难了解速度纵横向变化趋势,同时在实际工作过程中遇到速度标定存在大的误差问题,这对于钻井部署工作造成困难。主要遇到两个难题:一是采用周边已钻井的时深关系,预测深度与实钻深度存在较大误差;二是莺歌海盆地东方底辟区DF1A井VSP标定速度与区域速度存在较大的偏差。笔者针对两大速度难点展开方法研究,提出了具有针对性的方法思路,提高了探区速度预测的准确性。

The Yingqiong basin possesses abundant natural gas resources ; nevertheless, except for a few large gas fields which have al- ready been put into production, the exploration extent there is rather low. As the drill holes are insufficient in this basin it＇s very diffi- cult to understand the longitudinal and horizontal variation trends of the velocity. Besides, the work of velocity calibration often encoun- ters remarkable errors, which causes difficulty in drill hole employment. There exist mainly two difficult problems： one is the existence of considerable error between the predicted depth and the drilling depth when the time-depth relationship of the surrounding drilled well is adopted; the other is the existence of rather large deviation between the VSP calibration velocity of DFIPO well in Dongfang diapiric area of the Yingqiong basin and the regional velocity. Aimed at solving these two difficult problems, the authors conducted methodologi- cal study and put forward effective train of thought and means, thus improving the accuracy of velocity prediction in the study area.