Abstract:
The key link of well control safety technology for offshore HTHP (high temperature and high pressure) well drilling is to evaluate the geological risks of shallow gas reservoirs accurately and prepare control measures rationally. In this paper, the mathematical model on P-wave velocity of shallow sediments in the Yingqiong Basin based on dual-parameter (i.e. porosity and density) of shallow strata was established according to the principle that shallow gas responds to the seismic velocity differently. Then, based on the shallow seismic and logging data of some existing wells in the Yingqiong Basin, the P-wave velocity tendency curve of shallow strata in this basin was plotted, and its four risk levels (blue, yellow, orange and red) were predicted. And finally, drilling risk evaluation chart of shallow gas reservoirs in the Yingqiong Basin was prepared and the corresponding risk control programs were formulated. When this chart was actually applied in the Yingqiong Basin, the evaluation accuracy was over 90%. And it is indicated that this chart is better suitable for the Yingqiong Basin.