Abstract:

The calcarenaceous sandstone reservoir in the 4th Member of Xujiahe Formation in Fenggu area are of the characteristics of low GR, high resistance and high impedance. The impedance of gasbearing reservoir, which will reach a lower value than common nonegasbearing one, is still higher than or close to that of mudstone. By jointly using the reverse of impedence and GR, the influence of mudstone imposing on the gasbearing reservoirs can be eliminated, and the plane distribution characteristics of calcarenaceous sandstone gasbearing reservoirs can be predicted. The analysis has come to the conclusion that 8~10 meter thick effective reservoirs can be recognized through joint inversion of impedance and GR therefore such inversion can produce a higher vertical resolution. The credibility of the reservoir prediction mainly depends on the number and distribution of the wells concerning with the inversion process. The method has been successfully applied to improve the vertical and horizontal resolution during the gasbearing reservoir prediction through multiwell restriction inversion in the area with enough and evendistribution wells.

Key words: calcarenaceous sandstone, inversion, impedance, GR, gasbearing reservoir prediction