The genesis of low-contrast pay zones was complex and various,the low-contrast pay zones in fresh-water reservoirs were divided into five categories.

Indoor simulation experiment on exploitation of bottom water reservoir;

Research on horizontal well critical production pressure in bottom water reservoir;

Water extraction and cone control of horizontal well in exploitation of bottom water reservoir;

A calculation method of horizontal perforated interval length in bottom-water reservoir;

Calculation method for the water cone height of bottom-water reservoir;

The biggest problem for a horizontal well in bottom-water reservoir is water cresting,which restricts the horizontal well to be developed effectively.