Abstract: In view of poor studying water-out pattern and laws in horizontal wells,a typical model is established on the basis of the geological data of a certain block in Jidong Oilfield.Through the study on water cut and water-oil ratio derivative curve on the typical water-out pattern,several conclusion are obtained:1.One-point water-out;for heel water out,the water cut and water oil ratio derivative curves(WWDC) are smooth with two obvious water out points;for the middle water out,there are three water out points in the WWDC.As the high permeable zone moves to the toe,the duration of water free production becomes longer.2.Multi-point water-out,the number of peaks on the WWDC grows with the increasing of the water out point.3.Linear water out,there are obvious plateaus on the WWDC.4.The water free production period of one point water-out pattern is longer than that of the two patterns.A new method is established to study the water out point by using production data.

Key words: horizontal well, water-out pattern, numerical simulation, production performance, residual oil