Intercalation Pattern and its Impact on Development of Braided River in SAGD Test Area of Fengcheng Oilfield in Junggar Basin, Northwest China

Haiyan, Li; Yang, Gao

Fengcheng oil field lies in the northwest of Junggar basin and is a shallow buried structural lithologic reservoir with super heavy oil and high permeability. The oilfield is developed by SAGD (Steam Assisted Gravity Drainage) method, which uses two profile paralleled horizontal wells to produce heavy oil. After the hot steam with high dryness is injected into the upper well, the heavy oil is melted and flow downward with gravity and be produced by the lower well. The A and B test area have 37 and 134 vertical observation wells, and drilled 4 and 22 pairs of vertical wells respectively. The J3q belongs to braided river facies, and mainly develops channel and diara. The intercalations in the reservoir impact the expansion of steam chamber, and the development efforts will be severely impacted if the distribution of the intercalations is not clear.

From core-log calibration, the channel is bell curve and the diara is box curve. The recognition criterion of intercalations is determined by characteristics and return degree of well log curves, and the intercalations are recognized in each single well guided by the criterion. Based on the outcrop and modern sedimentation prototype, the intercalation pattern is summarized to be horizontal or diagonal, and the mechanism of the intercalations is analyzed. The horizontal intercalations mainly develop in the cut lap position of different flow periods, while the diagonal intercalations partly develop in the transitional contacts of channel and diara, and partly develop in the scoured surface of the same flow period. The summarized intercalation pattern is used to guide the cross well correlation, combined the static and dynamic data of dense wells, the continuity and space distribution of the intercalations are determined in different wells, and the oil water contact is modified. The intercalation expanded range is predicted by its scale and thickness, and then it is used to constraint the 3-D model establishment. The model of B test area is guided by the new intercalation pattern to avoid intercalations between upper and lower wells, thus the production is up to 158 barrels/day, much higher than 112 barrels/day of a test area.

AAPG Search and Discovery Article #90163©2013AAPG 2013 Annual Convention and Exhibition, Pittsburgh, Pennsylvania, May 19-22, 2013