Fishbone Wells Drilling Technology in Shallow Heavy Oil Field：A Case of Zhan 18-P1 Well in Shengli Oilfield in China

There are abundant shallow heavy oil resources in Shengli Oilfield, heavy oil reservoirs in the oil field have soft formation and shallow burial depth which ranges from 800 m to 1200 m in most blocks, fishbone wells are used to develop heavy oil fields by increasing the reservoir contact and thermal efficiency and thus getting high production. In order to drill the fishbone wells in shallow heavy oil field, some problems should be solved: the technology of big hole trajectory control in soft formation, big diameter casing run in high dogleg hole, avoiding the wall collapse between main bore and branches and running drill pipe or casing into main bore easily. In this paper, the technology of big hole trajectory control in soft formation, the suspended sidetracking technology in loose formation, and the drill pipe or casing design optimization are introduced. In order to increase the measurement accuracy of the well trajectory, the effect of different mud motor conditions on the measurement accuracy is analyzed and the formula for calculating the measurement error is obtained. Drilling technology in this paper was applied in Zhan 18 - P1 well, which provides good experience for heavy oil thermal recovery in Shengli oilfield. Key words: Fishbone wells; Shallow heavy oil; Trajectory control; Wall collapse; Production