A PILOT STUDY ON SCREW DRILL TOOL COMBINED WITH HIGH EFFICIENCY BIT FOR IMPROVEMENT OF DRILLING EFFICIENCY

The restriction of bit rotory speed improvement caused by rotory table combined with roller bit eliminates the penetration rate increasing in deep well and ultradeep well drilling. A pilot study on positive displacement drills combined with high efficiency bit was conducted in three intervals of well No. lengke 1 in Qinghai oil field in 1997. The first testwas done in interva13724. 40~3751. 87 m with a footage of 24. 47m and a ROPof 0. 87m/h, 20. 83% higher than that of roller bit;the second was in interval 3756. 77~3898. 83m with a footage of 142. 06m and a ROP of 1. 27m/h, 2 times more than the footage of roller bit and 75. 83% higher than the ROP of roller bit;the third was in interval 4200. 26~4305. 45m with a footage of 105. 9m and a ROP of 0. 74m/h, 60. 87% higher than that of roller bit. The pilot result showed that the combination of positive displacement drills with hlgh efficiency bit can not only increase the ROP in deeper interval, but also provide a great potential for ROP improvement if a good match of bit, formation and positive displacement drills is realized and other parameters are properly applied.