Increasing drilling speed in long horizontal intervals in Aktobe Kazakstan

Abstract

The Aktobe project is at the east margin of the Pre-Caspian Basin, where horizontal well is mainly used to develop the low porosity and permeability layers. To improve production per well, the horizontal interval increased from +/-400m to +1000m. Due to complicated geological structure, variable boundary and thickness of target layers, the RSS was employed to improve the rate in layer. But the average ROP was just 2.36m/hr, and average footage was just 335m per bit due to high strength of the formation. To solve this problem, the wearing characteristic of PDC bits was analyzed. The BHA and table rotary speed were optimized on the basis of drilling pipe vibrating calculation. Thus, the drilling technology for hard and long horizontal interval, including high performance PDC bit, RSS, PDM, BHA with 1/2 stabilizer, has been worked out. The technology was used in 5 wells, of which 4 wells at 60 rpm, had stick-slip index of less than 80%, the drill bits out of the wells had few cutters broken by vibrating; 1 well had stick-slip index of higher than 80% at 70-80rpm, and the drill bits out of the well had many cutters broken by vibrating. Compared with Well H814, the horizontal section drilling time shortened from 22.5d to 9.6d, by 57.7%, ROP increased by 261.4%, and the footage increased by 195.5%. The optimized horizontal drilling technology for hard formation could provide reference for the drilling of similar hard formation, especially for the other oilfields in the Pre-Caspian Basin.