APPLICATION OF GAS BASED FLUID UNDER-BALANCED DRILLING TECHNIQUE IN HUOBEI AREA
Huobei area reservoir in Zhungeer basin belongs to Permian Pingdiquan group,reservoir buried depth is 2500 ~2800m,the thickness of surface Carboniferous nappe is 1000 ~2300m,stratigraphic dip is large,and drillability is poor,the average ROP in well Huobei 2 was only 1. 2m / h using conventional mud drilling,drilling cycle was 158 days. Through application of gas / atomization drilling in well Huobei 021 and 022,drilling footage of two wells was 2163m and 1732m respectively,average ROP was 5. 01m / h and 5. 79m / h,penetration rate was increased by 3. 85 times and 4. 2 times,drilling cycle was saved 70d and 67d respectively,the obvious economic benefit was obtained. The gas based fluid under- balanced drilling technique suited for Huobei Area was formed.