Practice of Fuzzy-Ball Drilling Fluid Technology in Qinping CBM Well 12-11-3H with Six Branch Holes

The 3# high rank coal in Qinshui basin frequently takes place of falling block, sloughing hole, leaking and pipe-stuck during drilling operation. The third open of 12-11-3H well in Qinping is consist of 2 main-branch and 6 sub-branch, using fuzzy-ball drilling fluid for 3 days accomplishing a footage of 4 189.49m. In order to adjust performance of drilling fluid, mix 4 fuzzy-ball drilling fluid additives SDS, SDBS, HES PAM together according to different well condition. The density of this drilling fluid is from 0.96 to 1.08g/cm3. The plastic viscosity of it is from 7 to 17mPa.s, the yield value is from 4.0 to 10.22Pa. After using this fuzzy-ball drilling fluid, the drilling rate has increase to 95%, completing the geological demand with an average drilling rate of 12.65m/h. Compared with adjacent well, the drilling rate has been raised 11.55% with no serious falling block, sloughing or leaking in whole well. However the solid control equipments still need to be strengthened for further improving drilling rate and economic benefits.