Drilling difficulties in Huangcaoxia UGS and their countermeasures
There exist drilling difficulties in Huangcaoxia underground gas storage(UGS),such as big vibration in superficial zones,low rate of penetration(ROP)in the Triassic Xujiahe Formation,inconvenient directional drilling in gypsum salt rocks of Jialingjiang Formation,much longer treatment of complex lost circulation,and quick conversion from lost circulation to overflow in sulfur reser-voirs,which may restrict ROP increase.Thus,formation characteristics to drilling requirements were analyzed in the light of the last drilling data.And some information was summarized in terms of the optimization of bottom hole assembly(BHA),rapid lost-circula-tion treatment,and safe drilling and completion.Four countermeasures were taken as follows:(i)in the superficial Xujiahe Formation,one BHA of both cone bit and drill collar was utilized to drill the Ø660.4 mm borehole,and the other of multiple drill bits and screws for the borehole of Ø406.4 mm,all achieving fast and safe drilling;(ii)in Jialingjiang Formation,an oriented BHA combined the un-der-sized screw centralizer,the drilling collar with Ø203.2 mm with the heavy wall drill pipe,was introduced to alleviate directional backing pressure;(iii)the forced drilling with fresh water was available for the lost-circulation treatment in Xujiahe Formation while both rigid particle and bridge plug for Jialingjiang Formation,which might tackle complex lost circulation immediately;and(iv)in co-ordination with continuous hanging irrigation via fracturing trucks,the shut-in reverse propulsion was employed after lost circulation came across the sulfur target with low pressure to promise H2S not spill over to the surface and thus implement the safe drilling and completion.As a result,through these drilling technologies,the fastest cycle is shortened to 38.26 days in the second drilling period,36%lower than in the last cycle,and the accident time ratio is reduced by 39%.
UGSConversion from lost circulation to overflowLost circulation in returnDirectional backing pressureFast and safe drillingHanging irrigation
万方数据
维普
