Schlumberger

Case Study: Impact System Frees Stuck BHA in 7 Attempts After 6 Days Stuck Downhole

Combination of drilling jar and accelerator tool delivers 1,000,000 lbf of impact, eliminating need to redrill 5,000-m section and saving USD 9 million, Sakhalin

Challenge: Free a stuck BHA at 8,011-m MD to avoid it being lost in hole and to recover the well.

Solution: Run the Hydra-Jar AP double-acting hydraulic drilling jar and Accelerator AP impact tool to obtain the high impact and impluse forces needed to free the stuck drillstring.

Result: Saved the BHA and avoided the need to redrill the entire 5,000-m section, which saved approximately USD 9 million in rig time and operating costs.

Recover lost BHA during fishing operation

An operator was performing extended-reach drilling (ERD) offshore Sakhalin, Russia, and the risk of solids-induced packoff and mechanical and differential sticking was very high. These issues amplify the possibility of stuck pipe, which can incur extensive costs. Previous offset wells drilled in the same field have experienced lost-in-hole BHAs due to mechanical issues caused by the wellbore rugosity, and similar issues were expected to occur in this well.

While drilling ahead of the 12 1/4-in interval at 8,011-m MD, the operator experienced a sudden twistoff on the drillpipe. Downhole, the BHA was susceptible to openhole conditions as well as becoming stuck and potentially lost in hole. In an attempt to recover the drillstring, the operator ran a screw-in sub to engage the top of the fish. After the sub engaged the top of the fish, the drillstring would not rotate or move axially, indicating that the BHA had become stuck. More than 100 jarring attempts were made at a hook load of 560,000 lbf to prevent damage or unscrewing from the affected box, and each attempt was unsuccessful. The operator required another solution to recover its stuck BHA.

Use a jar-accelerator impact solution

Based on the previous experiences from offset wells and historical data, the Schlumberger team recommended running the Hydra-Jar AP jar and the Accelerator AP tool on the drillstring to provide maximum impact. The Hydra-Jar AP jar enables jarring up or down with varying impact force to free stuck drillstring components, minimizing NPT and avoiding sidetracking. Running the drilling jar with the Accelerator AP tool delivers up to 1,000,000 lbf of impact. The combination protects the drillstring and surface equipment from shock and reduces the costs associated with lost equipment, plugback, and sidetrack operations by offering total impact control.

Recovered stuck drillstring and saved the BHA

With the Hydra-Jar AP jar and Accelerator tool included in the drillstring, the operator was able to recover its multimillion-USD BHA after it had been stuck downhole for 6 days. The drillstring was reengaged at 500 m from surface after multiple attempts to back off deeper in the hole. The drillstring was jarred free after 7 attempts at a hook load of 750,000 lbf. The operator resumed drilling after replacing the BHA, avoiding the need to redrill the entire 5,000-m section and saving approximately USD 9 million in rig time and operational costs.


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Impact System Frees BHA and Avoids Section Redrill for USD 9 Million in Savings

Impact System Frees Stuck BHA in 7 Attempts After 6 Days Stuck Downhole
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