Well Control in Carbonate Zone – Total Loss and Kick in Gas Reservoir

摘要

North Senoro Gas Field is located onshore at Sulawesi Island, operated by JOB PERTAMINA – MedcornE&P Tomori Sulawesi. The aim of North Senoro Project Development is to produce gas from limestonernreservoir (Mentawa reef) which has unique characteristic formation that total loss hazard wasn’t found atrnthe adjacent well. One of effort to solve the problems is bullheading. In this paper, it will explain howrnbullheading might become a sufficient method for controling pressure during stripping operation whilerncuring loss circulation problem. Well control situation in sandstone and carbonate formation has differentrncharacteristic. In carbonate, well control issue is mostly come by total loss which caused the mudrnhydrostatic pressure was less in the wellbore. Curing loss circulation was the first major to controlrnpressure on the well. Also on sandstone formation, has more compact if hasn’t fault or fracture on there.rnThe well control issue happened in 8-1/2" hole section; the situation occurred when suddenly got totalrnloss in the bore hole. It was followed by the increasing number of background gas from the cutting. Shutrnin well, got record of SICP is 1700 psi and SIDP is 0 psi. The operations continued with circulate gas outrnthrough choke simultaneously with original mud and LCM to try plugged the loss zone and filled up thernhole. The result was same with no indication of curing the loss problem. Decided to circulate on the twornside, through annulus and inside drill string, while circulate mud and LCM through drill pipe got plugged.rnThe engineer team made some analysis then created few scenarios, such as severing BHA, perforate drillrnpipe to make communication with annulus, continued pumping mud and LCM via annulus (bullheading),rnor stripping operation. With all assumptions and condition, the stripping operation while bullheadingrnbecame the best choice to POOH BHA and running OE to cure loss circulation with BDOP/BDOC, thenrncontinue with circulate out gas/kick. Finally, with 2 spot BDOC and the last BDOC was modified usingrnLCM to mitigate micro fracture in cement, loss circulation solved then following circulate out gas byrndriller method.rnFor total loss and kick issue, the important thing that we have to assure is pressure gradient andrnavailability of water and LCM material. Setting casing shoe at the high rating pressure will give us muchrnpossibility to select the way of curing loss circulation and kick. RIH OE pipe and spot BDOP & BDOCrnthrough OE pipe became success story to curing the loss for next well. Finally, the safety for crew,rnenvironment and production target is achieved with this option at North Senoro Gas Field.