Perpustakaan Digital ITB

Drilling underbalanced has several advantages related to minimize problems, such as lost circulation, pipe sticking, formation damage, etc. From several drilling fluid, only two types are available in this field and nitrified mud is choosen for several reasons and based on qualitative method regarding factors: wellbore diameter, water influx, gas production, and Extended Reach Drilling (ERD). Gas injection methods are also reviewed. Coiled Tubing Drilling (CTD) has reached its popularity in last two decades. In principle, CTD provides hydraulic horsepower which is transfered to the bottomhole. CT itself, in operation, has advantages and disadvantages compared to jointed pipe. CT Unit (CTU) are complete package consists of surface and subsurface equipments. Field “A” located in Indonesia will be drilled dual lateral using underbalanced drilling technique. The reservoir has been highly depleted, low reservoir pressure about 1130 psi and high bottom hole temperature about 350oF. This field produced natural gas and condensate which contains 80-100 ppm H2S, 15% CO2, and water. Underbalanced drilling is conducted due to minimize potential problems. From several choices, Coiled Tubing with nitirified mud is selected to perform underbalanced. Combination of CTD and underbalanced drilling, which is dual lateral drilling, delivers maximum productivity improvement compared to single lateral. This is obtained from well performance study or upflow performance study from existing wells. This study is conducted to estimate productivity improvement for various lateral configurations, liner diameter, and well position Eventually, for Field “A”, dual lateral UBD system with 7” liner and lateral length 1500 ft results the highest PI improvement, which is 3.67 times higher. Drilling fluid used is nitrified mud due to several technical reasons. From five well configurations, CT 2-7/8” with 6” hole is the best drilled using Neyrfor-Weir Motor. Recommended liquid rate is from 10 gpm to 25 gpm and gas injection rate is from 1100 scfm to 1725 scfm.