Unconventional Drilling in Southern Sumatra Area. Evolving Technique for the New Drilling Culture

Abstract

Recent drilling operations in Southern Sumatra area, especially Jambi and South Sumatera district, have experienced various problems upon drilling the top section, intermediate section, as well as production section.

Overpressures, loss circulation and narrow window between pore and fracture gradient are common problems when drilling the top hole section. In some wells, coal caving and shale sloughing are claimed to be the reason of drilling day extension in this particular section. Overpressure zone within permeable system have cornered several field operators to activate well control system. Some field operators even had to experience blow out. The upper zone of intermediate section sometimes experience tight hole and shale sloughing, which require adequate drilling fluid management. In several wells, reactive shale is identified within the lower intermediate section, which requires the operators to utilize oil based mud to avoid clay swelling. Total loss circulation inflicted with high gas content is a normal condition when penetrating the intermediate and production section. This condition increases operational days when drilled conventionally with high potential of pipe stuck, complications in formation evaluation such as cuttings recovery and well logging, or even forcing the operators to side track the well due to sloughing. Extensive well bore clean out period also have been experienced by some operators when drilled with high barite concentration within the production zone.

This paper elaborates a new drilling convention that has been practiced by the operators within these areas, evolving the commonly known Managed Pressure Drilling technique into a culture when penetrating such problems. Success stories will be highlighted when drilling through the top section, intermediate, and production section presenting risks associated from economical and operational perspective.