Abstract
The correct selection and application of the innovative near balance drilling (e-nbd) technology combining the automatic surface backpressure control of Managed Pressure Drilling (MPD) with continuous fluid circulation method (e-cd) has demonstrated a key impact during the first application in country.
In 1998 an operator company drilled a well targeted to the Lower Cretaceous Goru and Sembar Sands as a primary objectives but it encountered a high pressured sequence (continuous increase in the background gas/formation pressure) and was not possible to continue drilling because of well construction limitations (at 3500m MD all available casing strings were consumed and in 6" hole was not possible to manage the coexistence of high background gas and losses). The objective formations in this field were considered not reachable with conventional drilling practices and even with technologies available at that time. Eleven years after this first attempt, another operator decided to target the Lower Goru (3500m MD) and Chiltan Formations (4900m MD), never explored in the Kirthar Fold Belt using the near balance drilling technique (e-nbd) technology combining the automatic control of surface backpressure of managed pressure drilling (MPD) together with the proprietary technology of the continuous circulating valves (e-cd) achieving to drill through the intervals in the Lower Goru formation, pushing the technical limit of drilling to the deeper horizon of the carbonates sequence of the Chiltan formation by first time ever.
Throughout the targeted two last hole sections for the MPD technology, Constant Annular Pressure technique was successfully applied drilling 45% more hole length than the previous reference well reaching the planned target with a bigger hole size than the offset, by precisely monitoring micro influxes and pressure losses in the annulus. The returns from annulus were taken through the MPD full automatic system in order to control the ECD and the flow from the well flow once drilling into expected high pressure gas formations.
