Historically difficult, complex section challenges drilling efforts

The objective of OMV Petrom for the 728-P Baicoi Sare well was to drill the 8 1/2-in 3D curve section in one run and to stay within the well AFE. Historically, this had been a difficult section to drill because of complex geology (salt, coal, faults, and the soft and interbedded Sarmatian Formation) and gas influx events that contribute to wellbore instability and lead to high risk of stuck pipe and inadvertent sidetracks. There is also high collision risk, with an oriented separation factor of less than 1 for several producing offset wells. The maximum dogleg tolerated by the planned completion was 7°/30 m, which was very close to the planned dogleg. The objective to stay within the upper part of the Sarmatian reservoir afforded only a narrow target window of 10 - 15 m, and the formation was bounded by an oil/water contact and faults.

Integrated drilling and logging technologies address all requirements

Schlumberger experts worked with OMV Petrom to identify the different drilling technologies that would be needed to meet the drilling challenges. After an in-depth offset well analysis and risk assessment, it was clear that a rotary steerable system (RSS) was required for hole cleaning and closed-loop steering control.

PowerDrive Archer RSS was placed in the BHA near the bit because the high-build-rate RSS enhances directional control in soft and interbedded formations. Additionally, Schlumberger included the TeleScope high-speed telemetry-while-drilling service in the BHA to provide real-time data transmission. The near-bit direction and inclination (D&I) and gamma ray acquired by combination enabled enhanced geosteering capability to help OMV Petrom stay within the narrow target window, mitigate collision risk, and support accurate well placement.

The BHA was further refined in several ways. The NeoScope service was introduced because a sourceless neutron generator was required. Simulations in the IDEAS integrated drillbit design platform guided the selection of a directionally certified MDi616LPXG bit from Smith Bits, a Schlumberger company. M-I SWACO, a Schlumberger company, contributed a recommendation for oil-base mud, a loss-control strategy, and hole cleaning.