Integrated approach for the U-type horizontal well drilling & geosteering in shallow Turonian sands

Production drilling in Turonian sands was started in 2018 in Yamal region, Russia. The novelty was the U-type trajectory up to 114 degrees inclination, placed ultra-shallow, at 700m true vertical depth in complex geology formation considering technical limits.

High dogleg severity (DLS) required to drill 8 11\16in section to target depth, was the main challenge of drilling engineering proposal. The bottom hole assembly with rotary steerable system was specially modelled to achieve necessary DLS in soft unconsolidated sands. There were no wells in region at all, drilled within the same conditions. Another risk was casing stuck due to sinusoidal buckling and microDLS caused by excessive trajectory corrections.

High uncertainty of Turonian top position, variable reservoir thickness, local structural dip variance led to added geosteering complexity.

The planned trajectory design was divided to fixed clusters with defined sequence and type. The parameters of each cluster were set by drilling and well placement engineers on planning stage, based on technical limitations and geological uncertainties. Further the cluster parameters were adjusted while drilling, based on geology. Each cluster had predefined drilling\geology scenarios to achieve maximum net to gross ratio.

This approach allows to make rapid decisions and reduce technical risks while geosteering