Challenges of Drilling Horizontal Wells in Shallow Viscous Oil Formations

摘要

The viscous oil resource of Kuwait poses special challenge since about 40-50% of the resource is distributed over a very large area with pay thickness in the range of only 20-30 ft. These low pay thickness areas are considered marginal for conventional thermal EOR and may need an innovative approach for economic exploitation. Horizontal wells, both for primary production as well as for thermal EOR, have been successfully used in such reservoirs (Araque-Martinez et.al. 1996, Malik, S. et.al, 2010). In this context, drilling of horizontal wells for this viscous oil reservoir is considered a key milestone for development of this vast resource. The challenges for the shallow viscous oil formation drilling, requires shallow horizontal medium-radius wells in extremely soft formation, with kick off from 150 ft MD. The initial plan was to drill six horizontal wells in the early phase, followed by a field study, before further expansion into horizontal drilling. Baker Hughes has successfully drilled three horizontal wells of the six wells, and has set the benchmark for shallow horizontal medium-radius wells in the extremely soft Shallow viscous oil formations formation. The horizontal wells require kick off from 150 ft MD in the loose sand formation of Shallow viscous oil formations, posing a strong directional drilling challenge. Maximum TVD for the wells are approximately 715 ft TVD RKB, which requires landing the wells in less than 5 ft TVD, with tolerance for navigation in the 6.125 in. lateral section within +/-1 ft (i.e., less than bit OD). The requirement is to geosteer along reservoir sand with the help of proactive geosteering services, maintaining optimum drilling parameters for good borehole quality. The solution included the geosteering services with rotary steerable systems, LWD density, porosity and distance-to-bed boundary tools. With average horizontal section lengths of 1,100 to 1,200 ft, drilled in reservoir sand of shallow viscous oil formations formation, Baker Hughes has drilled the longest horizontal section of 1,307ft in the soft formations. The synchronized team efforts from Kuwait Oil Company along with the Baker Hughes team resulted in consistent good execution of the three shallow horizontal medium-radius wells in Shallow viscous oil formations project, with optimal well placement, achieving 100-percent reservoir exposure.