Abstract
In southern and central Oman, a field development campaign involves a major steam injection pattern across stacked horizontal producers for enhanced oil recovery. With a yearly goal of more than 350 wells drilled with 5 automated drilling rigs comprising injectors and stacked horizontal laterals targeting 3 different reservoirs on top of each other, efficient drilling and the reduction of time-based costs with no collision incidents have been the main concern. Because of the fast drilling pace, numerous drilling challenges were presented by the field, including losses in the top section, unconsolidated washable formations, trajectory control, shocks and vibrations, and bit walk tendencies in abrasive loose sand reservoirs causing equipment damage.
The typical horizontal producer well design planned for a 16-in. vertical and a 12½-in. section kicking off from vertical to 90° inclination, followed by an 8½-in. lateral section.
Several collaborative drilling practices were implemented in the 12½-in. buildup section to optimize drilling while building from vertical to almost 90° inclination using the steerable motor assembly delivering a dogleg severity (DLS) of 5°/100ft in unconsolidated formations. Drilling performance and hole cleaning were optimized in the 8½-in. lateral section by pumping up to 600 gal/min using a fully rotating rotary steerable point-the-bit system with PDC bit standardization to counteract the bit walk tendency at a penetration rates of 500 to 600 ft/hr. An added feature of the point-the-bit rotary steerable system is the inclination at the bit, which facilitates drilling through a 3-ft total vertical depth (TVD) tolerance window and promotes proactive decision making to avoid collision with the reservoirs above or below, with a TVD separation of up to 30 ft.
This field experience lead to a total saving of 3 drilling days in the AFE for each well. Using a point-the-bit rotary steerable system in the lateral, with added savings from eliminating openhole sidetracks, avoided a trip cost of 0.5 days. The high quality of the wellbore saved 0.5 days by avoiding a wiper trip and stuck incidents. The lateral is drilled in the narrow target using continuous inclination at the bit, which improved well outflow capabilities. Casing was run without any hang-up problems, eradicating any remedial cost.
This paper explains the methodology followed to improve the performance of drilling horizontal wells and attain 100% well delivery with a smooth borehole. It was also a step change in drilling horizontal wells using the fit-for-purpose approach (i.e., optimized trajectory, proven bit, and recommended drilling parameters derived from simulations compared to actual) to deliver wells in a cost-effective manner.
