Successfully Drilled the 1st Undercut Profile Well Exposing the Reservoir Positioned Underneath the Surface Location into the Least Stress Direction, Case Study from Kuwait
Authors: Bashir J. , Al-Khaja M. , Taha B. , Sindhu S. , Al-Manaseer A. , Ali. J. , Malik A. , Al-Haddad H. , Al-Otaibi Y. , Jamal. J. , Ajmi A. , Rashidee T. , Al-Enezi S. , Nouh W. , Farhi N. , Ishak G. 
Published: October 2023

First, find optimal KOP across the Top 16-in Section to have a smooth profile before building 11⁰ into the opposite side of the target reservoir point in Azimuth 325⁰ (the minimum stress direction) with a low Dog Leg Severity of 1.83º/100 ft to minimize the Casing wear expected while drilling the lower sections.

Once started, the lower 12-1/4-in Section started to drop the 11⁰ inclination in Mutriba Formation with 2.86⁰/100’ DLS reaching back to Vertical in Mishrif Formation. By that level, it kicked off toward the reservoir direction in azimuth 145⁰ (the minimum stress direction), building an angle to 40⁰ inclination through five formations and holding this angle to the well TD in the bottom of the lower Burgan Formation.

All risks and challenges were considered to drill the final 12 1/4-in Section throughout eight challenging formations in one run to the well TD that has always been drilled in one azimuth away from the least stress direction while keeping optimized Mud weight and Rheology for upcoming high permeable and depleted sand zones.

This paper provides an overview about the preparations and execution of both the 16-in Top section with a low angle from the shallow formations, getting the required displacement in the opposite direction, and keeping all the section tangent to the 13-3/8-in Casing point to minimize the casing wear while drilling the 12-1/4-in Section.

Addressed all the risks and challenges of drilling the 12 1/4-in section to the well TD through eight formations with different challenging behaviors as well as the wellbore pressure that always leads to splitting into two sections.

It was a major challenge to wisely model the geo-mechanical characteristics of each formation and decide the mud weight range and rheology that can stabilize the wellbore through the eight formations with higher ECD values expected due to the undercut profile that can break formations and get mud losses to complete loss.

A mitigation plan was executed to have a window of mud weight to stabilize the high-pressurized formation and ECD control for formation break avoidance.

Consequently, optimizing mud weight and drilling parameters while managing differential stuck in Maudud depleted zones with close monitoring of real-time ECD at the same time helped into stabilize the high-pressurized zones and deliver the well to the desired TD.

First time in Kuwait for the assigned direction company to drill an undercut profile throughout a long 12 1/4-in section, commingling eight formations with different properties and geo-mechanical reactions.

Differential stuck hazards were addressed by geo-mechanical modeling for the eight formations to decide the mud weight window for optimum hole cleaning.

Stabilize the pressurized formations controlling the ECD and ROP in some zones, achieving a ROP higher than the Average for the field.

Following the best practice for hole cleaning allows to avoid breaking the other formations. Later, the longest production liner in the field was deployed and had excellent cement quality, providing optimal zonal isolation among the entire open hole segments.