With the focus on continuous drilling optimization, a collaborative effort was implemented to analyze and assess drilling challenges encountered while drilling extended horizontal wells in the Khurais field in Saudi Arabia. The primary requirement was to enhance the efficiency of conventional downhole motor directional drilling systems in the challenging horizontal reservoir section.

The Khurais field is located in a remote area in the central part of Saudi Arabia approximately 200 km from the Saudi capital Riyadh, and 300 km from the Eastern port city of Dammam. The producer wells are drilled in the middle of the field and the water injector wells are drilled close to the field boundaries.

An average of 12 rigs worked simultaneously throughout the duration of the project to drill and complete the required increment wells. The horizontal wells are comprised of the producers, trilateral producers and power water injectors. The wells were drilled to an averaged measured depth of 14,000 ft, with an average of 6,500 ft of open hole section across the reservoir. The 6⅛" horizontal hole section is particularly challenging and is drilled with steerable mud motors with the assistance of real time geosteering and logging while drilling (LWD) tools to maintain the horizontal open hole section of the well close to the top of the reservoir within a window of 3 ft.

The fracture intervals coupled with high permeability makes the drilling of this section particularly challenging, as mud losses are frequently encountered in this section. The main difficulties to improve the efficiency of the directional drilling process were high drag and differential sticking.

To overcome the challenges mentioned above, the drilling team utilized a new sliding technology that interacts with the drilling rig top drive to break the static friction improving the weight transfer to the bit, and thereby increase the rate of penetration (ROP). Through the virtual elimination of differential sticking and reduction of buckling problems, this system smoothly helps to deliver weight down to the bit. Additional benefits of this innovative technology are the prevention of stalling of the mud-motor, steady orientation of tool face and easier steering.

The authors will describe the innovative system utilized to improve the ROP during the sliding process by almost 50% and will present real cases supported by field data. They will also illustrate the importance of post-actions review and rig crew training in the achievement of record ROP in sliding mode. Historical cases will be presented and the benefits of the application of this technology in these wells will be explained.

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