Shallowest Horizontal Well Drilled in the Middle East: Challenges and Successes

Abstract

This article, written by Senior Technology Editor Dennis Denney, contains highlights of paper SPE 142439, ’Shallowest Horizontal Well Drilled in the Middle East: Challenges and Successes,’ by Abhijit Dutta and Bader M. Al Azmi, Kuwait Oil Company, and Hakim Al Abri, and Musab Ali, Halliburton, prepared for the 2011 SPE Middle East Oil and Gas Show and Conference, Manama, Bahrain, 25-28 September. The paper has not been peer reviewed. Major plans are underway to exploit heavy-oil resources in very shallow regions of Kuwait. Drilling horizontal wells poses great challenges in these shallow formations and requires high dogleg severity (DLS) through extremely loose formations while drilling with a conventional Kelly-drive rig. The use of multitier planning and exact execution enabled successful drilling and completion of the shallowest horizontal well in Kuwait on the first attempt. Introduction The Lower Fars is a shallow unconsolidated heavy-oil reservoir in northern Kuwait. The reservoir is mainly in the southern part of the Ratqa field. The lithology sequence from the surface to the Lower Fars includes the surface Kuwait-series sand, which has the Dibdiba freshwater aquifer (approximately 150 to 250 ft deep) and a brackish-water channel just above the shale cap of the heavy-oil-sand strata. Because the unconsolidated-sand reservoir is at an extremely shallow depth of approximately 700 ft and is in close proximity to infrastructure, it is attractive for exploitation by vertical wells but poses many challenges for drilling horizontal wells with an extremely shallow kickoff point (KOP) and high DLS. More than 75 vertical wells have been drilled, with coring, sampling, vertical-seismic profiling, full-suite logging (including imaging), and extended leakoff testing in many wells to evaluate the friable, unconsolidated, and loose sand. The preferred production method is cyclic steam injection (huff-’n’-puff) to reduce the viscosity of the oil for enhancing production. Both casing strings (surface and production) in all wells drilled at Lower Fars are cemented with thermal cement that can withstand thermal-cyclic stress. Challenges Concerns were raised in regard to the technical viability of drilling these horizontal wells with a conventional Kelly-driven rig. A slant rig could eliminate many of the disadvantages expected with a vertical rig. However, the cost of hiring a slant rig and nonviability of deploying a vertical rig for workover operations in slant wells prevented use of this method. The biggest challenges in drilling a horizontal well were to maintain the directional trajectory and to lower the casing and liner by use of a Kelly-driven rig with little weight available. Drilling through shale at a high angle also was perceived as a potential challenge.