First Deep Slim Hole Design Well in Kuwait: Significant Achievement and Cost Optimization Drilling/Completing a 9.25-inch Hole Section

Al-kandari, Ayad M.E. (Kuwait Oil Company) | Al-Baghli, Waleed Jawad (Kuwait Oil Company) | Al-Khaldy, Ali Dawood (Kuwait Oil Company) | Al-Mekhyal, Abdullah Naser (Kuwait Oil Company) | Al-Mutawa, Faisal (Smith Bits) | Maliekkal, Harish (Smith Bits) | Ghoneim, Osama (Smith Bits, A Schlumberger Company) | Saleh, Mustafa


Kuwait Oil Company (KOC) launched North Kuwait Gas Development Project in 2007 to fast track production of gas/light oil from deep HPHT Jurassic reservoirs in six fields. The exploratory wells require a large-hole casing design to isolate problematic formations and allow the operator to reach the deep HPHT target zones with maximum hole size.

One of the most difficult/problematic hole sections is Zubair to Hith, traditionally drilled with 16-in bits. The formations are interbedded and consist of abrasive/pyritic sandstone, reactive shale, limestone and anhydrites with UCS that varies between 5-30kpsi. Historically, to complete the 3900ft section required more than three PDC bits or a combination of 4-5 PDC/TCI.

To reduce costs, the drilling team developed the first slim hole well plan and casing string design to explore Cretaceous formations in Northern Kuwait. The objective would be to downsize the hole section from Zubair to Hith to 9¼-in and drill to section TD with three PDC bits. The production casing would then be run from surface to TD instead of the conventional liner tie-back and cementing process.

The section was completed using the latest motor/PDC technologies in two bit runs saving 55% drilling time and the expense of a third bit. The operation set a new Kuwaiti record for the single longest 7¾-in production casing string (13,625ft) and cementing back to surface. Cement log indicated a good bond over all three zones of interest. The downsizing strategy and change in casing string design saved the operator over $1 million USD compared to a large hole and liner-string design. Production testing in Zubair, Ratawi and Makhul was positive, indicating a significant new oil discovery. The entire operation was completed with zero HSE related complications.