Document Type : Original Article
Department of Petroleum Engineering, Gachsaran Branch, Islamic Azad University, Gachsaran, Iran.
In Kupal oil field, drilling shaly and marly formations (such as Pabdeh and Gurpi) face some challenges such as stuck pipe, tight holes, increased drilling time and cost and in some cases unprecedented hole deviation. Water based drilling muds can be proper substitute for oil based drilling muds. Therefore, mud parameters were studied in this research and swelling of the shale samples were investigated both for water based and oil based muds using the swelling-meter apparatus. Using the experiemental results, water-based muds containing starch and ASAFASOOL showed to reduce the swelling for 11.5%; thus, theywere selected as well stabilizin the chaly-including compounds in Pabdeh and Gurpi formations. The Potassium ions were identified as the main reason for controlling shale swelling.