Analysis of the Horizontal Wells in Eastern Shallow Oil Zone, Elk Hills, Kern County, California

Abstract The Eastern Shallow Oil Zone (ESOZ) is part of the giant Elk Hills field in Kern County, California. ESOZ, discovered in 1919 and brought online in 1920, has been producing for over a century. With a cumulative oil production of 570 million barrels of oil (MMBO) and an estimated Original Oil in Place (OOIP) of 1.5 billion barrels (BBO), the reservoir boasts a current recovery factor of 38%. For 28 years, horizontal wells have been drilled under various recovery mechanisms and since 2005 under Gas Assisted Gravity Drainage (GAGD) effectively enhancing oil recovery. To date, more than 3,300 wells, including redrills, have been drilled and completed in the ESOZ reservoir. Notably, the first horizontal well was drilled in 1995. Since then, 145 wells drilled were horizontal, representing a significant progression in development strategy. Horizontal wells account for 12% of the wells currently producing and contribute 18% of the total ESOZ production.