Two re-entry horizontal wells were drilled and completed by short-radius method at Khafji field in 1989, which was the first experience on horizontal drilling in Saudi Arabia and Kuwait. In 1993 horizontal drilling activities were initiated by medium-radius method, and 31 new horizontal wells and 15 re-entry horizontal wells, including the above-mentioned two wells, were drilled and completed so far.In 1991 and 1992, “A Study of Completion of Lateral Holes” and “Rock Mechanics Study” were conducted to establish company's policy and to highlight formation damage control, wellbore stability analysis and drilling fluid properties, respectively. In 1997, “Engineering Study for Horizontal Drilling and Completion” was conducted to review the horizontal drilling performance from 1994 to 1996. In 2000, another review was conducted to further reduce the days and cost.At the beginning of the horizontal drilling activities, a new horizontal well was planned with 70 to 80 days and US 5 to 6 million and a re-entry horizontal well was planned with 45 days and US 3.2 million. Through the many field experiences and studies, the performances and costs of the horizontal wells were reviewed and improved. At the moment, a new horizontal well is planned with 40 to 50 days and US 3.5 million and a re-entry horizontal well is planned with 30 days and US 2.1 million.Our ambitious, aggressive and ultimate target is 25 to 30 days and US 2.5 to 3 million for a new horizontal well and 20 days and US 1.7 million for a re-entry horizontal well.