oa Improved drilling performance in re-entry wells using high-performance waterbased drilling fluid in Bahrain’s Awali field

Bahrain’s Awali field, the Arabian Gulf’s first field discovered in the 1930s, has declined in production by almost 50% over the past 30 years. Specialized drilling techniques, such as re-entry drilling, have brought new life to the field. Due to the highly deviated and challenging horizontal sections often encountered on re-entry wells in the Middle East, non-aqueous fluid (NAF) systems have typically been required to provide maximum drilling performance, wellbore stability and deliver lower overall well costs. However, environmental constraints, disposal restrictions, and risks associated with the handling of the NAF systems negate the benefit of their use. While providing the necessary level of compliance, conventional water-based mud systems used in the Awali field have proven to be particularly ineffective at providing acceptable rates-of-penetration and wellbore stability. As a result, non-productive time (NPT) has increased and larger holes sizes are needed for successful liner placement. A high-performance water-based mud<br>(HPWBM) has been successfully used by the Bahrain Petroleum Company (Bapco) in the Awali field as an environmentally compliant and cost effective alternative to traditional NAF. The HPWBM was able to provide considerable improvement in WBM performance in these re-entry wells. It also provided the necessary wellbore stability and reduced formation damage required for open-hole completion. Additionally, pre-planning and communication with Bapco’s engineers resulted in the targeting of potential problems, such as limited hydraulics and zones of poor hole cleaning, allowing corrective action to be taken throughout the drilling process. This presentation discusses case histories of several re-entry wells that have been drilled in the area, along with a detailed overview of the HPWBM system and its benefits. Additionally, a discussion of the engineering that went into the planning and execution of these successful reentry wells is presented.