This paper describes Saudi Aramco’s initial experience introducing Underbalanced Drilling (UBD) technology in the Ghawar field. The intention was to prove that a step change in performance could be achieved by the application of this technology. Thus the intent was to optimize well design that will result in reduced unit well cost. The reasoning for applying this technology in power water injection wells (PWI) was the low risk involved in drilling these wells. The primary objective of drilling wells underbalanced was to eliminate formation damage and improve injectivity, thereby eliminating the need for acid stimulation. Further, increased rate of penetration (ROP) will result in reduction in drill time and cost. A major campaign was implemented in the Ghawar field to evaluate UBD in Saudi Arabia. Injection rates were dramatically improved and the need for acid stimulation was eliminated. ROP increased significantly when compared to conventional PWI wells. By the time this paper was completed, three oil wells had been drilled underbalanced. The drilling operations and some of the safety issues only will be highlighted. The operations and results are still being evaluated and hopefully will be presented in the near future.

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