Role of Infill Drilling in Increasing Reserves of the Western Desert of Egypt: Case Studies

Abstract

Summary In 2010, Qarun Petroleum Company (QPC) started an extensive infill-drilling campaign in the Western Desert of Egypt for nine fields, aiming to improve recovery after waterflooding. The well spacing was reduced to half of its original value, and all infill wells were producers. In this paper, we present some key findings from the success stories and lessons learned from the failure cases. The fields of Samra, Asala, Diyur, North Diyur, Yomna, E Bah-C, E Bah-D, E Bah-E, and E Bah-F were developed by waterflooding either from the start of production or after a short period of depletion production. After approximately 2 years of production, high-water-production rates were observed although these fields did not achieve their planned recovery. Several analyses were carried out and showed that significant remaining oil existed. Reasons identified for bypassed oil include lateral-pay discontinuities, completion inconsistencies, and a high level of heterogeneity. Drilling a significant number of infill wells was the key technology suggested to recover bypassed reserves. Initially, the well spacing was approximately 450 m between producer/producer and injector/injector pairs. The well spacing was reduced to a maximum of 300 m to connect pay intervals better, especially for the Upper Baharyia (UBah) Formation reservoir, owing to its high complexity and heterogeneity level. After implementing the infill drilling within the nine main fields, a comprehensive monitoring plan was executed to observe the recovery improvement. Six fields (i.e., Samra, Asala, Diyur, North Diyur, Yomna, and E Bah-D) recorded additional reserves by infill drilling and the other three fields (i.e., E Bah-C, E Bah-E, and E Bah-F) did not achieve the expected increase. Comprehensive integrated analyses revealed that the heterogeneity level and maturity (age) of the waterflood were the main controlling factors in the success of infill drilling. Five main lessons learned are presented (supported with data) for the successful implementation of infill drilling in low-permeability and heterogeneous reservoirs. Analysis workflows are presented for waterflood-candidate selection and for infill-drilling evaluation.