Successful Application of Production Optimization Models to Sustain Field Target and to Defer Capital Investment in Offshore Khafji Field

Abstract

Abstract Khafji field, lies in the Arabian Gulf 40 km offshore east of Al-Khafji, Saudi Arabia, commenced production in 1961, and is currently producing with average rate of over 300MBOPD. The artificial lift, by limited capacity of 25 MMSCF/D of lift gas, was introduced in 1988 which could successfully sustain field target.Although the additional artificial lift energy was required to sustain the target rate, production optimization was found one of the solutions to prolong to sustain the target, which could result in deferring a huge capital investment. The paper describes the construction and use of general optimization and allocation models for Khafji field which simulates the combined performance of the reservoirs, wells and surfaces gathering network. Individual well models and surface gathering network have been built from the mid of perforations to separators at GOSPs.The more accurate multiphase flow correlation has been selected to generate performance curves.These models were calibrated and validated against actual field data with (−1.2%) average percentage error, (2.5%) average absolute percentage error and (3.5%) standard deviation, then lift gas was automatically re-distributed between wells. A marginal gain of approximately 12,000 BOPD was concluded by lift gas optimization, and an additional gain of 15,000 BOPD can be obtained by flowline de-bottlenecking with some additions and revisions of flowline network to reduce wellhead back pressure. Finally, these models are useful tool for production optimization to sustain field target also for routine production operations taking into account the field and system constraints, furthermore prediction of future system requirements.