Production Enhancement for Khafji Field Using Advanced Optimization Techniques

Abstract

Abstract The gas lift, by limited capacity of 25 MMSCF/D, was introduced for Khafji field in 1988 which could successfully sustain target rate until mid of 2004. Artificial Lift is part of the long term production sustainability solutions for Khafji Field necessitated by the increase of field water cut and depletion of reservoirs. In order to make up for production decline in Khafji Field and to sustain the field target rate and defer large investments associated with exploration and drilling new wells as well as commissioning new facility expansions, Production Optimization and de-bottlenecking of the existing production system was found to be the best cost effective solution. For that purpose, general optimization and gas lift allocation models have been built and applied for Khafji field as presented by Ghoniem et al1, 2. This paper is an extension to the previous papers for Khafji Field cited above. The optimization approach presented in this paper is based on a field-wide production planning solution, which is achieved by combining steady-state multiphase network simulation with a nonlinear, multivariate optimization technique called Genetic Algorithm (GA) through a newly developed and commercially available optimization application called Avocet Gas Lift OptimizerTM. The present work therefore represents the introduction of a new optimization platform for Khafji crude production and its results with a particular focus to:Building a comprehensive network model for Khafji Field (including wells and production facilities).Demonstrating production gain by the use of advanced optimization techniques (e.g.GA) to sustain field quota.Optimally distributing limited gas lift availability to Khafji Field to enhance production, while taking into multiple well and field constraints. Introduction Khafji field lies in the Arabian Gulf, 40 km east of Al-Khafji city, Saudi Arabia (Fig. 1).The field is composed of several reservoirs for sweet crude. The most prolific ones are 1st and 2nd Bahrain sand. Where, a strong and an active aquifer provides pressure support and water drive to 2nd Bahrain and to a lesser extent to 1st Bahrain. In addition, four other oil reservoirs are currently active namely Ahmadi limestone, B-limestone, Wara sand and Zubair sand which are commonly referred to as minor reservoirs. In Khafji field, there are approximately a hundred wells which are already completed with gas lift injection system. Even though, many remaining gas lift wells are still producing naturally with lower rate, some others are currently being shut in. Thus, the most effective wells for gas lift operation were defined by performing lot of screening using gas lift allocation models.