Abstract

This paper presents how streamline technology in combination with conventional water injection management indicators was used to effectively manage water injection in a giant field. Describing the relationship between injectors and producers is obtained from a streamline simulation model. Adjusting injection requirements only, based on well streamline injection efficiencies, is not possible for all regions of the reservoir since a good history-match is not always achieved in all regions, particularly for a giant simulation model with 520 producers and 160 injectors. Thus, conventional water injection management indicators like injection/production ratio(IPR) target per segment, reservoir pressure distribution and maximum water injection plant facilities should be taken into consideration to distribute the water efficiently.

The new proposed methodology, through an iterative process, links the streamline simulation results to the practical aspects of conventional peripheral water injection management considering water injection facilities constraints and routine reservoir performance metrics. The new approach improves injection efficiency for all segments simultaneously in a single run. We have accounted for redistributing water injection among several segments connected to a single/multiple water injection plants (WIPs). Results indicated that a similar oil production rate can be obtained through optimization. The main benefit is that water injection is managed more effectively with the excess amount of water not injected in a particular month or quarter, could be transferred and injected into other fields.

Introduction

Water injection is the most common pressure maintenance scheme in many carbonate reservoirs. Streamline-based simulation is highly efficient in solving large, geologically complex systems where fluid flow is controlled by well positions and heterogeneity 1,2,3,4. Streamline simulation has been applied successfully to a wide range of reservoir engineering problems such as ranking geological models 4,5, upscaling from fine scale models 4,5, injection efficiency 6, well allocation factors and pore volumes 4,7, integration of water cut and tracer data into reservoir description 4, and history matching 4,6,7.

Ghori et al 3 formulated an optimization methodology to enhance the overall injection efficiency across a giant field and generate injection rates using streamline simulation on a segment basis. The proposed methodology was based on the premise that in any given segment the overall injector efficiency of the segment can be improved by increasing the injection rates of good injectors and decreasing the injection rates by the same amount in poor injectors. The formulation assumes that the changes done to injectors located in that segment will not impact other nearby segments. This formulation is missing the link to the practical aspects of water injection management since there is inter-segment fluid flow among segments. In the practical context, the reservoir engineer should set up the targets for all wells connected to a WIP on a monthly or quarterly basis.

Injection/production ratio (IPR) is a key performance indicator as part of the reservoir management process metrics 8. The new proposed methodology presented improves water injection management by liaising the streamline injection efficiency concept with the IPR ratio. This ratio is a conventional reservoir management key performance indicator. In addition, the proposed injection rates are constrained when taken into account the maximum injection rate at a well, segment, and water injection plant.

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