Horizontal completions in deepwater fields over the last five years have utilized gravel packing as the preferred technique for the retention of mitigating sand production in these often immature sands. Poor gravel packing, completion techniques, and/or the subsequent cleanup of deepwater, openhole completions can result in relatively high intervention costs when less than expected production is realized. Recent literature details the advantages of using an oil-based (OB) or water-based (WB) reservoir drill-in fluid (RDF) as well as the potential problems and concerns associated with both systems. The literature also discusses, in varying levels of detail, the need for cleanup of the residual filter cake, either immediately after completing the gravel pack, or with a post-intervention technique, usually coiled tubing.

The authors will discuss the development of a water-based cleanup system that was utilized in an openhole gravel-pack fluid and as the cleanup system for recent deepwater horizontal wells in a West African field. This developing technique utilizes a chelant and an amine surfactant for dispersing the residual oil-based filter cake. This cleanup is an aqueous system that has demonstrated compatibility from a reversible invert emulsion system. This system has exhibited a delay-period, whereby, the gravel-pack and subsequent isolation of the lateral section can be completed with minimal losses. To date, no post-intervention has been required to clean up serious skin damage and production histories, from these wells, have been impressive.

This paper details the laboratory development of a chelating cleanup system for a reversible RDF. Discussion of the placement of this cleanup system is included. The optimization of the chelating chemistry is discussed with respect to providing a reversal of the invert emulsion filter cake. The need for delaying the reversal is discussed with respect to the evolving completion style, thereby, providing flexibility for future designs. In addition, three field trials are presented for this novel cleanup system.

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