This paper describes a laboratory evaluation of Loss Control Materials (LCM) commonly used to control fluid-loss during completions and workovers and the development of on-site Quality Control procedures for monitoring the performance of the LCM at the well site. In addition to the laboratory results, case histories are provided detailing application of the findings in gravel-packed completions.

Conoco has recently completed five gravel-packed wells in the North Sea. The gravel packs were conducted in two stages: a perforation pre-pack and an annular gravel pack. During this completion procedure, LCM was used to wash excess gravel out of the casing following the pre-pack and to control fluid-loss. Analysis of the first completion indicated production was restricted through the completion. Subsequent evaluation of the completion procedure and LCM products indicated the most likely source of formation damage was residual LCM filter-cake.

Laboratory tests monitoring fluid-loss control, rheology, and formation damage were performed on commonly-used LCM candidates. These candidates included sized-salt formulations, sized-calcium carbonate systems, and polymers from a variety of commercial suppliers. In addition to the evaluation of LCM products, remedial treatment options and a new delayed-release breaker were tested.

Based on test results, an LCM composition using sized-salt, biopolymer, starch, and a slowly-soluble, acid breaker was selected. This composition provided maximum fluid-loss control, maintained adequate rheology, and minimized formation damage in laboratory tests simulating anticipated completion conditions.

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