Additive Effectiveness and Contaminant Influence on Fluid-Loss Control in Water-Based Muds

Abstract

Summary The proper fluid-loss control of drilling muds becomes more difficult when drilling high-temperature, high-pressure formations. Chemical additives for reducing fluid loss differ considerably in effectiveness; in turn, these differences vary, often unpredictably, with temperature and pressure. This paper discloses the results of static-filtration experiments that compare capabilities of various additives to minimize filtrate invasion at elevated temperatures when the mud contains certain common contaminants. The effects of mud weight, high-temperature aging, and the presence of asphalt on mud fluid loss were also investigated. The additives selected for study were WL-100™, carboxymethyl cellulose (CMC), Dextrid™, CC-16™, Resinex™, and several asphalts. Certain combinations of these were also studied. The contaminants used typify those originating from drilled formations: sodium chloride, calcium sulfate, sodium sulfate, cement, and Rev Dust. On a cost-equalized basis, a combination of Dextrid and CC-16 was found to be a good additive for controlling fluid loss at high temperatures and pressures regardless of whether contaminants were present. The additives WL-100 and Dextrid were also effective.