Abstract
Development of water-based mud systems that approach the performance of oil-based muds is an ongoing effort. Starch-lubricant compositions were developed as environmentally safe, non-toxic, stable dispersions in water-based drilling muds. Starch-lubricant compositions were prepared by jet cooking mixtures of water, starch, and lubricant to produce aqueous starch dispersions containing suspended lubricant droplets 1-10 microns in diameter. These droplets do not separate or coalesce. The dispersions were drum dried and milled to dry, non-oily powders containing 28% lubricant by weight.
These dry powders were then tested at 5 lb/barrel in laboratory-prepared lignosulfonate drilling muds. Various commercial olefins, esters and/or polybutenes were evaluated as lubricants. Standard laboratory tests indicated that starch-lubricant compositions lowered both API and HTHP fluid loss values. More importantly, coefficient of friction values were 12-25% of the untreated base mud and were similar to the average values for oil-based muds. Muds formulated with starch-lubricant compositions usually contained only 0.5% lubricant (v/v), yet performed better than a typical field mud control containing 3% lubricant (v/v).
These exceptionally good results with one-sixth the amount of a typical lubricant suggest that the size and distribution of lubricant droplets achieved in these systems may enhance lubricant efficiency. Therefore, further investigation of such formulations is warranted, including a field test to evaluate the advantages of this newly-patented technology.
