In the Gulf of Mexico and other parts of the world, bit balling and differentially stuck pipe has resulted in lengthy and costly drilling delays. In recent years the most effective mud system to combat these problems has been oil-base muds. Oil muds provide superior shale inhibition characteristics and excellent lubricity. However, due to increasing environmental concerns and regulations, in certain cases oil muds have become unacceptable options. Viable water-base alternatives, on the other hand, have been developed to incorporate the desired inhibitive and lubricous properties associated with oil-base muds without the problems associated with disposal. Recently an operator planned an offshore Louisiana multi-well program of directional wells through depleted sands. Past problems in the area include bit balling in hydratable shale sections and differentially stuck pipe in subnormally pressured zones. Until recently oil muds have provided the only solution. After researching the field and testing various inhibitive water-base fluids, the operator implemented a polyglycol (PPG)/aluminum complex water-base system. This system imparts lubricity and shale inhibition characteristics approaching that of an oil-base mud but without the environmental liability. To date nine wells have beep successfully drilled with the PPG / aluminum complex fluid with no occurrence of stuck pipe, bit balling, or wellbore instability. Additionally, the operator has been able to reduce its total well costs which can be attributed to the following: (1) reducing the number of bits, (2) reducing the number of drilling days, (3) reducing the size of the drilling rig, (4) eliminating the incidence of stuck pipe, and (5) eliminating disposal costs.

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