Abstract
Water shows in the Gachsaran Formation in Iran occur primarily in limestones and may be of high pressure and volume. These high-pressure water shows, often exceeding overburden pressures, and their erratic distribution are thought to be attributable to the tectonic conditions of the Gachsaran Formation.
Drilling through these high pressure water bearing and plastic formations requires mud hydrostatics that generally equal and are sometimes higher than overburden pressures.
High mud weights, with their inherent high solid ratios, create problems that are unique and can be solved only with proper, formulation problems that are unique and can be solved only with proper, formulation and close control.
These muds must be followed with cement slurries of approximately the same weights to prevent water flows during casing cementations. The various additives that go into these slurries are selected with utmost care so that heavy weight slurries can be mixed with good stability and flow characteristics.
1. Super Heavy Weight Drilling Fluids
In South Iran drilling through the Gachsaran formation, which is plastic and charged with high pressure formation water, frequently requires mud hydrostatics in excess of overburden pressures.
