Abstract
This paper focuses on solving drilling problems that includes slow penetration rate, hole tightening, and short bit life. The goals are achieved through the alteration of chemophysical properties of the plastic, troublesome shales (i.e. "gumbo" shale.) Our studies of these issues show that most efforts of the past concentrated more on enhancing the penetration rate through the manipulation of weight on the bit, rotary speed, and other variables rather than by changing the chemistry of rock and drilling fluid and their interaction. As evidenced by setting two world drilling records in 1997, we were able to drill deeper and cheaper by designing and using a new Modular Drilling Fluid System, (MDFS) for the purpose of solving costly drilling problems. The properties and functions of MDSF are as follows. (1) It contains, through a reaction, a host of "anion" radicals linked to esters. Having a low surface tension, the mud filtrate with these radicals diffuses in the shale/rock capillaries rapidly like an "Anionic Wedge." The excess anionic charge adsorbed on the clay fraction of shales and mud particles cause strong repulsive forces within the shale capillaries. These forces in the rock/fluid interaction area weaken the rock shear resistance which result in the enhanced penetration rate due to the removal of the "sticky balling" material from the drill bit. (2) Unlike ordinary surfactants, the MDSF deposits a long lasting and lubricating coat on the shale and mud particles. The chemical "coat" changes physical properties oft the shale and mud particles (i.e. the particles with low friction cause enhanced bit life and less abrasion of drilling equipment).
By applying the new technique of changing chemophysical properties of formation and drilling fluids to the modern drilling technology, the contractors have successfully drilled more than 400,000 ft of hole over the last two years. Both the contractors and the operators have realized the considerable savings over the comparable footage drilled in the past.
