Record Performance Achieved on Gulf of Mexico Subsalt Well Drilled with Synthetic Fluid

Abstract

Subsalt wells are notorious for drilling difficulties encountered while penetrating both the salt and adjacent shales. Slow penetration rates, poor hole integrity, lost returns, bit balling, and pack-off problems are typical in these formations.After experiencing a number of these problems when using a conventional saturated salt mud to drill a Gulf of Mexico discovery well through a salt formation, one major operator switched to a synthetic invert-emulsion fluid for the subsequent delineation well. Both wells penetrated approximately 8,000 feet of salt to reach total depth (TD). However, performance improvements resulting from use of the synthetic fluid in the second well reduced drilling by 78 days, generating an estimated savings of $12 million. In addition, the second well included a record bit run of more than 10,000 feet. This paper describes the drilling programs used in the two wells, recounts drilling performance, and discusses the savings achieved.

Cementing Casing Strings across Salt Zones: An Overview of Global Best Practices

“…Typically, pseudo, oil-based (Meize et al 2000), or possibly salt-saturated drilling fluids are used to drill wellbores through large salt sections in an effort to minimize the creation of such washouts. However, it is important to recognize that, even with salt-saturated drilling fluids, washouts can still occur because these fluids are saturated at surface, not downhole, conditions.…”

A Comparative Study of Lost Circulation Materials

“…He added that the product would lack in acid solubility, but prove to be highly soluble in alkaline solutions to increase permeability. Later, Meize et al (2000) investigated recovery of synthetic based drilling fluids using drying methods. Verret et al (2000) also indicated that a water-based gunk treatment was used to drill while penetrating salt and adjacent shale and native clay-making formations.…”