The Compatibility of Egyptian Bentonite during Drilling Shale Formations

摘要

Drilling fluid is a vital element of the drilling process, and any drilling fluid must have common properties that facilitate safe and satisfactory completion of the well. The main component of water-based mud is clay (mostly bentonite). The present consumption of bentonite clay in drilling operations alone can reach over 100,000 tons a year and all of it is imported. The high consumption and import costs of this material have led to an attempt to find a local substitute. In this work, we are concerned with the changes that take place in the rheology and properties of the water-based mud using Egyptian bentonite from the south Hammam area, which is produced by the Egyptian Drilling Derivatives Company, instead of imported bentonite and study the behavior of the Egyptian bentonite during drilling through the shale rocks due to the swelling and expansion of the shale. The water-base mud was prepared using Egyptian bentonite from the south Hammam area and circulated with shale under the same conditions of the well borehole using and oven roller device and the rheological properties and filtration characteristics were determined in order to evaluate the local bentonite. The swelling phenomenon in rocks results from the change in crystal dimensions or grain boundaries, which arises when water is incorporated into the crystal structure or absorbed onto the grain boundaries. This occurs when drilling through the shale formations, in which such swelling affects the rheological properties of mud fluids. Tests were carried out on the shale derived from wells encountered in the shale formation (Eocene-Oligocene) in the northern Western Desert using a roller oven device for the circulation of shale with water-base mud using the local bentonite. This was to determine the percentage of edging shale with aging time and to study the rheological changes of the mud fluids as a result of this circulation, including density by using a mud balance meter, viscosity by using a V-G cup meter, and filtration loss by using a filter press and measuring the filter cake thickness.