A weighted, all-oil fluid system was developed to activate oil-swell packers and maintain compatibility with water-based filtercakes. This fluid system has enabled the successful installation of multiple openhole gravel pack completions to date.
Traditionally, base oils, such as diesel, serve as activating fluids. The low density of the base oil risks compromising well control and/or borehole stability. There are products available to viscosify the base oil and suspend weight material for some applications, but jobs most require special shearing equipment operating at temperatures above safe limits for base oil. Other products are required at significant concentrations that risk adverse reactions with the water-based filtercake and filtrate. Invert emulsion systems offer greater density and viscosity, but they are incompatible with the water-based filtercakes, risking formation damage.
This new fluid system utilizes a new viscosifying agent that easily mixes using rig equipment along with an acid-soluble, treated weight material to maintain a dispersion in oil. All of the products are micronized to reduce any risk of plugging downhole completion equipment. The all-oil system is spotted in the open hole, allowing the swell packers to expand. The system may either remain in the wellbore to flow back with production or circulate out of the wellbore prior to gravel packing. Flexibility in additive concentrations aids to effectively displacing the fluid in and out of the well.
This paper discusses the development process of this all-oil system in the laboratory and the challenges overcome to deliver a rig-practical solution. A review of field planning and execution is included for the initial wells employing the system.