Wellbore fluid loss additive composition

Abstract

Abstract The novelty lies in the use of a group of thermoplastic resins in the form of solid particles which serve as bridging materials, i.e., they plug the pores and fissures of a porous zone of wellbore formation and form a base on which a filter cake may form. The bridging particles are incorporated in the circulating fluid, and are deposited therefrom on the porous formation. The composition of the bridging particles is best described as a saturated thermoplastic resin derived from the polymerization of hydrocarbons; the resin is preferably amorphous or crystalline, and has a relatively high melting point, considerably higher than the temperatures in the wellbore, so that in its preparation it can be mechanically crushed and in use has sufficient strength to avoid deformation. The site of the particles is essentially greater than 50 microns. The class of resins suitable for the purpose is essentially insoluble in aqueous wellbore fluids, but is soluble in produced hydrocarbon fluids such as oil and condensate. After bridging the pores and fissures with such resin, fluid loss control is established by the use of colloidal additives such as lignosulfonates complexed with a trivalent cation and a divalent base. Pressure in the wellbore fluid is maintained at a pressure exceeding the formation fluid pressure during all operations being performed, e.g., drilling through the productive zone, running in casing, cementing, etc. When the well is properly prepared for production, fluid pressure within the wellbore is reduced below the formation pressure, and oil in the formation flows toward the hole. The plug is dissolved by the oil itself, owing to the solubility of the bridging particles in the oil, and production is commenced without the need for acidizing, mechanical abrasion of the plugged zone, or the like.

Inventors

• 👤 Jack M Jackson
• 👤 Arlynn H Hartfiel

Bibliographic Details