Shell Oil Comapny

James H Lybarger

Edwin A Richardson

Ronald F Scheuerman

Charles C Templeton

Joseph Reisberg

David C Berkshire

Portions of a subterranean reservoir are temporarily plugged by injecting an aqueous liquid solution which contains nitrogen gas-generating reactants, a foaming surfactant and a pH controlling system arranged so that the solution remains relatively unreactive within the well but forms a relatively immobile foam within the pores or other openings within the reservoir formation.

Temporarily plugging a subterranean reservoir with a self-foaming

The clay dissolving capability of an aqueous mud acid solution of weak acid, weak acid salt and fluoride salt (of the type described in the E. A. Richardson U.S. Pat. No. 3,889,753) can be increased by including in the solution a partial salt of an aminopolyacetic acid chelating or complex-forming agent.

Increasing the clay dissolving capability of a buffer-regulated mud acid

The clay-dissolving capability of a self-generating mud acid comprising an aqueous solution or dispersion of a fluoride salt, an ester of a 1-5 carbon atom aliphatic alcohol and a 2-5 carbon atom fatty acid suitable for use at temperatures exceeding about 180.degree. F is improved by adding an effective amount of an aminopolyacetic acid salt chelating or complexing agent.

Increasing the clay-dissolving capability of a relatively high pH

A subterranean reservoir is plugged by injecting a suspension containing solid particles of a resin capable of softening and resolidifying at the reservoir temperature. The particle sizes are correlated with the reservoir pore sizes so that particles are screened-out within and along the face of the reservoir formation. And, the particle compositions are correlated with the reservoir temperature so that the screened-out particles in and along the reservoir formation become fused into a substantially impermeable layer.

Plugging a subterranean reservoir with a self-sealing filter cake

The fluid productivity of a relatively unconsolidated oil producing subterranean siliceous reservoir is improved by a limited flow rate sequential injection of oil solvent, relatively dilute hydrogen fluoride-free acid, and relatively dilute hydrogen fluoride containing-acid, and a gradual returning of the well to production.

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Houston, TX, United States of America

James H Lybarger