Self-generating foamed drilling fluids

A method for controlling production of hydrocarbons from a well bore during drilling operations, which method comprises:

• a. providing a drilling fluid, which drilling fluid comprises an aqueous solvent, a polymer, a surfactant, and a first foam generating agent;
• b. admixing a second foam generating agent into said drilling fluid, whereupon said first and second foam generating agents react to generate a gas within said fluid and thereby to foam said fluid;
• and
• c. introducing said fluid into said well bore prior to or after admixing said second foam generating agent.

A method for controlling production of hydrocarbons from a well bore during drilling operations, which method comprises:

• a. pumping a drilling fluid comprising an aqueous solvent, a polymer, a surfactant, and a first foam generating agent into a drill string with a hydraulic pump;
• b. admixing a second foam generating agent into said drilling fluid after said drilling fluid has exited said hydraulic pump, whereupon said first and second foam generating agents react to generate a gas within said fluid and thereby to foam said fluid;
• c. circulating at least a portion of said foamed drilling fluid through said drill string into the annulus between said drill string and said well bore;
• d. recovering said drilling fluid from said annulus.