Steam foam methods for steam-assisted gravity drainage
Methods for making efficient use of steam in a steam-assisted gravity drainage (SAGD) process for recovering heavy oils from tar sands and similar petroleum deposits are disclosed. The methods utilize a surfactant to generate steam foam in ways that maximize efficient use of steam. In some aspects, steam foam is used in water layers or gas caps that reside above steam chambers to prevent loss of steam from the steam chamber. The predominant use of relatively dry steam in SAGD processes makes it challenging to find ways to introduce surfactants and generate steam foam. However, decreasing the mobility of the steam by converting at least some of it to foam allows the wellbore and steam chambers above the injection site to be more fully developed, provides for more effective heat transfer to the heavy oil and rock, improves production, and allows recovery of the heavy oil with a minimum amount of steam usage.
1. A method for improving steam utilization in a SAGD process for crude oil recovery, the method comprising:
(a) providing a horizontal SAGD well pair comprising a steam injection well and a production well, said injection well located above the production well;
(b) before, during, or after introduction of steam into the injection well, introducing a surfactant into the injection well through a capillary tube;
wherein the surfactant is selected from the group consisting of alpha olefin sulfonates, alpha olefin sulfonate dimers, internal olefin sulfonates, alkylaryl sulfonates, alkylaryl ethoxy sulfonates, and mixtures thereof; and
whereby the surfactant exits the capillary tube and combines with rising steam to produce a steam foam in the injection well.
2. The method of claim 1 wherein the injection well comprises a steam stringer, and the capillary tube is located inside the stringer.
3. The method of claim 1 wherein the injection well comprises a steam stringer, and the capillary tube is located outside the stringer.
4. The method of claim 2 wherein the capillary tube comprises a spray nozzle, frit, or other dispersing device.
5. The method of claim 3 wherein the capillary tube comprises a spray nozzle, frit, or other dispersing device.