Method for variable density acidizing
AssigneeMobil Oil Corporation
InventorAlfred R. Jennings, Jr.
Life of this patent
Estimating the term…
Abstract
A process for acidizing a formation where variable density acids are utilized. A substantially low density non-reactive fluid is loaded into an interval of the formation to be treated. Afterwards, a high density first stage acid is injected into the interval. Thereafter, a low density spacer fluid is injected into the interval being treated. Next, a second stage high density acid having a density lower than the first stage acid is injected into said interval. Subsequently, a low density spacer is injected into the interval. Volume increments are repeatedly injected with decreasing fluid densities until a desired zone has been treated. The entire treatment is then overflushed with an inert high density fluid.
Claims22
A method for acidizing a formation where variable density acids are utilized comprising:
- a) loading via a wellbore all productive intervals of the formation with a low density non-reactive fluid which fluid is compatible with the composition of the formation;
- b) injecting a first stage acid into the wellbore which acid has a density greater than the non-reactive fluid and is sufficient in density to flow to the bottom of the wellbore so as to be in fluid communication with a lower productive interval of the formation;
- c) injecting thereafter a low density spacer or non-reactive fluid into the wellbore which spacer has a density less than the first stage acid;
- d) injecting next a second stage acid into the wellbore which acid has a density less than the first stage acid spacer injected in step c) which precludes liquid acids from mixing with each other as the second stage acid enters a productive interval above the interval in step b);
- e) injecting a spacer into the wellbore above the second stage acid which spacer has a density less than the spacer in step c) and previously injected acid stages thereby preventing mixing of the liquids;
- f) repeating the acid stages and spacer injections with decreasing densities of liquids until all desired productive intervals have been treated with acid;
- and
- g) overflushing all intervals of the formation with a non-reactive fluid that has a density greater than any of the previously injected acid stages or spacers thereby forcing them into the intervals and cleaning out the wellbore.
A method for acidizing a formation where variable density acids are utilized comprising:
- a) loading via a wellbore all productive intervals of the formation with a low density non-reactive fluid which fluid is compatible with the composition of the formation;
- b) injecting a first stage acid into the wellbore which acid has a density greater than the non-reactive fluid and is sufficient in density to flow to the bottom of the wellbore so as to be in fluid communication with a lower productive interval of the formation;
- c) injecting thereafter a low density spacer or non-reactive fluid into the wellbore which spacer has a density less than the first stage acid;
- d) injecting next a second stage acid into the wellbore which acid has a density less than the first stage acid spacer injected in step c) which precludes liquid acids from mixing with each other as the second stage acid enters a productive interval above the interval in step b);
- and
- e) overflushing all intervals of the formation with a non-reactive fluid that has a density greater than any of the previously injected acid stages or spacers thereby forcing them into the intervals and cleaning out the wellbore.
Dependencies are inferred from the claim text.