Abstract
Objectives/Scope:

The objective of this work was to evaluate the impact of bullhead acid injection on production behavior in an existing unconventional well. Distributed acoustic (DAS) and temperature (DTS) data was collected with deployed fiber optics during production and injection periods. Common wisdom suggests bullhead acid injection is presumed to enter the heel-most clusters, leaving the toe untreated. Although the entire lateral was not logged, the interval of the heel logged provides answers on whether injected fluid treats the heel only or the entire lateral.

Methods/Procedures/Process:

Distributed fiber optics were deployed into an unconventional well during stable production, covering 20% of the lateral.

After the production profile was understood, acid was injected at 5bpm for several hours, during which an injection profile was captured. Following injection and soak, the post-acid treatment production profile was captured and compared to the pre-acid treatment production profile. Both production profiles and the injection profile were derived from an acoustic constrained temperature model.

Results/Observations/Conclusions:

Baseline production profile showed 77% cluster productivity increase to 82% cluster productivity. Liquid production increased 50% following acid treatment.

Overall, 30% of the acid treatment injected entered the heel 20% of the lateral, with the remaining 70% fluid volume going below the logged interval.

Both (1) clusters took fluid under injection and (2) the volume injected varied over time, from 15% to 32% of the total fluid injected, corresponding with pressure gradient change during the injection period.

Displaced solids appear to have activated some previously inactive clusters, and after displacement downhole, to have obstructed some previously productive clusters.

Applications/Significance/Novelty:

Because the bullhead was single-phase, a new, DAS-only flow profile method was used. Multiple injection profile snapshots were captured over several hours, and standard deviation in injectivity was calculated for each cluster to understand if/how injection changed as a function of time, pressure, or other factors. DAS profiles were compared to a temperature-only profile with ∼80% agreement; 20% of the lateral where the injection profiles did not agree correlated with high standard deviation in time-based DAS injection profiles.

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