Thousands of wells completed in the Midland and Delaware basins demonstrate steep decline over the first months of production due to poor production management or suboptimal completions. This paper will present how a fit for purpose acid restimulation program with Chlorine Dioxide (ClO2) in legacy Wolfcamp wells, originally completed between 2016 and 2019, improved reservoir/well conductivity resulting in increased reservoir fluid production and recovery.
Basic acid treatments utilized in the beginning of the program to reactivate near-wellbore conductivity resulted in industry average results. In the second phase of this workover program, an integrated acid restimulation methodology was utilized. This took into consideration reservoir depletion, wellbore-reservoir connection loss events, landing zones geology and geomechanics, oil/water chemical analysis, and scaling tendencies. Its core element was the use of ClO2 as an oxidizer in the water stages of the acid stimulation treatments to improve reservoir well connectivity. ClO2 (>4,000 ppm) carried in water was used as an activation agent to help re-establish near well bore conductivity and re-activate the reservoir’s natural fractures.
In the geographic area of the wells used in this study, the reservoir fluids contain high iron-sulfide and calcite concentrations resulting in scale deposits in both the near well region and the wellbore causing a degradation in reservoir - well conductivity and therefore, a loss in production. A notable improvement in flowback and production was recorded in wells in which ClO2 was used in acid restimulation. Readings from downhole pressure sensors revealed an increase in bottomhole pressure of as much as 2,000 psi after the acid restimulation. Wells using an artificial lift system demonstrated improved production between 50% to 300%.
Acid restimulation with Chlorine Dioxide (ClO2) as a downhole oxidizing agent helped to improve well - reservoir conductivity with no significant added cost or operational complexity. Increased bottomhole pressure and reservoir fluid production in more than 10 wells is a proof of concept that could be utilized to revitalize hydrocarbon production in thousands of legacy stimulated wells.
