Acid Fracturing of Low Permeability Carbonate Formation Lessons Learned

Abstract

This paper provides information on the journey and lessons learned from one well’s acid MSF from the required lab design, through on-site fluids’ QA/QC findings, to the 4 days of flow back sample analyses indication. Several pre-job lab assessments were conducted to: Optimize the diversion fluids rheology, assure sufficient acid corrosion inhibition, and eliminate the incompatibility issue between all pumped fluids and the reservoir acid sensitive crude oil. Additionally, on-site QA/QC critical findings for each stage fluid resulted in taken corrective actions for assured acceptable concentration and stability of mixed acid recipes and the adequacy of fracturing fluid viscosity. The 4 days of flow back samples analyses revealed the need for a longer cleanup time. In addition, ion composition of flowback samples were used to identify areas of improvement and enhancement in fracturing fluid design. The successful massive multistage acid fracturing was achieved with over a two-fold increase in production rate. A major part of the success is attributed to a scheme of the fluid’s optimization, quality control, on-site QA/QC and cleanup monitoring progress. In addition, on-site fracture treatment evaluation for each stage individually has a major impact on operational success utilizing pressure sensors response and fracturing simulation software. Finally, a comprehensive analysis for an acid fracture job and the lessons learned from this operation will be shared. The journey of lessons learned started from the lab to the field, and back to the lab, with strong guidelines for all future acid fracturing jobs in similar oil fields

Innovative Encapsulating Acid with Release Dually Controlled by the Concentration of Hydrogen Ions and Temperature

“…As an essential means of oil and gas well stimulation, acid fracturing has been widely used. − Acid fracturing can establish a high-conductivity oil and gas flow path from the deep formation to the wellbore, relieve near-well zone damage, and improve the productivity of oil and gas wells. − However, the rapid chemical reaction between acid and rock minerals limits the acid fracturing efficiency, whereas the rapid acid–rock reaction near the well reduces the effective penetrating distance (EPD) of a fresh acid. , The existing measures to increase the effective distance of acid include usage of a preflush liquid to cool down, retarded acid application, − and improvement of the construction displacement . The above methods can improve the EPD of the acid to a certain extent, but there are still some problems to be considered.…”