Field Proven Effectiveness of Near Wellbore and Far Field Diversion in Acid Stimulation Treatment Using Self-Degradable Particulates

摘要

In acid stimulation treatments, acid will enter the most permeable or the least damaged zones. Most of the fluid will flow into the path of least resistance leaving large portions of the formation untreated. A critical factor to the success of an acid stimulation treatment is proper placement of acid so that all productive intervals are contacted by sufficient volumes of acid. The original stimulation fluid flow was altered to achieve uniform placement of treatment fluids during acid stimulation in candidate wells. Particle bridging technique utilizing self-degrading particulates of multiple grain sizes was utilized to achieve successful diversion and fluid placement across the entire interval of interest. Particle size distribution was calibrated for use with both near wellbore bridging across perforations and far field diversion inside wormholes and natural fractures. For self-degradable particulates to be successful as effective diverter, it should have accurate particle size distribution, therefore, a comprehensive well data analysis performed during design stage to recognize the opportunity for combination of far-field and near wellbore diversion systems for acid stimulation treatment. The combination of far-field and near wellbore self-degrading particulate diversion systems allowed the entire intervals to be treated evenly under matrix and fracture conditions, which is usually hard to achieve during acid stimulation treatments utilizing conventional chemical diversion systems, especially in cases where separate sets of perforations would need to be treated with a single stage. Evaluation of the diversion effectiveness was done by running temperature log immediately after the stimulation, which demonstrated satisfactory cool down effect across perforation intervals. This diversion technique was found to be more enhanced to effectively acid stimulate in high temperature carbonate reservoirs of Saudi Arabia. The utilization of self-degrading particulates of various grain sizes for far-field and near wellbore diversions during acid stimulation in high temperature carbonate reservoir was a unique approach and can be further optimized to resolve the challenges of multistage acid stimulation treatments.