Successful Deployment of Acid-Resistant Dissolvable Frac Ball for MuLti-Stage Acid Stimulation Application in an Offshore Multi-Lateral Well
Authors: Arias Rommel , Bernal Ricardo , Shakeel Muzzammil , Normand Marc 
Published: October 2022

Abstract
Multi-stage matrix acidizing is a common stimulation technique applied in low permeability carbonate reservoirs to increase hydrocarbon production. Frac balls are utilized to activate stimulation sleeves to achieve pin-point stimulation. Frac balls used during each stimulation stage also help in isolating the already stimulated lower zones. However, subsequent milling interventions are required after stimulation to remove conventional composite or steel frac balls. Utilization of dissolvable frac balls eliminate the need of milling interventions and allows an obstruction-free path to the produced fluids. An overview of acid-resistant dissolvable frac balls deployed in a multi-lateral offshore multi-stage stimulation (MSS) application in conjunction with acoustic sensors is presented in this paper.
A tri-lateral offshore well was drilled and completed with stimulation sleeve completions to perform multi-stage acid stimulation. The lower completion consisting of open-hole swellable packers and stimulation sleeves was successfully deployed with a metal-to-metal seal expandable liner hanger. The stimulation sleeves were successfully shifted open by the dissolvable frac balls. An additional real-time confirmation of the stimulation sleeve opening event was recorded with an acoustic system for every acid stimulation stage.
Acoustic sensors provide increased operational efficiency through real-time diagnostic of dissolvable frac balls as they reach their respective baffles. Prior to deployment, the dissolvable frac balls were tested in a laboratory at downhole conditions to ensure that self-dissolution requirements of the frac balls are fulfilled. The dissolvable frac balls were successfully deployed in the offshore tri-lateral well, achieving required zonal isolation and hydraulic pressure integrity during multi-stage acid stimulation. Acoustic sensors provided real-time detection of each stimulation sleeve shifting open once the dissolvable balls reached their respective baffles. After the successful acid stimulation treatments, the frac balls dissolved from downhole conditions alone, allowing the return of full well-bore access on the three laterals for production. The utilization of dissolvable frac balls eliminated the subsequent coiled tubing milling interventions required with conventional frac balls after the stimulation. Significant costs and rig time was saved with this technology optimizing the post-stimulation phase of this tri-lateral well while achieving complete stimulation objectives. The dissolvable frac balls have proven to be acid-resistant in nature, with a differential pressure rating of up to 8,000 psi and temperature rating of up to 300°F.
The paper presents the successful application of an acid-resistant dissolvable frac ball deployed in a challenging offshore environment. The dissolvable frac ball technology proved to be successful under these challenging environments, saving significant time and intervention costs. Additionally, the application of an acoustic sensors is also discussed, which allowed efficient completion design and seamless execution.