Lessons Learned and Guidelines for Matrix Acidizing With Viscoelastic Surfactant Diversion in Carbonate Formations

Abstract

TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractTo conventionally drill, complete and produce horizontal and multilateral wells with zero skin is not an easy undertaking. Much attention has been given to "best oil field practices" in both drilling and production processes, but the reality is that formation damage will often have to be addressed sometime during the life time of the well.Formation damage due to drilling and scale formation is common problem in carbonate reservoirs that can be remediated using chemical means. The success of any treatment however, requires a complete understanding of the problem and a solution that will address the majority of the damage. The solution evolves with time and experience. Extended reach intervals with variable permeability complicate the process. Reservoir and fluid characteristics, cleanup fluid chemistry, and operational considerations must always be considered.The acidizing experience and an improved understanding of how to effectively treat long and heterogeneous intervals in carbonate formations is rapidly evolving in Saudi Arabia. Water injectors, oil producers and wastewater disposal wells have been treated and are reviewed in this study. These wells have different configurations including: vertical, horizontal, extended reach, and multilateral with open hole and cased completions. Several acid placement and diversion techniques have been applied and a specialized treatment package was developed based on the latest coiled tubing and chemical diversion technologies. Laboratory studies, lessons learned and specific design guidelines from both successful and less than expected well treatments are highlighted in this work.

Recent Advances in Viscoelastic Surfactants for Improved Production from Hydrocarbon Reservoirs

“…Upon the reaction of acid with carbonates, the pH increases and the concentration of divalent cations in solution increases and therefore the VES-based acid system starts to build viscosity. At pH around 4, the viscosity of the spent acid will be high enough to divert the fresh acid to low permeability un-contacted zones and fresh acid starts to penetrate and react with these rocks to form wormholes (Nasr-El-Din et al 2006b;Crews and Huang 2007;Huang et al 2008b;Yu et al 2011). The viscosity of VES fluids can be reduced upon mixing with hydrocarbons.…”

Innovative Combination of Dynamic Underbalanced Perforating with Emulsified Acid and Non-Damaging Viscoelastic Surfactant-Based Fluids Boost Productivity in Low-Permeability Naturally-Fractured Carbonates

“…A principal feature is that it can reach high viscosity without adding solids, polymers, or metals to the mixture, achieving a better stimulation placement without leaving residues that may damage the formation. The diverter is designed to break when it comes in contact with the produced hydrocarbons or solvents (Arangath et al, 2008;Lungwitz et al, 2004;Nasr-El-Din et al, 2006).…”

Application of Viscoelastic Surfactants as Mobility-Control Agents in Low-Tension Surfactant Floods

“…Surveying the papers published during the past two years we may conclude that practical application of VES in hydraulic fracturing as component of fluids 13,14 , foams 15-18 and diverting system 19 became almost universal in low permeability porous and fractured reservoir. They have been widely used in matrixacid treatments 19,20 and acid fracturing in unconventional gas production 21 for stimulation of deep gas wells. These experiences clearly demonstrate that improvements of turbulent drag reduction, less formation damage, easier production rehabilitation combined with favorable flow and rheological properties are such physical and chemical properties of VESs, that make them extremely attractive for utilization in other areas of oil and gas production including primarily the IOR/EOR technologies.…”