Diversion and Cleanup Studies of Viscoelastic Surfactant-Based Self-Diverting Acid

• DOI: 10.2118/86504-pa
• Publication Date: 2007-12-06T23:47:00Z
• Authors: Bernhard R. Lungwitz; Christopher N. Fredd; Mark Edward Brady; Matthew Jack Miller; Syed Afaq Ali; Kelly N. Hughes
• Keywords: Brine

Summary A self-diverting-acid based on viscoelastic surfactant (SDVA) has been successfully used recently numerous stimulation treatments of carbonate formations in various fields. The decrease acid concentration during the spending process viscosifies fluid through transformation from spherical micelles to an entangled wormlike micellar structure while penetrating rock. highly viscous acts as a temporary barrier and diverts into remaining lower-permeability treating zones. After treatment, SDVA breaks when contacted either by formation hydrocarbons or pre- postflush fluids. Quantifying diversion, efficiency, cleanup are important factors for successful candidate selection job design. Laboratory tests defining these key presented this paper. This paper demonstrates diverting ability function permeability, characterized introducing concept maximum pressure ratio (dPmax/dP0) supported core-flow conductivity using limestone dolomite cores. Results demonstrate high dPmax/dP0 high-permeability cores low low-permeability Retained permeability measurements that assess level cleanup. Flow-initiation experiments spent systems with gas brine were performed illustrate behavior comparison gelled under conditions encountered oil wells. results indicate clean up easily provides higher regained than conventional systems. Background purpose matrix reservoirs is wormholes, which can bypass damaged areas increase effective wellbore area. When enters highest injectivity it creates conductive flow channels, called dissolving carbonate-containing minerals. Consequently, will be further increased. other zones left untreated acid. To overcome problem, agent used. Mechanical diverters such ball sealers, degradable rock salt, benzoic flakes alone conjunction chemical foams polymeric gels (Williams et al. 1979; Economides Nolte 1989). These materials work effectively only narrow contrast may result residual damage (Lynn Nasr-El-Din 2001). characteristics undesirable, particularly low-pressure wells, long vertical horizontal sections. Polymer-based in-situ crosslinked acids (XLGA) have field self-diverting rely pH-triggered viscosity process. Essentially, pH change activates metallic reagent crosslinks polymer chains, resulting causes resistance (Mukherjee Gudney 1993; Saxon 1997). Further deactivates crosslinker down original linear gel dissociated chains. However, because nature potential occur Recently, new polymer-free system was developed stability temperatures greater 300°F (Taylor 2003; Chang applied both (Al-Mutawa 2001) acid-fracturing (Al-Muhareb Artola 2004) treatments. It rapid development throughout reduction concentration, together simultaneous release ions solution, promotes worm-like micelles, increased fluid. subsequently treatment lower reducing loss improved zonal coverage interval. Diversion multiple parallel varying permeabilities showed all presents data providing insight understanding unique properties laboratory studies. Specifically described physical fluid, including efficiency relevant reservoirs.