Field Trials of a Novel Fiber-Laden Self-Diverting Acid System for Carbonates in Saudi Arabia

Abstract

Acid stimulation of carbonate formations using hydrochloric (HCl) acid-based systems to improve hydrocarbon production or water injection has been a common practice since the early days of the oil and gas industry. The challenge of achieving full zonal coverage with the stimulation fluid still persists. This task is even more difficult in highly slanted layered, naturally fractured reservoirs exhibiting high permeability and porosity contrast.During acid stimulation treatments, the fluid has a natural tendency to take the path of least resistance, penetrating layers with the highest porosity and permeability while little or no acid is injected into lower-quality zones. Excessive fluid loss to these highquality thief zones results in a nonhomogenous distribution of stimulation fluids across the targeted interval. These higher-quality zones are essentially over stimulated, allowing them to contribute the most to post-treatment production. This leaves neighboring lower-quality zones unstimulated, preventing them from reaching their maximum potential.A novel fiber-laden polymer-free self-diverting acid system was introduced in Saudi Aramco to improve zonal coverage across the entire interval of interest in vertical and highly slanted wells during stimulation treatments. This diversion system combines fiber and a self-diverting acid, which utilizes a nondamaging viscoelastic surfactant that gels as the acid spends. The combination of the self-diverting acid and fiber enhances the diversion process by combining the aspects of both particulate and viscosity-based diversion techniques. The fluid system has a distinct advantage in that it does not contribute to reservoir damage as the viscoelastic surfactant will break down upon contact with hydrocarbons, and the fiber will dissolve with time and temperature.The fiber-laden self-diverting acid system has been applied in new developments and producing gas wells in the Khuff reservoir of Saudi Aramco with impressive results. The diversion and acid reaction signatures were evident in the acquired treating pressure plots during acidizing with the fiber-laden polymer-free self-diverting acid system. The initial results indicated substantial pressure responses and excellent gas production performance.

Creating Multiple Fractures in Cemented Horizontal Laterals: An Efficient Way to Improve Productivity of Tight Carbonate Formations in Saudi Arabia

“…In the case of an OH completion, additional leakoff through the OH section between packers will further worsen the situation. Introduction of fiber-enhanced viscoelastic diverter for acid fracturing treatments helped address this challenge by keeping BHTP above fracturing extension pressure during most of the acid fracturing treatment time (Al-Ismail et al 2008;Jairo et al 2010, Jairo et al 2011Bukovac et al 2012). • When a large horizontal OH section isolated in between two packers is treated, the fracture initiates at the point of local min .…”

Use of Technology to Enhance Sustained Gas Production in Saudi Arabian Carbonate Reservoirs — Key Enablers

“…FVSDA has multiple benefits over PSDA: it is non-damaging to the reservoir and has a stable viscosity gain while acid spends, higher diverting efficiency in matrix and fissures due to stable viscosity and degradable fibers, fracture-tofracture diversion, and some others. Previously published papers (Al-Ismail et al 2008;Leal Jauregui et al 2010;Leal Jauregui et al 2011;Bukovac et al 2012) already showed the efficiency of this diverter for the carbonate formation. Figures 12 and 13 show normalized PI values for vertical and horizontal wells, respectively.…”