Viscosity-Reducing Agents (Breakers) for Viscoelastic Surfactant Gels for Well Stimulation

Abstract

The stimulation of oil and gas wells is an essential component of hydrocarbon production. One of the ways to perform well stimulation is to use gels. These gels have been used along with breakers to prevent the gels from blocking the pathway for reservoir hydrocarbons to flow into the newly stimulated wells. Viscoelastic surfactant (VES) gels have several advantages over polymer gels because they present a lesser risk of formation damage than polymer gels. However, there is no compilation of breaker classes used for VES gels. Given the importance of breakers and VES gels, the review compiles the types of breakers available for VES gels and describes the viscosity reduction mechanisms induced by the breakers. VES gel breakers can be classified into external and internal breakers. External breakers contact the VES gels in the reservoir, while internal breakers are injected into the reservoir along with the VES. External breakers include reservoir oil, mutual solvent, and microorganisms, such as bacteria. Internal breakers consist of proteins, acids, alcohols, polymers, modified nanoparticles, oxidizing agents, or a combination of these classes. Laboratory studies have shown that internal breakers are more efficient than external breakers. As to how viscosity reduction occurs, the breakers change the wormlike micelles in the gels. Wormlike micelles could be converted to microemulsions or shortened. In some cases, the molecular structure of VES is altered, leading to the destruction of the wormlike micelles. Nevertheless, some of the proposed mechanisms have not been confirmed because their delineation relied only on rheological data. Finally, there are reports on the successful use of both external and internal breakers in the field. To conclude, breakers have been used successfully with VES gels to improve hydrocarbon production. However, internal breakers may significantly improve hydrocarbon production when compared to external breakers.

Specific-Ion Effects Unveil a Route for Modulating Oxidatively Triggered Acid Systems for Reservoir Applications

“…FT-IR spectra were recorded on an Agilent Technologies MicroLab spectrometer (4000−600 cm −1 ). 1 (aq)] solution was then added to the acid solution under continuous stirring. Additional ammonia solution was added until the pH of the solution reached ∼8.5.…”

“…Oxidizing agents are ubiquitous material additives in the upstream sector of the oil and gas industry. Historically, they are used as biocide agents and viscosity modifiers in hydraulic fracturing fluids. − More recently, a new type of reactive fracturing fluid was proposed, and its chemical properties enable oxidative degradation of kerogen, a polymer-like intertwined organic material, present in unconventional source rock. This unique reactivity allows for increased hydrocarbon recovery by physically cracking the organic matter and opening conductive channels to enable the flow of hydrocarbons. , Another unique use of oxidizers for potential reservoir stimulation applications is in situ acid generation where bromate (BrO 3 – ) can selectively oxidize ammonium (NH 4 + ) to liberate acid (H + ) yielding a series of inorganic acids …”

Performance Evaluation of Enzyme Breaker for Fracturing Applications under Simulated Reservoir Conditions

“…Second, they can effectively “break” guar polymers into monosaccharides or oligosaccharides, leading to a significant reduction in the amount of residue generated [ 19 ]. Third, the gel-breaking reaction performed using enzyme breakers is mild and controllable, guaranteeing a sufficient supporting force at the initial stage of fracturing construction to enable crack formation and deliver the proppant [ 20 , 21 ]. However, the stability (spatial structure) of enzyme breakers is strongly affected by environmental factors, such as temperature and pH [ 22 ].…”

Deducing the Relation between Viscosity and Oil-Induced Structural Changes of Viscoelastic Surfactants Using a Kinetic Approach

“…The hydrophobic sections of the molecules are inward in the WLM, making the core of the WLM a favorable environment for the hydrophobic moieties to reside. The solubilization capabilities of WLMs are exploited in drug delivery for the treatment of cells and tissues and well stimulation applications such as acidizing and fracking . Solubilization also needs to be considered in the formulation of hair and body care products .…”

“…The solubilization capabilities of WLMs are exploited in drug delivery for the treatment of cells and tissues 16 and well stimulation applications such as acidizing and fracking. 17 Solubilization also needs to be considered in the formulation of hair and body care products. 18 Given the importance of solubilization in these sectors, studies have been undertaken to explore the changes solutions with WLMs undergo with time during solubilization.…”