by The oil and gas industry relies on various stimulation techniques and chemicals in order to maximize recovery from underground reservoirs. As reservoirs age and depletion sets in over time, it becomes increasingly important to improve recovery factors through processes like hydraulic fracturing and acidizing. In this article, we will explore some of the main stimulation chemicals and technologies used to enhance oil and gas production.
Hydraulic Fracturing Fluids
Hydraulic fracturing, commonly known as “fracking”, involves pumping fluid down a wellbore under high pressure in order to fracture tight source rock formations. The fracturing fluid consists of a mixture of chemicals tailored for the specific geology and reservoir conditions. Base fluids such as water, gel polymers, foam or emulsions are used to carry proppant particles like sand deep into the fractures.
Gel polymers: Common gelling agents include guar gum and derivatized guar, which help suspend proppant particles and prevent them from settling out during the fracturing process. Gel polymers increase the viscosity of water-based fluids to effectively transport proppant.
Crosslinkers: Agents like borate or zirconate salts are added to help crosslink the gel polymers and further increase viscosity over time as the fluid interacts with the reservoir rocks. This improves the ability to proppant transport and placement.
Breakers: Enzymes or oxidizing breakers are included to ensure the viscosity break down over time, allowing flowback of fluid after fracturing is complete. This prevents damage to permeability.
Friction reducers: Polymers like polyacrylamide help reduce friction pressure during fluid recovery which is crucial for long horizontal well completions.
Surfactants: Surfactants or emulsifiers allow the use of oil-based or emulsified fluid systems which can carry more proppant capacity compared to water.
Biocides: Biocides protect against bacterial growth which can damage viscosity and fluids over long term exposure downhole.
Scale inhibitors: These chemicals help prevent mineral scale deposition from water onto the fracture faces and inside the produced formation.
Acidizing Fluids
Acidizing involves injecting acid to dissolve minerals in order to increase pore space and permeability near the wellbore. Various acids are used depending on the specific mineralogy to be dissolved.
Hydrochloric acid (HCl): The most commonly used acid, HCl dissolves carbonate minerals like limestone and dolomite very effectively.
Acetic acid: Used for its ability to dissolve carbonates at more moderate temperatures than HCl. Provides slow reaction rates suited for damage removal.
Hydrofluoric acid (HF): Used to dissolve siliceous materials like quartz when present. Requires special handling due to high toxicity.
Chelants: Materials like EDTA help control the rate of acid reaction by chelating or sequestering reactive cations in the formation. This allows for controlled, deep penetration of acid.
Corrosion inhibitors: Chemicals like tallow amines or volatile corrosion inhibitors protect the steel infrastructure from pitting and general corrosion during acid contact.
Surfactants: Surfactants are added to acid systems in order to lower surface tension and enable acid to penetrate through small pore throats and naturally fractured reservoir zones more effectively.
Fluid loss control: Polymers or other materials like calciumbased weighting agents help control fluid leakage off into the formation during the reaction period. This maximizes acid exposure to the target zone.
Biocides: Help prevent bacterial damage to the acid or fluid system as it remains downhole for the reaction duration.
Detergents and breakers: These chemicals are utilized to clean acid residue from the formation and enable flowback after the job is complete. Enzymatic and oxidative breakers also ensure polymers fully degrade.
Corrosion Inhibitors
Given the corrosive nature of many oilfield production fluids, corrosion inhibitors play an important role in many stimulation applications and production operations. Different chemistries are selected depending on the production fluid composition.
Film-forming corrosion inhibitors: Carbonate, tallow amine and maleic-based products form a hydrophobic mono-molecular layer on metal surfaces to prevent corrosive agents from contacting the substrate.
Passivating inhibitors: Corrosion resistant metal species like nitrates, chromates or rare earth chlorides can form a protective oxide layer.
Vapor phase inhibitors: Volatile products like iso-butanol can protect in gaseous environments through condensation on metal surfaces.
Emulsified corrosion inhibitors: Internal oiling amines or other corrosion inhibiting chemistries can be emulsified for injection downhole in hydrocarbon bearing zones.
Surfactants: Synergistic blends of surfactants along with film forming inhibitors provide improved emulsification for downhole placement in oil/water systems.
scale/paraffin prevention
Scale and paraffin deposits negatively impact flow assurance over time. Chemicals are employed to maintain production flowlines and facilities in optimal operating condition.
Scale inhibitors: Phosphonates, polyacrylates and other chelating polymers work by crystal modification or crystal lattice distortion to inhibit scales like calcium carbonate, barium sulfate or strontium sulfate.
Dispersants: Copolymers help disperse small scale crystals preventing aggregation and deposition.
Paraffin dispersants/inhibitors: Surface active chemicals prevent paraffin crystallization and adhesion by lowering surface/interfacial tension or crystal lattice embedding. Thermal or catalytic degrading products also remove existing waxy deposits.
Corrosion inhibitors are also often incorporated into scale prevention treatments for comprehensive flow assurance protection. Proper inhibitor selection matched to the specific downhole conditions helps maximize production asset integrity and uptime over the long well life cycles.
Conclusion
As explored across various oilfield stimulation and production applications, a wide spectrum of chemical technologies plays a vital role in enhancing production from oil and natural gas reservoirs. Continuous innovation ensures these chemistries can be optimally designed to improve recovery in increasingly challenging resource developments. Proper chemical selection and execution coupled with reservoir and geomechanical engineering ensures their safe and effective implementation to realize the full productive potential of oil and gas assets for many years into the future.
*Note:
1.Source: Coherent Market Insights, Public sources, Desk research
2.We have leveraged AI tools to mine information and compile it
