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  • Lucas Evangelista

Application of enzyme-based green solvents for the recovery of subsurface fluids

This invention relates generally to the recovery of fluids with an enzyme-based green solvent and, more particularly, to improvement of hydrocarbon recovery from an unconventional reservoir during primary, secondary, or tertiary production, while minimizing unfavorable impacts on formation fluid and rock systems and improving environmental profile through green chemistry and manufacturing.

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A method for recovering subsurface fluid from rock formations by adding an enzyme-based green solvent to a carrier fluid and injecting the enzyme-based green solvent and the carrier fluid into a production well. The enzyme-based green solvent and the carrier fluid are directed down a flow path of the production well.

The green solvent soaks in the production well before reversing the flow path of the production well. The enzyme-based green solvent and the carrier fluid travel up the flow path with a plurality of recovered deposits from the production well in the enzyme-based green solvent.

Shale Challenges

Oil recovery factors from majority of shale and tight formations are reported to be less than 10%. Therefore, enhanced oil recovery (EOR) techniques are massively explored to help with improving the recovery from these formations, in which permeability is usually less than 0.1 mD and pore sizes in rock formations are mostly less than 100 nm in diameter.

The complex fluid flow and phase behavior of these formations make them more challenging in many operational aspects including finding the most economic and efficient EOR technique.

These complications resulted in a need for alternative methods such as the application of aqueous solutions like surfactants. Continuous solvent/surfactant flooding is impractical in unconventional reservoirs since sweep efficiencies are very low and the injected solvent cannot mobilize oil out of the matrix from one well to another (except through high-permeability conduits such as a fracture, if present).

Inefficient Materials

A significant drawback of surfactant assisted EOR techniques using fossil fuel-derived surfactants is the adsorption of surfactant material onto the reservoir rock. This reduces the surfactant performance over time and leaves permanent negative impacts on rock formations and water. Surfactant instability and dissociation at various reservoir temperatures and salinities is another issue that may cause permanent damage to the reservoir. Generally, the cost of the surfactant is the single most expensive item in the cost of a chemical EOR.

Available Deployment Method

Therefore, a cyclic approach like a huff n′ puff is needed where sweep efficiencies are low. In the “huff” phase, solvent is injected into a reservoir where the solvent travels through a fracture network. Following this period, an injection well is shut-in to allow the solvent to penetrate rock by spontaneous imbibition into a matrix and replace reservoir oil during a “soak” interval. After enough soaking time, the injection well—along with any potentially impacted wells nearby—is re-opened at a low pressure to produce an expelled oil phase and a solvent-rich phase.

Enzymes play an important role in the manufacture of many biobased surfactants.

Better Material Additives

Replacement of chemical surfactants with biobased surfactants such as enzymatic green solvents (detergents) that can change the wettability of formation rocks and fluid systems by changing the interfacial tension, has been investigated. These solvents are mostly aqueous, and their hydrogen bonding makes them very diffusible in the water phase.

Additionally, enzymes—in whole or in part—are derived from biological products and are globular proteins that are eco-friendly. This minimizes any adverse long-term impact on rock and water in formations. The use of enzymes provides many advantages compared with chemical processing, including lower energy use, lower amounts of waste products and by-products, the absence of toxic metal catalysts or acids/bases, and safer operating conditions for HSE.

FIG. 12 shows production well apparatus and the enzyme-based green solvent
FIG. 12 shows production well apparatus and the enzyme-based green solvent

In combination with (water +) other additives, enzymes can change adhesion behavior of an oil-water-rock system by pushing away hydrocarbons from rock surfaces, allowing hydrocarbons to flow.

Multiuse Fluid

The collected deposits can be recovered from the production well via the enzyme-based green solvent using a wide variety of common crude production processes. Such processes include, but are not limited to, primary recovery, initial fracturing, secondary recover, re-fracturing, and huff n′ puff processes.

1. Primary Fracturing/Refracturing

Embodiments of this invention may be applied as a part of a primary fracturing or refracturing work on a well. The addition of enzyme-based green solvents to a fracturing fluid provides an uplift to primary post-fracturing production by allowing enzyme-based surface activating agents to contact a rock formation during the primary fracturing time. Thus, the application of an enzyme-based solvent during initial hydraulic fracturing or re-fracturing facilitates significant injection flow of a relatively low enzyme concentration (preferably 5%) to achieve an efficient and cost-effective additional recovery of deposits while the enzymes are effectively distributed within the rock formation in suitable concentrations.

2. Fracture-Hit Mitigation

Embodiments of this invention may be applied as a part of Fracture-hit mitigation or managing parent-child well interactions. Well-to-well communication, known as “frac-hits” during hydraulic fracturing, is common in unconventional oil and gas development. When the fracture network of a newly drilled well connects to an older well's fracture network, the older well may be filled with sand and fluids, requiring an expensive cleanout to restore production. To help mitigate frac-hits, the enzyme-based green solvent can be used, with or without the slurry of nanoparticles, to re-pressurize the older well and improve the recovery of additional oil.

3. “Huff n′ Puff”

Embodiments of this invention may include a high-volume continuous injection stream of a carrier fluid combined with a relatively low concentration of enzyme-based solvent injected into a rock formation followed by a soaking period. Then, by reversing the flow (flow-back) of the injection stream, a well can get back recovery of deposits during the flow-back. This “huff n′ puff” technique allows use of the same well for both production and injection and eliminates high sweep efficiency requirements.

4. Secondary/Tertiary Recovery

Embodiments of this invention can also be applied as part of secondary or tertiary subsurface fluid recovery. This applies to enhanced/improved oil recovery (EOR/IOR) from unconventional rock formations. EOR/IOR relates to different techniques with the aim of recovering remaining hydrocarbon deposits from oil in a rock formation, after an initial production period.

Enzyme-assisted enhanced oil recovery for secondary or tertiary subsurface fluid recovery according to this invention can be achieved by using an oil recovery system that includes at least one well and one injection pump system. Where the enzyme-based green solvent is aqueous, the solvent may rely on an existing well and surface infrastructure of the well to reduce the need for significant transformation of well-site facilities and associated expenses.

Where sweep efficiencies are achievable between the wells, enzyme-based green solvent may be injected to the formation through one well and produced from a neighboring well. Where inter-well communication exists due to the presence of fractures/permeability, multiple wells get impacted by the injection of the enzyme-based green solvent in one well.



Patent number: 11643912

Type: Grant

Filed: Feb 12, 2021

Date of Patent: May 9, 2023

Patent Publication Number: 20210262328



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