Carboxylates and their derivatives for improved hydrocarbon recovery and geological storage of hydrogen and carbon dioxide

Problem

Water injection, also called “water flooding,” is the most widely used method to increase production from oil reservoirs. It usually follows the primary production stage, in which the oil production relies on the reservoir’s natural energy. One of the main factors that affect the efficiency of water flooding is the wettability of the reservoir rocks. In general, the reservoir oil is more easily displaced by water if the surface of the reservoir rocks is in a more water-wetting state. However, a substantial amount oil can remain unrecovered by conventional water flooding, especially in reservoirs of oil-wet rocks. Use of surfactants has been studied to change the reservoir-rock wettability to more water wetting, but it is difficult to implement in high-salinity and/or high-temperature reservoirs.

Additionally, injection of carboxylates and their derivatives into a geological formation leads to the storage of a large quantity of hydrogen and carbon dioxide. This stored hydrogen in the form of carboxylates and their derivatives can be reproduced by using the existing technologies of the chemical conversion between carboxylates and their derivatives and hydrogen.

Solution

This invention is concerned with use of carboxylates and their derivatives as novel additives to water-based methods of oil recovery. These compounds were found to be effective in making the rock wettability more water-wet, yielding increased oil recovery in comparison to conventional water flooding. Low-salinity water flooding has been extensively studied to increase the oil production using the same mechanism, but carboxylates and their derivatives can further improve the oil production as additives for water flooding. Carboxylates and their derivatives are environmentally benign and commercially available at low costs. They are easy to handle for oil field applications, as they are highly water-soluble, solid compounds even at high-salinity, high-temperature conditions, where common surfactants are unstable.

Injection of a certain volume of the aqueous solution containing carboxylate(s) into an oil reservoir renders the wettability more water-wet. This increases the efficiency of oil displacement by water, resulting in an increased oil production. The injection of the carboxylate solution can be coupled with other methods of improved oil recovery and enhanced oil recovery (e.g., surfactants, low-salinity brine, polymer, solvents, hydrocarbon gases, and carbon dioxide).

Carboxylates and their derivatives can be converged from carbon dioxide and water using existing electrochemical techniques. The invented injection of carboxylates leads to a large amount of storage of carbon dioxide and hydrogen. The stored hydrogen can be reproduced by using the existing conversion technologies from carboxylates and their derivatives to hydrogen.

Features

Carboxylates and their derivatives interact with rock surfaces and they change the wettability to more water-wet. The interaction between these compounds and rock surfaces is expected to remove a certain amount of polar oil components from the rock surfaces, which renders the surface more water-wet. These compounds are highly soluble in water, environmentally benign, commercially available at low cost, stable, and easy to handle as they are in solid form.

Benefits

The injection of carboxylates and their derivatives can increase the oil production in comparison to conventional water flooding. It is superior to low salinity water for the cases tested so far. The amount of the incremental oil production by the invented technology depends on the reservoir properties, such as initial wettability state, reservoir heterogeneity, and operational methods.

These compounds can act as tracers when injected as part of the aqueous solution as they do not exist in the original reservoir fluid. That is, they can be used effectively in optimizing the field operation using the carboxylate-assisted water or polymer flooding. Also, these compounds can act as corrosion inhibitors.

This invention leads to a large amount of hydrogen storage that is safer and more efficient than storing hydrogen as gas. Existing technologies of the chemical conversion between hydrogen and carboxylates and their derivatives can be used for on-demand production/injection of hydrogen. For example, a typical solubility of sodium formate in formation water is equivalent to storing 40 liters of hydrogen gas at standard conditions in 100cc of water.