Field of invention

The present invention relates to separation and production of hydrogen generated in situ of the oil or gas fields by heterogeneous catalysis conversion, acquathermolysis or oxidation reactions.

Background of the invention

There is a common understanding that the emissions of “greenhouse” gases due to the rapid expansion of fossil energy consumption has led to global warming. In the same time with increasing human population, growing energy demand and developing petrochemical industry in the world there is a challenge to recover in environmentally acceptable way:

• Gas and oil from non-commercial and depleted fields,

• Heavy oil and bitumen.

In-situ conversion of these hydrocarbon reserves to hydrogen with further separation, accumulation, storage and production of hydrogen will allow to exploit green energy from “hard to recover” hydrocarbon reserves as well as producing it from new and already in production oil and natural gas fields.

The present invention process of hydrogen separation and production without “black carbon” and “greenhouse” gases production to the surface and release to the atmosphere opens a new immense source of commercial hydrogen for chemical industry and clean energy use. Invention

This invention relates to a process for separation and production of hydrogen generated in situ of oil or gas fields. Conversion of hydrocarbons to hydrogen sub terrain in a field can be achieved as a result of one or several of the following chemical reactions:

• Heterogeneous catalysis conversion:

CH + H2O -> CO + 3H ₂ DH = 206 kJ/mol (1)

Steam Methane Reforming (SMR) reaction is highly endothermic. If for SMR conversion reaction products contain three moles of hydrogen and one mole of CO, for heavier hydrocarbons this ratio decreases:

CnH ₂ n ₊₂ + nH ₂ 0 ^® nCO + (2n+1)H ₂ + DH (2)

• Water Gas Shift (WGS) moderately exothermic reversible reaction:

CO + H ₂ 0 C0 ₂ + H ₂ DH= - 41 kJ/mol (3)

• Acquathermolysis heavy oil reactions:

RCH ₂ CH ₂ SCH ₃ + 2H ₂ 0 RCHa + C0 ₂ + H ₂ + H ₂ S + CH4 (4)

Different reactions of pyrolysis, hydrogenation, ring opening, ring closing and desulfuration are involved in aquathermo!ysis of heavy oil.

• Oxidation reactions in case of air injection:

2CH + 0 ₂ 2CO + 4H ₂ DH = -75 kJ/mol (5)

2CnH ₂ n ₊₂ + n0 ₂ 2nCO + (2n+2)H ₂ + DH (6) The process of hydrogen generation in situ involves raising the temperature of the catalyst-containing zone of the reservoir to a temperature at which hydrogen generation occurs, above 500°C, especially at least 600°C, for example 700 to 900°C. In this first stage of the hydrogen generation process sub terrain catalyst will be placed in the reservoir (US8763697 and Eurasian 021444 patents). The catalyst can be applied in the reservoir over as large a horizontal distribution as possible, e.g. using a horizontal, deviated or vertical well 1 in Figure 1. If desired, injection may be at two or more depths so as to create two or more vertically stacked reaction zones, for example so that as the reaction progresses vertically it reaches zones of the reservoir that are pre-seeded with fresh catalyst. Raising the temperature in the reservoir may be achieved in at least two ways: by injection of superheated steam or by the injection of oxygen (e.g. as air) and initiation of hydrocarbon combustion within the reservoir. The introduction of oxygen and/or water may occur at the same sites as catalyst introduction in well 1 (Figure 1). In the above mentioned chemical reactions in situ (1-6) hydrogen is generated with by products including environmentally undesirable "greenhouse" gases, such as carbon and nitrogen oxides (if air is injected), hydrogen sulfide (if the oil field contains sulphur) being more dense and soluble than hydrogen.

This innovation presents a process of achieving efficient segregation of generated hydrogen from environmentally undesirable "greenhouse” gases in the reservoir. A well 2 drilled to the crest of the anticline reservoir or structural top of the faulted block or lithological trap accumulation of hydrocarbons will be used in the first stage of the process to inject water or water and dissolved catalytic system or pre-cursor to form catalyst already in situ (Figure 1). The injection well can be vertical or multi-branch well. The injected in well 2 water segregates gravitationally due to significant density difference between water and all gases present in situ and flow downwards to the reservoir section saturated with gases resulting from one or several conversion reactions (1-6).

Solubility of H2 in water is 100 times less than solubility of CO2, 200 times less than solubility of H2S and 20 times less that solubility of CFU, CO and N2(Figure 2).

At the second stage of the process (Figure 3), water, injected in the well 1 at the top of the reservoir, will be descending gravitationally downwards passing through the gas phase with hydrogen, gases generated in catalytic and oxidation (in case of air injection) reactions (1-6), remaining methane (and hydrocarbon gas components in oil fields). Hydrogen being almost insoluble in water, with its solubility ranging 0.0010-0.0013 g/kg at reservoir conditions, will be escaping almost completely the liquid water phase accumulating gravitationally at the top of the reservoir as shown in Figure 3. During its descent and flow to the bottom of the reservoir the injected water will entrain downwards environmentally undesirable "greenhouse” gases being much more soluble in water than hydrogen. The forming artificial gas cap of segregated hydrogen at the top of the reservoir will be expending and providing additional force to displace water phase with dissolved gases downwards. Well 1 is converted to saturation monitoring well and possible geothermal well in the future. Separated and accumulated hydrogen can be produced from the top of the reservoir at the stage three of the process from the water injection well 2 after its conversion to hydrogen production well (Figure 4).

This invention of separation and production of in situ generated hydrogen allows to sequestrate “black carbon” and environmentally undesirable "greenhouse” gases in situ without their production to the surface.

Claims

1. A process for separation and production of hydrogen generated from hydrocarbons in situ of the gas or oil fields. Segregation and accumulation of hydrogen in situ is achieved by utilising gravity forces, solubility and density differences of gases and liquid phases. Said process comprising the stages of

• introducing a catalyst into a hydrocarbon-containing zone in said reservoir using horizontal, deviated or vertical wells;

• raising the temperature in said zone to a temperature at which catalyzed conversion of hydrocarbons to hydrogen occurs by injection of an oxygen-containing gas in the well and partial combustion of hydrocarbons in situ or injection of overheated steam into said reservoir;

• injecting water or water with catalyst chemical system in the vertical or multi-branch well at the top of the reservoir allowing water or water with catalyst chemical system to segregate gravitationally, flow downwards through hydrogen conversion zone;

• dissolving in water and removing from the gas phase environmentally undesirable "greenhouse” gases produced in the catalytic hydrogen generation reactions;

• accumulating hydrogen, being almost insoluble in water and escaping almost completely from descending water phase, flowing upwards to the top of the reservoir;

• recovering the segregated and accumulated hydrogen from the top section of the reservoir by producing it from the well, which was earlier converted from water injector to hydrogen gas producer.