Date of Award

January 2023

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Petroleum Engineering

First Advisor

Hui Pu

Abstract

Is it possible to curtail flaring in the Williston basin while simultaneously sequestering carbon dioxide, harvesting economic quantities of natural gas liquids, helium and other valuable products? Utilizing a novel approach described here, diatomic hydrogen and elemental helium, as well as other products, can be profitably extracted from the gas streams produced from horizontal, hydraulically-fractured Middle Bakken Member wells, in the Devonian-Mississippian Bakken Formation of the Williston Basin, North Dakota, USA.However, there are two vastly different methods employed to extract these gasses. Hydrogen is harvested from the gas stream by physically reforming methane (CH4) through the application of one or another of two-stage processes: “Autothermal Reformation + Water Gas Shift (WGS) reaction”, known as ATR; or “Steam Methane Reforming”, SMR. Both yield H2, plus CO (carbon monoxide) in the first phase, and CO2 (carbon dioxide) after the second. Elemental diatomic hydrogen (H2) can be used in fuel cells to generate electricity or directly in certain internal combustion engines; primarily turbines, as primary fuel. The produced CO2 can be captured (CCUS: Carbon Capture, Utilization and Sequestration) and injected downhole for both reservoir energy enhancement and CO2 sequestration, or sold for industrial use because of its purity. Helium, on the other hand, is inert and therefore it is unnecessary to expend the amount of energy required to reformat methane to liberate hydrogen. There are several methods commercially available to economically extract 99.995% pure helium from gas streams where the helium concentration can be as low as 0.010%. The extraction of crude helium from natural gas requires three processing steps. The first step removes impurities through deamination, glycol absorption, nitrogen rejection, and desiccant adsorption, which remove CO2, H2O, N2, and H2S; a typical gas pre-treatment process. The second step removes high-molecular weight hydrocarbons (Natural Gas Liquids), if desired, while the third step is via cryogenics, which removes the final methane. The result is 75-90% pure helium. Final purification, before liquefaction, is accomplished via activated charcoal absorbers at liquid-nitrogen temperatures and high pressure, or pressure-swing adsorption (PSA) processes. Low-temperature adsorption can yield helium purities of 99.99 percent, while PSA processes recover helium at better than 99.9999 percent purity. However, with the advent of selective zeolite or organometallic membranes, the cryogenic extraction of He from the CH4 stream step can be eliminated. Heating the gas stream and passing it through selective semi-permeable membranes allow for the helium, with its much smaller size, and higher energy, pass while excluding the relatively massive CH4 molecule. The helium can be isolated and purified via pressure swing adsorption (PSA) methods to achieve 99.999% purity. The heated methane can then be directly ported to a Steam Methane Reformer unit for extraction of hydrogen. Both H2 and He extraction procedures eliminate the need for gas flaring, as both yield salable products such as LNG and NGLs, and the opportunity to capture and sequester carbon dioxide (CO2) from the produced gas stream. This extracted so-called “Blue Hydrogen” is slated for use in transportation via fuel cells or use in internal combustion engines and sells for approximately $3.00/MCF, depending on the cost of the feedstock natural gas. “Metallurgical helium” or “Grade-A Helium” (i.e., > 99.9999% pure), with myriad industrial and scientific uses, brings ~US$498/MCF (02-2023). The cost of hydrogen vs. helium extraction is difficult to compare. Hydrogen production depends on the cost of natural gas as a feedstock, which is particularly variable. The cost of helium extraction depends on the volume of gas being processed, as most helium extraction units could handle 10-12 Bakken wells simultaneously. However, as a straight-up market product, helium revenue exceeds hydrogen by a factor of 100. Doing both coincidental from the same gas stream will enhance the revenue of each.

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