Sealing
of wellbores in geothermal and tight oil/gas reservoirs
by filling the annulus with cement is a well-established practice.
Failure of the cement as a result of physical and/or chemical stress
is a common problem with serious environmental and financial consequences.
Numerous alternative cement blends have been proposed for the oil
and gas industry. Most of these possess poor mechanical properties,
or are not designed to work in high temperature environments. This
work reports on a novel polymer-cement composite with remarkable self-healing
ability that maintains the required properties of typical wellbore
cements and may be stable at most geothermal temperatures. We combine
for the first time experimental analysis of physical and chemical
properties with density functional theory simulations to evaluate
cement performance. The thermal stability and mechanical strength
are attributed to the formation of a number of chemical interactions
between the polymer and cement matrix including covalent bonds, hydrogen
bonding, and van der Waals interactions. Self-healing was demonstrated
by sealing fractures with 0.3–0.5 mm apertures, 2 orders of
magnitude larger than typical wellbore fractures. This polymer-cement
composite represents a major advance in wellbore cementing that could
improve the environmental safety and economics of enhanced geothermal
energy and tight oil/gas production.
Degradation of material properties by high-pressure hydrogen is an important factor in determining the safety and reliability of materials used in high-pressure hydrogen storage and delivery. Hydrogen damage mechanisms have a time dependence that is linked to hydrogen outgassing after exposure to the hydrogen atmosphere that makes ex situ measurements of mechanical properties problematic. Designing in situ measurement instruments for high-pressure hydrogen is challenging due to known hydrogen incompatibility with many metals and standard high-power motor materials such as Nd. Here we detail the design and operation of a solenoid based in situ tensile tester under high-pressure hydrogen environments up to 42 MPa (6000 psi). Modulus data from high-density polyethylene samples tested under high-pressure hydrogen at 35 MPa (5000 psi) are also reported as compared to baseline measurements taken in air.
High pressure hydrogen effects on the friction and wear of polymers are of importance to myriad applications. Of special concern are those used in the infrastructure for hydrogen vehicle refueling stations, including compressor sliding seals, valves, and actuators. While much is known about potentially damaging embrittlement effects of hydrogen on metals, relatively little is known about the effects of high pressure hydrogen on polymers. However, based on the limited results that are published in the literature, polymers also apparently exhibit compatibility issues with hydrogen. An additional study is needed to elucidate these effects to avoid incompatibilities either through design or material selection. As part of this effort, we present here in situ high pressure hydrogen studies of the friction and wear on example polymers. To this end, we have built and demonstrated a custom-built pin-on-flat linear reciprocating tribometer and demonstrated its use with in situ studies of friction and wear behavior of nitrile butadiene rubber polymer samples in 28 MPa hydrogen. Tribology results indicate that friction and wear is increased in high pressure hydrogen as compared both with values measured in high pressure argon and ambient air conditions.
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