No abstract

A novel cement additive, capable of creating an insoluble barrier at the first sign of acid attack, is offered. When present in small quantities, it allows ordinary Portland cement (OPC) to protect itself from acid corrosion as shown by laboratory tests. This corrosion resistance is critical especially in regards to attack from carbonic acid produced when CO2 combines with water or from naturally occurring H2S in the well. These acids can turn OPC porous and weak, rendering it incapable of maintaining zonal isolation. CO2 gas can enter the wellbore as part of either a stimulation technique to energize production or to sequester this green-house underground in hopes of reducing global warming. Cement used in a CO2-sequestering well must maintain its integrity for hundreds if not thousands of years to keep the CO2 trapped; otherwise, the CO2 can reenter the atmosphere. Damage to the cement sheath in the short -term can lead to contaminated aquifers or annular leakage of natural gas, both of which can have devastating results. Laboratory testing of this commercially-available additive was performed under temperature and pressure in CO2-saturated brines for weeks. Corrosion of the tested cement samples was measured optically and through a variety of chemical analysis procedures. Samples of OPC containing the additive stopped penetration of carbonic acid near the surface whereas sample without suffered deep corrosion penetration. When it is known in advance that the well will be highly acidic it may be cemented with acidresistant alumina-silicate cement (ASC) rather than OPC. However, this technique requires specially isolated pumping equipment to avoid flash set of the ASC, making the process more expensive and error-prone. Addition of the novel dry-powder, acid-activated, barrier-creating compound is much easier. The additive remains inert in the set OPC until acid corrosion occurs. Release of calcium ions by acid attack triggers the formation of an insoluble barrier which reduces further acid damage.

No abstract

For the past several years, thermoplastic pultrusion technology develop ment has concentrated on high-performance polymers, for example: polyetheretherketone (PEEK), polyetherimide (PEI), and polyphenylene sulfide (PPS). While these polymers are more likely to find use as engineering materials for aircraft and spacecraft, lower tem perature, lower cost fiber reinforced thermoplastics have a greater potential in the automo tive, industrial, recreational, and building supplies markets.

Developing a pultrusion process for fabricating composites using a graphite reinforced high-performance thermoplastic presents a technological challenge to the pultruder. Unlike conventional pultrusion of thermosets containing monomeric reactants and solvents which react in the pultrusion die causing polymerization, high-performance thermoplastic polymers either do not contain solvents or contain solvents which must be removed before polymerizing. In either case, consolidation is performed with rigid or