Removing chlathrate inhibitors from contaminated petroleum streams

Abstract

A process is presented for treating crude oil that contains a clathrate hydrate inhibitor. In the process, a crude oil contaminated with the inhibitor is maintained in a vessel at inhibitor removal conditions to produce a treated crude oil having a reduced methanol concentration.

Description

TECHNICAL FIELD[0001]The present invention relates generally to processes and systems for treating petroleum streams to mitigate effects of hydrate inhibitors.BACKGROUND[0002]Natural gas hydrates or clathrate hydrates of natural gases (often simply called “hydrates”) form when water and certain gas molecules are brought together under suitable conditions of relatively high pressure and low temperature. Under these conditions the ‘host’ water molecules will form a cage or lattice structure capturing a “guest” gas molecule inside. Large quantities of gas are closely packed together by this mechanism. For example, a cubic meter of methane hydrate contains 0.8 cubic meters of water and up to 172 cubic meters of methane gas. While the most common clathrate on earth is methane hydrate, other gases also form hydrates, including hydrocarbon gases such as ethane and propane as well as non-hydrocarbon gases such as CO2 and H2S.[0003]Thermodynamic conditions favoring hydrate formation are ofte...

AI Technical Summary

Benefits of technology

[0005]Accordingly, a process is provided removing a clathrate inhibitor from a contaminated petroleum stream, comprising maintaining the contaminated petroleum stream at inhibitor removal conditions in a vessel having a liquid volume and a vapor volume, wherein the contaminated petroleum stream contains in the range of from greater than 50 ppm inhibitor to less than 5000 ppm inhibitor, to produce a treated petroleum stream having a reduced inhibitor concentration. In embodiments, the inhibitor is methanol. In embodiments, the petroleum stream is crude oil. In some such embodiments, the contaminated petroleum stream is crude oil that contains methanol. In some such embodimen

Problems solved by technology

This is highly undesirable because the hydrate crystals might agglomerate and plug the flowline and cause flow assurance failure and damage valves and instrumentation.

Increasingly, deepwater oil field developments face serious technical problems associated with hydrate formation causing blockage in flow lines exposed to very cold temperatures during well start-up or when flow rates are slowed.

For instance, the presence of relatively small amounts of methanol (e.g. greater than 50 ppm) in the crude upsets refinery waste water treatments systems and is undesirable to the refinery customers.

Either method can result in significant crude revenue loss.

Blending will reduce the methanol concentration, but very large quantities of on-spec crude are needed to achieve sufficient dilution.

If the diluted batch does not lower the contamination enough, the significantly larger amount of methanol contaminated crude will result in lost revenue.