# Experimental Determination of Wax Appearance Temperature (WAT) in Brazilian Presalt Petroleum via HPμDSC: Effects of Pressure and Gas Composition

## TL;DR

This study examines how different gases and pressures affect wax formation in Brazilian presalt crude oil, using high-pressure differential scanning calorimetry.

## Contribution

The novel contribution is the experimental characterization of wax appearance temperature under varying gas compositions and pressures in presalt crude oil.

## Key findings

- Nitrogen injection increases wax appearance temperature (WAT), while natural gas injection decreases it.
- Carbon dioxide injection shows variable WAT behavior depending on pressure intervals.
- The second crystallization event's temperature also shows pressure-dependent behavior with CO2.

## Abstract

Considered a primary energy source, crude oil is essential
for
the production of industrial inputs. With the increase in investments
in deepwater production systems, technological challenges emerge,
especially in the exploitation of the Brazilian presalt, where the
formation of hydrates and wax deposits can pose flow assurance risks.
In addition to conditions that favor deposit formation, such as low
seabed temperature, these fields also present a high gas/oil ratio
and elevated pressuresfactors that can alter the kinetics
and thermodynamics of the phenomenon. This study aims to experimentally
characterize the influence of three different gases (CO2, Natural Gas, N2, and N2 + n-hexane) at different pressuresup to 20.0 MPa gauge (MPag)
on the first and second crystallization events of a dead crude oil
sample from the Brazilian presalt. The experiments were conducted
using HPμDSC high-pressure cells, with pressure increased by
the slow and gradual injection of each gas under study. It was found
that N2 injection increases the WAT, while Natural Gas
injection, in contrast, reduces the WAT. In the case of CO2 injection, pressure intervals were observed in which WAT increases,
and others in which it remains constant; this behavior was also observed
for the crystallization temperature of the second event.