A Critical Review of Controlling Paraffin Deposition in Production Lines Using Chemicals

Abstract

Wax deposition in oil and gas pipelines is considered one of the most severe operational problems, and significant efforts have been made to prevent and remediate this flow assurance issue. Chemical wax control strategies have received considerable attention, especially in certain cases where applying the mechanical and thermal treatment is inconvenient and difficult. However, until now expensive and inefficient “trial-and-error” procedures were used in fields, possibly due to the lack of the fundamental understanding of how these chemicals work in different operating conditions. Here, a comprehensive review of the available literature on chemical wax control strategies is presented. The key performance parameters used in assessing the chemicals in the laboratory are systematically reported. All commonly used wax inhibitors, pour point depressants, and wax dispersants are described based on the types, affecting factors, working mechanisms, and testing facilities. Solvents that are used to dissolve the wax deposits or to reduce the viscosity of the fluid are also discussed. Finally, future challenges ahead for chemical wax control research are discussed.

Wax Formation Mechanisms, Wax Chemical Inhibitors and Factors Affecting Chemical Inhibition

“…This causes the crude oil flowing in the pipeline to experience a radial thermal gradient. This means that the temperature of crude oil situated closer to the pipe wall is lower compared to the temperature of the crude oil at the center of the pipeline [34]. When the temperature of the crude oil reaches the cloud point, the crystallization of wax takes place in the cold region closer to the pipe wall.…”

A review of heat‐transfer mechanism for solid deposition from “waxy” or paraffinic mixtures

“…The PPT can be measured by cooling a sample, statically, in steps of 1 C and determining the lowest temperature at which the liquid sample is able to move. [11,54] The measurement of PPT involves a subjective criterion; hence, the PPT is normally used only for comparison purposes. [72] The solid-like state of the "waxy" mixture at PPT is more like a "gel," which is formed under static conditions (ie, in the absence of any shear, with the same overall composition as the original mixture).…”

“…The prepared "waxy" mixtures, used in previous investigations, have been of different compositions, F I G U R E 3 Carbon number distribution of multicomponent wax and solvent samples used in wax deposition studies [16,55] which were intended to represent the variability in "waxy" crude oil compositions without introducing additional uncertainties. [11,38,51,[53][54][55]70,73,75,103,105,[108][109][110] Figure 3 presents the carbon number distribution of different multicomponent waxes and solvents that have been used in several wax deposition studies completed at the University of Calgary. [51,[53][54][55]70,73,75,108] It is pointed out that there is no overlap between the carbon number distributions of the multi-component solvent and wax samples used in previous studies.…”

“…[10] A review of chemical wax control strategies and their assessment performance parameters for pipelines was published recently. [11] Mechanical remediation methods involve periodic use of various devices to physically scrape off the wax deposit from the pipe wall, such as flowline pigs, rod scrapers, paraffin cutters, and plunger lifts. [7,12] Thermal methods involve either the application of external heat on the deposition surface or the minimization of heat losses from the pipeline.…”

Study on wax precipitation characteristics of wax deposit in pipes

“…In worst‐case scenarios, the pipe can be completely blocked, resulting in prohibitively expensive economic damages . Mechanical pigging is a widely used approach for wax remediation in the field . During pigging, the pig motion is determined by the strength of the wax deposit.…”