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Paraffin Control - Chemicals Services
Paraffin’s are naturally occurring >c18- saturated linear and branched alkane molecules that are found in most liquid crude hydrocarbons are completely soluble in the hydrocarbon under virgin reservoir conditions.
The paraffinic components are not discreet molecules, but rather occur as a mixture of alkane- saturated hydrocarbons in the order of c1-c140, and even higher carbon chain lengths when branched. The presence of paraffin’s does not indicate the potential for a paraffin problem, and most paraffinic crudes are produced without precipitation or the need for chemical or physical treatment. Paraffin can become problematic when the fluids are subjected to various physical changes required to produce and separate the crude4 oil.
Three physical processes in particular encourage precipitation of paraffinic fluids:
Pressure Change
This causes the light ends of the crude oil to vaporize, reducing the overall solubility of the high MW paraffin’s in the remaining liquid hydrocarbon, which can lead to precipitation. Strong pressure changes occur at the formation face, chokes / valves, the wellhead and separations.
Temperature Change
Cooling of the crude oil reduces the solubility of the paraffin’s, which start to associate with them and crystallize from solution, observed as a cloud point.
Particularly problematic locations can be oil storage vessels and flow lines, especially long-distance subsea tiebacks.
Perhaps due to temporary degassing of fluids and impingement of wax crystallites on pipe walls, high turbulence flow areas are also known to be problem areas for paraffin deposits, typical example can be downhole pumps, treatment vessels, wellheads. Paraffin begins by forming needle – like or plate-like structures, and is initially observed as a cloud point in the produced fluid. These deposits can be very different in nature from system to system. Some form mushy, readily dispersed deposits, others hard waxy deposits – the letter being more problematic from a remediation perspective. In general, the letter waxy – type forms from the higher C-chain length linear alkanes – typically >C25 n-alkanes and above. These problems high molecular weight paraffin are more prevalent in crude oil than condensates. The principle concern with paraffin deposits is the restriction rates.
This may be due to paraffin deposits is the restriction in the near _ wellbore, restricting flow of hydrocarbon into the well ,or more often deposition in production pipe work leading to restriction of diameter and therefore flow rate. Also the paraffinic crystallites, if precipitated in the bulk hydrocarbon, can increase the viscosity of the fluids, reducing pipeline throughput.
At worst, if the paraffin crystal network is allowed to continue to grow and fuse, such as during a shut _in, wax gelling can occur and it may be impossible to reinitiate fluid flow, causing the pipe to be abandoned.
Paraffin control regimes can be either premeditative or pre-emptive. Modern reservoir developments design the production system to minimize the physical factors that can induce paraffin formation. However, paraffin formation may still be an issue. Paraffin remediation techniques include soaking the deposits with an appropriate solvent, often including a dispersant. Redemptive treatment involves the continuous injection of dispersants, inhibitors, pour-point depressant, or combinations thereof.
SAPESCO Chemical Solutions (SCS) has developed high-performance chemical additives to help tackle even the most challenging paraffinic crudes and condensates either in paraffin remediation or in continuous treatment regimes.
These products fall into three categories:
Paraffin dispersants - surfactants used either in solvent treatment of pre-existing deposits or in continuous application to keep paraffin crystallites suspended in the solvent/crude and flushed out of the system without redepositing.
Paraffin inhibitors - oil soluble polymers that reduce the temperature of appearance of the cloud-point, inhibiting the formation of paraffinic deposits.
Pour-point depressants - used to limit wax gelling, usually induced by cold temperature exposure, by interfering with the crystallization process and keeping the bulk fluid mobile.
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