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Technical Paper: A Simulating Application of Well Production Allocation to Optimize Wax Formation and Pigging Frequency in Subsea Pipeline for a Gas-Condensate Field

Society: SPE
Paper Number: 176333
Presentation Date: 2015
 Download: A Simulating Application of Well Production Allocation to Optimize Wax Formation and Pigging Frequency in Subsea Pipeline for a Gas-Condensate Field (1.92 MB PDF) Login | Register

 

Abstract

Wax deposition is one of the most critical flow assurance issues for the pipeline and regular pigging is a popular method for dealing with them. Predicting and controlling the wax precipitation in the pipeline can help operators to optimize the pigging frequency, this in turn will create significant impact as subsea pigging can be very risky and costly. Yet wax deposition is also difficult to simulate as they are complex mixtures of heavy components from well fluid that freeze out when the temperature is low enough.

In this article, a methodology is developed to optimize pigging frequency. Simulation of wax deposition calculates the precipitation and dissolution due to the variation of fluid flow rate and inlet temperature into the pipeline. The simulation model takes into account all the heat transfer phenomena and hydrocarbon phase behavior along the pipeline. Due to the heat transfer along the production tubing from the reservoir to the well head, the tubing head temperature and respectively the pipeline inlet temperature increase with production flow rate from wells. In other words, the inlet temperature into the pipeline can be adjusted by the wells production allocation. This is one of the key factors that help to optimize the pigging frequency, as a proper wells allocation for a fixed production flow rate can give a high pipeline inlet temperature and flowing temperature, which can help not only to prevent wax formation but also to melt the wax that precipitated earlier.

The methodology is applied to a wax-riched gas condensate field in Vietnam. A proper well allocation plan has been developed, and as a result, the pigging frequency for the infield pipeline for this field can be optimized from conducting monthly to conducting yearly, significantly reducing risks and costs for the operator.

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