HyReQ: High Recovery Crude and Condensate Stabilization Process
Authors: Jothy Arul , Ooi Boon Lee , Hum Weng Loong 
Published: May 2011

A process has been developed that enhances the recovery of Natural Gas Liquids (NGLs) on oil production facilities by maximizing the absorption of C4+ components into the stabilized crude stream. The process involves 3 operating steps where the crude is first stripped of C3- components using a steam stripping column and then C4+ components which are in the gas stream are extracted using a dew-point control system coupled with a depropanizer. Finally the crude stream and condensate streams are comingled under conditions that will ensure that the vapor pressure specification of the product liquid stream is met. The process configuration and controls ensures that irrespective of the amount or proportion of crude and condensate produced, the amount of C4+ components in the stabilized product stream is maximized and the amount of C3- components minimized. This yields increased stabilized liquid production compared to a conventional 3 stage separation process and improved stabilized crude quality, among others.

The performance of the new process was examined and benchmarked against conventional system using industry proven simulation software - Hysys.

Introduction

The current global situation of depleting crude oil reserves, escalating crude oil price, coupled with an increasing environmental awareness and legislation on the management of CO2 emissions requires more responsible development of hydrocarbon assets. According to estimates made in year 2005 to 2009, some 14 to 16 bcf (billion cubic feet) is flared daily in the world. Gas flaring also has a global impact on climate change by adding some 400 million tons of CO2 in annual emissions. To address these issues, operating companies are investigating and implementing strategies to enhance crude oil recovery by maximizing recovery of NGLs and minimizing flaring.

The HyReQ process has the potential to increase the recovery of oil by between 5 to 30% over conventional processes. This is achieved by using crude oil from production wells to absorb intermediate hydrocarbon components (C4+) from a natural gas stream whilst maintaining the stabilized crude product within its vapor pressure specifications (TVP/RVP). This also results in improved crude oil quality (increased API gravity, reduced viscosity) and reduction of greenhouse gas emissions by up to 50% depending on whether associated gas is flared and due to the use of leaner fuel gas. Besides that, reduce safety issue for storage production oil by minimising volatile components (C2, C3) in composition of crude oil production. The process configuration is simple and easily retrofitted on existing facilities. The process is suitable for both onshore and offshore installations.

Theory

The HyReQ concept uses the ability of crude oil to absorb some of the C3 components and essentially all the C4+ components from the gas stream and to retain within the stabilized crude oil product these valuable NGL products. This results in increased stabilized crude oil recovery and improved quality of crude, namely, higher API gravity and reduced crude oil viscosity.

The following Figure 1 demonstrates this. Crude oil stabilized with conventional methods, i.e. using multiple stages of flash separation, is inherently inefficient with small quantities of C2- components still remaining in the stabilized crude stream.