Oil & Gas From exploration to distribution Week 3 V16 Production : Process Isabelle Rey-Fabret

W4V16 - Process p. 1 IFPEN - IFP School 2015 / TOTAL SA 2015 / IFP Training 2015

Introduction We have seen how the fluid is produced and transported from the well heads to the inlet of the process. Now, lets describe the processing unit. During this lesson, we will focus on a typical processing plant, the fluid feeding this plant and the final products obtained. Then, we will describe more specifically the oil treatment, followed by the gas and the water treatments. Typical processing plant In order to define the role of this specific part of the system, lets focus on a typical oil field processing installation. The production wells send the effluent to the process unit, where it is treated to obtain oil to be stored. What treatments are required? We will describe on the one hand the fluid entering the process, and on the other hand the final products and their use. When an effluent enters the process, it is composed of hydrocarbons, including light ends, water, and impurities. Moreover, the fluid is made up of 2 phases: liquid and gas.

What do we want to obtain from the process? The oil is treated to be stored, the gas is partially used for gas injection and gas lift activation of the production, and the produced water is treated for re-injection and/or rejection.

W4V16 - Process p. 2 IFPEN - IFP School 2015 / TOTAL SA 2015 / IFP Training 2015

Oil treatment Lets focus on the oil. Lets consider one by one 3 specific components of it :

1. the light ends fraction, 2. the water and salt, 3. and the hydrogen sulfide.

Why and how to remove them? The oil produced at the outlet of the process unit is stored in tanks, transported in pipelines or tankers in safe conditions. For that, the amount of evaporated oil during this part of the production chain has to be reduced: it is necessary to remove most of the dissolved light ends from the effluent. In practice, stabilization (or degassing) is the process which removes dissolved gas from crude oil.

Most often, water or brine (salt water) is present in the crude oil as free water and/or as emulsion. Chlorides present in the brine are very corrosive for the steel equipment, such as the flowlines, the pipelines, tanks, and so on. It is the case for hydrogen sulfide and carbon dioxide. To conclude, water, salt and acid gases have to be removed from the effluent.

W4V16 - Process p. 3 IFPEN - IFP School 2015 / TOTAL SA 2015 / IFP Training 2015

The Crude oil DEHYDRATION or DESALTING is the process for removing brine from the crude oil stream. It lowers simultaneously the amount of free water and the amount of salt. For healthy concerns, the limit of hydrogen sulfide remaining in the stored oil is typically lower than 20 to 80 ppm mass. Most often, the stabilization process is sufficient to decrease the amount of H2S in the oil below this limit. Gas and water treatments The associated gas available at the outlet of the stabilization process is treated depending on its end use, either power generation, export, re-injection for reservoir pressure management, or activation of the production by gas lift. The last part of the effluent is the water, which is treated in order to be re-injected in the reservoir for the pressure management or rejected

The aim of this part of the process is to remove the remaining droplets of oil contained in the water after the stabilization phase. Different techniques are used to decrease drastically the amount of oil in water. 2 to 3 treatment steps allow the remaining particles to be less than 3 to 10 microns meters.

W4V16 - Process p. 4 IFPEN - IFP School 2015 / TOTAL SA 2015 / IFP Training 2015

In the case of a gas field, the effluent entering the process is composed of gas and liquid, named condensate. Therefore, the first processing step is a separation called primary separation, in order to send the resulting gas and liquid to 2 different treatment chains. Hereafter, the gas treatment and the liquid treatment will be described in the next chapters.

W4V16 - Process p. 5 IFPEN - IFP School 2015 / TOTAL SA 2015 / IFP Training 2015