Advanced Oil & Solids Removal Process for Oilfield Reinjection Water

I. Current status, existing problems, and solutions of produced water in oilfield

Most of oilfields in China have entered into the later stage of exploitation and utilization, especially the development of low-permeability oilfields, which require the injection of a large amount of water to maintain good permeability pressure. During the exploitation of oilfields, the water content of the crude oil extracted increases year by year, and the amount of produced water also rises accordingly. The main methods for treating the produced water are oil and suspended solids removal.

Especially for the produced water from ASP flooding, its characteristics include high viscosity, high content of oil displacement agent, high alkalinity, high mineralization, tiny particles, and difficulty in oil-water sedimentation and separation. The traditional treatment process, which consists of "two-stage sedimentation" followed by "two-stage filtration", can no longer meet the requirements of re-injection water quality. This process has led to issues such as reducing capacity of equipment processing , prolonging sedimentation period, and causing unqualified outlet water.Thus, it is necessary to adopt new processes and materials, improve oil removal equipment, and develop a new type of oil removal equipment that integrates gravity oil removal, coalescence oil removal, and new material for demulsification to meet production needs.

Our company's R&D has developed and designed a process for removing oil and suspended solids from produced water in oilfields , drawing on the early pretreatment process of oil removal for petrochemical refining wastewater. Based on research and analysis of the characteristics of produced water in oilfields and the requirements for re-injection water. This process meets the requirements of re-injection water in low-permeability oilfields.

II. Process of removing oil and suspended solids in re-injection water from oilfields

Description for treatment process:

• The tank-within-tank technology primarily utilizes hydrocyclone technology to separate suspended solids, floating oil, and large dispersed oil particles from the outlet of the three-phase separator tank;

• The WYS-XX horizontal oil-water separator utilizes separation technologies such as hydrocyclone, coalescence, and W-shaped corrugated plate coalescence to coalesce and grow the tiny dispersed oil in water, achieving separation of oil-water ;

• The ZJYS-XX fine oil-water separator utilizes the demulsification and coalescence functions of  separation materials for demulsification to demulsify most of the emulsified oil in water, turning it into dispersed oil. The dispersed oil then grows larger through coalescence by the coalescence materials, and is finally separated from the water.