Water Injection Treatment Technology for Conventional Oilfield Blocks
As China's petroleum industry develops and oilfields enter the mid-to-late stage of development, declining oil output has become common across the industry. To maintain productivity and improve recovery, waterflood development has become the most important tertiary recovery method. However, the quality of reinjection water directly affects waterflood performance and oilfield production economics, and places higher demands on environmental protection.
Reinjection water in conventional blocks comes mainly from produced water treated to discharge standard, and is characterised by high oil content, high suspended solids and severe bacterial growth. If reinjection water fails to meet quality standards it causes formation plugging, higher injection pressure and lower recovery, and in severe cases even well shut-ins. Choosing an economical and efficient reinjection water treatment technology is therefore crucial.
Analysis of Treatment Difficulties
Reinjection water treatment in conventional oilfield blocks faces three major technical difficulties:
First, oily wastewater is hard to treat. Produced water contains dissolved, emulsified and dispersed oil; emulsified oil forms a stable thermodynamic equilibrium with water, with droplet sizes mostly between 1 and 50 microns, which conventional gravity separation and filtration cannot effectively remove.
Second, suspended solids exceed limits. Mud and sand, corrosion products and bacterial metabolites carried in during production give a high suspended solids content; these particles are very fine and easily plug formation pores, reducing injection permeability.
Third, bacterial growth causes corrosion. The wastewater contains micro-organisms such as sulphate-reducing bacteria and iron bacteria, whose metabolism produces acidic substances that accelerate corrosion of injection equipment and pipelines and shorten service life.
Limitations of Conventional Technology
Current reinjection water processes in oilfields mainly use 'oil separation - flotation - filtration' combinations, which have clear shortcomings:
Oil separation tanks remove emulsified oil poorly and can only take out most free oil, doing nothing for fine emulsified oil. Conventional flotation equipment produces larger bubbles (50-100 microns) with a low probability of contacting fine oil droplets, so deoiling is limited. Quartz sand filters have only average precision, limited interception of suspended solids, and easily compact with poor backwashing.
In addition, conventional processes occupy large areas, consume large amounts of chemicals and carry high O&M costs, making it hard to meet oilfields' need to cut costs and raise efficiency.
SINOKLE's Integrated Solution
To address reinjection water treatment in conventional oilfield blocks, SINOKLE has introduced a complete solution built around the CDFU swirl dissolved-air flotation unit and the KFM modified filter media filter.
CDFU The swirl dissolved-air flotation unit is a core product independently developed by SINOKLE. It organically combines swirl centrifugal separation with dissolved-air flotation and uses CFD-optimised flow-field design to generate ultra-fine bubbles only 5-30 microns in diameter. These micro-bubbles fully contact and attach to emulsified oil droplets, forming flocs lighter than water that separate oil from water with ease. Compared with conventional flotation equipment, CDFU deoiling efficiency is more than 50% higher and effluent oil content can be stably controlled below 5 mg/L.
KFM modified filter media filter uses a high-quality activated carbon-based medium with well-developed pores and high adsorption capacity. The medium surface is specially modified for excellent interception and adsorption of oil and suspended solids. KFM filtration has high precision and effectively removes fine suspended solids, keeping effluent suspended solids below 1 mg/L. The medium also backwashes thoroughly, resists compaction and lasts 5-8 years.
Process Advantages
SINOKLE's oilfield reinjection water solution has notable advantages:
Good treatment performance: CDFU + KFM combined process delivers stable, compliant effluent quality, achieving up to discharge-standard levels of oil < 5 mg/L and suspended solids < 1 mg/L, fully meeting the oilfield reinjection water quality standard (SY/T 5329-2012).
Small footprint: the equipment is skid-mounted, and a CDFU unit handling 200 m³/h occupies only 15 square metres - more than 60% less land than conventional processes.
Low operating cost: purely physical treatment needs no chemicals and causes no secondary pollution, significantly reducing O&M costs. With a high degree of automation the equipment can run unattended.
Wide applicability: the solution adapts well to reinjection water treatment in ordinary heavy-oil fields, conventional blocks and low-permeability oilfields.
Reinjection water treatment in conventional oilfield blocks is an important part of ensuring sustainable oilfield development. SINOKLE's CDFU + KFM combined process, with its efficiency, energy saving and stability, offers a reliable technical choice for oilfield reinjection water treatment. The solution has been successfully applied in several oilfields, accumulating rich engineering experience and creating significant economic and environmental benefits for oilfield companies.
