Produced Water in Dispersed Oilfields: Why a Mobile Skid Beats Fixed Plant
The mismatch between mature oilfields and fixed treatment plant
Waterflooding is the workhorse of enhanced oil recovery, and after enough years of it the water cut of produced fluid climbs steadily. Handling that growing volume of oil-bearing produced water is now one of the constraints on efficient oilfield operation. The problem sharpens in fields that produce from many small, scattered blocks: a single block may yield only 300–500 bbl/d, far too little to justify a permanent treatment facility, yet too much to ignore.
Fixed equipment does not relocate, takes a long time to deploy and adapts poorly to changing production patterns. The result is the familiar set of complaints — low treatment efficiency, high operating cost and growing pressure to stay inside environmental limits. What these fields need is a treatment unit that arrives, works, and then moves on to the next block.
A treatment train inside a 40-foot container
SINOKLE built exactly that: a two-stage skid-mounted mobile unit combining CDFU cyclonic dissolved-air flotation with KFM filter technology, designed specifically for dispersed production. Every core treatment component sits inside a 40-foot standard container, so the unit can be factory-prefabricated, fully skid-assembled and then commissioned on site as a plug-and-play package.
The design figures are deliberately modest in scale and tight in footprint. Treatment capacity is 3 m³/h, overall dimensions are 12000 mm × 2350 mm × 2690 mm, and the skid weighs 12000 kg net and 21000 kg in operation. That combination moves readily on ordinary transport and can be relocated to the next block as soon as one is finished, so the same asset keeps working across a field instead of being abandoned when a block declines.
Inside the two-stage process
The train is purely physical from end to end. No chemical agents are added, which removes the secondary pollution risk that comes with dosing and keeps operating cost predictable. Design specifications put influent oil content at 2500 mg/L or below and suspended solids at 150 mg/L or below; after treatment, effluent oil content is 10 mg/L or below and suspended solids 5 mg/L or below, with pH held between 6 and 9. Those figures clear the requirements for produced water reinjection and for environmental discharge, which is what allows the water to be recycled rather than merely discarded.
Stage one: two-stage CDFU cyclonic dissolved-air flotation
The CDFU stage does the oil removal work. It combines cyclonic centrifugal separation with dissolved-air flotation and uses a flow field optimised through CFD simulation to deliver high efficiency in a compact vessel. The unit is a vertical sealed pressurised tank operating between 0.05 and 0.08 MPa. Twin tangential inlets build a stable, uniform rotating field that generates 5–30 μm micro-nano bubbles, which collide with and attach to dispersed oil, emulsified oil and suspended solids so that demulsification, coalescence and flotation separation happen together.
An internal central cylinder and guide vanes divide the flotation volume into several zones, and a cyclonic desanding design at the base sheds grit and silt while the unit is removing oil. Shock resistance is a design feature rather than a claim: the unit tolerates 50% flow fluctuation. SINOKLE holds a number of CDFU-related patents plus a software copyright for the technology.
Stage two: KFM modified activated filter media
The KFM filter sets the final effluent precision. It uses super-hydrophilic modified quartz activated filter media manufactured through 60 processing steps. The media surface carries a negative charge and combines hydrophilic, oil-repellent and oxidative purification characteristics, forming super-hydrophilic micro-nano pores that capture small droplets and suspended solids efficiently. Compared with conventional anthracite and emery media, it holds high mechanical strength, a wear rate of 0.2% or less and a breakage rate of 0.5% or less, resists oil contamination strongly and does not compact or block.
Backwash efficiency reaches 100% and the media service life exceeds 15 years, five times that of conventional materials. A single filtration stage replaces the usual multi-stage arrangement, cutting footprint by 20% to 30%. Backwash differential pressure is 0.1–0.15 MPa and each cycle takes about 10 minutes, with the backwash effluent returned to the upstream produced water tank for recirculation.
Automation that lets one person run the unit
Operation is automated across the whole process, which is what makes a remote oilfield block practical. Three layers — a field control layer, a monitoring layer and a management layer — are coordinated through a PLC plus SCADA intelligent control system. It collects water quality, flow, pressure and level parameters continuously and runs the full sequence of intake, air dissolution, oil discharge, gas venting, filtration and backwash without prompting.
Level control governs water and oil discharge, pressure control regulates gas intake and venting, and the filter triggers backwash on differential pressure. Remote and mobile monitoring support web client, mobile app and mini program access, so equipment status, water quality data and alarms can be checked from anywhere, along with remote start and stop, parameter adjustment and fault diagnosis. Distributed storage and encryption protect the operating data, and daily and monthly reports are generated automatically; trend analysis then provides early warning of equipment faults and water quality drift.
The economics that decide adoption
Operating cost is usually what makes or breaks an oilfield equipment decision. Because the process is purely physical and the design is energy-lean, total continuous operating power is 17.5 kW, which at an electricity price of ¥0.5/kWh works out to roughly ¥1.934 per tonne of water treated. No chemicals are purchased at all, and filter media lasts for years rather than months, so consumable replacement cost is minimal and only routine wear parts such as pump sets and the purification air system need periodic attention. Automated operation removes most of the labour line as well.
Set against conventional produced water treatment equipment, that cost structure is the real argument for a relocatable unit. It has been deployed across multiple oilfield projects, and as the industry moves toward lower-carbon operation, the ability to treat and recycle produced water at the block level — with flexible relocation, efficient purification, intelligent operation and low running cost — is what turns an environmental obligation into a manageable part of production planning.