SINOKLE's Innovative Process Streamlines Oilfield Acidising Fluid Treatment

Acidising is a core stimulation method in oil and gas fields, effectively improving oil and gas recovery. However, the acidising fluids produced afterwards have a complex composition and are difficult to treat, becoming a key obstacle to green oilfield development. As environmental policies tighten and the concept of water recycling advances,"oil content ≤5mg/L and suspended solids ≤5mg/L" dual ≤5 standards have become mandatory requirements for acidising fluid treatment, and treated water must be routed into produced water for reinjection. Drawing on its accumulated technology, SINOKLE has innovatively introduced a two-stage CDFU+coagulation-sedimentation+KFM filter combined process that achieves efficient purification without demulsifiers, ensuring compliant reinjection of treated water and providing a one-stop environmental solution.

1. Background: industry difficulties and market demand in oilfield acidising fluid treatment

Acidising is widely used in developing low-permeability reservoirs, but acidising fluids are highly corrosive and complex in composition. Direct discharge or reinjection without treatment pollutes the environment, plugs formations and corrodes equipment. As China's oilfield development enters the mid-to-late stage, acidising fluid volumes are rising and environmental standards continue to tighten, making the dual ≤5 standards a basic requirement.

Conventional processes have many limitations:

• demulsifiers must be added, risking secondary pollution and higher costs;

• pre-treatment is ineffective and treated water struggles to comply consistently;

• equipment corrosion resistance is insufficient and operation is unstable; treated water cannot meet reinjection requirements.

The market urgently needs efficient, eco-friendly and stable treatment processes, and SINOKLE's combined process precisely addresses these industry pain points.

2. Water quality analysis: core characteristics and treatment challenges of oilfield acidising fluids

Oilfield acidising fluids consist mainly of unreacted acid, formation contaminants and additives, showing the characteristics of "high corrosivity, heavy pollution and high variability", with prominent treatment challenges:

• Strong acidity + high chloride ions require extremely high corrosion resistance, and ordinary materials are easily damaged;

• large amounts of floating oil, emulsified oil and fine suspended solids are present; emulsified oil is stable and suspended solids settle poorly, making compliance a key difficulty;

• water quality fluctuates sharply, with pH value and pollutant concentrations changing widely, testing the process's shock resistance;

• reinjection requirements are strict: no chemical residue and pH compatibility with produced water are needed to avoid damaging the reservoir. Conventional processes struggle to balance treatment performance, environmental protection and reinjection compatibility.

3. Process approach and description: two-stage CDFU+coagulation-sedimentation+KFM and filter, staged purification for reinjection compatibility

The process follows a "staged pre-treatment→deep purification→fine filtration→reinjection compatibility" approach, using two-stage CDFU(316L material) as the pre-treatment core, coagulation-sedimentation for deep purification, and KFM filters as the final safeguard - achieving compliant reinjection without demulsifiers through a simple, highly automated flow.

(1) Core process approach

Given the characteristics of acidising fluids and reinjection needs, the approach focuses on three points: two-stage CDFU units in series for physical pre-treatment, achieving chemical-free demulsification and removing most pollutants; coagulation-sedimentation for deep purification of residual fine impurities; KFM fine filtration as the final safeguard to ensure compliant reinjection; 316L material ensures long-term stable operation of the equipment.

(2) Detailed description of each process unit

1.  Pre-treatment unit: two-stage CDFU swirl dissolved-air flotation units (316L material)

As the key equipment for chemical-free demulsification, the two-stage CDFU units both use 316L stainless steel, suited to highly corrosive conditions, and achieve oil-sludge separation purely physically through a two-stage treatment.

CDFU Combining swirl centrifugation and dissolved-air flotation, it uses centrifugal force together with ultrafine bubbles, requiring no demulsifier and avoiding secondary pollution. The first-stage CDFU removes most of the large waste oil and suspended solids; the second-stage CDFU optimises parameters to remove residual pollutants and eases the load on downstream processes.

316L material can withstand media with pH>3; it is corrosion-resistant and long-lasting, reducing maintenance costs.

2.  Deep purification unit: coagulation-sedimentation

After pre-treatment, a small amount of fine impurities remains. The coagulation-sedimentation unit doses a dedicated chemical that, through neutralisation, adsorption and bridging, aggregates fine pollutants into large flocs for settling and removal.

The dedicated chemical is dosed in small amounts with good flocculation performance, avoiding chemical residue and safeguarding reinjection compatibility, with simple operation and low sludge production.

3.  Fine filtration and reinjection safeguard unit: KFM filters

serve as the core of the final safeguard, with advantages in media and process design: high-purity quartz media modified for super-hydrophilicity, acid- and salt-resistant and non-ageing, offering high filtration precision and retaining trace impurities; a graded media design delivering + automatic backwashing for stable, convenient operation and a high degree of automation with no manual attendance. Treated water has no residue and is pH compatible with produced water, so it can be routed directly into produced water for reinjection, achieving water recycling.

4.  The complete process flow:

acidising fluid→two-stage CDFU→coagulation-sedimentation tank→KFM filters→compliant treated water routed into produced water for reinjection; sludge is dewatered, solidified and properly disposed of, with no secondary pollution.

4. Process advantages: efficient, eco-friendly and suited to reinjection

Compared with conventional processes, SINOKLE's combined process offers clear advantages:

• chemical-free demulsification is greener - physical separation needs no demulsifier, reducing pollution and cost;

• staged purification gives stable, compliant treated water meeting the dual ≤5 standards and suited to reinjection;

• KFM filters offer high filtration precision, corrosion resistance, durability and convenient O&M;

• 316L stainless steel equipment is corrosion-resistant and stable, with long service life and low maintenance costs;

• strong shock resistance handles water quality fluctuations;

• the skid-mounted design allows flexible deployment and short construction periods;

• a high degree of automation makes O&M efficient;

• water recycling is achieved, balancing environmental protection and economic benefit.

5. Future trends: green, low-carbon, intelligent and efficient, leading industry upgrading

As the "dual carbon" goals advance and green oilfield development deepens, acidising fluid treatment will move towards green, low-carbon, intelligent, efficient and deeply resource-recovering solutions. SINOKLE will follow these trends: optimising CDFU technology to strengthen chemical-free demulsification and low energy consumption; advancing intelligent system upgrades for real-time monitoring and remote O&M; exploring resource recovery of sludge and waste oil; improving process adaptability with customised solutions; and promoting standardised, skid-mounted equipment to improve cost-effectiveness. SINOKLE will continue to put technological innovation at its core, supporting the sustainable development of the oil and gas industry and achieving both environmental and economic gains.