Case Study: Liquid Filtration Bags for Oil & Gas Produced Water Treatment
Produced water is the largest byproduct of onshore and offshore oil and gas extraction, containing suspended solids, crude oil droplets, dissolved minerals, and corrosive chemicals. Unfiltered produced water causes severe issues including pipeline scaling, injection reservoir clogging, pump abrasion, and environmental discharge violations. This case study focuses on a mid-sized onshore oilfield in northern China that adopted industrial liquid filter bags for produced water pre-filtration and reinjection treatment, covering actual working conditions, applied filter bag specifications, operational challenges, and final optimization results.
The oilfield processes approximately 1,200 cubic meters of produced water daily for well reinjection and standard discharge. The original treatment system only adopted simple mesh strainers, failing to remove fine suspended particles and dispersed oil effectively, resulting in frequent equipment blockage and substandard water quality. To standardize technical data and clarify application parameters, the on-site working conditions and matched filter bag specifications are summarized in the table below for intuitive reference.
|
Category |
Parameter Item |
Technical Data |
|
On-Site Working Conditions |
Daily Water Treatment Capacity |
1200 m³/day |
|
Operating Water Temperature |
40–75°C |
|
|
System Continuous Working Pressure |
0.6–1.0 MPa (with instantaneous pressure fluctuation) |
|
|
Water Quality Property |
Weak alkalinity, high chloride ion concentration, slight corrosiveness |
|
|
Raw Water TSS Content |
80–150 mg/L |
|
|
Raw Water Residual Oil Content |
15–25 mg/L |
|
|
Contaminant Particle Size Range |
2 μm – 100 μm |
|
|
Filtration Bag Specifications |
Standard Size |
#2 (180×810 mm) |
|
Filter Material |
High-density needled polypropylene (PP) |
|
|
Filtration Precision |
10 μm (nominal rating) |
|
|
Max Tolerable Temperature |
95°C |
|
|
Effective Filtration Area (Single Bag) |
0.75 m² |
|
|
Maximum Dirt Holding Capacity |
2.8 kg |
|
|
Allowable Pressure Difference |
0.1 MPa |
|
|
Processing Technology |
Seamless ultrasonic welding (no fiber shedding) |
Under the above harsh and stable operating conditions, the original strainer equipment could not intercept fine particles and dispersed oil efficiently. Long-term operation caused pipeline scaling, precision filter clogging, pump body abrasion, and increased field maintenance frequency, severely restricting the stability of produced water reinjection and up-to-standard discharge.
To completely solve on-site water treatment problems, the oilfield adopted customized PP liquid filter bags fully adapted to produced water working conditions. As shown in the table, the selected #2 standard filter bags are universally compatible with conventional stainless steel bag filter housings, featuring strong practicability and convenient replacement. The high-density needled PP material boasts excellent acid and alkali resistance and chloride corrosion resistance, perfectly matching the weak alkaline and high-chloride water quality. With a maximum temperature resistance of 95°C, it far covers the actual operating water temperature range, ensuring no material deformation or performance attenuation in long-term high-temperature service.
In terms of core filtration performance, the 10 μm precision design balances efficient interception and unobstructed water flow, avoiding excessive system pressure drop. The seamless ultrasonic welding structure eliminates fiber shedding, preventing secondary pollution to produced water. A single filter bag provides 0.75 m² of effective filtration area and 2.8 kg dirt holding capacity, suitable for the oilfield’s high-flow and high-pollution continuous filtration scenario. The system is set with a warning pressure difference of 0.05–0.1 MPa; timely bag replacement at this threshold ensures long-term stable operation of the filtration system. Compared with ordinary polyester filter bags, PP material has outstanding hydrophobicity, which greatly optimizes the removal effect of tiny oil droplets and suspended solids.
After three months of continuous field operation, the filtration system achieved remarkable optimization effects. The TSS content of treated produced water stably drops below 15 mg/L, and residual oil content is reduced to less than 5 mg/L, fully meeting oilfield reinjection and environmental discharge standards. The blockage frequency of subsequent precision filters and water injection pipelines decreased by 85%, and the maintenance cycle of water injection pumps was extended from 15 days to 90 days. The filter bags show stable structural performance under long-term high-temperature and corrosive working conditions, with no deformation, damage or fiber shedding. The standardized size allows fast replacement, reducing system downtime and improving overall water treatment efficiency.
This case verifies that matched liquid filter bags are economical and efficient core equipment for oil and gas produced water treatment. Reasonable material selection, precision configuration and structural design enable filter bags to adapt to harsh produced water working conditions, stabilize water quality, reduce operational and maintenance costs, and provide reliable protection for oilfield water reinjection and clean production.
