Current Status of Produced Fluid on Offshore Platforms and Its New Treatment Technology
1. Current Status of Produced Fluid Treatment on Offshore Platforms
Offshore oil fields are strategically important for energy supply. Taking China as an example, the production has exceeded 50 million tons, contributing nearly 60% of the country’s crude oil increase. Among this, heavy oil production accounts for more than half of the total offshore crude oil output. The continuous and efficient extraction of offshore heavy oil has become a key part of ensuring national energy security. In this context, enhanced oil recovery technologies such as steam flooding and chemical flooding have been widely applied due to their good adaptability to offshore heavy oil reservoirs.
However, with the prolongation of oil extraction, several issues related to oil field extraction technologies have become more prominent. For example, in polymer flooding oil fields, the long-term injection of polymer agents has significantly altered the physical and chemical properties of the produced fluid, leading to several processing bottlenecks:
· Emulsification intensifies, and separation load becomes heavy: The polymer causes the oil-water mixture to form an exceptionally stable emulsion, significantly increasing the difficulty of separation. As a result, the oil content in the produced water increases sharply, and the water content in the crude oil after treatment becomes difficult to stabilize within the standard.
· Reduced efficacy of additives, increased operating costs: Traditional demulsifiers show a marked decrease in effectiveness when treating polymer flooding produced fluids. To meet processing requirements, the dosage of additives has to be greatly increased, directly pushing up operating costs.
· Equipment challenges and increased maintenance burdens: Existing treatment units (such as heat exchangers) encounter issues like coking and clogging when dealing with polymer flooding produced fluids. This requires frequent shutdowns for cleaning, which not only increases maintenance workload but also affects the continuous and stable operation of the entire treatment system.
· Difficulties in disposal of by-products, impacting downstream processes: The large volume of viscous oily sludge produced during the process brings operational issues and continues to affect the normal operation of downstream facilities.
In conclusion, with the continuous development of offshore oil fields, the composition of produced fluids is becoming more complex. Existing traditional treatment processes, under the combined effects of these factors, can no longer meet the current demand for efficient and intensive production, making process upgrades and technological innovations imperative.
2. Current Status of Produced Fluids on a Platform in the Bohai Sea, China
A certain offshore oil platform in the eastern Bohai Sea of China is rich in oil and gas resources. Exploration began in 1996, the first well was drilled in 2000, and system output evaluation was completed in 2005. The proven petroleum reserves of this oil field reached 5222.07×10^4 m³, with heavy oil reserves of 4187.87×10^4 m³, accounting for 85%, making heavy oil extraction significant. The temperature range of the produced fluid processed by the platform's jet pump power fluid separator is 35–60℃, with an oil content that can reach 20%. The medium contains a large amount of foam and is severely emulsified, resulting in poor overall water quality. Currently, the separation efficiency of the produced fluid is unsatisfactory, affecting the stable operation of subsequent treatment processes and limiting the platform's overall production system's treatment efficiency and standard compliance capability.
3. New Produced Fluid Treatment Process
To address the above challenges in produced fluid treatment, the project team conducted a systematic survey and comprehensive comparison of various mainstream treatment technologies on the market. After evaluating the applicability, maturity, and processing effectiveness of each technology, they ultimately chose the Shenzhen Clear Science & Technology Co., Ltd (SINOKLE)’s patented product - Cyclonic Dissolved Gas Flotation Unit (CDFU). This technology has accumulated reliable operational data in actual industrial scenarios and has been successfully applied in multiple projects, including PetroChina’s Dushanzi Petrochemical desalinization wastewater treatment, oil wastewater treatment in Turpan-Hami Oilfield, and offshore platform oil wastewater treatment in CNOOC’s Bohai area.
CDFU, or Cyclonic Dissolved Gas Flotation Unit, is a technology that integrates the centrifugal cyclone separation and dissolved gas flotation separation, forming a synergistic and efficient treatment system. The device significantly enhances the collection and removal of oil droplets and suspended solids through the combined action of the cyclone field and dissolved micro-nano bubbles. This not only greatly improves flotation efficiency but also shortens the hydraulic retention time, achieving efficient and rapid purification of oily wastewater, especially suitable for treating various difficult-to-process industrial oil (and suspended solids) wastewater.
The process diagram is shown in Figure 1.
Figure 1. Process Diagram for Oilfield Produced Fluid Treatment
4. Conclusion
After the CDFU treatment device was put into production, the treatment effect of the produced fluid became stable, and the oil-water separation was significantly improved. The average oil content in the produced fluid decreased from approximately 1275.2 mg/L to about 114.7 mg/L, with an average reduction of 1160.5 mg/L, and the oil removal efficiency reached 90.99%, far exceeding the 80% design requirement.
The application of the CDFU treatment device successfully solved the problem of poor power fluid separation during daily operations on the platform, while effectively reducing the operational load of downstream processing equipment. The CDFU treatment device has broad application prospects in offshore platform produced fluid treatment processes.
