Field Test of Lithium Extraction in Oilfield Associated Water: A Case Study of YQ Treatment Station

Abstract The oilfield associated water is complex in composition and poses significant hazards, necessitating treatment to prevent environmental pollution. Taking the Yingqian Treatment Station as an example, it processes approximately 2,400m³ of water daily. Sampling and testing revealed that the total hardness of the water exceeds 20,000mg/L, with a Mg2+ concentration of about 1,200mg/L. Most importantly, the Li+ concentration reached 150mg/L, meeting the requirements for economic development (≥50mg/L). Consequently, related research and experiments were promptly initiated. Owing to the associated water's high total hardness and low lithium content, which significantly differ from saturated brine, traditional lithium extraction techniques cannot be directly applied. In response, research has identified that manganese-based adsorbents offer the advantage of high adsorption capacity, but require concentrated acid for desorption. Conversely, bipolar membrane electrodialysis has the merit of producing lithium products with high purity; however, the byproduct concentrated acid is a hazardous chemical that necessitates proper disposal. Consequently, a combined technological approach has been proposed to leverage the strengths of both methods. The lithium extraction experiment from oil-gas field associated water at the YQ Treatment Station in China was conducted from May to June 2023, successfully producing 2.05kg of monohydrate lithium hydroxide from 116m3 of associated water. However, the experiment encountered numerous issues. For instance, the LiCl solution after a single desorption with HCl failed to meet the feed concentration requirements for subsequent processes. After extensive argumentation, the solution was adjusted by using a mixture of LiCl and HCl from the first desorption to replace HCl as the desorbent, and adjusting the desorption process from one stage to two, thereby increasing the LiCl concentration. The daily production of associated water in blocks such as Yingqian (YQ), Keshen 8 (KS8), and Dabei (DB) in the Western China Oil-gas Field exceeds 7,000 m3, indicating potential for lithium resource development. In the near future, as these lithium resources are gradually harnessed, they will yield substantial economic benefits and reduce the overall cost of water treatment.