Abstract
In light of the difficulty of solid-liquid separation of waste PEM drilling fluid in the Bohai oilfield, constructing an inorganic-organic flocculation system is proposed and the processing method of destabilization technology is optimized. The biggest influence factor on the flocculation process of PEM drilling fluid was determined by designing an orthogonal test. The flocculation mechanism was researched through single factor optimization, combined with zeta potential and particle size distribution test. The results showed that the most significant factors affecting the flocculation of waste PEM drilling fluid were the dosage of inorganic flocculant CaCl2 and flocculation pH value. When the dosage of inorganic flocculant CaCl2 was 1.2% (w/v), the dosage of organic flocculant SDYJ-2 was 0.05%, the flocculation pH value was 3, and the flocculation time was 5 min, the flocculation technology reached the optimization and then the liquid yield can reach 70.96%. The mechanism of flocculation and destabilization was as follows: the inorganic flocculant of CaCl2 mainly reduced the zeta potential of clay particles through electric neutralization. 1% CaCl2 could reduce the potential mean value of drilling fluid system from -38.1 mV to -32.5 mV, and then decrease the repulsion among suspensions. Through bridging curling and electric neutralization, the organic flocculant of SDYJ-2 can absorb and wrap the clay particles after flocculation destabilization to form a network spatial structure, which made clay particles aggregate into large flocs and particles. D50 can increase by 21.5 times, when the concentration of SDYJ-2 was 0.15%.
Highlights
Bohai Sea is the only semi-enclosed inland sea body in China, and the ecological environment has a serious impact on the daily life of coastal residents
In order to improve the flocculation destabilization efficiency and simplify the field construction for the characteristics of waste PEM drilling fluid in Bohai oilfield, this paper proposes to build an inorganic organic flocculation system, optimize the optimal treatment methods of different flocculation destabilization processes, and analyze its flocculation destabilization mechanism for waste PEM drilling fluid in Bohai oilfield
When the CaCl2 dosage is less than 1.2%, with the increase of CaCl2 dosage, the liquid yield of waste PEM drilling fluid increases slowly after solid-liquid separation
Summary
Bohai Sea is the only semi-enclosed inland sea body in China, and the ecological environment has a serious impact on the daily life of coastal residents. With the increasingly strict requirements for environmental protection, more attention has been paid to the effective disposal of waste drilling fluid by offshore drilling (Malachosky et al, 1993; Hou-ming et al, 2012). Solid-liquid separation is one of the best methods for environmental protection due to the limitation of spatial position on offshore drilling (Wang et al, 2021). Wang Youhua et al (Cui et al, 2011) applied low pressure distillation technology to solid-liquid separation of drilling fluid. This process mainly contains such three steps as chemical destabilization, fold and spiral dehydration, and low pressure distillation. In order to improve the flocculation destabilization efficiency and simplify the field construction for the characteristics of waste PEM drilling fluid in Bohai oilfield, this paper proposes to build an inorganic organic flocculation system, optimize the optimal treatment methods of different flocculation destabilization processes, and analyze its flocculation destabilization mechanism for waste PEM drilling fluid in Bohai oilfield
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