Revealing patterns in the aggregation and deposition kinetics of the solid phase in drilling wastewater

Oleksii Shestopalov,Oksana Hetta,Valeriia Ananieva,Nadegda Rykusova,Oleksandr Chynchyk

doi:10.15587/1729-4061.2019.157242

Abstract

We have investigated the influence of the concentration of the solid phase of drilling wastewater on a change in the sedimentation rate of the solid phase at aggregation when applying a physical-chemical method of water purification using flocculants and coagulants. This is important because a change in the concentration of the solid phase in wastewater is an uncontrolled process during reagent-based purification and it significantly affects the aggregation mechanism, as well as the kinetics of a solid phase sedimentation. The study was performed using the model wastewater prepared by diluting the used drilling mud with tap water. It was found that the use of flocculants without coagulants is not effective and does not lead to aggregation. It was established that the optimum dose of the coagulant aluminum sulfate that is capable of disrupting the stability of the disperse system of drilling wastewater is 65 mg/g, while increasing the dosage of coagulant has no effect on the rate of flake deposition. Among the flocculants, the most active one is the anionic flocculant A-19. Sludge thickening results in the destruction of floccules; in 9 minutes, the floccule deposition rate is reduced two-fold. Increasing the concentration of a flocculant from 0.8 mg/g to 1.6 mg/g leads to an increase in the deposition rate of the solid phase by 2‒2.5 times. It is shown that the solid phase concentration affects the sedimentation rate of floccules; optimum conditions for aggregation are observed at a concentration of 4‒6 g/l. Mechanical impacts on aggregates exert a destructive effect depending on the concentration of the solid phase. It has been established that changes in the dispersed system can be observed based on a change in pH, which varies depending on the concentration of the solid phase in drilling wastewater. Increasing the concentration of the solid phase from 1 to 10 g/l leads to the change in pH from 7.2 to 8.3; the introduction of coagulant reduces pH, while the subsequent destruction of aggregates leads to an increase in pH. The data obtained in the course of our research, as well as the proposed procedure, could be used in order to select the optimal dosages of reagents during drilling wastewater treatment

Highlights

Energy independence of any country requires increasing amounts of oil and gas production
Our study into the influence of a coagulant dosage on deposition rate of the solid phase in drilling wastewater (Fig. 2) has shown that increasing a dose over 65 mg/g slightly alters the kinetics of deposition
As a result of research into the influence of dosing of reagents on deposition kinetics of the solid phase in drilling wastewater, it was established that the introduction of flocculants without coagulants does not lead to aggregation while an increase in the coagulant dosage has no effect on the settling velocity of flakes from the solid phase

Summary

Introduction

Energy independence of any country requires increasing amounts of oil and gas production. A complex chemical composition, which depends both on a drilling technology in a given area and the geological structure of underlying gas reservoirs, as well as the presence of a thin fraction of soak clay in wastewater, complicate the processes of its treatment. In each case, at each well, it is necessary, depending on the conditions for wastewater formation, to explore a possibility to treat DWW, as well as adjust reagent consumption. It is an important scientific and practical task to undertake a research and devise a procedure for treating the actual drilling wastewater, which would be applicable at wastewater treatment plants

Literature review and problem statement

The aim and objectives of the study

Conclusions

Findings

15. Coagulation of bentonite suspension by polyelectrolytes or ferric chloride