Oily sludge is one of the main wastes produced during oilfield development. The composition of oily sludge is complex, resulting in difficult separation and high processing cost. The existing technologies such as landfill, microbiological deterioration, heat treatment and solvent extraction are difficult to meet the needs of oily sludge treatment. It is necessary to develop a highly efficient and cheap reutilization technology for oily sludge. For this reason, we have proposed to recycle the oily sludge which can be utilized to profile control in water injection and thermal recovery wells.
In the process of research, we have developed five aspects of work: First, three-phase separation of oily sludge was carried out by distillation, and water quality, oil-phase composition and solid particle size were analyzed. The compatibility of oily sludge and oil reservoir was investigated. Second, the mechanism and influence factors of the oily sludge for profile control were studied by long core model test and microscope observation. Third, suspension analysis and mobility analysis were developed on oily sludge, and experimental results were used to research oily sludge profile control agent. Fourth, numerical simulation was used to optimize the engineering design of Oily Sludge Profile Control (OSPC). Fifth, ground process flow of oily sludge for profile control was designed.
The following conclusion can be drawn from the study: OSPC is a Reutilization Technology for oily sludge, which could seal up oily sludge in-situ in oil reservoir and be favorable for increasing production of oil wells through profile control. Through the rheology and plugging test, it was clear that OSPC could greatly reduce the pollution risk of oily sludge and the ground treatment cost, and solid phase and oil phase of mud were retained in the formation. It could plug high permeability channels and high permeability area (the plugging rate was more than 90%) to adjust water/steam injection profile of water/thermal recovery wells. Profile control agent, engineering design method and ground process flow for oily sludge were developed. The technology applied 72 wells in the oilfield, 184 thousand tons of oily sludge were used in total, production of crude oil was increased by 84 thousand barrels, and a lot of sludge treatment costs could be saved.