A Resource-Oriented Method of Oily Sludge Disposal in ASP Flooding Production

AbstractIn the field practice of alkaline/surfactant/polymer (ASP) flooding, there is more oily sludge produced and accumulated in settling tank, dehydrater, recycling pool, etc. Timely and effective disposal of oily sludge has already played an indispensable role in establishing the surface and subsurface integration pattern with chemicals EOR. Many conventional disposal methods faced to the challenges of separation efficiency, facilities pollution, healthy and environmental threats, and economical justification with the appearance of alkali, surfactant and polymer in produced liquid (mixture of oil and water of wells). We focus on using physical comprehensive effects to remove the emulsified oil and absorbed water, and the in-situ utilization of the left sludge was regarded as a method development to address the challenges recently. A laboratory investigation of characterizing the properties of oily sludge in ASP flooding production was recently carried out. The heating-washing-centrifuging combination treatment process was practiced. After removing its emulsified oil and absorbed water, the sludge transported to filter bed to form a suspended sludge blanket was studied and the feasibility of in-situ utilization of filtering separated water was also evaluated. The application effects of the resource-oriented disposal method were assessed, and the integration technology and operation parameters were designed and optimized.The results indicate that the oily sludge with ASP flooding is characterized by high caloric value, high water cut, high viscosity, strong electronegativity and stability, and there is relatively high melting temperature, more wax and asphaltenes in oil phase. There appears to be a linear relationship between the scale of oily sludge deposition in surface facilities and the appearance concentration of chemicals in produced liquid of production wells. Compared with the previous thermochemistry demulsification disposal methods, dirty oil recovery ratio increased more than 15%, and running expense was reduced around 20%. The dirty oil content in the sludge was less than 2% when disposed under the combination disposal process and operation parameters. Furthermore, the formed suspended sludge blanket has the functions of in-situ purification of separated water, achieving the cyclic utilization in washing process. The probable impacts of its direct discharge into the normal sewage treatment system reduced and secondary pollution decreased spontaneously. This study is beneficial to provide a robust and potential way for disposing oily sludge in the production and operation of chemicals EOR, and it is also significant to understand the surface and subsurface integration idea and further accelerating ASP flooding application in high water cut oilfields.