Research And Application Of Environment-friendly Aluminum Cross-linking Profile Control Agent

The oil and gas resources of low-permeability oilfields are abundant.The natural fractures are developed and complex artificial fractures are formed as a result of fracturing operation development.With the development of long-term water injection,the water cut of oil well in the well groups increase,and even some of these oil wells become flooded.The conventional delayed cross-linking profile control agents,such as phenolic and chromium cross-linking agents are highly toxic,environmental unfriendly,and the gelation time cannot meet the sealing of deep fractures and large pores.Therefore,the environmental friendly aluminum cross-link profile control agent has been studied.In this paper,aluminum citrate powder was bonded into a granule core using gelatinized starch solution.An environmental friendly aluminum cross-linker was prepared by an inverse suspension crosslinking polymerization technique.The acrylamide was taken as the monomer and the N,N-methylenebisacrylamide was taken as the cross-linker.The structure and morphology of the environmental friendly aluminum cross-linker was characterized by infrared spectroscopy and electron microscopy.The relationship between the release rate and time of the environment-friendly aluminum cross-linker was measured by the spectrophotometer.The performance of the environmental friendly aluminum cross-link profile control agent was evaluated based on the optimized formula?2500mg/L HPAM,1300mg/L environment-friendly aluminum cross-linker,2500mg/L stabilizer W-2?,the experimental results are as follows:the capsulized environmental friendly aluminum cross-linker surface was covered completely on the surface,there were some micro-pores,the encapsulated membrane was cross-linked polyacrylamide.The release rate of Al³⁺increased with the rising of temperature,decreased with the rising of salinity.The release rate of Al³⁺was influenced seriously under strong acid/alkaline environment.The release of Al³⁺reached equilibrium(The release rate of Al³⁺were about 64%)after 32h under the temperature of 45°C,the salinity of 5.0 g/L and the pH of 7.The environmental-friendly aluminum cross-link profile control agent is suitable for the medium and low temperature reservoir with neutrality conditions.The environmental friendly aluminum cross-link profile control agent gelled in 3 to 5 days with the time controlled.With the good salt resistance,the gel did not dehydrate at 45°C for 180 days.With the good resistance to erosion and selective sealing,the plugging rate reached more than 97%.Based on the results of the laboratory study,the pilot test was successfully conducted in the7448 well group and 7409-1 well group in the Siwan oil zone of the Zichang oil field.After the implementation of profile control using the environmental friendly aluminum cross-link profile control agent in 7448 and 7409-1,the starting pressure was significantly increased.The average cumulative oil increased over 170 tons in the well group,and average water content decreased about 12%,it is benefit for increasing the production of the oil when decrease the water cut.Meanwhile,the research results could popularized to other well groups in the area.