Study On The Secondary Cross-linking Gel System And Its Profile Control Performance Evaluation Of Low-temperature Conglomerate Reservoir

The conglomerate reservoir had the complex mode pore structure,and extremely strong heterogeneity.This complex geological structure made development more difficult.This paper focused on KD area of Xinjiang karamay oilfield.This zone used water-flood in the early stage,and the comprehensive water content was up to 92.9%by the end of 2014.At the same time,hydraulic fracturing was carried out during the process of development,which aggravated water channeling.So this oil field was badly in need of taking the effective plugging technology.In view of the profile control problem of low temperature conglomerate reservoir in KD area,this paper mainly studied the secondary gel system and the following research contents were completed:(1)On the basis of analyzing the cross-linking mechanism,the article investigated the effect of different factors on the primary gel-forming performance,such as the type of polymer,the mass ratio of the polymer to the crosslinking agent and accelerator.In the end,two gel systems which suited for low temperature(15 to 35 degree centigrade)were selected:?0.1%HP-3+ 1.0%formaldehyde/phenol+(0.01?0.02)%DF-1+(0.1?0.2)%NCO;?0.2%KY+ 1.0%formaldehyde/phenol+(0.02?0.04)%DF-1+(0.1?0.2)%NCO.(2)The experimental investigated the rheological properties of the two systems,which showed that the gel systems were a typical pseudo plastic fluid.After shearing half an hour with the shear velocity of 150s-1,the regained-viscosity recovery factor is more than 85%,and the HP-3 system had a good shearing resistance.(3)After analyzing the mechanism of secondary crosslinking,the suitable primary gel system were selected to carry out the secondary cross-linked experiments.The studies investigated the influence of polymer type,crosslinking agent,coagulant and shearing action on secondary crosslinking.The results show:The first crosslinking agent and the coagulant had an obvious effect the secondary crosslinking process,and the second crosslinking agent influence in weaker.Moreover,the shear action caused polymer chain to fracture,which increased the gel time of the secondary crosslinking gel and weakened the gel strength.(4)Under the environmental scanning electron microscope,the second crosslinking gelation system presented a geometric uniform three-dimensional network structure,and the crosslinking network was denser than first gel.Besides the HP-3 system has a higher crosslinking degree and a more stable performance.(5)Through the core flow experiments,the paper investigated the performance of the gel system in porous media:? the single core experiments showed that the resistance coefficient of primary gel in the fracture core is between 25 and 45.In additional,the filtration loss of the gel system in the migration process was present,and the weak cross-linked structure of primary gel can effectively reduce the damage to matrix of gel solution.The second gel system which the sealing rate was above 97%,showed excellent adhesion and stress deformation ability,and would form effectively plugging.? the parallel cores experimental results showed that:Because the core had a fracture in it,the proportion of the core water absorption is close to 1:1 before profile control,which was hardly changed by the core permeability.After the profile,the relative water absorption of the parallel core is obviously improved.And with the increase of the permeability differential,the effect of secondary gel to improve the water absorption profile was better.