Abstract
Water shutoff and profile control is one of the most important technologies to enhance oil recovery. To ensure the success of this technology, the key is to accurately determine gelation time and gel strength during gel flow in porous media. The HPAM (Hydrolyzed PolyAcrylaMide) system and redox system (sodium bichromate and sodium sulfite) is widely used, whose static gelation time in ampoule bottles and porous media was determined, as well as the dynamic gelation time in an agitator and porous media. The shear rate was considered one of the major factors affecting gelation time. The results showed that the static gelation time in porous media was much longer than that in ampoule bottles. The Initial Gelation Time (IGT) in porous media was two or three times that in ampoule bottles, while the final gelation time in porous media was six times that in ampoule bottles. Under shearing in an agitator, the gelation process was divided into four phases: induction, sudden increase, stability and decrease. With the increase in shear rate, gelation time was prolonged and gel strength decreased. There was a critical gelation shear rate, above which there was no gel formed. Shear had almost no influence on gel strength during the induction stage but in the process of sudden increase, shear could degrade gel strength sharply. The time of dynamic gelation in porous media was much longer than that of static gelation in porous media and ampoule bottles. When HPAM and RS (Redox System) concentrations increased, the IGT of dynamic gelation in porous media was shortened.
Highlights
With the development of oilfields, the strips of high permeability emerge in the process of water flooding; and it is very important to enhance the volumetric sweep efficiency after water flooding
The gelation time, which is divided into Initial Gelation Time (IGT) and Final Gelation Time (FGT), was determined by measuring viscosity [3]
The results showed that the process of gelation could be divided into three phases: slow induction, sudden increase and stability
Summary
With the development of oilfields, the strips of high permeability emerge in the process of water flooding; and it is very important to enhance the volumetric sweep efficiency after water flooding. There are many methods to obtain the static gelation time, such as the code of gel strength [1], the change in viscosity with time [2], the measurement of the storage modulus and loss modulus, application of electrical conductivity and so on. There has been some research on the effect of shear on gelation time, application performances and re-formation after shear [8,9,10,11,12] This was conducted under the condition of static gelation. The relationship between the static gelation time and dynamic gelation time was established, and the critical gelation shear rate was determined with the agitator
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