Abstract
In order to clarify the major influence factors of resistance coefficient and residual resistance coefficient, so as to provide the basis for optimizing the polymer flooding schemes in oilfield Z of Bohai Sea, artificial cores were made by simulated the characteristic parameters of real reservoir and the spacing of production-injection wells. The main parameters considered include reservoir permeability, polymer solution concentration and polymer injection rate. Core experiment of polymer flooding was taken by considering all the main parameters. The result showed that resistance coefficient and residual resistance coefficient decrease with the increase of core permeability. Resistance coefficient and residual resistance coefficient increase with the increase of concentration of polymer solution. The increment of displacement pressure in low permeability core is higher than in medium and high permeability core. The resistance coefficient increase with higher displacing velocity, and the increment in high permeability core is higher than in low permeability core. The displacement velocity has little effect on the residual resistance coefficient. The experimental results can effectively guide the formulation of polymer flooding scheme in offshore oilfields, and optimize the appropriate injection rate and concentration of polymer solution for different properties of reservoirs, thus ensuring the effectiveness of polymer flooding in offshore oilfields.
Highlights
IntroductionWith the increase of oilfield development age, the water cut of oilfield rises rapidly, which leads to a large decline in production and a lower economic benefit, especially for the water flooding oil field; injected water is liable to form channeling, oil production following declined seriously as a result
According to the existed literature introduction [19], resistance coefficient is defined as the ratio of water mobility to polymer solution mobility, it is usually represented by Rf, It reflects the ability of polymer solution to control displacing phase mobility in porous media during polymer flooding
The factors which affecting the resistance coefficient and residual resistance coefficient can be conferred through Formula (1) to Formula (3), the permeability of the core, the flow of the displacing phase and the viscosity of polymer solution, in addition, formation water salinity and reservoir temperature have some influence on resistance coefficient and residual resistance coefficient, whereas, for destine oilfield, the change of water salinity and reservoir temperature is small, the viscosity of polymer solution, the core permeability and the velocity of polymer solution flooding are the main factor of this research
Summary
With the increase of oilfield development age, the water cut of oilfield rises rapidly, which leads to a large decline in production and a lower economic benefit, especially for the water flooding oil field; injected water is liable to form channeling, oil production following declined seriously as a result. Resistance coefficient and residual resistance coefficient are important indexes for evaluating polymer properties [10]-[15] These two indexes are largely influenced by reservoir conditions and fluid properties, and the existing research on the factors affecting resistance coefficient and residual resistance coefficient is mainly carried out in the onshore oilfields, which with lower production rate and smaller injection-production spacing [16] [17] [18]. Compared with onshore oil fields, offshore oilfields have the characteristics of fast production speed, large injection-production well spacing and strong reservoir heterogeneity.
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