Formula Design and Performance Evaluation of Chemical Sand Stabilization of Unconsolidated and Low Permeability Reservoirs
The low-permeability reservoir is a typical loose low-permeability reservoir,which has the characteristics of poor reservoir physical properties,high shale content and fine sand grain size.Sand control and release oil well productivity are the key to the exploitation of similar low-permeability and loose reservoirs.At present,the applicability of conventional mechanical sand control technology is poor,and the screen pipe is easy to be blocked by mud and fine silt.According to the characteristics of loose and low permeability reservoirs,new polymer sand stabilizing agents CWW-1 and DWS-1 were developed based on the mechanism of electrical adsorption.The effect of composite sand stabilizing system composed of these two kinds of sand stabilizing agents was better than that of single sand stabilizing agent.The composite anti-swelling and stabilizing sand system can adsorb fine silt into fine silt aggregates,so that the problem of fine silt control can be solved into the problem of medium and coarse particle size sand control,and the critical flow rate of sand production can be improved to stabilize the sand and release the productivity of oil well to the greatest extent.Taking permeability recovery value and median change rate of fine silt particle size as indexes,the chemical sand stabilization system suitable for low permeability reservoir is optimized through core displacement test and particle size determination of fine silt before and after sand stabilization.It is found that the core permeability recovery value of 25×10-3 μm2 is close to 70％and that of 300x 10-3～1 000×10-3 μm2 is between 80％～100％after treatment with chemical stabilization system of 0.8％CWW-1+2％DWS-1;the median particle size of fine silt after treatment is about 3 times larger than that before treatment,which can reach the good grade of evaluation standard(the change rate of particle size before and after treatment is 200％～400％)After the chemical sand stabilization system(0.8％CWW-1+2％DWS-1)treatment,the critical sand production flow and the critical sand production pressure were increased by 9 times and 10 times respectively.The permeability reduction after sand stabilization was less than 10％,which could meet the development needs of oilfield.
chemical stabilizationloose low permeability reservoirsand productionfine silt
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