A new approach to obtaining relative permeability curves during chemical flooding process in a low-permeable reservoir

Abstract

It is always difficult to obtain the relative permeability curve for a low-permeable reservoir using chemical flooding, as there are so many problems associated with the current measurement methods, especially when interfacial tension r, wettability cosh and pore-throat radius ratio m are considered as the main factors that influence the shape of the relative permeability curve, and thereby the oil recovery. This paper presents a new concept of modified capillary numbers (N CM ), associated with these three factors. First, laboratory experiments were carried out to get relationship between N CM and the residual oil saturation S OR under different conditions. Second, oilwater relative permeability curves for a target oil layer using the steady-state flow method were determined. Using these two steps, a relative permeability curve under different conditions of interfacial tension r, wettability cosh and pore-throat radius ratio m has been drawn. Based on the calculated relative permeability curves, the oil displacement efficiency and flow capacity were determined. Subsequently, the relationships between the relative permeability curve, oil displacement efficiency, flow capacity and the factors for a low-permeable reservoir were established using chemical flooding.Keywords Low permeable Á Chemical flooding Á Relative permeability Á Modified capillary number Á Pore-throat radius ratio Á Wettability Á Interfacial tension List of symbols hWetting angle (°) coshAverage contact angle cosine, the parameters of the wettability (-) N CM Modified capillary numbers (-) mPore-throat radius ratio (-) S OR Residual oil saturation (%) rInterfacial tension (mN/m) V wsp Water absorption oil discharge quantity in the Amott wettability index measurement experiment (ml) V wt Volume of oil by water displacement (ml) I W I W = V wsp /(V wsp ? V wt ) shows that the degree of water-wet (-) V osp Oil absorption water discharge quantity (ml) V ot Volume of water by oil displacement (ml) I O I O = V osp /(V osp ? V ot ) shows the degree of oil-wet (-) Amott wettability index I A

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