A New Composite Viscosity Reducer for Abnormal Low Temperature Extra-Heavy Oil Reservoir with High Acid Value

M7 block of Santanghu oilfield is an abnormal low temperature tight oil reservoir. The effective development is very difficult. In this paper, we develop a new composite viscosity reducer called CSY-1. The synergistic effect of these agents provides the reducer with both dispersion and emulsification capacities. Based on orthogonal experiment and cost evaluation, the optimum formula of CSY-1 is 0.5% OP-10, 1.8% SDBS, 0.1% Tween 80, and 1% NaOH (or Na2CO3). The rheology property of heavy oil changed fundamentally before and after the addition of CSY-1. Oil-in-water emulsion with very low viscosity can be obtained and the viscosity reduction rate can be over 99%. Simulation results showed that the oil production of a single well can be increased from the current 3.74 t/d to 8.12 t/d with the application of this reducer.