Optimization Of Chemical Methods To Improve Oil Recovery Rate

Changqing Wang 20-06 well located in the north of shaanxi, the reservoir pore types contain the primary intergranular pore, dissolution intergranular pore and dissolution intragranular pore, which belong to the typical low permeability reservoir. Reservoir propertis are poor,heterogeneity is serious, non-darcy seepage flow and threshold injection pressure are high, capillary force is strong, so that the remaining oil stay in the porous media is difficult to start. Wettability is neutral and slightly water wet, it is the high salinity blocks that salinity in50000~100000mg/L. The oil acid value is low, so it’s not suitable for alkaline drive. During the high water cut development, water content rising rapidly and production decline seriously. The current recovery degree is 17.3%, water ratio is 53.2%.To meet better economic benefits, we must use appropriate methods to restrain the negative impact so as to improve the oil recovery degree. But now, the most effective methods for chemical flooding in eor mainly are surfactant flooding, alkaline flooding and polymer flooding. But all of them have different disadvantages.Surfactant flooding have badly absorption loss, poor heat resistance salt resistance, low displacement efficiency. More demanding and alkaline flooding demand the oil acid value must under 0.5 mg KOH/g. Alkaline can cause oil-water phase p H increases, change the double electrode layer of rock surface, and electrostatic repulsive force make particlesreleased from the rock surface, increase the reservoir damage. Under high p H, the divalent ions content, such as Ca2+ and Mg2+, is also high,it’s easy to cause scaling and salt sensitivity phenomenon. Due to the activity of rigid structure and hydrophilic functional group on modified polymer molecule chain is low, that lead to poor water soluble. A small amount of high molecular weight polymers and surfactants composited Dual-compound drive, it can improve recovery greatly, but due to the side effects of polymer, it also increased the reservoir damage. So from the perspective of reducing reservoir damage, this topic selection surfactant flooding.Against the problems of Changqing Wang 20-06 reservoir, this study designed a highly active compound surfactant systerm CY-1.0.3%~0.6% solution can drop the interfacial tension to 10-3m N/m in ten mins, which reduce the capillary effect and reservoir starting pressure effectively. Heat resistance to 80℃, and salt resistance to 100000mg/L salinity. Adsorption amount is less than 0.5mg/g oil sand, below the enterprise standard. Single surfactant displacement efficiency on an average of 9.44%, polymer/surfactant Dual-compound displacement efficiency is as high as 11.74%, showing excellent comprehensive performance, satisfies the requirement of test application.