Abstract

Steam stimulation has already been proved as an important thermal recovery technology. In Daqing, the development and management of high-heterogeneous heavy oil reservoirs plays an important role in stabilizing the oil output. To combine the good features of steam injection and cyclic injection, a cyclic steam flooding has been conducted in the Fuyv reservoir, Daqing. This paper aims to present a detailed process of the cyclic-steam injection. The target Fuyv reservoir in this research is located on the edge of the Songliao Basin. The reservoir characterized by high heterogeneity has a permeability range from 61.5 to 3650 mD. The viscosity of crude oil is averagely 3200 mPa.s. A simulation investigation was performed to instruct the pilot design. The nitrogen co-injected cyclic steam injection is also proposed and analyzed. The mechanisms of EOR by nitrogen assisted cyclic steam stimulation are studied. The pilot injection was fulfilled on the basis of fundamental investigation. The simulation results showed that the heated radius is a function of injection cycles. When the injected steam is only enough to forfeit the heat loss to caprock and beneath formation, the heated radius or heated area will not expand. The limited heated radius and steam overlapping vertically results in a poor sweep efficiency and oil-steam ratio, a large amount of oil untapped. The factors effecting production and injection performance are analyzed, and the injection parameters are optimized. The pilot injection has obtained foreseeable results.

Key words: Cyclic, steam inject, heavy oil, Fuyu reservoir, N₂-foam.