The Feasible Conditions Study of Steamflooding for Heavy Oil Reservoirs In China After Cyclic Steam Injection

Abstract

Abstract China is rich in heavy oil reserves. In recent ten years, the production of heavy oil has rapidly grown through application of steam injection and the annual production reached up to 11.9 million tons in 1993. At present, with the increase of cycles of steam injection, the effectiveness becomes poorer and the challenge of changing steam stimulation into steamflooding has to be confronted. Because of heavy oil reservoirs in China characterized with complex geological conditions, deeply buried, multi-layers and serious heterogeneity, especially some complicated conditions occurring in steam cycling, the effectiveness of steamflooding pilots has not been ideal commonly. Therefore, it is urgent to study and determine the comprehensive conditions at which the reservoirs are feasible to be converted from steam cycling to steamflooding at the present technological situation. In this paper, based on three typical types of heavy oil reservoirs, systematic studies have been conducted to investigate the effects of oil viscosity, oil formation thickness, vertical permeability difference, reproduction ratio of injected water in steam cycling and channelling path etc. on steamflooding effectiveness. Then, a practical screening criterion of steamflooding is proposed to provide technical bases for the conversion. Introduction The commercial thermal recovery for heavy oil in China started in the late of 70's and the beginning of 80's. Although the conditions of China heavy oil reservoirs are generally not ideal, characterized with many types, most buried deeply (900-1,600 m) and complex geology, thermal recovery technology has been developed rapidly in China in the last more than ten years through the advancement of science and technology, and heavy oil production has steadily increased. As the result, China has became one of the main heavy oil production countries in the world. P. 569