Study of massive water huff-n-puff technique in tight oil field and its field application

Abstract

Abstract Based on the characteristics of horizontal oil wells in tight reservoirs during their late stage, which are exploited by elastic drive of natural energy and stimulated by large-scale volume fracturing; the massive water huff-n-puff technique is proposed for the use of supplementing the energy of the depleted formations, which can effectively increase the productivity of single horizontal oil well in addition to its financial benefits. In this paper, the massive water huff-n-puff technique is defined and discussed from the following aspects of the mechanism, reservoir engineering, laboratory experiments and so forth. Additionally, comprehensive analyses of the advantages of applying this technique in the development of tight oil reservoirs are provided. By the studies of the pressure composition diagram and the definition of residual injection pressure (RIP) in reservoirs, a massive water huff-n-puff mathematical model was established and the critical parameters for water-flooding were calculated. Laboratory experiments of this technique have shown that it can induce a certain number of micro-fracture networks and its application in actual oilfields also shown positive results. The pilot tests have achieved remarkable increases in productivity and economic benefits. For example, the average daily oil production from a single well is increased by 4.5\u202ft/d (0.8\u202f→\u202f5.3\u202ft/d), the formation pressure has increased by 9.3\u202fMPa (6.9\u202f→\u202f16.2\u202fMPa), accumulated oil production has reached 1,987t, and its input-output ratio has shown an enhancement in the range of 1.00:1.74–1.00:4.06. The research results of this technique provide a new way and an important model for efficient development of horizontal wells in tight oil reservoirs.