Abstract
When superheated steam flows along the horizontal wellbore, it may change to saturated steam at some point of the wellbore. In this paper, to accurately predict the heat radius of cyclic superheated steam stimulation with horizontal wellbore, the distribution of thermophysical properties of superheated steam along the horizontal wellbore is considered. The heating process is divided into 4 stages for superheated steam and 3 stages for saturated steam when the phase change undergoes in the wellbore. On this basis, the mathematical model for heat radius of cyclic superheated steam stimulation with horizontal wellbore was established according to energy conservation principle and Laplace transformation method. The calculation result of the new mathematical model is in good agreement with that of the numerical simulation (CMG STARS) for the same parameters from a specific heavy oil reservoir, which verified the correctness of the new mathematical model. The effect of degree of superheat and the cycle of stimulation are analyzed in detail after the new mathematical model is validated. The results show that the heat radius of superheated zone, steam zone, and hot fluid zone all decrease with horizontal well length and increase with the cycle of stimulation. The higher the degree of superheat is, the farther from the heel of the horizontal wellbore the phase change undergoes. Besides, the radius of superheated zone, steam zone, and hot fluid zone increases with the degree of superheat, but the value increases little at steam zone and hot fluid zone.
Highlights
By far, steam injection is the most extensively adopted enhanced oil recovery process in heavy oil resources development because the viscosity of heavy oil reduces rapidly with temperature and the flowing ability of heavy oil is significantly improved [1,2,3]
The results show that the heat radius of superheated zone, steam zone, and hot fluid zone all decrease with horizontal well length and increase with the cycle of stimulation
Cyclic superheated steam stimulation with horizontal wellbore can fully exert the advantages of horizontal well and superheated steam, and it is an important method for developing heavy oil reservoirs, especially thin reservoirs
Summary
Steam injection is the most extensively adopted enhanced oil recovery process in heavy oil resources development because the viscosity of heavy oil reduces rapidly with temperature and the flowing ability of heavy oil is significantly improved [1,2,3]. Marx-Langenheim [15] and Willman [16] have done pioneering work in establishing mathematical models to calculate the heat radius of cyclic steam stimulation with vertical well according to energy conservation principle. On this basis, Li Chunlan [17, 18] and Zhou Tiyao [19] established mathematical models for heat radius with the consideration of the nonisothermal distribution of the formation temperature in the heating area. Ni Xuefeng [22] and Liu Chunze [23] derived calculating models of heat radius along horizontal wellbore according to the fact that horizontal wellbores are different from vertical wellbore in terms of heating process and mechanism
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