Abstract
Accurate calculation of heat efficiency in the process of superheated steam injection is important for the efficient development of heavy oil reservoirs. In this paper, an integrated analytical model for wellbore heat efficiency, reservoir heat efficiency and total heat efficiency was proposed based on energy conservation principle. Comparisons have been made between the new model results, measured data and Computer Modelling Group (CMG) results for a specific heavy oil reservoir developed by superheated steam injection, and similarity is observed, which verifies the correctness of the new model. After the new model is validated, the effect of injection rate and reservoir thickness on wellbore heat efficiency and reservoir heat efficiency are analyzed. The results show that the wellbore heat efficiency increases with injection time. The larger the injection rate is, the higher the wellbore heat efficiency. However, the reservoir heat efficiency decreases with injection time and the injection rate has little impact on it. The reservoir thickness has no effect on wellbore heat efficiency, but the reservoir heat efficiency and total heat efficiency increase with the reservoir thickness rising.
Highlights
Nowadays, the thermal recovery methods, such as cyclic steam stimulation (Gina and Hugo, 2011; Tewari et al, 2011; Wu and Kry, 1993), steam drive (Du et al 2012; Shie and Todd, 1980; Wu et al, 2015), steam assisted gravity drainage (Miura and Wang, 2010; Wei et al, 2014) are still the most extensively adopted enhanced oil recovery process in heavy oil reservoirs
The thermal recovery methods, such as cyclic steam stimulation (Gina and Hugo, 2011; Tewari et al, 2011; Wu and Kry, 1993), steam drive (Du et al 2012; Shie and Todd, 1980; Wu et al, 2015), steam assisted gravity drainage (Miura and Wang, 2010; Wei et al, 2014) are still the most extensively adopted enhanced oil recovery process in heavy oil reservoirs. In those thermal recovery methods, high-temperature steam is injected into the pay zone, and the viscosity of heavy oil decreases and its flow ability is improved (Liu et al, 2008a; Yu and Zhang, 2016; Yu, 2001) During the process of steam injection, not all heat carried by the steam can be used to heat the pay zone, because part of heat will loss to surrounding formation during the steam flowing in the wellbore and part of heat will loss to the cap and base rock as steam enters the pay zone (Liu, 1997; Roger, 1991)
Comparisons have been made between the new model results, measured data and Computer Modelling Group (CMG) results for a specific heavy oil reservoir developed by superheated steam injection
Summary
The thermal recovery methods, such as cyclic steam stimulation (Gina and Hugo, 2011; Tewari et al, 2011; Wu and Kry, 1993), steam drive (Du et al 2012; Shie and Todd, 1980; Wu et al, 2015), steam assisted gravity drainage (Miura and Wang, 2010; Wei et al, 2014) are still the most extensively adopted enhanced oil recovery process in heavy oil reservoirs. It should be pointed out that these models derived on the basis of steam injection, they do not apply to superheated steam injection This is due to the fact that the distribution of temperature in pay zone in the process of superheated steam injection and conventional saturated steam injection is totally different (Zhou et al, 2010). He et al (2017b) established an analytical model to calculate the heat radius by considering the distribution of temperature in pay zone in the process of superheated steam injection. This model didn’t consider the steam overlay effect. The effect of injection rate and reservoir thickness on wellbore heat efficiency and reservoir heat efficiency are analyzed based on the proposed model
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