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Steam-assisted-gravity-drainage (SAGD) is a widely employed method to enhance heavy oil production and efficiency, and the key to ensuring its steady operation is the maintenance of a steam chamber. Heat conduction and convection of steam to connate water are essential factors in the heat transfer process. In this paper, we developed a novel analytical model to investigate the heat transfer process on the boundary of the steam chamber, driven by the pressure difference between the injected steam and the original reservoir. Both conduction and convection are considered in this new model, and the calculated results are in good agreement with the simulated data by using CMG-STARS. After model validation, the effects of physical properties and operating conditions (relative permeability, initial water saturation, and steam temperature) on the heat transfer process are investigated. The results reveal that connate water saturation plays a large role than the steam temperature in conductive heat flux; low saturation leads to more efficient crude oil exploitation. This work provides new insights into the recovery mechanisms of a SAGD process. [ABSTRACT FROM AUTHOR]

Steam-assisted-gravity-drainage (SAGD) is currently an effective technology for heavy oil recovery. The pre-heating stage is important to affect the overall process of SAGD development. In this paper, flow and heat transfer model in vertical well section and horizontal well section and thermal connectivity judgment model during cyclic pre-heating stage were established. Model calculation results are in good agreement with actual measurement results. The effects of steam injection rate and steam quality on the distribution of steam parameters along the whole wellbore and the distribution of heat transfer were compared. Besides, the optimization of steam injection parameter combination was provided. Ultimately, the effect of horizontal well spacing on pre-heating thermal connectivity was discussed. The results show that: With the increase of steam injection rate and steam injection quality, the pressure and temperature drop of the fluid increase. Wellhead required steam injection pressure and temperature increases and even superheated steam appear with the increase of steam injection rate and steam injection quality. The position where the pre-heating backflow turns from wet steam to subcooled water gradually shifts to the wellhead. With the increase of steam injection rate and steam injection quality, the heat transfer between annulus and reservoir decreases, but the uniformity of pre-heating in the horizontal section increases. The time required for cyclic pre-heating to form thermal communication between double wells increases significantly as the horizontal well spacing increases. To simultaneously integrate the uniformity and economy of pre-heating on the oilfield site, the steam injection quality at the heel end of the horizontal section of 0.7, the steam injection rate of 80 t/d, and the horizontal well spacing of 5 m were recommended. [ABSTRACT FROM AUTHOR]

Superheated steam‐enhanced steam‐assisted gravity drainage (SSE‐SAGD) is a promising enhanced oil recovery method. However, the existence of aquathermolysis reactions makes the development process more complex. In this paper, the application potential of SSE‐SAGD in an oilfield was analyzed based on the estimated oil recovery and the production cost. A numerical model with aquathermolysis reactions was established, and after the model validation, the effects of steam superheats on the steam chamber's expansion were analyzed by taking the heat loss into account. Subsequently, the cumulative enthalpy‐oil ratio (cEOR) was introduced to characterize the production cost. The results show that as the superheat degree increased, the recovery factor was improved, but the cEOR increased simultaneously. Comparing with saturated steam, the superheated steam with a superheat of 50 ° led to a 16.42% increase in oil production and a 7.11% increase in cEOR. We proposed a new development scheme with a step increasing in superheat to weaken the impact of aquathermolysis reactions. The scheme achieved a 12.82% increase in oil production at a 3.93% increase in cEOR over saturated steam injection. Our findings could provide new insights in the use of superheated steam to enhance SAGD. [ABSTRACT FROM AUTHOR]

In-situ combustion (ISC) technology is a promising method to exploit heavy oil. In this study, 1D tube combustion experiments and the thermogravimetric analysis were combined to investigate the combustion characteristics of the ISC process at the temperature range of 100–600 ℃. First, the temperature intervals of the three combustion stages of the ISC process were determined by thermogravimetric analysis and examined by the 1D tube combustion experiment. Then the activation energies of the three stages were estimated through the Flynn-Wall-Ozawa (FWO) method and the Kissinger-Akahira-Sunose (KAS) method. Results showed that after the ISC reactions, the gravity of the crude oil was upgraded, and the key to maintain the ISC process is keeping the crack reactions continue. The activation energy varies between 66 and 75 kJ/mol in low-temperature oxidation, 197–218 kJ/mol in fuel deposition, and 92–109 kJ/mol in high-temperature oxidation. The different characteristics of the three stages were traced to the occurrence of different reactions, and the high activation energy value of the FD stage was traced to the high proportion of the resins and asphaltenes fractions of the crude oil. Conclusions of this work can help to understand the ISC process better. [ABSTRACT FROM AUTHOR]