Catalytic Effect of Cobalt Additive on the Low Temperature Oxidation Characteristics of Changqing Tight Oil and Its SARA Fractions

Tengfei Wang,Jiexiang Wang

doi:10.3390/en12152848

Tengfei Wang, Jiexiang Wang

Open Access

https://doi.org/10.3390/en12152848

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Abstract

Air flooding is a potential enhanced oil recovery (EOR) method to economically and efficiently develop a tight oil reservoir due to its sufficient gas source and low operational costs, during which low temperature oxidation (LTO) is the key to ensuring the success of air flooding. In addition to inefficiency of conventional LTO, air flooding has seen its limited applications due to the prolonged reaction time and safety constraints. In this paper, a novel air injection technique based on the catalyst-activated low temperature oxidation (CLTO) is developed to improve the operational safety together with its oil recovery in tight oil reservoirs. Experimentally, static oxidation experiments are conducted to examine the influence of the catalyst on the LTO reaction kinetics of Changqing tight oil and its fractions. The catalytic oxidation characteristics are identified by applying a thermogravimetric analyzer coupled with Fourier transform infrared spectrometer (TG-FTIR) with respect to tight oil and its SARA (i.e., saturates, aromatics, resins, and asphaltenes) fractions. Accordingly, the catalyst can obviously decrease the LTO reaction activation energy of the Changqing tight oil and its SARA fraction. Cobalt additive can change the LTO reaction pathways of the SARA fractions, i.e., promoting the formation of hydroxyl-containing oxides and CO2 from the oxidation of saturates, aromatics and resins, while inhibiting the formation of ethers from the oxidation of aromatics and resins. The LTO of each SARA fraction contains both oxygen addition reaction and bond scission reaction that can be effectively promoted with the cobalt additive. The catalytic effect on the bond scission reaction is continuously enhanced and becomes gradually stronger than that on the oxygen addition reaction as the reaction proceeds.

Highlights

Air flooding is a cost-effective technique for exploiting oil reservoirs, which is remarkably effective for tight oil reservoirs and conventional reservoirs in the late stage of waterflooding [1,2,3,4]
The activation energy of crude oil is reduced to 21,864 J/mol from
At the end of the test, the mass loss of catalyst-activated low temperature oxidation (CLTO) of the resins is 9.0%, which is 2.07% higher than that of the noncatalytic low temperature oxidation (LTO)

Summary

Introduction

Air flooding is a cost-effective technique for exploiting oil reservoirs, which is remarkably effective for tight oil reservoirs and conventional reservoirs in the late stage of waterflooding [1,2,3,4].Recently, there have seen numerous researches and field pilots for air flooding in the North Sea [5,6], Indonesia [7,8], Argentina [9], Buffalo Red River Unit (BRRU) [10], West Hackberry [11,12], CoralCreek [13], Ekofisk [6,14], Buffalo [15,16], and Horse Creek oilfields [17] with good performance. There have seen numerous researches and field pilots for air flooding in the North Sea [5,6], Indonesia [7,8], Argentina [9], Buffalo Red River Unit (BRRU) [10], West Hackberry [11,12], Coral. After air is injected into a hydrocarbon reservoir, the oxygen of air reacts with hydrocarbons in various ways, generating a lot of flue gas and heat, and enhancing the oil recovery. To enhance the safety of air flooding, the injected oxygen should be completely consumed before produced. To improve the safety of air flooding without changing flooding pattern in a depleted reservoir, it is a good method to increase the oxygen consumption rate of crude oil by adding catalyst to the LTO process.

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Conclusion