## 1 Introduction  
China's offshore heavy oil reserves are huge, among which the reserves of heavy oil with a viscosity of more than 350 mPa\(\cdot\)s are as high as 670 million tons. This type of heavy oil has poor water injection development effect and must be developed by thermal recovery. Since 2008, the CNOOC (China National Offshore Oil Co., Ltd.) has successively carried out pilot tests, expanded scale tests, and large-scale thermal recovery. By the end of 2023, the output of offshore heavy oil thermal recovery has exceeded 2 million tons, of which the output of heavy oil thermal recovery in 2023 has reached 850,000 tons. The CNOOC also makes China the world's only country with offshore heavy oil thermal production capacity [1; 2]. Offshore heavy oil thermal recovery is still dominated by steam injection, and the annual oil production by steam huff and drive technology will exceed 680,000 tons in 2023 [3; 4; 5]. However, traditional steam huff and puff technology have problems of high carbon emission and high cost [6; 7; 8; 9]. Existing offshore thermal recovery boilers have high requirements for fuel and water consumption, high cost of oil-water treatment, high energy consumption, and large amount of CO\({}_{2}\) emission [10; 11; 12]. At the same time, energy supplement is weak in the later stage of huff and puff, and with the consumption of natural reservoir energy, there is insufficient energy for reservoir pressure exhaustion in the later stages. After multiple cycles of steam huff and puff, water cut near the well is high, heat injection heating efficiency is low, and the heat utilization rate drops sharply. The low water recovery rate of steam huff and high specific thermal water near the well affect the effective utilization of injected heat [13; 14; 15]. Multi-component thermal fluids are used as injection mediums in some sites. Multi-component thermal fluid technology uses the combustion injection mechanism of space rocket engines to inject diesel (crude oil or natural gas) and high-pressure air into the combustion chamber to heat high-pressure injected water, forming a multi-component thermal fluid mixed with hot water, steam, nitrogen, carbon dioxide, etc. into the formation to exploit heavy oil [16; 17]. Due to the characteristics of N\({}_{2}\), CO\({}_{2}\), and thermal oil recovery, the injection of multi-component thermal fluid can increase reservoir pressure, reduce crude oil viscosity, and improve the oil displacement swept area and heavy oil recovery efficiency. In addition, the equipment required by the multi-component thermal fluid technology has the advantages of small size and light weight, which is suitable for the installation of offshore platforms, and has achieved certain stimulation effects in the implementation of offshore heavy oil reservoirs [18; 19; 20]. However, the traditional multi-component thermal fluid technology has the following problems: (1) the production method has the characteristics of high energy consumption, low conversion rate, low heat utilization rate, and low energy efficiency of the total system; (2) it has a high dependence on diesel, crude oil, natural gas, and other fuels; (3) there is ineffective cross-flow of thermal fluid in the low oil saturation area, oil production gradually decreases in the late stage of development, the comprehensive water cut increases, and the production effect becomes worse; and (4) it produces a large amount of oil production wastewater/high concentration of oily sewage, which has a negative impact on the environment. Therefore, it is urgent to develop a new method of enhanced oil recovery with a high heat utilization rate and high interaction efficiency with heavy oil. Since 2015, supercritical multi-source, multi-component thermal fluid independently developed by China National Offshore Oil Co., Ltd. Has gradually attracted attention as a new injection medium, which mainly consists of supercritical water, supercritical N\({}_{2}\), and supercritical CO\({}_{2}\).