یک مدل برنامه ریزی پویا از ذخیره نفتی استراتژیک چین: استراتژی عمومی و اثر شرایط اضطراری

To protect the security of energy supply, China is building national strategic petroleum reserve (SPR). We present a dynamic programming model to determine the optimal stockpiling and drawdown strategies for China's SPR under various scenarios, focusing on minimizing the total cost of reserves. In contrast to previous research, the oil price given in our model is exogenous on a monthly instead of annual basis, with a view to more realistic simulation of optimal strategies each year. Our model results show that in the case where stockpiling affects oil prices, a given SPR size will be achieved earlier than when stockpiling does not affect oil prices. In different emergency conditions, the optimal stockpiling and drawdown strategies of China's SPR are very different. When an emergency occurs, the shock of stockpiling on the oil price per barrel could range $0.49–$6.35, while the impact of drawdown on the oil price per barrel could range −$6.22 to −$0.48. Highlights ► We present a model to determine the optimal stockpiling and drawdown strategies for China's SPR. ► We set international crude oil prices exogenously to yield more accurate results. ► The impact of the stockpiling on oil prices is slightly higher than that of its drawdown. ► The optimal stockpiling or drawdown strategies for China's SPR vary greatly in each emergency.

Oil crises prompt the development of national Strategic Petroleum Reserves (SPR), which effectively reduce the impact of such crises. During the first world oil crisis in 1973–74, oil prices quadrupled, causing enormous economic losses to the major industrialized countries. The rates of GDP growth of the United States and Japan, for example, decreased from 5.6% and 8.4% respectively in 1972 to − 0.47% and − 1.2% in 1974 (World Bank, 2010). To reduce oil supply shortages and their impacts on national and global economies, the Organization for Economic Cooperation and Development (OECD) established the International Energy Agency (IEA) in 1974, which required all member states to establish the SPR equivalent of 60 days of net import volume (later increased to 90 days). During the second world oil crisis in 1979–80, oil prices soared from US$13 to US$41 per barrel. The strategic petroleum reserves of major industrialized countries at that time had already begun to take shape and played an active role in stabilizing markets and guaranteeing supply such that the resulting economic losses were relatively confined. The growth rates of GDP in the United States and Japan, decreased from 5.6% and 5.3% in 1978 to − 0.24% and 2.8% respectively in 1980 (World Bank, 2010). This paper investigates how to stockpile and draw down China's SPR to minimize the impacts of different potential future crises on society and the economy, including the costs of stockpiling when future emergencies such as oil supply shortages cause fluctuation of oil prices. When China again became a net importer of petroleum products in 1993, researchers began recommending a national SPR in order to protect energy security. After a decade of debate, the Chinese government officially approved the establishment of the national SPR in 2003 with a planned total reserve capacity of 500 million barrels (about 68 million tons) and an estimated total investment of about 100 billion Yuan RMB (NDRC, 2010). Establishing the SPR will take about 15 years to complete and is being undertaken in three phases, incrementally adding reserve capacities of 88, 205, and 205 million barrels, respectively. Phase I began in March 2004, with four reserve bases concentrated in coastal areas: Zhenhai of Ningbo, Daishan of Zhoushan, Huangdao of Qingdao, and Xingang of Dalian (the later names of each being municipal jurisdictions). Among these, Zhenhai is the largest, established in August 2006 to stockpile crude oil with an inventory of 33 million barrels. The other three bases were completed by the end of 2008, with a total inventory of 103 million barrels for Phase I. Unlike the U.S. SPR, which is stored in caverns in subsurface salt domes, Phase I of China's SPR was mainly constructed in above-surface tanks. Although such tanks have several advantages, notably fast construction, flexible site selection, and ease of use, their disadvantages include relatively high costs and low safety compared to underground caverns (Davis, 1981). Therefore, Phase II of China's SPR includes not only above-surface tanks but also subsurface caverns. The site selection is shifting also in part to inland areas, including Lanzhou of Gansu province and Shanshan of Xinjiang autonomous region, as shown in Fig. 1 By 2009, Shanshan of Xinjiang and Binhai of Tianjin municipality had commenced construction under Phase II: the total inventory of Phase II is 168 million barrels. Full-size image (48 K) Fig. 1. The spatial distribution of China's strategic petroleum reserves.

In contrast to previous studies, the reserve cost function adopted in this paper integrates the GDP loss caused by oil supply shortages to provide a more realistic simulation of the optimal SPR strategy. We also set international crude oil prices exogenously to yield more accurate results. Oil price is a critical factor affecting an optimal SPR strategy and is itself determined by many factors. If the price is determined simply by supply and demand, it is very difficult to accurately portray future oil price trends in the current international oil market. Accordingly, we used oil price forecasts issued by the EIA as a reference for oil prices in our model and used wavelet pattern matching to change annual to monthly data for more realistic simulations. The main results for our SPR simulation model are as follows: (1). Without consideration of emergencies, the optimal stockpiling strategies for China's SPR vary greatly under different oil price scenarios. In the low price scenario, the optimal stockpiling strategy is to maintain the current reserve sizes constant or to stockpile little to reduce holding costs in the early stages. In the reference scenario, the optimal strategy is to stockpile intermittently and modestly while the oil prices are relatively low, and the inventory will show a stepwise upward trend. In the high price scenario, it is important to stockpile rapidly to reach the peak inventory. (2). The optimal stockpiling and drawdown strategies for China's SPR vary greatly in each emergency scenario. In the sudden natural disaster scenario, the optimal strategy is to rapidly draw down about 12–36 million barrels of SPR (depending on prevailing world prices at the time) to stabilize oil prices and ease supply shortages. In the financial crisis scenario, the optimal strategy is to sell a relatively small part of the SPR (about 6–18 million barrels) in order to take advantage of high oil prices and then quickly stockpile while the oil prices are relatively low. The maximum stockpiling amount should not exceed 77% of the total reserves so as to reduce the cost. In the local armed conflict scenario, the optimal strategy is to continuously and rapidly draw down about 36–77 million barrels of the SPR to protect the oil supply security. (3). Oil price fluctuations vary under the different scenarios, and thus the rates of optimal stockpiling or drawdown also vary greatly. In the financial crisis and local armed conflict scenarios, the optimal stockpiling or drawdown rates should often be at the maximum marginal rate of 6.0 million barrels per month. In the sudden natural disaster scenario, the optimal rates should often be between 0 and 6.0 million barrels per month. Therefore, controlling the rate of stockpiling or drawdown is also an important dimension of optimal management of China's SPR. (4). The impact of the stockpiling of China's SPR on international oil prices is slightly higher than that of its drawdown, over all emergency scenarios. The shock of stockpiling on oil price can range from $0.49–$6.35 per barrel. During a local armed conflict scenario, the stockpiling of China's SPR can make the international oil price rise by as much as $6.35 per barrel. In a financial crisis, the impact of stockpiling on price is relatively weak, with a minimum of only $0.49 per barrel. The impact of China's SPR drawdown on oil price is -$6.22 to −$0.48 per barrel. In a local armed conflict scenario, the maximum impact of the drawdown of China's SPR on oil prices is −$6.22 per barrel. In a financial crisis, the impact of drawdown is relatively weak, with a minimum of −$0.48 per barrel. In our dynamic programming model, there are some parameters and scenarios directly referencing the historical data of U.S. SPR. As the first phase SPR of China just finished at the end of 2008, it is very difficult to find the real parameter values from Chinese statistical data. Despite limitations and assumptions, our model provides a valuable approach for studying China's optimal SPR strategies under different emergency scenarios and also simulates the impact on international oil prices from those strategies.