General situation of physical geography

Hefei Basin is the largest basin with the lowest exploration degree in eastern China. It is located in the middle of Anhui Province, between Dabie Mountain, Zhangbaling, fengyangshan and Shili Changshan Mountain. The east-west length is about 200km, the north-south width is 150km, and the area is 2.3× 104 km2 (bounded by Longmei fault). It is a large basin with a rectangular overall shape. Geographical coordinates are: east longitude116 ~18, north latitude 31020 ′ ~ 32 40 ′. The basin is surrounded by mountains. The basin spans more than ten counties and cities such as Hefei, Lu 'an, Yingshang, Huoqiu, Shouxian, Dingyuan, Feixi, Feidong, Shucheng, Jinzhai and Huoshan (Figure 1- 1), and most of the surface is covered by a thin Quaternary system.

Figure 1- 1 Geographic Location Map of Hefei Basin

1. Terrain

Hefei Basin is surrounded by Dabie Mountain, Zhangbaling, fengyangshan and Shilichang Mountain. The southern part of the basin is located in the Dabie Mountain remnant vein, with an altitude of 100m or more. Chaohu Lake in the southeast is low-lying, about 20 meters above sea level. The eastern and northern parts of the basin are low hills with an altitude of 40 ~100 m; The basin is mainly composed of low hills and undulating plains, hills and depressions appear alternately, and the top slope is gentle. Only in the low mountains around Fang Hushan, Feixi County, southeast of the basin, the elevation is below 100 meters, and the overall trend is east-west. The western part of the basin is characterized by high south and low north. In the east, Hushan is the watershed, showing a geographical pattern of two lows and one high.

2. River

Hefei basin is located in the Jianghuai watershed, with relatively developed rivers and lakes. Like a pearl, the rippling Chaohu Lake is embedded in the southeast corner of the basin, surrounded by Chengdong Lake, Wabu Lake, Dongpu Reservoir, Xietang Reservoir, Zhongxing Reservoir and Modun Reservoir. The Huaihe River flows through the northern edge of the basin, and many tributaries of the Huaihe River originate in Dabie Mountain area, and flow through the western part of the basin from south to north to supplement the Huaihe River, so that the Huaihe River flows eastward into Hongze Lake in a rapid way. In the middle and east of the basin, it is necessary to prevent Hushan from being used as a watershed, and the rivers on the northern slope of Hushan flow into the Huaihe River from south to north. The water system flowing from north to south to Shannan, Fang Hushan, and the water system from south to north in Dabie Mountain meet at Hangbu River and flow eastward into Chaohu Lake.

3. Climate

The main stream of Huaihe River is an important dividing line between subtropical humid area and warm temperate semi-humid area in China, and the north of Huaihe River belongs to warm temperate semi-humid monsoon climate. South of the Yangtze River is a subtropical humid monsoon climate. Hefei basin is located between Huaihe River and Yangtze River, with mild and humid climate and four distinct seasons. The annual average temperature is 14 ~ 16℃, in which the monthly average temperature in Leng Yue/kloc-0 is -3 ~ 3℃, the average temperature in the hottest month (July) is 27 ~ 28℃, the frost-free period is 200 ~ 250 days, and the annual average rainfall is 60.

Step 4 transport

Hefei basin is located in the middle of Anhui province, with towns all over the basin, which is the most densely populated area in Anhui province. Hefei is the capital of Anhui Province, the largest city and the political, economic and cultural center in the province. Roads, railways and air transportation in the basin are relatively developed. Anqing-Bengbu Railway and Beijing-Kowloon Railway pass through the basin. The roads are centered on Hefei, Lu 'an and Shouxian, forming a nationwide road network. At present, Hefei-Nanjing, Hefei-Xuzhou, Hefei-Tongling, Hefei-Wuhu and other expressways pass through the basin. In addition, Hefei-Lu 'an and Hefei-Huangmei expressways will soon be completed and opened to traffic. The completion of these large-scale road networks facilitates the transportation of large-scale oil exploration and drilling equipment, but the road networks among counties, townships, villages and villages in the basin have not yet been formed, which has a certain impact on field construction.