Analysis Of Hydrogeological Setting And Groundwater Resources Evaluation In Longdong Region

Longdong region is the main oil producing area of Changqing Oilfield. Resources reserves is 2.847 billion tons, Xifeng City of Longdong region has already proven geological reserves of more than 400 million tons, and the development prospect is broad. longdong region is the semi-arid areas, water resources are relatively scarce, and in certain region, groundwater qualities are bad; between 2007 and 2010 period, with the oilfield building scale expanding each year and needed water is expected to about 50000m~3 / d .At present the water supply system has already come to a full load, water shortage situation is more prominent.To meet the water demand of oil production in longdong region, based on a detailed analysis of existing data and the results of previous studies, this thesis not only systematically studied hydro-geological conditions of longdong region, but also analyzed the distribution of water resources and water quality and conduct a comprehensive evaluation and zonation of exploitation conditions, which will provide a scientific basis for the development and utilization of oilfield process water, and the main research content and conclusions of this thesis are as follows:(1) The main recharge of groundwater in study area is the infiltration of precipitation.; The runoff of phreatic water is mainly controlled by landform patterns, and the direction of runoff often changes. Flow of Cretaceous groundwater is obviously controlled by structural characteristics of water-bearing formation, and water flows mainly through the layer. The total law is as follows: Phreatic water flows from higher terrain to lower terrain, confined water flows from the eastern part of Ziwuling, north Qingyang and the western town to the center of Malian River pool, and then runoff to the south; discharge of groundwater in longdong region contain spilling to surface water and artificial exploitation.(2) Water abundance of Cretaceous groundwater is mainly controlled by lithology and lithofacies. The general law is: Luohe group and Rohan hole group which mainly contain coarse sand and fine sand are relatively rich of water. Water abundance in ring group which mainly contains fine sand, aleurite and mudstone is relatively weak.(3) Chemical characteristics of Cretaceous groundwater in study area present obvious zonation. The general chemical characteristics of groundwater in the study area are: salinity of groundwater increased from the edge to the center, chemistry type evolutes from bicarbonate to Sulphate and chloride-type.(4) According to calculation, the total natural water resource of groundwater in the study area is 3.22×10~8m~3/a, which contains four parts: precipitation is 2.97×10~8m~3 / a, lateral recharge is 316.5×10~4m~3 / a, the rest is recharged by surface water and irrigation water. Static reserves of groundwater in the study area 17674.86×10~8m~3 / a, and the total exploitation permission of groundwater is 1.51×10~8m~3 /a which contains two parts: unconfined water supplies 0.37×10~8m~3 /a, Cretaceous groundwater supplies 1.14×10~8m~3 / a.(5) Groundwater quality evaluation is based on collecting water quality data of the study area. Evaluation results of drinking water are: surface water qualities in most drainage area are general or poor except in the Honghe drainage area; most of groundwater qualities in Cretaceous Luohe group and ring group are bad, the others are good. Evaluation results of irrigation water are: most of the water in the west of the White Horse Shop is not suitable for irrigation and the other is good. Evaluation results of industrial boilers: water qualities of Qingyang,Xifeng city and Heshui are better than Zhenyuan distry,Gaijia river and Ningxian Region, and the others are normal.(6) Integratedly analyzed water resources of the Quaternary and Cretaceous layers in the study area, In accordance with the uneven distribution of water resources and water quality change, evaluated comprehensively the grad distribution of water under different circumstances of water resources and water quality in the study area, and divided into different regions for the exploitation conditions.