Vertical variability of hydrogeological characteristics of Luohe Formation by double packer system pumping test

To investigate the hydrogeological conditions of the thick Luohe Formation in Ordos Basin and quantitatively evaluate vertical variation characteristics of its aquifer’ s water-rich, proposes the method of using the coefficient of transmissibility to evaluate the water-rich of the aquifer, and give the seven level classification standard of water-rich by the method of determining coefficient of transmissibility. The double-packer system was used to carry out the pumping tests of 10 vertical sections of fixed thickness of the Luohe Formation in the DJ1 and DJ2 boreholes in the Gaojiabao mine field, shaanxi, and the hydrogeological parameters were calculated. Using the comprehensive water-rich index method to stratify the Luohe Formation vertically and analyze its hydrogeological characteristics vertically. The results show that: (1) The water-rich standards of coefficient of transmissibility are given; when T≤1 m²/d, 1 m²/d<T≤10 m²/d, 10 m²/d<T≤50 m²/d, 50 m²/d<T≤100 m²/d, 100 m²/d<T≤200 m²/d, 200 m²/d<T≤400 m²/d and T>400 m²/d, the water-rich is very weak, weak, medium, strong, very strong, especially strong, and extremely strong. (2) The Luohe Formation is vertically divided into four aquifers including the upper, middle-upper, middle-lower and lower aquifers by the comprehensive water-rich index method. (3) The Luohe Formation vertical hydrogeological characteristics are different. The middle-upper and middle-lower formation are the main aquifers, which are dominated by sandstone strata and relatively thick (122.20-124.30 m and 113.30-148.70 m, respectively), the permeability coefficient K (0.598 9-0.708 5 m/d and 0.111 5-0.211 5 m/d, respectively) and coefficient of transmissibility T (65.60-116.94 m²/d and 11.05-30.89 m²/d, respectively) have relatively large values, and the water-rich are from medium to very strong; The upper and lower formation are the secondary aquifers, which are dominated by sand-mudstone strata and relatively small (20.45-35.20 m and 57.60-91.19 m, respectively), the permeability coefficient K (0.064 6 m/d and 0.005 1-0.009 0 m/d, respectively) and coefficient of transmissibility T (1.58 m²/d and 0.34-0.66 m²/d, respectively) have relatively small values, and the water-rich are from very weak to weak. (4) The coefficient of transmissibility has a definite calculation relationship among multiple aquifers. The coefficient of transmissibility method is used to evaluate the vertical water-rich of the Luohe Formation, and there are significant differences. Therefore, the application was successful.