Underdamped slug tests with unsaturated-saturated flows by considering effects of wellbore skins

Liang, Xiuyu1,3; Zhan, Hongbin2; Zhang, You-Kuan1; Liu, Jin3

2018-03-30

10.1002/hyp.11471

HYDROLOGICAL PROCESSES   影响因子和分区

0885-6087

1099-1085

An analytical solution is presented for the slug tests conducted in a partially penetrating well in an unconfined aquifer affected from above by an unsaturated zone. The solution considers the effects of wellbore skin and oscillatory responses on underdamped slug tests. The flow in the saturated zone is described by a two-dimensional, axially symmetric governing equation, and the flow in the unsaturated zone above the water table by a linearized one-dimensional Richards' equation. The unsaturated medium properties are represented by the exponential constitutive relationships. A Laplace domain solution is derived using the Laplace and finite Fourier transform and the solution in the real-time domain is evaluated using the numerical inverse Laplace transform method. The solution derived in this study is more general and reduces to the most commonly used solutions for slug tests in their specified conditions. It is found that the unsaturated flow has a significant impact on the slug test conducted in an unconfined aquifer. The impact of unsaturated flow on such a slug test is enhanced with a larger anisotropy ratio, a shorter well screen length, a shorter distance between the well screen and the water table, or a larger well screen radius. The impact of unsaturated flow on slug tests decreases as the degree of penetration (the length of well screen) increases. For a fixed well screen length, the impact of unsaturated flow on slug tests decreases as the distance between the centre of screen and the water table increases. A large dimensionless well screen radius (>0.01) leads to significant effects of unsaturated flow on slug tests. The unsaturated flow reduces the oscillatory responses to underdamped slug tests. The unsaturated zone has significant impact on slug test under high-permeability wellbore skin.

analytical solution slug test unsaturated-saturated flow

SCI ; EI

英语

第一 ; 通讯

Department of Science and Technology of Jiangsu Province[BE2015708]

Water Resources

Water Resources

WOS:000428523900009

WILEY

20181404972429

Aquifers ; Inverse problems ; Laplace transforms ; Numerical methods ; Time domain analysis

Groundwater:444.2 ; Oil Field Equipment:511.2 ; Mathematics:921

ENVIRONMENT/ECOLOGY

Web of Science

1.Southern Univ Sci & Technol, Sch Environm Sci & Engn, Shenzhen 518055, Guangdong, Peoples R China
2.Texas A&M Univ, Dept Geol & Geophys, College Stn, TX 77843 USA
3.Nanjing Univ, Sch Earth Sci & Engn, Nanjing 210023, Jiangsu, Peoples R China

Liang, Xiuyu,Zhan, Hongbin,Zhang, You-Kuan,et al. Underdamped slug tests with unsaturated-saturated flows by considering effects of wellbore skins[J]. HYDROLOGICAL PROCESSES,2018,32(7):968-980.

Liang, Xiuyu,Zhan, Hongbin,Zhang, You-Kuan,&Liu, Jin.(2018).Underdamped slug tests with unsaturated-saturated flows by considering effects of wellbore skins.HYDROLOGICAL PROCESSES,32(7),968-980.

Liang, Xiuyu,et al."Underdamped slug tests with unsaturated-saturated flows by considering effects of wellbore skins".HYDROLOGICAL PROCESSES 32.7(2018):968-980.