WELLBORE STORAGE AND SKIN EFFECT ON HORIZONTAL WELL PUMPING TESTS

Horizontal wells have screen sections parallel to the horizontal directions. These wells have been widely used in petroleum engineering, agricultural and civil engineering in the past. With the advances of technology in directional drilling, they gained significant interests among hydrogeologists, environmental scientists and engineers in recent years because of their enormous contact areas with the aquifer. The direct extension of the theories of horizontal well from petroleum engineering may cause some problems in hydrogeologic application because of the different interest. When applying horizontal wells in hydrogeological studies, the knowledge of hydrodynamics taking place near the wellbore is crucial in remediation works because horizontal wellbores are installed directly into the contaminated zones while in the petroleum engineering, far field is their main interest. For a finite diameter horizontal well, because the hydraulic head distribution at wellbore surface continuously changes along the length as well as circumference, it is almost impossible to describe wellbore storage and skin effect analytically. Almost no studies have ever been carried out before to investigate the hydrodynamics of horizontal wells including finite-diameter source, wellbore storage, and skin effect until now. For accessing this problem, we first separate the problem into the source problem that includes wellbore storage and skin effect and the geometry problem that purely focuses on aquifer and horizontal wellbore geometry. And then, we combine these two problems to generate the solution for the head distribution of a finite diameter horizontal well. Graphically integrated computer program FINHOW is written to generate type curves of groundwater flow to a well. The influence of the well, the wellbore storage, the skin effect, the leaking parameter, and the aquifer anisotropy that substantially affect the near-well early time drawdown is thoroughly analyzed. This research provides a better tool for interpreting finite-diameter horizontal well pumping tests.