Effect of mud invasion on pressure transient obtained from wireline formation tester

Abstract

In this study, a reservoir simulator is used to generate pressure responses from wireline formation tests for single layer homogeneous reservoir, invaded reservoir due to mud invasion, and stimulated reservoir. Then, the well test interpretation software is used to estimate reservoir parameters from the simulated pressure response. A single layer homogeneous reservoir is used as a base case to investigate the effect of probe size and permeability anisotropy ratio. Then, a single layer reservoir with an invaded zone is investigated to evaluate the effect of mobility ratio and effect of radius of invasion. Finally, a single layer with stimulated zone is investigated to evaluate the effect of mobility ratio and effect of radius of stimulated zone. All the investigations are performed to determine whether the results from wireline formation test conducted in particular systems can provide satisfactory information under different reservoir scenarios and tool limitation. The study concludes that for both damaged and stimulated reservoir, the pressure response obtained from the single probe wireline formation test can provide accurate estimate of reservoir permeability. Therefore, the single probe wireline formation test can be readily used in both invaded reservoir and stimulated reservoir.