Practical approach to determine formation permeability using MDT test data

Formation permeability is an important parameter to evaluate reservoir capacity while wireline formation test data can be used to estimate the formation permeability quickly and accurately. Based on the theory of fluid mechanics in porous medium, this paper systematically analyzed and studied the flow characteristics during wireline formation testing process. The mathematical models of spherical flow and radial flow is solved. The pressure and pressure derivative curves are made. The curves' characteristics and influencing factors are also analyzed. Results show that there are three flow patterns in probe testing: pure pipeline storage period,transition period and spherical flow period; five flow patterns exist in dual packer testing: pure pipeline storage period, transition period, radial flow period within the pack thickness, spherical flow period and radial flow period of the entire formation. On this basis, we compiled a MDT test data interpretation software, and field application examples of the software proved the validity of this interpretation.