Analyzing Anisotropy in Permeability and Skin Using Temperature Transient Analysis a Thesis Submitted to the Department of Energy Resources Engineering of Stanford University in Partial Fulfillment of the Requirements for the Degree of Master of Science

In many reservoir studies, anisotropic permeability values in orthogonal directions are often considered to have simple relationships. Often, this permeability anisotropy is modeled only between the vertical and horizontal directions as a certain ratio of values, while permeability values in a horizontal plane are considered equal. In reality, the depositional history of the reservoir results in more complex behavior. Knowledge of the permeability field has important implications in several different types of scenarios, thus it is important to have accurate estimates of these directional permeability values. A partially-penetrating well that allows for vertical flow to occur in the reservoir at depths below the bottom of the completed interval requires knowledge of vertical permeability anisotropy. In addition, improved estimates of horizontal permeability values would have significance for directional drilling purposes. In this work, the utility of temperature data as a matching parameter was investigated to estimate these directional permeability values. The study utilized a full physics reservoir simulator and a nonlinear, least-squares regression algorithm for parameter estimation. By modeling block temperatures near the well that are output from the simulator, the study attempted to replicate the temperature data gathered from a Distributed Temperature Survey (DTS) which uses fibers to measure temperature history at the well. Using this method, the directional permeability values in the two scenarios described previously were estimated successfully with a high degree of accuracy. Additionally, the effects of a damaged zone surrounding the well in the horizontal case were investigated. In this case, the near-well, damaged zone permeability values were estimated successfully using temperature signals as well.