Abstract

The Direct Synthesis Technique (TDS), introduced by Tiab,1 is a well test interpretation methodology noted for its practicality and accuracy, utilizing distinctive features observed on log-log plots of pressure and its derivative to enhance reservoir characterization. The shape factor, CA, originally proposed by Dietz,2 is crucial for estimating average reservoir pressure. While several authors have explored its estimation using the TDS Technique, previous equations often yielded results in the range of 10-13, diverging from the expected 1-100 due to the omission of the skin factor. This study addresses this gap by incorporating the skin factor into new simplified equations. The new equations provide more accurate and reliable estimates of the shape factor compared to conventional analyses. The proposed expressions are validated through their application to vertical and horizontal wells in homogeneous reservoirs, naturally fractured reservoirs, and hydraulically fractured wells in homogeneous reservoirs. Results show a significant improvement, aligning closely with those obtained from conventional straight-line analysis methodologies. Two examples are given to show the results of the new equations. This advancement enhances the accuracy and reliability of reservoir characterization using the TDS Technique.

Keywords

shape factor, pressure derivative, pseudosteady-state, conventional analysis