A Modified Approach for Volumetric Evaluation of Shaly Sand Formations from Conventional Well Logs: A Case Study from the Talhar Shale, Pakistan

作者：Ehsan, Muhsan^*; Gu, Hanming; Ahmad, Zulfiqar; Akhtar, Malik Muhammad; Abbasi, Saiq Shakeel

来源：ARABIAN JOURNAL FOR SCIENCE AND ENGINEERING, 2019, 44(1): 417-428.

DOI：10.1007/s13369-018-3476-8

• Shaly sand formations
• Volumetric shaly sand evaluation
• Gamma ray logs
• Porosity logs
• Resistivity logs
• Well log indexes

In potential shale-gas basins, due to limited data availability, volumetric evaluation of shaly sand formations is a challenging task for researchers, as well as for exploration and production companies, with the use of conventional well logs. This paper is intended to provide a better understanding of volumetric evaluation in unconventional shaly sand formations. Petrophysical parameters derived from conventional well logs play a significant role in the volumetric estimation of shale. The assessment was performed using numerical equations, well log indexes, and cross-plot analysis. Deep and shallow resistivity logs overlap with each other; this phenomenon indicates that the Talhar Shale in Pakistan can be considered to be an unconventional formation. The average values of shale volume, total porosity, effective porosity, and matrix volume are 29, 16, 12, and 59%, respectively. The Talhar Shale is dominantly characterized by intergranular porosity. It has been observed that at low shale volumes (10-20%), porosities (total and effective), and resistivity measurements (deep, shallow, and microlaterolog), well log signatures have close contents with the shale volume. In contrast, for the remainder of the shale volume, there is significant separation of log signatures. Well log indexes indicate significant responses in 10-20% shale volume zones.

• 出版日期2019-1
• 单位中国地质大学（北京）