Petrophysical evaluation of well log data for reservoir characterization in Titas gas field, Bangladesh: a case study

Abstract

The petrophysical evaluation of the Titas gas field (Titas-15) has been carried out for its reservoir characterization and to quantify the reservoir hydrocarbon prospects and gas productivity. The Quick Log Analysis Tool (QLAT) of PE2 Essentials software has been utilized for the computer-processed interpretation inputting the various well log data such as gamma-ray (GR), density log (RHOB), density-porosity (DPHI), neutron porosity (NDHI), resistivity logs, etc. Among the three reservoir sand groups, three gas-bearing sub-zones have been identified in the upper sand group, which are primarily producing gas from the least net-pay of 9.5 m, 39.5 m and 28.5 m, respectively. The shale volume is calculated based on GR, caliper logs and neutron-density (N-D) cross-plot (minimum shale volume) methods whose average value is comprised between 26.3 and 33.9%. The range of effective porosity is 18.4–18.6% indicating a good reservoir quality; permeability is 14.11–25.95 mD; recognizing as the well-sorted nature of sands. Additionally, the hydrocarbon saturation in the respective zones varies from 48% to 60%, suggesting a good hydrocarbon reservoir, whereas the water saturation is 40–52%. Moreover, the range of measured ‘gas initially in place’ in upper, middle and lower gas sands are 2371.6–2579.1, 10330.7–11206.1 and 6373.1–7110.5 MMscf, respectively, implying an adequate gas reserve on commercial criteria. From the evaluation of petrophysical properties, the Titas reservoir has a higher ability to enhance hydrocarbon accumulation and production.