Assessment of storage and productivity potential of a frontier unconventional shale oil play in a rift basin, Lower Barmer Hill Formation, Barmer Basin, India

Abstract

The Eocene Lower Barmer Hill (LBH) Formation is the major regional source rock in the Barmer Basin rift, located in Rajasthan, India. Thick sections of organic-rich black shales reaching 400 meters thickness with TOC up to 14 wt. %, were deposited during a period of widespread basin deepening. Type 1 oil prone kerogens dominate the north, with mixed type 1 and III kerogens in the south. Thermal maturity varies across the basin, from early oil in the north to dry gas in the south.

Extensive Rock Eval pyrolysis and source rock kinetic databases were combined with petrophysical analysis to determine log-based porosity and saturations and productive potential. Basin Modeling using Trinity software provided probabilistic ranges of generated and expelled hydrocarbons to determine storage capacity. The modeled oil window storage capacity varies between 6 to 13 mmstb/km², comparable to the values observed in Eagle Ford and Bakken Shale plays.

Excess pore pressure was modeled using the kinetics of kerogen-to-oil conversion. These pressure-gradient maps, along with oil properties (viscosity and oil mass fractions) derived from the geochemical model, are used to compute the producibility index. Composited storage capacity and the producibility index maps are high-graded to potential pilot areas. Work is ongoing to understand the rapid syn-rift facies variations of interbedded brittle zones such as silty porcellanites or thin turbidites, which make this play considerably different from established trends such as the Eagle Ford or Bakken Shales. Testing these concepts will be an important step in unlocking future unconventional potential in other rift basins.

AAPG Datapages/Search and Discovery Article #90350 © 2019 AAPG Annual Convention and Exhibition, San Antonio, Texas, May 19-22, 2019