Shale Gas Potential of Lower Goru Formation over Lakhra High in the Lower Indus Basin, Pakistan

Siddiqui, Fareed Iqbal; Adhami, Asad; Asghar, Afnan; Hussain, Atif; Khan, Wahaj Uddin

Due to the continuous depleting nature of conventional reserves in Pakistan, the unconventional resources particularly shale gas has gained significant importance. Potential of shale gas in Lower Indus Basin remains largely unknown due to limited data in shales because wells are usually drilled at the highs targeting conventional reservoirs. On the other hand, mature source rocks are located in the lows or synclines. However, an attempt has been made to evaluate Shale Gas potential of Lower Goru Shales over Lakhra High in the Lower Indus Basin by using geochemical and geological data from seven wells.

Lakhra High is a north-south oriented, gentle fold between the Laki Range and the Indus River, and it appears to be the eastern most structure resulting from collisions of the Arabian, Eurasian, and Indian tectonic plates. To date only eight wells are drilled in the vicinity of the high targeting Early Cretaceous age Lower Goru Formation at structural traps. The conventional potential of these wells is unproductive due to poor quality reservoir. However, unconventional potential of Lower Goru Formation over the High still needs to be developed. The Lower Goru Formation was deposited in the deltaic settings over the westward dipping passive margin. The Formation is divided into seven members namely; Upper Sands (Youngest), Upper Shale, Middle Sands, Lower Shale, Upper Basal Sands, Talhar Shale and Lower Basal Sands (Oldest).

Results of the current study show that all shale units comprise of Type II and Type III Kerogen with a TOC in a range of 0.5-5.0%. All the shale units are more than 50m thick and are present at a depth of 2700-3500m. The Upper and Lower Shale units are considered as immature whereas Talhar Shale is in the wet gas to dry gas window based on the maturity data of surrounding wells. Talhar Shale possess the required brittleness for hydraulic fracturing.

The study lead us to conduct 3-D basin modeling study, specialized core analysis and re-evaluation of available geochemical data in future to refine our results and establish prospects for shale gas.

AAPG Search and Discovery Article #90163©2013AAPG 2013 Annual Convention and Exhibition, Pittsburgh, Pennsylvania, May 19-22, 2013