Abstarct: Dashtak formation, deposited in Lower to Middle Triassic, is a cap rock for Kangan and Dalan gas reservoirs in Persian Gulf. This formation is a sequence of carbonates, anhydrite and shale. As this formation has not been important as a hydrocarbon reservoir, hence no petrophysical evaluation is carried out there yet. However some recent drilling data confirm presence of gas in some parts of this formation. Considering the point that Dashtak is a cap rock and features some shale laxyers, gas could be related to these shales. The purpose of this study is to evaluate Dashtak formation for determining its gas potential and shale laxyers as a probable shale gas. In this study, well log data of a new drilled well 2SK-1 is used to assess key parameters involved in gas potential of Dashtak formation. Thus several rock models were used for probabilistic analysis of different geological laxyers to estimate porosity, gas-filled and water-filled porosities and shale volume. The results show that calcareous laxyers in upper part of Dashtak formation equivalent to Arabic Gulailah member of approximately 270 meters which is mainly from limestone being substituted alternatively by anhydrite and dolomite, is a gas zone. Log interpretation of Gulailah member suggests that total porosity, gas-filled and water-filled porosities and shale volume is averagely measured as 6, 1, 5 and 10 percent, respectively. Some shale laxyers were detected in upper part Sudair member having illite as the dominant clay mineral. Presence of calcite causes the third shale laxyer of Sudair member of 35 meters thick to be a high porosity zone. This high porosity might be an indicator of organic richness. So total organic carbon (TOC) determined in this laxyer using △log-R method showing TOC amounts exceed 2% in the richest parts. Aghar shale located in bottom of Dashtak formation separates it from Kangan formation. Organic richness is investigated in this laxyer too. The results suggest that roughly 5 meters of Aghar shale have TOCs more than 2% which leads to conclusion that Dashtak shaly parts could be the source rock for itself.