What is shale gas and tight oil?

What is shale gas and tight oil? And what are the technologies to extract shale gas and tight oil? Shale gas refers to natural gas that is trapped in shale formations. Shales are fine-grained sedimentary rocks that are rich sources of petroleum and natural gas. Sedimentary rocks are rocks formed by the accumulation of sediments at the Earth’s surface and within bodies of water. Conventional gas reservoirs are created when natural gas migrates toward the Earth’s surface from an organic-rich source formation into highly permeable reservoir rock, where it is trapped by an overlying layer of impermeable rock. In contrast, shale gas resources form within the organic-rich shale source rock.

The low permeability of this shale greatly inhibits the gas from flowing to more permeable reservoir rocks. Therefore, without horizontal drilling and hydraulic fracturing, shale gas production would not be economically feasible because the natural gas would not flow from the formation at high enough rates to justify the cost of drilling.

There are two major drilling techniques to be used to produce shale gas: Horizontal drilling and Hydraulic fracturing. First let’s discuss Horizontal drilling first. What is Horizontal drilling? Horizontal drilling is used to provide greater access to the gas trapped deep in the producing formation. First, a vertical well is drilled to the targeted rock formation. And at the desired depth, the drill bit is turned to bore a well that stretches through the reservoir horizontally, exposing the well to more of the producing shale. Hydraulic fracturing is commonly known as “fracking” or “hydrofracking”.

This is a technique in which water, chemicals, and sand are pumped into the well to unlock the hydrocarbons trapped in shale formations by opening cracks (fractures) in the rock and allowing natural gas to flow from the shale into the well.