Geology

Geologically, the Province of Alberta is part of the Western Canadian Sedimentary Basin that covers most of western Canada. The Western Canadian Sedimentary Basin is the northern portion of the Western Interior Basin that stretches south to the Gulf of Mexico. These geological regions are rich in hydrocarbons including coal, oil and gas.

These hydrocarbons were created over millions of years. During the Cretaceous Period (about 140 to 65 million years ago), the interior of the landmass of North America was covered by a large inland sea (sometimes called the Western Interior Seaway or the Cretaceous Seaway). The sea was rich in tiny microscopic plants and animals that, as part of their life cycles, absorbed the Sun’s energy and converted it into carbon. As these organisms died, they created layers of organic sediment at the bottom of the sea. Over millions of years, this sediment was subjected to intense heat and pressure resulting in the formation of sedimentary rocks and

petroleum. Petroleum, depending on the pressure and temperature to which it was subjected over time, exists in various states as a gas (natural gas) or as a liquid (crude oil); each form of petroleum can be refined into various fuels and other products. Natural gas containing primarily methane is often referred to as dry gas. Gas containing hydrocarbons heavier than methane (such as ethane, butane and propane) is often referred to as wet gas. Gas containing sulfur compounds is called sour gas. Through a variety of refining processes, these heavier hydrocarbons and sulfur can be removed from the natural gas and marketed.

Deep in the Earth, petroleum is contained in porous rocks, such as sandstones and coarse-grained limestone that resemble solidified sponges. The petroleum, which is mixed with water, occupies the spaces within the rock. An impenetrable layer of rock, like shale, forms a cap rock that prevents oil, gas and water from moving to the surface.

The Turner Valley oil and gas field stretches from the Quirk Creek and Millarville area in the north to the Highwood River near Longview in the south. In geological terms, it is a dome-shape formation described as a sandstone trap anticline containing gas on top, then oil, and, finally, water at the bottom. The initial Turner Valley discovery, by the Dingman No. 1 well on May 14, 1914, was in shallow, porous sandstone formations. Additional petroleum reserves were discovered as deeper drilling continued over the next twenty-two years.

The Turner Valley field contained both wet and sour gas. Wet gas, closer to the

surface and discovered first, was found in a layer of Jura-Cretaceous sandstone, formed 65 to 199 million years ago. It consisted of normally liquid hydrocarbons suspended within natural gas, a solution often called naphtha. The wet gas was sweeter, containing lower levels of hydrogen sulfide. The deeper gas, found later, was sour with much higher levels of hydrogen sulfide. The hydrogen sulfide gave the gas a noticeable rotten egg smell. Sour gas is highly unstable, corrosive and dangerously toxic. In the Turner Valley field, the sour gas occurred in a deeper layer of Mississippian limestone formed 318 to 359 million years ago.