Frac’ing sandstones represents the low-hanging fruit our industry has chased since the late 1940.
This accumulated resource has relatively high permeability. Commercial production can rely on the hydrocarbon molecule - oil or gas- to flow through the matrix of the rock to travel thousands of feet to a single fracture in a vertical well. The conductivity of the fracture is often important due to flow conversion in the reservoir surrounding it, and we want to avoid it for being the bottleneck for a well’s production.
Unconventional shale frac’ing is different. The hydrocarbon molecule cannot travel far in the low-permeability source rock, so we need to bring the fracture to the hydrocarbon molecule to limit its travel distance. Commercial production requires a focus on the extent and density of the fracture system. This is achieved through horizontal drilling and multi-stage hydraulic fracturing, using low-viscosity fluids like slickwater to create complex fractures and to effectively distribute fluid and proppant across a massive radiator-like system that provides a large inflow area for oil& gas once frac’ing is completed.
This happened for the first time in the ultra-tight Barnett Shale near Fort Worth, Texas, in the late 1990s. Mitchell Energy perfected the slickwater frac recipe in vertical wells to encourage growth of fracture surface area; then Devon Energy combined it with horizontal drilling to complement the extent of the fracture network.
The technological marriage of horizontal well drilling with multi-stage frac’ing provides Americans with more than half of all their primary energy today. It’s a perfect match made in Texas.
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