GTI research on gas production from shale resources has yielded significant new knowledge. An early effort in the Michigan geologic basin involved field experiments in the Antrim Shale that helped the industry better understand fracture geometry in this complex formation—eventually taking it from a little-known resource to a cost-competitive source of natural gas. Reservoir engineering methods were developed for the Antrim, and field-based research projects identified restimulation and recompletion candidates, estimated the potential production improvements in these candidates, and developed cost-effective workover procedures.
By studying 2,000 wells, GTI developed methods that could double production rates. Because of the properties of shale, GTI was able to capitalize on results from earlier and parallel research on tight-sands fracturing and coalbed methane, using two-stage, deeper hydraulic fracturing to release more gas, establishing more efficient methods to promote gas flow from fractured rock, and using mechanical pumps to remove water from gas wells.
We also devised new ways to assess gas content in core samples in as little as one day and to use existing well logs and the new sampling method to help find gas beyond current wells.
In the Appalachian basin, GRI developed a fairly sophisticated understanding of the character of shale reservoirs through log analysis, reservoir testing and geologic models to target more productive zones and better predict productivity of the wells. This allowed for better size fracture treatments based on a more accurate estimate of the reservoir’s productivity. Vertical wells had limited potential and very large treatments did little to improve production. GRI research showed producers how to optimize the economics of fracture treatments by sizing of the treatment to real expectations of the reservoir conditions.
GTI also pursued research on gas production from shale formations in Illinois and Texas. Several horizontal wells in the Barnett Shale were tested and evaluated with multiple fracture treatments, and a calibrated formation evaluation was performed with a cooperative Mitchell Energy well.
A big breakthrough occurred when GTI drilled the Stella Young well with Mitchell Energy in the Barnett Shale—a novel well drilled at a high angle, rather than vertically, then stimulated with modern-day technology—resulting in three times greater production. It established that the productivity of deep shales can be significantly improved if the well can be fractured and reservoir contact increased.
In 2002, when Devon Energy Corporation acquired Mitchell Energy, it combined hydraulic fracturing with horizontal drilling to further improve the productivity of shale gas wells. This activity truly kicked off the significant production at Marcellus and all of the other shales that are now producing gas in greater volumes than ever before thought possible.