Is There a Hydraulic Fracturing ‘Blind Spot’ in Conventional Reservoirs?

Almost all notable advancements in hydraulic fracturing technology over the past 2 decades have stemmed from the rise of the tight-oil and -gas industry. During this time, completions equipment evolved from the analog workhorses of yesteryear into increasingly sophisticated, digitized, and efficient machines that rival anything found in the oilfield technology portfolio. The transformation also includes mountains of scientific research that have enabled engineers and specialists to model and stimulate tight reservoirs with greater confidence and accuracy. But amid all this success, a question has been brewing for years: Can modern fracturing technology be effectively applied beyond the tightest, lowest-quality rocks? Martin Rylance and a team of completions experts from independent oil producer Liberty Resources and modeling firm ResFrac Corp. argue that the industry has developed a “blind spot” when it comes to low—but not ultralow—permeability conventional reservoirs. They believe these formations could be effectively developed using modern fracturing techniques, but they have largely been overlooked. According to Rylance, industry veteran and managing director of IXL Oilfield Consulting, this blind spot exists because North American onshore operators became focused on fracturing hard, tight rock in the 1970s and 1980s with fractured vertical wells. “We skipped a step,” Rylance explained. “The technology for fractured horizontal wells in conventional rock wasn’t in place when we were developing tight-ish rock across North America. That’s now the challenge that the rest of the world faces—there’s no supporting extensive database to draw upon for the development of conventional fractured horizontals.” This gap in knowledge didn’t hinder the expansive development of tight rock across the US and Canada, but it has left a significant opportunity untapped. Rylance and his coauthors lay out their case in two new papers, SPE 223561 and SPE 223562, which support the idea that horizontal multistage wells can outperform fractured vertical wells—perhaps by orders of magnitude in certain cases. Both papers were presented at this year’s SPE Hydraulic Fracturing Technology Conference and Exhibition (HFTC) in the Houston area, where the authors made their case for revisiting low‑quality conventional formations with a new perspective—and carefully selected technology. Rylance spoke to SPE 223561 and highlighted a concept known as the resource triangle, first introduced by a group led by the late hydraulic fracturing pioneer Stephen Holditch. At the top, the triangle illustrates the scarcity of high-quality conventional reservoirs, as opposed to its base where we find a much larger but economically challenging category of tight oil, shale gas, and other unconventional plays that, despite their difficulty, have reshaped global energy markets. “As you move down the triangle, you get more certainty regarding the resource,” said Rylance. “But also increasing cost, decreasing recovery factors, and a growing technology requirement to develop—more energy in, less energy out, typically.” The key takeaway, Rylance said, is that “fracturing is an inevitably” as the industry exhausts the so-called good rock. What remains are long overlooked pay zones that lie between the middle and the bottom of the triangle. “Those familiar with the classics know that Dante’s Inferno has nine levels of misery on the journey to hell—perhaps there is a tenth: hydraulic fracturing. Frac crews globally are at the bottom of this triangle, gleefully awaiting everybody’s arrival, and we need to be there with the right solutions to help them out,” said Rylance.