The Bakken Shale underlying North Dakota and parts of Montana could be the last oil and gas production zone where child wells are increasing output from parent wells, said James West, senior managing director of research at Evercore ISI.

It might not be long, however, before the Bakken joins the Permian Basin and Eagle Ford Shale, where negative parent-child well relationships continue to dog producers.

Child wells, which are drilled near an original, i.e. parent well, reportedly have caused production interference and reduced output in some basins. In April, for example, Raymond James & Associates Inc. forecast slowing U.S. well productivity growth in part because of the well interference.

Some upstream operators also have discussed this negative parent-child well relationship at length on quarterly earnings reports. Tulsa-based WPX Energy Inc.’s management team said in May it’s conducting various spacing tests in the Permian to find a way to hedge parent-child well interference.

In the Bakken, however, producers are still reporting that output from child wells is boosting output in the associated parent well, according to North Dakota Petroleum Council President Ron Ness.

Continental Resources Inc., for example, is seeing parent well output increases with the advent of new child wells, said investor relations chief Rory Sabino. 

Ness said the child wells may stimulate the parent well in the same way refracturing (refracking) is done. “I’m hearing it more and more from various operators,” he said. “By stimulating the child well you get a new stimulation on the parent well, it’s like a mini re-frack.”

Refracking and child well interference may both stimulate a parent well and boost output, but they are distinct processes.

“A refrack is the re-stimulation of an existing well, either a parent or child well. Parent-child well interference is when the stimulation of the child well causes communication or interference (either good or bad) with the parent well,” West said. Refracking is intentional whereas parent-child well interference is coincidental, he added.

North Dakota Industrial Commission’s Lynn Helms, who directs the oil and gas division, confirmed that he’s observed child wells boosting output from parent wells.

The positive parent-child well relationship was more common in the earlier days of the unconventional drilling boom when fewer wells were drilled per pad, and fewer fracture stages were implemented,  West said. The less intense activity of the early days left wells “understimulated.”

However, as the age of mega-completions took hold around 2014 and a downturn in oil prices motivated companies to refracture wells instead of drilling new wells, the parent-child relationship turned negative as the wells were hyper-stimulated and shorter-lived.

Such mega-completions, where an operator may drill 20 wells per pad and implement 30 fracture stages for each one, are commonplace in most major shale formations in the United States, and are beginning to make their mark on the Bakken, West said.

Currently, there are still enough positive parent-child well relationships in the Bakken that operators can take advantage by refracturing the understimulated wells, the analyst said.

Once the mega-completions strategy fully overtakes the Bakken in the near future, that parent-child well relationship will likely turn negative as it has in the Permian Basin, West said. At that point, Bakken operators may join operators in other formations in turning to technology and experimentation.

Newer technologies developed to mitigate parent-child well interference generally focus on one of two approaches, West said. The first uses chemicals that can absorb “frack hits” and better protect and insulate the parent well from the child wells. A frack hit is a cross-well interaction initiated as hydraulic fracturing solutions are injected into the ground.

The other method uses technology to “pin-point frack” the child wells, essentially forecasting more precise locations for child wells that may cause minimal interference with the parent well.

Tomball, TX-based Deep Imaging recently announced a technology that it said may help operators see in realtime where injected fluid is going during well completions, thereby giving them the chance to possibly intercept frack hits before they happen.