Shell Exploration & Production Co., an arm of Royal Dutch Shell PLC, is a good example. The company, which began such drilling in Wyoming's natural-gas fields about five years ago, has been moving back to its 60 or so existing work sites, to produce additional wells rather than creating new pads — and disturbing more landscape.

Shell says it built only two new pads this year but added more than 70 wells.

"This is a major transformation in operating practices in the field," said Pete Stark, vice president of industrial relations at IHS Inc., a provider of technical information and decision-support tools. "It's a big-time change — a change in response to the increasing confrontation between environmental interests and energy-security interests. It started in the Rockies, but it's spreading elsewhere."

Keren Murphy, the Sierra Club's oil and gas expert in Washington, said the environmental group acknowledges that bunching wells together can prevent disturbance, but it's trying to make sure certain areas don't become "throwaway zones."

"It does help protect areas that are deemed pristine, but it also has the potential to create some sacrifice zones," Murphy said.

The move to multiple wells off single pads also is linked to energy companies' expanding production of unconventional sources such as "tight" sands and shale — geographic formations that make it tougher to unlock gas and require more wells.

"They're getting more out of the ground, but it's taking more holes to do so," Stark said.

The U.S. Energy Information Administration says 31,587 natural-gas wells were drilled for exploration and production in 2006, up from 16,728 just four years earlier.

Still, natural-gas producers have struggled to keep up with demand. And despite the surge in drilling activity — buoyed by strong market prices — there's no expectation the industry will add significant supplies soon. Another key factor making it easier for companies to perform multi-well directional drilling is new rigs.

Drilling contractors Helmerich & Payne Inc. and Nabors Industries Ltd. in the past few years began building rigs with enhanced power that customers report is cutting the time to complete drilling operations by 20 percent to 30 percent.

What's more, in many cases, the rigs slide on rails to their next destination, greatly reducing disturbance to the environment and the time it would take to move a conventional rig from one location to the next.

For now, the Interior Department's Bureau of Land Management will continue to strongly suggest drillers use multi-well pads, though it may eventually require it, said BLM spokeswoman Jaime Gardner.