Thirty years ago, a Motorola engineer developed the Six Sigma management approach to guide manufacturing in batch operations. Six Sigma measures, analyzes and creates specific steps to improve manufacturing by eliminating defects. The concept spread rapidly through the manufacturing sector in the 1990s.

A parallel evolution is underway in oil and gas as operators pursue capital efficiency by optimizing drilling and completion practices in unconventional reservoirs. This philosophical approach is important, because a majority of new oil will originate from growing hydrocarbon recovery in the very best reservoirs rather than from extending the conveyor belt of freshly discovered shale plays.

Picture unconventional oil and gas development as a means to maximize hydrocarbon recovery within a 3-D geological cube. Operators spent the last half-decade addressing spacing during completions, including narrowing the distance between frack stages along a lateral and seeking optimal spacing between adjacent laterals on a pad, or between new multiwall pads and legacy wells. Think of spacing as the first “S” in the recipe to improve hydrocarbon recovery.

The second “S” evolved concurrently in the multipay-zone Permian Basin and Eagle Ford and involves stacking and staggering laterals, often in a wine-rack offset pattern to squeeze additional hydrocarbons out of the reservoir matrix without interfering with existing production. Stacking and staggering adds a vertical dimension to the traditional planar approach in horizontal drilling, expanding the zone of recovery in a 3-D geological cube.

Now industry focus is turning to the third “S” in the philosophical approach to greater recovery. This comes via the concept of sequencing, or the order in which individual stages are fracked within a lateral, and the order in which individual laterals are completed on a pad. Speakers referenced sequencing multiple times during Hart Energy’s DUG Eagle Ford conference in San Antonio and Executive Oil Conference in Midland, both held in the fourth quarter of 2015.

At the Midland event, J.D. (Joey) Hall, executive vice president, Permian, for Pioneer Natural Resources Co., was candid about his company’s several-decade plan for developing the Wolfcamp and Spraberry formations across a multicounty acreage position in the Midland Basin. Hall noted that operators can identify the best hydrocarbon zones, ascertain frackability through the interplay of clay and silica, call upon historical well control, and deploy multiple variations of a completion recipe that ranges from slickwater to linear or crosslinked gels that incorporate varied pumping rates and sand volumes.

Those variables constitute the toolkit. But Pioneer is now discovering that sequencing is an outsized factor that influences recovery from the 3-D geological cube.

“Do I zipper frack all the wells drilled together?” Hall asked. “Do I come back later and drill? How long after I do the laterals below before I come back and do the ones above? We all understand spacing, stacking, but we’re discovering sequencing has a bigger impact than we thought.”

During an interview at the DUG Eagle Ford event, Daniel Mohan, senior vice president with Austin, Texas-based big data firm Ayata, outlined how using artificial intelligence and machine learning incorporating multiple data sources has suggested recoveries could be improved by sequencing during completions for individual laterals on pads.

“There wasn’t necessarily one pattern that was dominant, but what is important is that order—timing—between stages and sequencing of the full pad did have an impact on production. It was an impact that was not before quantified or captured,” Mohan said.

Everyone is impatient to discover a silver-bullet solution for unconventional development. Sequencing is part of that. But sequencing itself has multiple variables that must be adjusted to the unique circumstances, not only in a single wellbore but also for neighboring wells. Consequently, completion engineers have an array of options that, when properly understood and competently executed, can move hydrocarbon recovery higher.

How much higher? In the Midland Basin, operators are working on techniques that will advance hydrocarbon recovery from 6% to 8% up to 12% to 14%. That is significant.

“The answer,” Pioneer’s Joey Hall said, “is there are 100 answers. Getting it right in each area is the most important thing.”

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