From Reuters: Turning To Frack Tech, Stricken U.S. Oil Drillers Test New Limits; Unheard Of Cluster Spacing Could Increase Bakken Initial Production By 50% -- March 13, 2016

Link here.

Top U.S. shale producers are pushing fracking technology to new extremes to get more oil out of their wells, as they weather lower-for-longer oil prices.

While the impact of the techniques may be scarcely noticeable on current U.S. output with so few wells in operation, it could mean drillers are able to accelerate production more fiercely than ever once prices recover.

Regular readers are pretty much aware of all this, but here are some data points.

• Pioneer Natural Resources is increasing the lengths of stages in its wells
• Hess Corp is increasing the number of stages
• Whiting Petroleum and Devon Copr are adding more sand
• analysts suggest initial production could increase by 5 to 50%
• Pioneer plans to cut spacing between "clusters" (perfs) to as little as 15 feet -- a move "unheard of" in the past
• for a typical well in the Bakken, a jump to 15-foot spacing could easily boost initial output by as much as 50 percent -- Monte Besler, FRACN8R Consulting, North Dakota

More:

"The increase in proppant amounts and fluid amounts and the decrease in cluster spacing, all of those are directions that industry in general has been headed," said Jennifer Miskimins, senior consulting engineer with Barree & Associates in Lakewood, Colorado.

"The increase in proppant amounts and fluid amounts and the decrease in cluster spacing, all of those are directions that industry in general has been headed," said Jennifer Miskimins, senior consulting engineer with Barree & Associates in Lakewood, Colorado.

"In some places it is helping with long-term recoveries and that's why we're starting to see people push the envelope a little bit."

More data points:

• in 4Q15, Pioneer in the Permian slashed stage lengths by 60 percent,  added one cluster per stage, and pumped more fluid, about 36 bbls/foot up form 30; the results: IP jumped by more than 15% 
• Hess: IP's increased by more than 20% after increasing stage counts about 40% to 50
• increasing amount of sand: Whiting, Devon, CLR: 2,500 to 2,700 lbs/lateral foot in some wells, might raise IP as much as 50%

Other links:

Impacts of the number of perforation clusters and cluster spacing on production performance of horizontal shale-gas wells, February, 2012
Multistage hydraulic fracturing has become the key technology to complete horizontal wells in shale-gas reservoirs. In each stage, multiple perforation clusters are used to create multiple transverse fractures. How these clusters are placed significantly affects both the short-term and long-term production performance of horizontal shale-gas wells. The author's previous work has demonstrated that when more than two fractures are created, mechanical interaction among fractures creates strong stress concentrations around the inner fractures. As a result, the fractures between two edge fractures (i.e., subcenter and center fractures) experience only limited dilation, and their widths are much smaller than the edge-fractures' width.

Methods improve stimulation efficiency of perforation clusters in completions, Halliburton, JPT, April 1, 2014: 
The average daily gross perforated interval per stage (top perforation to bottom perforation) that Halliburton completed in the Haynesville and Bossier shales from 2010 to 2013 was analyzed. The data encompasses nearly 11,000 stages for more than 30 operators. It illustrates that many operators began to reduce their gross perforated interval per stage across the play by the middle of 2011. In July 2011, it was 272 ft and by mid-2012, it declined to 150 ft, falling at a relatively constant rate as operators increasingly went to a shorter isolated stage interval.
This indicates closer stage spacing (plug to plug) or more stages per well, with lateral length remaining relatively constant. These trends continued into 2012 and a dramatic improvement was seen not only in the slope of the projected production decline curve, but also in the estimated ultimate recovery (EUR) for the wells being brought online.
The 72-month cumulative production average for wells completed in 2010 and 2011 was roughly the same at 4.5 Bcf per well, but for wells completed in 2012, it rose to 5.5 Bcf per well (Kaiser and Yu 2013). This marked a 22% improvement and was largely because of the reservoir-specific completion optimization progression, such as closer stage spacing.

Advanced Well Stimulation Technologies, 2014
Perforation patterns are typically shot in clusters separated by 10.7 to 22.9 m (35 to 75 ft) or more (King, 2010). Each cluster is 0.305 to 0.71 m (1 to 2 ft) in length with about 20 perforations per meter (6 perforations per foot). The idea of a cluster is to initiate one main fracture from each cluster; the multiple perforations within a cluster help to find the easiest fracture initiation point. With the narrow spacing between perforations in a cluster, only one fracture will grow, because of the effects of the fracture on the local stress field that tend to suppress any other fractures trying to emerge from the cluster (King, 2010). For a typical stage interval of 61 or 91.4 m (200 or 300 ft), this results in about 4 to 7 clusters per stage.