The distance between horizontal wells in the North American shale patch is almost always reported as a single measurement, often in clean round numbers, e.g. 450 ft or 600 ft. The problem with accepting such figures as the whole picture is that they are too simplistic, which can lead shale producers to make multimillion-dollar mistakes when it comes to drafting up the next drilling campaign.

This is the conclusion reached by Enverus (formerly Drilling Info), which says in a recently published report on well spacing that it has adopted a new method to determine the distance between horizontal wells and analyze the impact that distance has on production. The analytics and business intelligence firm points out that it had been using “simple” spacing calculations that it now considers to be “inaccurate.”

The traditional method, used not just by Enverus but others across the shale sector, relies on a single parameter known as a midpoint measurement between wells. The new method presented by Enverus uses 300 different inputs to come up with a better answer.

“Well spacing is complex and incredibly important in today’s current free-cash-flow era,” said Sarp Ozkan, the energy analysis director at Enverus. In a press release he compared trying to understand the issue with “peeling back an onion.”

Some of the layers Enverus is using to better assess well spacing and its impact on production include taking into account that wellbore separation can vary all along the laterals. Horizontal distances represent the conventional way to look at well spacing, but Enverus says vertical separation must also be considered, which is especially relevant to stacked formations. When an operator’s directional drilling data is not avail-able, the company is modeling “synthetic” well trajectories.

This enhanced analysis is all part of a well-spacing toolkit Enverus has rolled out in recent months. Its arrival comes as capital markets are hitting the brakes on funding the US shale sector due to disappointing well results and difficulties in establishing free cash flow.•

As a result, many producers have pivoted their focus from production growth to drilling lower-cost wells that have stronger rates of return. However, this shift has not necessarily delivered all the answers on how far apart to drill infill wells to avoid fracture interference and excessive crosswell communication.

Midpoint Malaise

Enverus used several case studies in its report to show that misjudging optimal well spacing has led shale producers to over drill their assets. The result of landing just one or two unneeded wells is a severe downgrade in a drilling section’s net present value.

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