Challenge of Eagle Ford well spacing remains a moving target
BY KURT ABRAHAM, EXECUTIVE EDITOR
DENVER -- Everyone knows that the Eagle Ford shale of South Texas is challenging the Bakken shale of North Dakota for status as the preeminent shale play in the U.S. However, as operators continue to drill and define the Eagle Ford, the nettlesome problem of which well spacing plan to utilize in many fields is begging for some common-sense solutions.
Gervasio Barzola, vice president of Subsurface & Development in the South Texas Asset Team of Pioneer Resources, spoke about some potential solutions during a topical luncheon Tuesday at the SPE/AAPG/SEG Unconventional Resources Technology Conference (URTeC) in Denver. Barzola noted that the top six operators in the Eagle Ford account for 700,000 boed of gross production, including 100,000 boed produced by his own firm. Accordingly, drilling in recent years has skyrocketed, prompting concerns about future well spacing. During 2010, Barzola said that just 500 new wells were drilled in the Eagle Ford. By comparison, during 2011-2012, 2,350 new wells were drilled. In that period, 7 million acres were effectively under appraisal via drilling.
In assessing well spacing and reservoir performance, Barzola said that several key performance drivers need to be considered, including seismic attributes and microseismic; thickness; “fracability,” the depositional model; depth and pressure; well execution; maturity/liquid yield; and data integration along the lateral. The challenge for well spacing, accordingly, he said, includes several items that must be evaluatedd, such as frac height assessment; drainage modeling; wellbore production contributions; and frac width assessment. “Already, in the Eagle Ford,” said Barzola, “activity, itself, is not a problem, but maybe too much activity is a problem.”
To help work on the problem, Barzola said his team developed a “well spacing tool kit.” It includes use of several methods/items, including radioactive tracers, chemical tracers, pressure data; and well interference. They considered such items as geochemical/seismic volumes; stress data; natural fractures detection; modeling with fracture stimulation software; and microseismic-derived stimulated reservoir volumes (SRVs). All of this work enabled his team to arrive at several potential well spacing scenarios, even though, as he pointed out, “the industry does not have a set strategy regarding well spacing.” As a base case, Barzola’s team established a spacing range of 300 to 600 ft, which, he says, would generate roughly $291 billion in production revenue for operators in the area. If a wider spacing scheme of 400 to 700 ft is utilized, then the production revenue would decrease to $231 billion. On the other hand, if a tighter spacing plan of 200 to 500 ft is implemented, then production revenue, the team calculated, would increase to just over $400 billion.
Right now, said Barzola, “There is a 600-ft spread in spacing across all Eagle Ford yield bands for pad wells. Yet, our 500-ft spacing tests have show that the performance of those ‘super-fraced’ wells is outperforming others.”