Without hydraulic fracturing treatments, most reservoirs being developed today cannot produce economic volumes of hydrocarbons. Obtaining maximum results from hydraulic fracturing requires stimulating all perforations in the treated interval. However, achieving such coverage is challenging in shale reservoirs because the fracture initiation pressure can vary widely within a perforated interval.

Because shale formations are characterized by extremely low permeability, operators use horizontal wells and hydraulic fracturing to develop them. Engineers frequently stimulate these formations through a method known as the plug-and-perf technique. This method divides a cased and cemented wellbore into geometric intervals, each of which is perforated, stimulated, and isolated in successive operations from toe to heel.

Traditionally, operators have divided the well into intervals of about equal length. However, because shales are often heterogeneous, engineers have begun using seismic and log data as the bases for limiting perorations and stimulation operations to those areas of the formation containing the highest potential production.

Within these selected areas, however, heterogeneity leads to preferential treatment of low-fracture initiation pressure rock, leaving more resistant rock untreated.

Schlumberger scientists have developed an answer in the form of a fracturing service that diverts treatments from more easily fractured formation rock to rock that might otherwise be bypassed.

An article in the Winter issue of Oilfield Review, “Unlocking the Potential of Unconventional Reservoirs,” tracks the development of the BroadBand Sequence service from the laboratory to its introduction into the oil field. Case studies from the US and Mexico demonstrate the well productivity improvements that have been achieved by applying this technique. 

Reference

Kraemer, C., Lecerf, B., Peña, A., Usoltsev, D., Parra, P., Valenzuela, A. and Watkins, H.: “Unlocking the Potential of Unconventional Reservoirs,” Oilfield Review (Winter 2014/2015) 26, No. 4, 4–17.