Producing gas from shale and tight-sand formations seems simple now, thanks to advanced drilling and completion techniques developed in formations such as the Marcellus, Fayetteville and Barnett. But what about getting oil from shales in such oily formations as the Bakken and Niobrara?

“Shales are highly fractured and laminated and have flow mechanisms, even though they are not the same between the Marcellus and the Bakken,” said Nathan Meehan, senior executive advisor, Baker Hughes, during the Drilling and Completions Technology panel at Hart Energy Publishing’s DUO conference in Denver.

“Each unconventional oil well needs to be studied quite carefully to get the best possible results, since each shale formation is slightly different, even within a field.”

Continually improving technologies of horizontal and directional drilling, fracturing, seismic monitoring and fracture-mapping techniques are already boosting well performance, and this trend will continue with development and discoveries in recent oil-shale plays such as the Bakken and Niobrara.

Developing efficient oil production from shales starts with good surface seismic surveys, including 3-D surface mapping to locate the best shale formation for development. “Old” tools such as core analysis and wireline logging are still helpful and remain valuable for understanding formations, Meehan said.

During drilling operations, geosteering tools such as powered rotary steerable system (RSS) and logging while drilling (LWD) techniques, shown by Jean-Francois Poupeau, president, drilling and measurements, Schlumberger, allow a drilling operator to drill a straighter and cleaner hole and more accurately target the sweet spot in a formation. Straighter and cleaner holes dramatically improve packer sets and packer performance. LWD imaging can also record in-situ faults and fractures.

One Schlumberger lateral study showed “that 30% of perforated stages will contribute 70% or more to production, many perf clusters contribute no or trace amounts of production, and production from perf clusters within same stage is often highly variable.” With inaccurately placed perforations or packer-sleeve completions, frac fluids are often ineffective and production can fall to an unacceptable range.

Downhole fracture mapping is a key tool in the development of shale reservoirs. For optimal resources, operators should employ a separate observation well with a downhole seismic receiver, said Leen Weijers, Rocky Mountain regional manager, Pinnacle, a Halliburton service. This increases the accuracy of downhole mapping for the deeper and longer wells are generally required in shale resource plays. Seismic source and receivers are still limited by distance between them, about 3,000 feet.

Although a second hole costs more, he said, downhole seismic and downhole tilt-mapping tools are invaluable to optimize horizontal well azimuth for fracture geometry before perforating, which ultimately maximizes production from a stimulated formation.

Peter Duncan, president, Microseismic Inc., wrapped up the panel with a look at state-of-the-art, field-scale microseismic monitoring arrays. In this application, sensors are placed around a field to provide real-time information on hydraulic and geomechanical processes taking place within a reservoir, remote from wellbores. Microseismic techniques are especially helpful in monitoring and detecting non-randomly distributed events during fracture stimulation, and plotting clusters can aid in delineating formations and in developing and managing reservoirs, he said.

Life-of-field microseismic arrays have been quite popular in the Haynesville play in East Texas and North Louisiana, and now have migrated north to the Bakken.

Microseismic Inc. has installed the largest buried array in the world at North Dakota’s Sanish Field for Whiting Petroleum. The $2-million installation features 292 stations across 152 square miles. It went live in March, and as of mid-May had monitored 324 stages in 17 wells, said Duncan.

Certainly, the application of new tools and processes has already yielded outstanding volumes of oil from the Bakken. Now operators across the country are looking anew at oil-prone resource plays, and bringing fresh ideas and new technologies to every phase of drilling and completion operations.