A new technology will get the most out of our nation’s oil and gas resources by helping engineers and geologists “see” how a well connects with an oil reservoir below the surface of the earth.

The National Energy Technology Laboratory (NETL) and other National Laboratories have partnered with industry to develop a breakthrough technology that is helping oil and gas producers connect their wells with the hydrocarbons stored in networks of fractures found in many of today’s most promising domestic oil and gas accumulations. Also known as “plays,” these accumulations exhibit complex geological characteristics. The technology combines subsurface sensors with powerful data collection and analysis software, to record the myriad of tiny microseisms (or microearthquakes) that occur as fluid is pumped into a well bore, creating a split or fracture in a subsurface rock formation holding natural gas or oil. The individual locations of these microseismic events are mapped to create an image of the fracture.

This image, which reveals both the direction and extent of the fracture resulting from a specific pumping procedure, can be used to optimize the placement of such fractures and their connection with networks of natural fractures within hydrocarbon-bearing rock formations, increasing the recovery of domestic natural gas and oil resources. Before this technique was developed, engineers could use computer models to indirectly infer the dimensions of the hydraulic fractures they were creating downhole, but had little direct evidence of their extent and orientation.

This new technology, called microseismic monitoring, is important because the United States’ national energy security is dependent on our ability to economically extract as much of our own hydrocarbon resources as possible. A growing portion of our domestic production is from “unconventional” reservoirs—underground formations that require hydraulic fracturing to release their oil and gas—and developing technologies that enable us to efficiently produce these resources is critical to any effort to reduce America’s need to import energy.

For example, the recent rapid expansion of natural gas production from the Barnett Shale play in central Texas has been made possible by large, multiple-stage hydraulic fracturing treatments (i.e., more than one created fracture per well bore) performed in horizontally drilled wells. Microseismic monitoring of these stimulations has played an important role in optimizing well performance and ensuring that each well produces at its full potential. Operators are now using this technology to overcome the complexities of similar shale reservoirs across North America, including the Bakken, Caney, Fayetteville, Marcellus, Muskwa and Woodford shale plays.

These unconventional reservoirs are seen by industry and government experts as providing a major component of our domestic energy production over the next two decades. The Barnett Shale play currently produces about 4 billion cubic feet of gas per day and production is expected to grow to as much as twice that amount over the next five years. Barnett’s Newark East Field is thought to be the largest gas field in the United States. The more recently explored Marcellus Shale play of West Virginia, Pennsylvania and New York has been described by some as having the potential to provide as much as 50 trillion cubic feet of technically recoverable gas. The Bakken Shale, an oil play in North Dakota and Montana, contains more than 3.6 billion barrels of recoverable oil, according to the U.S. Geological Survey. All of these geologically complicated reservoirs can be developed more efficiently through the application of microseismic monitoring technology.

The roots of this technological breakthrough stretch back to research and development funded by the U.S. Department of Energy (DOE) in the late 1970s. Additional R & D funded by DOE through NETL in the 1980s and 1990s enabled enhancements to the tools and techniques that were subsequently commercialized by Pinnacle Technologies, Inc.

During the past 10 years NETL has continued to work with Pinnacle and others parties to push the envelope by funding new R & D to refine and enhance the application of microseismic mapping technology. One project focused on the development of a hybrid technique that combines information from downhole seismic sensors with that from surface tiltmeters, to provide a more accurate depiction of the fracture being created underground. A second project with the University of Texas and Anadarko Petroleum employed Pinnacle’s microseismic monitoring to map fractures in East Texas’ Bossier formation and identified places where hydraulic fractures intersected faults and grew in unexpected directions. Another project, sponsored by NETL through the Stripper Well Consortium, introduced microseismic monitoring to smaller independent producers seeking to improve recovery from Appalachian shale gas reservoirs.

A fourth effort, currently underway, is helping to develop the technology needed to make “designer seismic” monitoring possible. This approach involves the drilling of multiple, strategically placed, small diameter, inexpensive microholes with permanently installed seismic receivers to enable highresolution and relatively inexpensive seismic monitoring of a reservoir over an extended period of time. The sensors are used to record seismic events resulting from fluid movements within the reservoir at successive points in time, enabling the mapping of injected fluid fronts moving through the reservoir. Such time-lapse monitoring will be a valuable tool as the oil and gas industry increases the application of enhanced oil recovery techniques to sweep residual oil from mature fields. This R & D project, sponsored by NETL in partnership with Lawrence Berkeley National Laboratory in Berkeley, California, and Lumedyne Technologies Inc. of San Diego, California, is focused on developing the small-sized, inexpensive geophones needed to make this possible.

The first systematic research into microseismic fracture mapping, done by Los Alamos National Lab (LANL) in Los Alamos, New Mexico, in the 1970s, was related to fractures in geothermal wells. Somewhat later, NETL collaborated with Sandia National Laboratories to build and deploy receivers for testing similar mapping technology. In the 1980s, this system was used at the NETL Multiwell Site experiment in Colorado, where major fracture experiments were successfully monitored.

When it became clear that single receivers would not be adequate for microseismic monitoring because of their limited accuracy, NETL sponsored a project to develop a multilevel receiver system that became the first generation of a number of successive systems. Pinnacle Technologies began using these receivers and developed a business that quickly grew to several hundred mapped fractures per year. NETL sponsored an additional research project with Pinnacle to help the company refine and enhance its technology. Recently the company has employed its microseismic and tiltmeter technology to monitor more than 12,000 hydraulic fracture treatments.

The important thread in this story is the significant role played by DOE, and in particular NETL, in helping to develop this technology over the more than two decades required to make it commercially workable for normal oil and gas activities. DOE’s early investment in basic research and NETL’s longterm support were critical to the development of microseismic monitoring as a modern tool for oil and gas producers. According to NETL director Carl Bauer, “The development and application of microseismic imaging technology has played and will continue to play an important role in facilitating more efficient production of natural gas and oil from the nation’s unconventional resource base.”

It is particularly timely that this technology is available for commercial application just as producers are looking for ways to improve their efficiency in developing unconventional reservoirs. Microseismic monitoring is a way to more precisely characterize reservoirs and related flow dynamics, enabling fewer wells to produce more oil and gas, more quickly, at lower cost and with fewer environmental impacts. This technology, which enhances the high-density drilling approach of conventional domestic oil and gas field development, will be an important element of future methodologies for developing our nation’s energy resources.