The Second Boom

Pennsylvania RTN is playing a key role in drilling for natural gas in the Marcellus Shale region.
by John Stenmark, LS

Ever since 1859 when America’s first oil well was drilled in northwestern Pennsylvania, geologists have kept tabs on the area’s petroleum reserves. The Pennsylvania oil boom lasted for decades; the state produced half of the world’s oil until it was displaced by the Texas boom of 1901. While much of the nation’s oil production now occurs in other regions, Pennsylvania is again rising to prominence in energy production, with natural gas driving the development.

A geological formation known as the Marcellus Shale stretches across the northern Appalachian region of the United States. The shale, which lies beneath much of Pennsylvania and extends into West Virginia, Ohio, and New York, is rich in natural gas. But there’s a problem: The valuable gas is locked into the dense black Marcellus rock, preventing it from moving to the surface or to other, more permeable formations. As a result, the gas can’t be removed using standard drilling processes.  

During the past decade, production companies have developed new techniques for gas recovery. To extract it, producers use horizontal drilling and hydraulic fracturing to create small cracks in the shale that allow the gas to collect and be pumped to the surface. The use of fracking has raised some environmental concerns, and developers work hard to ensure that the gas is extracted safely and with minimal effects on the environment.

As a result of the new methods, the quantity of recoverable gas in the Marcellus has increased significantly. In 2002, the U.S. Geological Survey estimated the formation contained 1.9 trillion cubic feet or TCF (54 cubic km) of recoverable gas. In 2009, the U.S. Department of Energy increased the estimate of recoverable gas in the Marcellus to 262 TCF (7,400 cubic km), based on the new techniques. That’s enough gas to supply the residential needs of the United States for more than 50 years, and some independent estimates are even larger. The quantities make Pennsylvania a major player in the gas business. Regarded as the cleanest of the fossil fuels, the abundant supply of natural gas will aid efforts towards clean, low-cost energy sources.

Marcellus gas has created a boom for development and production across northern Appalachia. Extracting the gas and delivering it to the market involves an array of activities including seismic exploration, land and site planning, construction, production, and maintenance. With rapid development throughout  the region, dozens of projects are currently underway across Pennsylvania. All of the activities take place under state and federal environmental and health controls, and developers comply with the regulations, many of which require accurate positioning and detailed geographic information.

To meet these needs, surveyors in Pennsylvania are implementing tools for positioning, analysis, and data management. Like other gas developments in the United States, many surveyors on the Marcellus use GNSS and RTK technology. With dozens of operations spread over hundreds of miles, the Marcellus is an ideal application for a real-time GNSS network (RTN).

In Pennsylvania, KeyNetGPS provides RTK GNSS correction services using Trimble VRS technology. Access to the network is by subscription. For a set monthly or annual fee for each rover, subscribers have unlimited access to the network’s RTK correction services. There are more than 500 subscribers in the multi-state region served by KeyNetGPS. On a typical day, as many as 200 different users connect to the network, with 30 to 75 users operating at any given time.

Permits and Plans

The early phases of developing a gas well include analysis and permitting to prepare a site for construction. Pittsburgh’s Gateway Engineers, Inc. provides assistance beginning with the first stages of a project. Gateway’s clients include the development and production companies that extract the gas and deliver it into the transmission pipelines. After meeting onsite with their clients and landowners early in the process to collect positions of a few features for preliminary analysis, Gateway staff develops a drawing that shows the parcel and surrounding area with some topography. This information helps the client make important decisions, such as if and when to go to the permitting phase.

Gateway stays involved as a project moves through permitting and planning into construction, providing design and consulting on pads, access roads, water impoundment ponds, and meter sites. The preliminary field survey work includes marking limits for clearing and erosion control.

To handle the drilling activities, well site pads can be as big as 300 by 500 feet (90 by 150 meters). Western Pennsylvania’s undulating terrain introduces challenges in grading for pads, roads, and water management.

“Some of our new clients are from out of state and have never dealt with the topography that we have here,” said Gateway field manager Tom Turner. “They aren’t used to dealing with the grading processes, plus the erosion and sedimentation controls that are common in this area. We are helping them through that learning process.”

For project fieldwork, Gateway uses Trimble R8 GNSS systems and S6 total stations with TSC2 controllers running Access software. The bulk of Gateway’s GNSS work is done in VRS RTK mode using the firm’s subscription to KeyNetGPS network. Pennsylvania permitting regulations call for coordinates of the well sites to be given in state plane coordinates (SPC). Because KeyNetGPS operates in the geodetic reference frame, surveyors can use commonly accepted field procedures to work directly in the SPC system. In areas of dense vegetation, the Gateway surveyors use optical total stations tied to control set using their GNSS equipment. Once the site is cleared for construction, they can resume work using RTK GNSS.

The evolving environmental regulations, including those dealing with fracking, are changing the process for permitting and approval of new wells. In Carmichaels, Pennsylvania, Dra-Surv Inc. provides extensive services in permitting activities for its clients. “All permits must have accurate before and after information; the plans have to be completely developed from start to finish, including post construction,” said Dra-Surv vice president Bill Miller. “As a result, we have had to become more precise in all aspects of our business.” Dra-Surv is an indicator of the effect of the Marcellus on Pennsylvania’s economy; the company has more than doubled in size since 2008 and expects to grow further as Marcellus development continues.

At the beginning of their work on a well site, Dra-Surv project manager Bryan Cole establishes control with static 
GNSS measurements by using the National Geodetic Survey Online Positioning User Service (OPUS) for post processing. For the field work, Dra-Surv uses a Trimble R8 GNSS system and R6 GPS receiver. Most of their construction sites have been cleared when the Dra-Surv crew arrives, so they use RTK for virtually all of their measurements. While much of their work is construction stakeout, Dra-Surv also surveys for volumes and as-built measurements for the sites and ponds, including erosion, sediment-control facilities, and storm-water management.

In addition to the surveying- and mapping-grade GPS and GNSS systems, 3D machine control is becoming more common for grading and construction by Marcellus developers. These companies typically require less construction surveying. “We set control points for the contractors who use 3D machine control,” Cole said. “We support the OPUS data with benchmarks and by double checking into existing elevation references in the field.”

Moving the Gas to Market

The new wells of the Marcellus are only part of the effort. Hundreds of miles of underground pipelines are needed to connect the well sites. Collection systems gather the gas from the wellheads and deliver it into midstream pipelines. The midstream lines connect to large, overland transmission lines that carry the Marcellus gas to major markets hundreds of miles away. In southeastern Pennsylvania’s Green County, Gary Kuroski, PS, is the survey manager and coordinator for Hatch Mott McDonald (HMM), a full-service engineering consulting firm. A large part of Kuroski’s work involves surveying for the construction of gas transmission lines.

To provide control, Kuroski establishes points in the work areas along the pipeline route. Some of his clients request control to be set using static GNSS methods; for these clients the HMM surveyors use two-hour sessions and post processing via OPUS. For others, he uses KeyNetGPS reference network and RTK. In some cases, Kuroski ties to control set by others, checking it with the real-time network.

“I always set the control with the most accurate, time-efficient methods, while making sure that we meet each project’s accuracy standards,” he said. “We make two three-minute observations on each point with the VRS and reinitialize between the observations. Compared to static observations, working with KeyNetGPS saves us roughly four hours of field time and processing for each control point that we set or check.”

With control in place, HMM crews provide surveys for design and construction. The new pipelines are not always the only utility in a given right of way, and sometimes the routes are already occupied or intersected by existing gas pipelines. Because a collision with an existing line could be catastrophic, the surveyors locate the existing pipes as accurately as possible so that construction crews know what is in the ground.

A key phase occurs when the pipe sections are welded together and lowered into the trench. Working with survey accuracy, the surveyors collect as-built positions on every weld, bend, and deflection point of the pipe. After the trench is backfilled, crews collect ground shots to confirm adequate cover over the pipe. Points are collected to a precision of 0.1 ft (3 cm) in horizontal and vertical, using a customized data dictionary in the crews’ controllers.

In the office, the field data is downloaded into Trimble Geomatics Office software, where it is checked and then exported to CAD and other systems. The final deliverable is a 3D profile of the pipe in SPC with 2D and 3D stationing and attributes of the line’s features. Over the entire length of the project, the 3D profile must be accurate to within 1 ft (30 cm). Kuroski receives consistently good results using KeyNetGPS, commonly checking into control with an accuracy of 0.1 ft (3 cm) or better. 

As part of the inspection process, a device called a pipeline inspection gauge (PIG) travels through the inside of the pipe to look for flaws. If the PIG detects a problem, the location is staked on the ground and the trench opened to inspect and resolve the issue. The PIG determines its position based on 3D distance along the pipe, so the correlation between the 3D stationing and SPC must be correct. Any discrepancy between the stationing and ground coordinates can result in costly, unneeded work.

Kuroski uses Trimble R8 GNSS systems for the control and as-built surveys along his projects. With several survey companies often working in one area, the limited number of UHF channels can affect the availability of telemetry links and control stations. Kuroski’s crews use a mix of UHF-based RTK and RTN RTK for GNSS positioning, taking advantage of the good cellular coverage on the hilltops for VRS using KeyNetGPS.

GIS: The Center of Action

The variety of information and deliverables makes GIS an important part of the process for planning, permitting, and development on the Marcellus. In northern Pennsylvania, Fisher Associates supports development and construction of gas facilities, including midstream and transmission pipelines. The company enters a project during the right-of-way and boundary phase and stays on the job until the pipelines are completed. Many clients are adept with GIS, and Fisher has developed new ways to add value.

In addition to its surveyors, Fisher’s staff includes specialists in environmental sciences, wetlands biology, and cultural resources who are trained in using the mapping-grade GPS. “For many years a wetland biologist would go out and flag a site, and then the surveyors would go out and collect the position data,” said Steve Boddecker, the company’s survey manager and vice president for geomatics. “Why make two trips? Today, a pipeline router can walk a route with GPS and recognize and capture positions on areas that aren’t suitable. We’ve adopted a mindset that is focused on problem solving.”

Fisher uses GIS equipment and systems for the bulk of its positioning for route planning, combining local cadastral information with field mapping data, orthophotos, and engineering information in their GIS. The result is an accurate map based on a rich data set. “We can turn a map into different kinds of drawings,” Boddecker said. “If it’s landowner plats for acquiring rights of way, we can develop that into a base topographic map using Pennsylvania’s extremely rich two-foot contour data. That lets us look at environmental controls and other items to meet the permitting requirements that require the two-foot data.”

In the field, Fisher crews use Trimble GeoXH handhelds running Esri ArcPad software. They have developed pull-down menus within ArcPad to customize field operations to their clients’ requirements. Each crew carries a laptop computer and processes field data using Trimble GPS Pathfinder Office software. The field crews can overlay their results onto orthophotos to perform quick quality checks before moving the data into the mapping systems. Once in the office, the GPS field data is post processed to sub-foot accuracy using data from regional Continuously Operating Reference Stations (CORS). From there, results are sent to Esri ArcGIS software.

Value Added: Positioning and Data Management

Competition, speed of development, and tight profit margins are daily facts of life for companies working on the Marcellus. The drive for productivity has created high visibility for surveying and engineering companies supporting the oil and gas industry, and strategic planning and implementation of positioning technology are important drivers. It’s clear that the RTN is playing a central role. In the past 12 months, daily log-ins to KeyNetGPS have increased by roughly 40%, and the total number of subscribers has doubled in the past two years.

The use of GPS/GNSS and the ability to move and manage information have repeatedly proven themselves as beneficial—if not essential—to the Marcellus effort. “It used to be that everything was about ‘turning the bit to the right,’ as they say, getting the hole drilled,” said Dra-Surv’s Bill Miller. “Now it has become equally important to have preliminary data and permitting that satisfies the governmental regulations and requirements. It’s causing an entrepreneurial approach: Those who stay on the cutting edge of technology, who have good relationships with their suppliers, and who are up to date on the regulations have the advantage. These are the items that will make companies successful and help them grow.”
John Stenmark, LS, is a writer and consultant working in the AEC and technical industries. He has more than 20 years of experience in applying advanced technology to surveying and related disciplines.

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