Marcellus Shale in PA, Part II
Appalachian Basin Natural Gas
& E.J. Breneman Roadway Repair
By Michael Polak
Who would have ever thought that Natural Gas would bring Breneman so much work? When we think of Natural Gas and whether a road restoration project might come from it, we would naturally think of a utility company like UGI digging up a roadway and Breneman or Paving going in to repair the trench. Who would ever have thought it would generate two months of work utilizing three of our Reclamation Crews? Until late last year no one. Both Rudy Schmehl and I received phone calls from some Natural Gas well drillers in September of 2009. This information was passed onto John DeMartino and since then it has been a huge part of John's time and the Operations Department work load. It has been a very intense and grueling process and to say the least a very well developed and executed piece of work by all those in Operations.
Marcellus Shale, also referred to as the Marcellus Formation, is a Middle Devonian-age black, low density carbonaceous (organic rich) shale that occurs in the subsurface beneath much of Ohio, West Virginia, Pennsylvania and New York. There are some smaller areas in Maryland, Kentucky, Tennessee and Virginia. As recently as 2002 the United State Geological Survey in its "Assessment of Undiscovered Oil and Gas Resources of the Appalachian Basin Province", calculated that the Marcellus Shale contained an estimated undiscovered resource of about 1.9 trillion cubic feet of gas. That is a lot of gas but it is spread over the enormous geographical extent of the Appalachians and was said not to be that much gas per acre. More recently in 2008 Terry Englander, a geosciences professor at Pennsylvania State University, and Gary Lash, a geology professor at the State University of New York at Fredonia surprised everyone with estimates that the Marcellus might contain more than 500 trillion cubic feet of natural gas. Using some of the same horizontal drilling and hydraulic fracturing methods that had previously been applied in the Barnett Shale of Texas, perhaps 10% of that gas (50 trillion cubic feet) might be recoverable. That volume of natural gas would be enough to supply the entire United States for about two years and have a wellhead value of about one trillion dollars. The Marcellus Shale is in most cases about one mile or more below the surface. These great depths make the Marcellus Formation a very expensive target.
With New York City, Philadelphia, Washington D.C. and the new England States and their metropolitan areas close to the deposits it was only good common sense for many gas production companies to see the economic advantage of gas exploration in the Marcellus Formation. Most wells in the Marcellus Formation are drilled using horizontal drilling technique; some of these horizontal drilled wells have had initial flows that suggest that they are capable of yielding millions of cubic feet of gas per day. To increase the productivity of a well a new technique has been adapted by the drillers. This is to increase the number of fractures using a technique know as "hydraulic fracturing" or "hydrofracing". This method uses high-pressure water or gel to induce fractures in the rock surrounding the well bore. "Hydrofracing" is done by sealing off a portion of the well and injecting water or gel under very high pressure into the isolated portion of the hole. The high pressure fractures the rock and pushes the fractures open. To prevent the fractures from closing when the pressure is reduced several tons of sand or other "propant" is pumped down the well and into the pressurized portion of the hole. When the fracturing occurs millions of sand grains are forced into the fractures. Once the pressure is reduced the sand grains will have propped open the cracks in the shale and this allows permeability for the flow of gas to the well.
On a local scale this gas well drilling has caused a huge amount of disruption for farmers, residents and in general for anyone traveling on local and state highways (whether they are commercial drivers, commuters or residential drivers). When these roadways were first designed, the estimated weight and structural numbers measured in EASL's were gathered and noone envisioned all this activity on the roadways. For the gas well drillers to be able to use the system "hydrofracing", they must, as previously stated, use large quantities of water. The next question is how do they get the amount of water needed to the wells and with a constant volume that is consistent for production.
Most of the water can be found in the valleys like the Susquehanna River Valley, but that water needs to be pumped into trailers, hauled up the hillsides, and into the country side where the wells are being drilled. To combat bad weather and insufficient water at times, the well drillers have rented many acres from farmers and built small reservoirs. The water is then trucked up to the reservoirs and pumped in to them. A pipe line is then placed from the reservoir to the gas well. The well drillers then have ample water to continue their process. It might take 500 trucks to fill one reservoir; this traffic has taken its toll on the local and state roadways. Many roadways are destroyed by the heavy loads of water and construction equipment used for the construction of the wells and the new pipeline needed to take the gas across country. E.J. Breneman L.P. has been instrumental in working with the gas companies and providing construction crews and equipment to deal with hundreds of miles of dilapidated roadways. Initially it took quite some time for Breneman to start its first FDR project in the Marcellus Formation. John DeMartino spent many hours talking to gas company representatives and attending meetings that sometimes did not provide much assistance or information to us. But with a lot of persistence, this endeavor eventually paid off for Breneman and we constructed our first roadways using Full Depth Reclamation (FDR) Portland cement stabilization. The system for biding FDR is not much different than any other bid we produce in the estimating department. Size of project (square yards), calculation of additive (Portland cement), number of pieces of equipment needed (reclaimers, spreaders, rollers, water trucks, graders), personnel on project (laborers, operators, truck drivers, supervisors and mechanics) are all considered. Other costs such as gas, diesel fuel, signs, traffic control, hotel costs and per diems need to be estimated. We also have to add sub-contractors like our Geo-Technical Engineers, Portland cement truck haulers and many other elements in the field. Once the bid is put together, it is delivered to the customer and at a certain time opened up. Once a "responsible bidder" is declared, the bid is awarded.
Because there has been such a public outcry to repair the roadways as soon as possible. Most contracts require you to start within a very short period of time. John DeMartino and the construction superintendent has done a great job of assembling a group of office and construction personal to coordinate the operation. It is not an easy task placing so many people in the field at one time, delivering product to them and constructing in accordance with specifications. The crews have completed an extraordinary task of completing these projects as bid. Time has been saved on several projects. The crews have been required to work six days of the week and have worked extremely hard to contend with all the frustrations of the work load. The location of the work means that although the crews are housed in hotels, the hotel may still be an hour or more from the job site. The commute from hotel to job site may be more than they have traveled from home to job site all year. The work load had a very short construction time, in two months the projects needed to be complete. Most of the roadways are Penn-DOT roads. This means that not only do you have to complete the projects correctly for the customer (the gas well drillers), but also in accordance with Penn-DOT specifications.
Full Depth Reclamation (FDR) takes place when weaknesses in the base and sub-base of a roadway cause the asphalt materials above to crack, pothole, corrugate and generally break down; in other words the roadway has lost its serviceable life. With FDR, a large four wheel drive all wheel drive by-directional reclaimer pulverizes the roadway materials down to a predetermined depth. The material sizing may differ depending on what types of material you are reclaiming. If there is large rock three to four inch size the reclaimer will not crush the rock as it is not built to do that. It will crush all the asphalt material as that is a lot softer and is flexible. Once the roadbed is pulverized and the soil, aggregate and asphalt mixed together, a pre-determined amount of Portland cement is added to the surface of the roadway by means of a towed behind spreaders or truck mount spreaders. A Geo-Technical Engineering Company will gather sample material from the affected roadways and take the material to a laboratory for testing before any construction takes place. The material is mixed with different percentages of Portland cement at the same depth required in the field, but using different percentages of Portland cement to generate different psi (pounds per square inch). This material is then loaded into six inch round cylinders compressed and left to cure over seven days, fourteen days and twenty-eight days.
The cores will then be destroyed using weights which exhibit the strengths gained on the specimens during that time. A core may gain in seven days a strength of 190 psi using 5% Portland cement. The recommended strength for the project might be 250 psi. If so, you need to use one of the tests that had a higher percentage of Portland cement to gain the required psi in the time frame. Once the Portland cement is laid on the surface of the pulverized roadway, the reclaimer will once more pulverize the roadway material the Portland cement and water to make a homogeneous mix. It is imperative to make sure all the Portland cement is hydrated (saturated to the point that no dry material remains); this is why water is one of the main ingredients in any successful stabilization project. Breneman then pre-rolls the mixed base material before using a motor grader to strike off a new cross slope and shape the roadway back to its original or desired section.
Once the new Portland stabilized road base is graded it is compacted using suitable compaction equipment. There are many types of rollers that might be used. The idea behind any compaction is to make sure you are meeting density requirements. If you do all the preparation, mixing and grading and you do not compact the finished material correctly the project will fail. The last part of any FDR project is the "Prime Coat." A prime coat does two things:
- Of the stabilized base. If the base cures too quickly it will prematurely crack because it shrinks too fast. As the new base dries, it gets dusty since it is a Portland cement treated base. To stop the dust getting airborne, the prime coat seals the top of the new reclaimed base so the dust is suppressed.
- Once the Portland cement base has cured a new Hot Mix Asphalt Pavement is laid on top at a depth of three to eight inches depending on the loading the roadway will take in the future. This part of the project is usually subcontracted to a local paving contractor.
Breneman looks forward to working in the Marcellus Shale area again in 2011.
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