Understanding Shale and Shale Gas Production
Shales are fine-grained sedimentary rocks that can be rich resources of petroleum and natural gas. These rocks are characterized by high porosity and low permeability due to high tortuosity, meaning the ratio between the length of the pores and their diameters is very high. Additionally, some shales, particularly those of the Montmorillonitic type, can swell when in contact with water, further blocking the connecting pores. To extract gas from such rocks, a preferential path is created by creating fissures and propping them open with sand and other chemicals during the process of hydraulic fracturing.
What Is Shale Gas and Why Is It Important?
Shale gas refers to natural gas that is trapped within shale formations. These formations are sedimentary rocks that have the potential to store both oil and natural gas. Over the past decade, the combination of horizontal drilling and hydraulic fracturing has enabled access to large volumes of shale gas that were previously uneconomical to produce. This has brought a significant revival to the natural gas industry in the United States, as noted by the Energy Information Administration (EIA).
The Marcellus and Utica Plays
The Marcellus and Utica Shale plays are geological formations that have been formed by the accumulation of sediment into seas, eventually buried over thousands of years, and compressed to produce organic-rich black shale. The Marcellus Shale dates back to the Devonian period and stretches from the northeast to the southeast, while the Utica Shale dates back to the Ordovician period, with sediment deposited between 488 and 443 million years ago. Both formations are rich in fossil fuels and are deeper on the southeast edge, becoming progressively shallower as they head northeast.
Why Now and the Future of Shale Gas
The industry has recently ramped up exploration and production (EP) activities in the Marcellus and Utica Shale plays. This is driven by two main factors: the success of the Barnett Shale play in North Central Texas, which has allowed technology transfer to other regions, and the proximity of the population centers in the Northeast to these shale plays. As America continues to demand more energy, it remains uncertain how natural gas will fit into this demand, but it is clear that the Marcellus and Utica plays are likely to play a key role in meeting this demand. The impacts of this industry are also uncertain, given the historical volatility of the energy sector.
The Lifespan of Shale Gas
The natural gas development process can be divided into three phases: pre-drilling, drilling, and production. According to industry surveys, 98% of natural gas exploration and development jobs are found in the pre-drilling and drilling phases. While the duration of the drilling phase within the Marcellus and Utica plays is uncertain, estimates range from 10 to 70 years. This range reflects the uncertainty caused by future fluctuations in commodity prices, economic conditions, and technological changes. Different drilling scenarios are possible, ranging from a flurry of activity to high-intensity drilling and a sustained and moderate drilling approach that could last for decades.
Keywords: shale, shale gas, hydraulic fracturing