The Pros And Cons Of Shale Gas Environmental Sciences Essay

Shale gas development has significant negative and positive environmental impact. Negative environmental impact is due to the process of shale gas development and positive impact is through a substitution of clean natural gas to other energy sources. This paper is organised in three parts. In the first part, shale gas development and potential of shale gas is described. In the second part, environmental challenges in the development of shale gas are described. In the third part, environmental benefits as a result of shale gas are discussed.

Shale Gas and its potential:

Shale gas is natural gas. It is stored in organic rich rocks such as dark-coloured shale, inter bedded with layers of shaley siltstone and sandstone [1]. Shale is a fine-grained rock made up of ancient compacted clays or mud and can be the source, reservoir and the seal for the gas. Shale gas plays are classified as a “continuous” type gas accumulations extending throughout large areas, typically with low permeability [1]. Shale gas is considered as unconventional gas source and same techniques used for conventional shallow gas development may also be used with shale gas drilling [1].

Shale gas is extracted through a process known as hydraulic fracturing which was developed in the United States in 1948 [3]. Hydraulic fracturing involves injecting a mixture of water, sand and chemicals into rock formations to stimulate oil and natural gas production shown in the figure 1.

Figure1: Shale gas extraction process [2]

Hydraulic Fracturing creates fractures that extend from a borehole into shale formations. Hydraulic fracture is formed by pumping a fracturing fluid into the well bore at a rate sufficient to increase the pressure down the bore hole fracturing the surrounding shale rock formation [3]. Solid proppant (like sieved round sand) is added to the fracture fluid to keep the fracture open after the injection stops.

Shale gas potential:

Shale gas fields were largely untapped until recently due to the difficulty and cost to extract the gas. As conventional natural gas production has been decreasing, demand for the unconventional natural gas is more than ever now. This fact coupled with improvements in extraction methods has made it possible to explore the shale gas reserves.

Recoverable shale gas reserves increases total gas availability of the world by 40 percent per the report by Energy Information Administration (EIA) of USA. A new EIA-sponsored study reported initial assessments of 5,760 trillion cubic feet of technically recoverable shale gas resources in 32 foreign countries [6], with China topping the list with 1275 trillion cubic feet of shale gas reserves followed by USA with 862 trillion cubic feet [Appendix 1].

In 2010, U.S. shale gas production was 4.87 trillion cubic feet (23 percent of total U.S. natural gas production), compared with 0.39 trillion cubic feet in 2000. IEA predicts that shale gas will account for about 46 percent of U.S. natural gas production by 2035[6]. Rising production from shale gas resources in the U.S. has been credited with both lower natural gas prices and declining dependence on imported natural gas [6]. In most of the developing countries, shale gas development has not started yet. Energy hungry countries like India and China can greatly benefit from their recoverable shale gas resource as recent oil prices trend shows that oil is no longer a cheap commodity. At the current level of consumption, world may have 250 years supply of natural gas as result of new shale gas reserves around the world as per International Energy Agency (IEA) [7]. Shale gas is “a huge deal” per Shell’s CEO Peter Voser. BP’s ex CEO Tony Hayward hailed shale gas as “complete game changer” [8]. These comments from the prominent energy experts show the importance of shale gas as future potential energy source.

Figure 3: Estimated global shale gas recoverable resources

As is often the case with any resource development, shale gas production also has raised local environmental concerns, largely centering on the amount of water used in the fracturing process and the need to handle, recycle, and treat fracturing fluids in a manner that addresses the risk of spills that can potentially affect water quality.

Do other countries have similar opportunities to develop shale gas? To begin to address that question, EIA sponsored Advanced Resources International, Inc., to assess 48 gas shale basins in 32 countries, containing almost 70 shale gas formations. This effort has culminated in the report: World Shale Gas Resources: An Initial Assessment of 14 Regions Outside the United States.

Technically recoverable natural gas resources in the assessed basins totaled 5,760 Tcf. Adding the estimated U.S. shale gas technically recoverable resources (862 Tcf) to the assessments in the study gives a total of 6,622 Tcf. For comparison, most current estimates of world technically recoverable natural gas resources include few if any of the resources assessed in this study and total about 16,000 Tcf.

“Adding identified shale gas resources to current estimates of other gas resources increases total world technically recoverable resources by over 40 percent, to more than 22,000 trillion cubic feet,” said EIA Administrator Richard Newell.

Estimates of shale gas resources in other parts of the world are highly uncertain. The practicality of using such resources has only recently become apparent, and many countries are just now beginning to understand how to conduct assessments of how much shale gas they may have. Nonetheless, the aggregate estimate is probably quite conservative, since the study excluded several major types of potential shale gas resources:

Nations outside the 32 countries studied. These include Russia and the Middle East, which have very large resources of conventional gas.

Some shale basins in the countries studied. In many cases, no estimates are possible yet for these basins.

Offshore resources.

Of the countries covered in the EIA-sponsored study, two groups may find shale gas development most attractive. The first is those countries that currently depend heavily on natural gas imports but that also have significant shale gas resources. These include France, Poland, Turkey, Ukraine, South Africa, Morocco, and Chile. The second group is those countries that already produce substantial amounts of natural gas and also have large shale resources. In addition to the United States, this group includes Canada, Mexico, China, Australia, Libya, Algeria, Argentina, and Brazil.

A new EIA-sponsored study reported initial assessments of 5,760 trillion cubic feet (Tcf) of technically recoverable shale gas resources in 32 foreign countries, compared with 862 Tcf in the United States. Technically recoverable natural gas resources in the assessed basins totaled 5,760 Tcf. Adding the estimated U.S. shale gas technically recoverable resources (862 Tcf) to the assessments in the study gives a total of 6,622 Tcf. For comparison, most current estimates of world technically recoverable natural gas resources include few if any of the resources assessed in this study and total about 16,000 Tcf. Adding identified shale gas resources to current estimates of other gas resources increases total world technically recoverable resources by over 40 percent, to more than 22,000 trillion cubic feet.

In terms of recoverable shale gas resources, China takes the top spot, with an estimated 1,275 Tcf. The US is second, with 862 Tcf, followed by Argentina with 774 Tcf and Mexico with 681 Tcf.

The growing importance of US shale gas resources is also reflected in EIA’s Annual Energy Outlook 2011 (AEO2011) energy projections, with technically recoverable US shale gas resources now estimated at 862 trillion cubic feet. Given a total natural gas resource base of 2,543 trillion cubic feet in the AEO2011 Reference case, shale gas resources constitute 34% of the domestic natural gas resource base represented in the AEO2011 projections and 50% of lower 48 onshore resources. As a result, shale gas is the largest contributor to the projected growth in production, and by 2035 shale gas production accounts for 46% of US natural gas production.