Karst Geology

Wells in Areas of Karst Geology (Senate Bill 387)

September, 14 2015

 

Recently proposed Senate Bill 387 aims to prevent the safe disposal and storage of fluids and gasses associated with the oil & gas industry in the few areas of Michigan that contain “karst geology,” a practice that has been taking place safely for decades. These myopic rules could have serious effect on an industry that has safely operated throughout Michigan for nearly a century.

 

What are disposal wells?

Disposal wells are used for a variety businesses; including oil and natural gas production, municipal waste disposal, agricultural uses, storm water drainage, septic systems, geothermal wells, domestic wastewater disposal wells and a variety of industrial and manufacturing purposes. Disposal wells exist throughout the state in both karst and non-karst regions. In Michigan alone, there are over 10,000 disposal wells of different types. There are currently 1,345 (class II disposal) wells regulated by Part 615, which covers disposal wells related to oil & gas operations in Michigan.

 

Energy security: Why are disposal wells important?

Public polling has shown that United States citizens are very interested in reducing our country’s dependence on foreign oil from foreign countries.  In order to do that and in order to provide the safe, abundant and economical source of natural gas that will help fuel Michigan’s energy future, we must drill wells for natural gas and oil.

Disposal wells are an important part of the process of producing oil and natural gas, both in Michigan and nationwide.  Not every natural gas or oil well needs a disposal well, but many of them do.  Disposal wells cut down on truck traffic which is an alternative to carrying the waste produced from oil and gas processes, as well as provide a scientifically proven, safe means of disposal. 

Over 80% of homes in Michigan are reliant on natural gas for heating and cooling, making natural gas particularly important to our state.

 

Where are the current disposal wells located that are in areas of karst geology?

There is no oil or gas present in karst zones because the caverns and passages would not hold it.  This is the same reason why you wouldn’t dispose of liquids into karst.  They would not stay. Instead you drill far below these areas into geology that will hold liquids.  In many cases drilling occurs over 1200 feet below karst areas – this is a distance of 4½ football fields!  As a well is drilled, thick concrete and steel casing will prevent fluid or gas from leaking into this zone.

Maps vary on the location of possible karst features in Michigan.  Known karst areas can include Presque Isle, Montmorency, Charlevoix, Otsego, Antrim, Monroe and Alpena counties.  There are nearly 400 active oil and gas-related disposal wells in Presque Isle, Montmorency, Charlevoix, Otsego, Antrim, Monroe and Alpena counties alone.  Monroe County (Summerfield Township) historically had one disposal well for oil and gas that was permitted in 1984 and closed in 2004. 

 

What is karst topography and why can’t you find natural gas in it?

Karst geology is a landscape formed at the surface when soft rocks like limestone get dissolved by rain water.  As it drains into fractures in the rock, the water begins to dissolve away the rock creating a network of passages. Over time, water flowing through the network continues to erode and enlarge the passages; this allows the plumbing system to transport increasingly larger amounts of water.

There is no oil or gas present in karst zones because the caverns and passages would not hold it.  This is the same reason why you wouldn’t dispose of liquids into karst.  They would not stay. Instead you drill far below these areas into geology that will hold liquids.  In many cases drilling occurs over 1200 feet below karst areas – this is a distance of 4½ football fields!  As a well is drilled, thick concrete and steel casing will prevent fluid or gas from leaking into this zone.

Expanding Part 615 to include the term “karst” also separates out a specific geologic feature that exists in small areas of Michigan while the purpose of the regulations are to maintain safety for all Michiganders throughout the state.

 

How do we keep water safe when using a disposal well?

Disposal wells for the oil and gas industry are regulated by both the Environmental Protection Agency (EPA) and the Michigan Department of Environmental Quality.  This dual regulation ensures that the most stringent safeguards are part of any decision to grant a permit for a disposal well.

One of the focuses of Part 615 is to prevent the migration of fluids, including water, between formations. In Michigan, fresh drinking water aquifers are present between 25 feet and up to about 600 feet deep. Below the fresh water aquifers are sedimentary rock formations which have porosity that contains either salty, brine water unfit for consumption or hydrocarbons. This is a separate and distinct area used for disposal.

The well construction requirements are designed specifically to protect fresh drinking water from contamination.  In addition to the well construction, the DEQ and EPA require continuous monitoring and reporting of disposal pressures, rates and amounts of liquids. 

Since the modern era of our industry’s rules (late 1980s), there has not be an impact of contamination to a drinking water well or surface water body from oil and gas activities that have been permitted in that timeframe.

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