What is the Difference Between an Exploratory Well and a Production Well?

Not all gas wells are the same. Gas companies actually drill several types of wells to obtain different information or resources.

Exploratory wells are drilled in areas that have not been previously shown to contain oil or natural gas.  They may also be drilled in areas near existing wells to find another reservoir of oil or natural gas. These wells are drilled in locations that have undergone seismic testing to determine the depth and thickness of potential sources of natural gas. As the wells are being drilled, the engineers analyze the various rock layers to determine which layers contain organic-rich shale and are potentially sources of natural gas. Exploratory wells are usually drilled only vertically, with horizontal drilling only occurring if the well is believed to be productive.

The term wildcat well is usually used to describe an exploratory well that has been drilled without prior seismic testing.

Service wells and monitoring wells are drilled in existing well fields to support the production of other wells.  Service wells can be drilled for injection of gas or water, disposal of fracking water, or observational purposes. Monitoring wells may be drilled to monitor changes in water wells quality in the area surrounding a well that is being drilled and fracked. Depending upon the needs of a well, service and monitoring wells may be sparsely distributed, or located in clusters near existing wells.

The term production well is commonly used to describe wells from which natural gas is actively flowing and being captured.  In some cases, exploratory wells may become production wells; however, not all exploratory wells become production wells.  Many exploratory wells are unsuccessful and produce too little gas for companies to invest additional money in producing natural gas from those wells.

There are no distinctive surface signs that a well is exploratory or productive. However, often you can deduce the type of well based on its location. For example, exploratory wells are often drilled in locations where no other wells previously existed. If the exploratory well is found to be productive, other wells will be drilled at various distances to take advantage of the underground resources. On the other hand, if the information collected during exploratory well drilling does not indicate a strong likelihood of the presence of oil or gas, the company may not proceed with fracking.

Finally, the Pennsylvania Oil and Gas Act, requires drilling companies to plug wells that are no longer being used.


Primary Author: Rachel Curtis ---- Posted: 25 March 2011 ---- Version: Original

Suggested citation style: Curtis, R. 2011. What other kinds of rock in northeastern Pennsylvania contain natural gas? Institute for Energy and Environmental Research of Northeastern Pennsylvania Clearinghouse website. http:energy.wilkes.edu/206.asp. Posted 25 March 2011.