The geological aspects of drilling horizontal wells in various geologic environments worldwide are reviewed. Predominantly development wells, they are often drilled in locations where a conventional well would not achieve the same geological and subsequently economic, objectives. This paper summarizes recent activity and demonstrates that geologic conditions play a large part in determining the success or failure of a horizontal drilling project. The examples cited in this paper are all taken from previously published literature and include horizontal drilling projects in the USA, United Kingdom, Norway, Italy, The Netherlands and Denmark.
This paper concludes that a large range of geological conditions have been tested by horizontal drilling with varying degrees of success, the results of which might prove helpful in assessing future prospects for horizontal wells.