Environmental Risk and Well Integrity of Plugged and Abandoned Wells
- George Everette King (Apache Corp.) | Randy L. Valencia (Apache Corp.)
- Document ID
- Society of Petroleum Engineers
- SPE Annual Technical Conference and Exhibition, 27-29 October, Amsterdam, The Netherlands
- Publication Date
- Document Type
- Conference Paper
- 2014. Society of Petroleum Engineers
- Cementing, Plug, Depleted Well, Plug and Abandonment, Environmental Risk
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This paper is the third in a series of environmental risk assessments covering hydraulic fracturing (SPE 152596) and well construction (SPE 166142). Risk assessment and well failure from SPE literature and governmental agencies have been used to construct a detailed but non-company associated study of plug and abandonment (P&A) objectives, problems, best practices, application details and methods. The objective is to identify technology improvements as well as potential or proven problem areas. Technology gaps will be related where they are identified by either problem reports or failures.
Case histories have been captured that illustrate a variety of abandonment reasons and approaches in plug setting, isolation and testing/monitoring methods. The study well groupings are divided by age and era or vintage of abandonment to examine the worth of technologies in force at the time of abandonment. Well age, well type and general geographic influences are presented with notation of specific problems and conditions that challenged effective isolation.
Special attention will be paid to cases of failed isolation as cited by the governmental inspection and/or governing body as well as repair methods that restore integrity. Attention will also be given to problems encountered in older wells. Lessons gleaned from this study will be of value to well construction and operational maintenance with consideration paid to well type, geological hazards, production history and durability of the isolation seal.
There have been over 4.3 million oil and gas wells and more than 15 million water wells drilled in North America (King & King, 2013). There is no question that un-plugged or improperly plugged oil and gas wells, dating from 1860’s to 1930’s and later, are a potential threat and, in some areas of early oil booms, unmarked wellbores still exist and pose a pollution pathway to aquifers from surface spills and a lesser risk from oil or gas well developments. This is a legacy issue that a few states have not adequately addressed. The paper will concentrate on the potential of groundwater pollution from old and more recent plugged and abandoned oil and gas wells and will offer a limited comparison to other non-oil and gas industry sources of pollution to groundwater.
Natural seeps of oil and gas, present on every continent, in every ocean and in virtually every oil and gas producing area, are indications of over-filling of some conventional reservoirs or geologic structure interruptions such as faults, natural fractures, karsts and other natural events. Natural seeps are the oldest oil and gas prospecting tool and were used hundreds of years ago by explorers to find the largest oil deposits of the time (Link, 1952). These natural seeps also appear to be one of the largest drivers in bringing oil and gas to the surface and creating oil and gas cohabitation of fresh water sands, as proved by Hart’s first US gas well in 1821 with a total depth of 28 feet to achieve gas production and Drake’s well near Titusville, Pennsylvania, striking flowing oil at 69-1/2 feet (ACS, 2000). This mixing of oil and gas in shallow water sands is common in areas such as New York and Pennsylvania.
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