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Surface casing vent flow (SCVF)
A surface casing vent flow (SCVF) is a condition where fluid or gas is flowing from the surface casing vent assembly. This term is typcially used in conjunction with land wells, and tests for surface casing vent flows are defined in regulations in Alberta Canada.
SCVF is related to annular pressure build up (ABP) and annular casing pressure (ACP). These terms are also related to well integrity. A well that has a leak, or a well integrity problem may exhibit signs of ACP, ABP, or SCVF.
If the annulus is closed and gas or fluid is building up in that annulus then there may be a pressure increase which can be referred to as ABP or ACP.
In jurisdictions where the wells are operated with a surface casing vent in the open position, then fluid or gas entering the annulus can escape through the surface casing vent resulting in a surface casing vent flow (SCVF). If there is a flow and the surface casing vent is shut, then it is likely that pressure will build up resulting in ACP/ABP. If this pressure is abnormal, then the well should be managed through methods described in the well integrity section.
Methods for testing for SCVF are detailed in AER directive 20 https://www.aer.ca/documents/directives/Directive020.pdf.
A SCVF test may also be referred to as a "Bubble Test" where one end of a hose is connected to the surface casing vent and the other end is submerged under 1" (2.5cm) of water. If 2 bubbles appear in 10 minutes, a SCVF is present. Note that the pressure equivalent of 1" of water is 0.036 psi.