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Annular capacity (bbl/ft) = (ID hole 2 - OD pipe 2) / 1029.4. where ID hole 2 = Inside diameter of the casing or open hole in inches OD pipe 2 = Outside diameter of the pipe in inches. Similarly Annular volume (bbls) = Annular capacity (bbl/ft) × length (ft) and Feet occupied by volume of mud in annulus = Volume of mud (bbls) / Annular ...
In larger diameters, this annular pressure is small, rarely exceeding 200 psi (13.79 bar). In smaller diameters, it can be 400 psi (27.58 bar) or higher. Backpressure or pressure held on the choke further increases bottom hole pressure, which can be estimated by adding up all the known pressures acting in, or on, the annular (casing) side.
In a completed well, there may be many annuli. The 'A' annulus is the void between the production tubing and the smallest casing string. The 'A' annulus can serve a number of crucial tasks, including gas lift and well kills. A normal well will also have a 'B' and frequently a 'C' annulus, between the different casing strings.
The purpose of surface casing is to isolate freshwater zones so that they are not contaminated during drilling and completion. Surface casing is the most strictly regulated due to these environmental concerns, which can include regulation of casing depth and cement quality. A typical size of surface casing is 13 + 3 ⁄ 8 inches (340 mm). [5]
Production casing is the final casing string set in a well and usually reaches from the surface to Target Depth (TD). The type of casing used depends upon the different conditions in the well. Commonly, production casing sizes range from 4 + 1 ⁄ 2 in (110 mm) to as large as 9 + 5 ⁄ 8 in (240 mm). It is the last string cemented in a well ...
Using this term, one can calculate many things in the same way as for a round tube. When the cross-section is uniform along the tube or channel length, it is defined as [1] [2] =, where A is the cross-sectional area of the flow, P is the wetted perimeter of the cross-section.
The inside casing is 9 + 5 ⁄ 8 in (240 mm) L80 47 lb⋅ft (64 N⋅m) −1. The collapse pressure of this casing is 4750 psi. Therefore, pressure at the shoe of the 'B' annulus cannot exceed this. Given a hydrostatic head of 2116 psi, the pressure at the wellhead must not exceed 2634 psi.
An annular-type blowout preventer can close around the drill string, casing or a non-cylindrical object, such as the kelly. Drill pipe including the larger-diameter tool joints (threaded connectors) can be "stripped" (i.e., moved vertically while pressure is contained below) through an annular preventer by careful control of the hydraulic ...