Blooey line

Air and natural gas are often used as a drilling fluid with no additives placed in the injected stream of compressed fluid. This type of drilling is also often referred to as dusting because great dust clouds are created around the drill rig when no formation water was present. However, modern air and gas drilling operations utilize a spray at the end of the blooey line to control the dust ejected from the well. Figure 4-185 shows a typical site plan for air drilling operations. 

Blooey Line. This special pipeline carries exhaust air and cuttings from the annulus to the flare pit. The length of the blooey line should be sufficient to keep dust exhaust from interfering with rig operations. The blooey line should have no constrictions or curved joints. 

Bleed-Off Line. This line bleeds off pressure within the standpipe, rotary base, kelly and the drill pipe to the depth of the top float valve. The bleed-off line allows air (or gas) under pressure to be fed directly to the blooey line. 

Air (or Gas) Jets. The Jets are often used when there is the possibility that relatively large amounts of natural gas may enter the annulus from a producing formation as the drilling operation progresses. The air (or gas) Jets pull a vacuum on the blooey line and therefore on the annulus, thereby keeping gases in the annulus moving out of the blooey line. 

Sample Catchers. A small-diameter pipe (about 2 in.) is fixed to the bottom of the blooey line to facilitate the catching and retaining of downhole cutting samples for geologic examination. 

De-Duster. This provides a spray of water at the end of the blooey line to wet down the dust particles exiting the blooey line. 

Gas Sniffer. This instrument can be hooked into the blooey line to detect very small amounts of natural gas entering the return flow from the annulus. 

Burn Pit. This pit is at the end of the blooey line and provides a location for the cutting returns, foam and for natural gas or oil products from the subsurface to be ignited by the pilot light and burned off. The burn pit should be located away from the standard mud drilling reserve pit. 

With the bit directly on bottom, start the air down the hole. Straight air should be pumped at normal drilling volumes until the surfactant sweep comes to the surface, appearing at the end of the blooey line and foaming like shave cream. 

Stable Foam. When a well is drilled with stable foam as the drilling fluid, there is a back pressure valve at the blooey line. The back pressure valve allows for a continuous column of foam in the annulus while drilling operations are under way. Thus, while drilling, this foam column can have significant bottom-hole pressure. This bottomhole pressure can be sufficient to counter formation pore pressure and thus control potential production fluid flow into the well annulus. 

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