Plug cementing methods

There are three methods for placing cement plugs. 

Dump bailing method utilizes a bailing device that contains a measure volume of cement slurry. The bailer is run to the appropriate depth on a wireline and releases its load upon bumping the bottom or a permanent bridge plug set at the desired depth (see Figure 4-408). 

Two-plug method is a rather new method and requires the use of the telltale catcher sub (Dowell Schlumberger) to set a cement plug in a well at a rather precise location with minimum contamination. The tell-tale catcher sub is made up to the lower end of a drillpipe string. The sub also has an aluminum tail pipe, a bottom wiper plug (which carries a dart) and a top wiper plug. The sub on the drillpipe is lowered to the depth desired for... 

Prevention of access is the least intrusive method since it need not have any irreversible consequences for the afferent pathway. The common entrance to both olfactory systems in newts is easily closed-off by plugging the nostrils (Kikuyama et al., 1997). A potentially reversible method threaded plugs into the NP canal of cats via the nasal cavity (Verbeme, 1980). This procedure produced a slight effect on male chemoinvestigation of urine and or scent marks. The advantages of avoiding tissue disturbance then, have to be offset by the lack of any estimate of the effectiveness of the blockade, especially if reversible. Tissue cement injections into the N-Pd can be applied to the larger... 

Boreholes must also be sealed. In one typical method, the surface casing and protective cap are removed to a few meters below the proposed final surface elevation. A plug is then installed in a competent stratum that is as close as possible to the intersection of the borehole with the mine roof. Finally, the borehole is filled with a nonshrinking cement grout, usually to within 2 feet (0.6 meters) of the surface, and the remaining length is fllled with dirt. 

It is clear that the permeability of material to water depends mainly on the volume of capillary pores. It is not linked with total porosity but depends rather on the pore size distribution. However, Marsh [133] gives attention to a fairly good correlation between the total porosity, determined by means of helium method, and permeability. This relation is shown inFig. 5.60 [133]. The diying of samples by substitution of water with propan-2-ol and -pentane was applied. Porosity and pore size distribution determined with mercuiy porosimeter do not correspond to the real stmcture, because the intmsion of mercury under a high pressure, causes the destmction of hydrates plugging the pores, particularly in the pastes of cements with fly ash. 

---