Method of plugging a well by injection of a clayey material into the shaft, where the material is injected with a low density inhibitor which is displaced by a subsequent injection of aqueous liquid

摘要

A predetermined quantity of clayey material is injected into a plugging zone at a preset depth in the shaft using an inhibitor fluid with a density less than that of water. A predetermined quantity of an aqueous liquid is then injected into the plugging zone to substitute for the inhibitor fluid and be put in contact with the clayey material. The inhibitor fluid is evacuated from the shaft : A rod structure is put into the tube in the shaft and positioned at the plugging level (F) so that the end of the rod is always immersed in the inhibitor fluid when the clayey material leaves the rod. The rod structure is operated to allow fluid circulation between the inside of the rod structure and the annular space between the rod structure and the tube in the shaft. The predetermined quantity of clayey material and inhibitor fluid is injected into the rod structure by its upper end into the plugging zone, preceded by a head stopper and followed by a tail stopper both made of a spacing fluid. A predetermined of following fluid is injected, the following fluid having a higher density than the inhibitor fluid, then the rod structure is raised to a new position of preset depth to allow a new fluid circulation. The inhibitor fluid migrates upwards in the annular space, putting the clayey material in contact with the following fluid so it expands in the plugging zone to form a first plug. After positioning the rod structure at the plugging level, the waste in the structure is circulated to verify and clean the internal volume. The plugging sequence is repeated to form successive plugs on top of each other., until the plug reaches the roof of the clayey cover of the reservoir(s) to be closed. The following fluid and/or the spacing fluid and/or the inhibitor fluid are recovered at the top of the rod structure. The clayey material is bentonite, in particular soda bentonite, or atapulgite or sepiolite and is injected in the form of spherical or pseudospherical pastilles of the same diameter, so the pastilles position themselves at the bottom of the working in a regular and optimal way. The pastilles leave a spacing of 0.4. The inhibitor fluid and/or the spacing fluid is EDC95-11.