| 摘要 |
934,165. Boring earth &c. SHELL INTERNATIONALE RESEARCH MAATSCHAPPIJ N.V. Jan. 16, 1962 [Jan. 18, 1961], No. 1570/62. Class 85. A well drilling fluid used in drilling a permeable formation does not form an impermeable layer on the wall of the formation, but decreases the permeability of the formation at some distance from the wall. The fluid may be aqueous and contain a lead salt or a soap which precipitates on contact with the dissolved salts in the formation liquid to clog the pores of the formation. Solutions of bitumen in pyridine, or paraffin wax in a keystone, which form a precipitate when diluted with the formation liquid are suitable fluids for drilling through salt layers. The fluid may comprise aluminium carboxymethyl cellulose dissolved in alkaline liquid, which solution greatly increases in viscosity as a result of dilution with formation water. The S.G. of the fluid may be raised to 1.15 or more by dissolving in it sugar, glycerine, or water-glass, or by weighting with insoluble particles so sized that they cannot form an impervious layer. The velocity of the fluid should be high during drilling so that the detritus does not form an impervious layer. |
