US2258829A - Method of ground fixation with bitumens - Google Patents

Description

Patented Oct. 14, 194i STATES METHOD OF GROUND FKA'II ON WITH BITUMENS Jacob van den Berg-e and Folkert Dijkstra, Amsterdam, Netherlands, assignors to Shell Development Company, San Francisco, Calif, a corporation of Delaware No' Drawing. Application June 26, 1939, Serial No. 2813M. In the Netherlands July 8, 1938 11 Claims.

The present invention relates to a method for impermeabilizing porous formations and pertains more particularly to a method for solidifying porous formations by the use of a non-aqueous solution of asphaltic bitumens.

Various methods have already been proposed to impermeabilize or consolidate the above men;- tioned formations by means, of bitumens. According to some methods, aqueous emulsions of bitumens are injected into the desired formation with reagents to break the emulsion within the pores of the formation. Other methods involve the injection of bitumens which have been liquefled by heating, or the injection of viscous bitumen solutions by the use of high pressures.

However, these processes are often unsatisfactory due to premature deposition of the asphaltic bitumen within the region immediately adjacent the point of introduction of the treating material. Seals or-plugs of this type are undesirable due to their low mechanical strength. It is preferable to seal porous formations by means of a method which permits penetration of the treating compound deep into the formation before deposition or coagulation takes place. In the case of aqueous emulsions premature deposition of the clogging material may be due to contact of the emulsion with electrolytes and other influential substances dissolved in ground waters'occurring within the formation to be plugged.

Likewise unsatisfactory are plugs or seals formed by injecting asphaltic bitumens liquefied by heating because asphalts of low melting points must be used and the plugs thus formed have low mechanical strength and are subject tore-liqueflcation by high temperatures often encountered in earth formations. When viscous solutions of asphalts are used, undesirably high pressures are required for injection and the plugs thus formed are held in the pores by the viscous nature of the material and are hence subject to movement and channeling by high tectonic pressures.

It is, therefore, an object of the present invention to provide a method for impermeabilizing porous formations by the use ofnon-aqueous solutions of asphaltic bitumens, whereby solidification of the porous formations is economically and effectively accomplished in a manner unaffected by materials dissolved in ground water.

A further object is to provide a method for the above treatment by the use of non-aqueous solutions of asphaltic bitumens, whereby the treating solution may penetrate deeply into the desired formation before solidification occurs.

Other objects will be apparent as the invention is hereinbelow more fully described.

The process of the present invention broadly comprises the steps of injecting into the porous formations to be impermeabilized a freshly prepared solution of asphaltic bitumens in a solvent and allowing said solution to set to a gel within the pores of the formation.

The asphaltic bitumens used in the present invention should be the hardest that may be conveniently used and are therefore preferably highly blown asphaltic bitumens. In fact, for

most favorable results it is desirable to employ asphaltic bitumens having the characteristics of a penetration index exceeding +7 and a penetration at 25 C. greater than 50. However, asphalts having a penetration index low er than +7 may be blended with certain heavy oils. such as lubricating oils, to give an asphaltic bitumen.

small amounts of aromatics, that is, up to about 20%, may be used if harder asphalts are used to offset the peptizing action of the aromatic content.

A solution of asphalt prepared according to the present invention is properly fluid whenfreshly prepared and therefore may be easily injected I into the desired formation without requiring heat to obtain fluidity or high pressures to effect injection. On standing for some time, i.'e., about 40 24 hours, depending upon the amount of solvent used, the solution changes to a jelly-like mass.

' Thus'jby the present process high-melting, hard asphalts may be introduced into porous formations to form a hard plug therein which is substantially unaffected by the relatively high temperatures encountered in many earth formations.

In a preferred embodiment the asphaltic bitumen is dissolved in just enough solvent to sufficiently decrease the viscosity to allow pumping of the solution into the desired formation. Thus, the composition of the asphaltic bitumen solution to-be applied, e. g., the concentration of the asphaltic bitumen in the solvent is determined by the nature of the formation to be treated as, for example, by the-size of the interstices. For example, if a stratum with small ports is encountered, a more fluid asphaltic bitumen solution should be used to penetrate such crevasses than in the case of a stratum having large openings. In general, however, from 40-120, and preferably from 50-100% of solvent by weight on the basis of the asphaltic bitumen is used. It is advisable not to increase the amount of solvent much above that required for providing the desired fluidity of the solution, since ifthe amount of solvent is taken too high, e. g. more than 120% of kerosene, the gelation of the asphaltic bitumen composition may be inhibited. After injection the freshly prepared solution is allowed to set within the pores of the formation, with resultant sealing and consolidation of the desired formation.

As illustrative of the present process, a blend of 70 parts by weight of a blown asphaltic bitumen having a penetration of at 25 C., a softening point (ring and ball) of 125 C., and a penetration index of +5.5 and 30 parts by weight of a Pennsylvania lubricating oil having an Englervisoosity of 75 seconds at 50 C. yielded an subsoil to be impermeabilized, and allowed to set to form a plugging or consolidating gel therein.

If desired, fillers such as lime powder, clay, ground basic slag, micro-asbestos, ground brick and sand, etc., may be added to the solutions in order to modify the consistency of the gel formed within the formation. In certain instances it may be advantageous to add to the asphalt solution capillary-active substances, such as alkali soaps, sulphonates, naphthenates or the like, to promote the penetration of the asphaltic bitumen solution into the capillaries oi. the formation. For example, when consolidating a formation containing relatively large pores, an asphalt solution containing a capillary-active substance may be practically flowed into the porous formation with no or little-,impressed pressure.

Although the example given describes the process as applied to subsoil fixation, it is apparent that the process can also be used for impermeabilizing or fixing earthy masses in not ural or artificial rocks, such as sand soils, gravel, brickwork or concrete construction, stone dumpings, and the like, by filling up and sealing the interstices and crevices and the like occurring therein. The process may'also be applied for sealing leaking dykes, tunnels and walls of cellars, for fixing loose soil layers, such as, for instance, foundations or dyke bodies, inconsolidating road beds, river beds, sand drifts, for closing cracks and crevices in rock formations, for sealing joints in brick settings and concrete, for rendering stone dumpings cohesive, either before, during or after construction, or for sealing wells or well walls.

To consolidate ground and other porous formations, the freshly-prepared asphalt solution of the present invention may be introduced thereinto, for example, by the methods described in U. S. Patent 2,075,244 to Van Hulst. When solidifying porous formations traversed by a well, the injection methods described in U. S. Patent 2,019,908 to Kennedy may be used. It is, however,-understood that it is possible to use, for this purpose of the invention, any other suitable method which will permit the asphalt solution aecaeae to, be injected into said mass and to set to a consolidating gel therein.

We claim as our invention:

1..The process of impermeabllizing porous structures comprising the steps of preparing a' pumpable solution of asphaltic bitumens in a hydrocarbon solvent of aliphatic character, said solution havingv a viscosity sufllciently low to penetrate said structure and introducing said solution into said porous structure and allowing said solution to set to a gel within the pores of said structure.

2. The process of claim 1 wherein the hydrocarbon solvent is kerosene.

\ ciently low to penetrate said structure and introducing said solution into said porous structure before said solution gels and allowing said solution to set to a gel within the pores of said structures.

5. The process of impermeabilizing porous structures comprising the steps of preparing a solution of asphaltic bitumens in a hydrocarbon solvent of an aliphatic character and introducing said solution into said porous structure, the amount of said hydrocarbon solvent being sufllcient, but not greatly in excess of that required, to reduce the viscosity of said asphaltic bitumens so that they penetrateinto said structure, and allowing said solution to set to a gel within the pores of said structure.

6. The process of claim 5 wherein the asphaltic bitumens have a penetration index of at least +7.

7. The process of impermeabilizing porous structures comprising the steps of preparing a solution of asphaltic bitumens in a hydrocarbon solvent of an aliphatic character, the amount of said hydrocarbon solventbeing from about 40 to 120% by weight of the said asphaltic bitumens, said solution having a viscosity sufllciently low to penetrate said structure and injecting said solution into said porous structure and allowing said solution to set to a gel within the pores of said porous structure.

8. The process -of impermeabilizing porous structure comprising the steps of preparing a solution of asphaltic bitumens in a hydrocarbon solvent of an aliphatic character, the amount of said hydrocarbon solvent being from about 50 to by weight of the said asphaltic bitumens, said solution having a viscosity suillciently low to penetrate .said structure and injecting said solution into said porous structure and allowing said solution-to set to a gel within the pores of said porous structure.

9. The process of impermeabilizing a porous structure comprising the steps of blending an asphalt having a penetration at 25 C. below 50 and a penetration index below +7 with a paraffinic lubricating oil to produce a blended asphalt having a measurable penetration at 25 C. above 50 and a penetration index above +7, dissolving the blend in an amount of a hydrocarbon aliphatic solvent for asphalt sufllcient but not greatly in excess of that required to reduce its viscosity so that it penetrates into said structure, and introducing the resulting solution into said structure wherein it is allowed to set to a gel.

10. The process of impermeabilizing porous structurescomprising the steps of blending about 70 parts by weight of a. blown asphaltic bitumen having a penetration of about 10 and at 25 C..

a softening point of 125 C. with about 80 parts by weight of a lubricating oil having an Engler viscosity of 75 seconds at 50 C. to produce an asphaltic mixture having a penetration of about '74 at 25 C., and a softening point greater than I 11. The process of impermeabilizing porous structures comprising the steps of preparing a pumpable solution of asphaitic bitumens in a hydrocarbon solvent of aliphatic character, said solution having a viscosity suiflcle'ntiy low to penetrate said structure and introducing said solution into said porous structure, said asphalt bitumens having a penetration index greater than +7 and a penetration at 25 C. exceeding 50 and allowing said solution to set to a gel within the pores oi said structure.

.mcoa vm em BE. FOLKERT DIJKS'I'RA.