Formation consolidation process
A formation consolidation process is described which comprises injecting into an unconsolidated or poorly consolidated subterranean formation penetrated by a wellbore an aqueous pumpable system comprising an insoluble silica source (e.g., colloidal silica, silica fume or fumed silica) and a source of calcium hydroxide (e.g., aqueous solutions of calcium chloride and sodium hydroxide). The aqueous system may contain a nucleation inhibitor. The components of the aqueous system react to produce a calcium silicate hydrate gel (C-S-H gel) having cementitious properties within the pores of the formation. After the C-S-H gel sets and hardens, the consolidated formation has a high compressive strength (e.g., 500 psi (about 3.5 MPa) or more). The technique can be performed as a remedial treatment or in new completions, but it is particularly useful in workover treatments for existing wells.
1. A formation consolidation process comprising injecting, into a subterranean formation penetrated by a wellbore, an aqueous pumpable system comprising an insoluble silica source and a source of calcium hydroxide, that forms particles of silica and particles of calcium hydroxide each small enough to enter the pores of the formation, and in an amount sufficient to allow the system to form a calcium silicate hydrate gel within the pores of the formation.
2. The process defined by claim 1 wherein the wellbore is a cased borehole and said aqueous system is pumped into contact with the formation through one or more perforations in the casing.
3. The process defined by claim 1 wherein the wellbore is open-hole.
4. The process defined by claim 1 wherein the source of silica is colloidal silica, silica fume or fumed silica.
5. The process defined by claim 1 wherein the source of calcium hydroxide is a combination of an aqueous calcium salt and an aqueous sodium hydroxide or potassium hydroxide.
6. The process defined by claim 5 wherein said calcium salt is calcium chloride or calcium chloride hydrate.
7. The process defined by claim 5 wherein the source of silica is colloidal silica, silica fume or fumed silica.
8. The process defined by claim 1 wherein the components of said aqueous pumpable system are blended on-the-fly as the aqueous system is pumped into the wellbore.
9. The process defined by claim 1 wherein the consolidated formation has a compressive strength of at least about 500 psi (about 3.5 MPa), as determined by API Spec 10.
10. The process defined by claim 1 wherein the aqueous system additionally comprises a nucleation inhibitor.
11. The process defined by claim 7 wherein the aqueous system additionally comprises a nucleation inhibitor.
12. A consolidated formation produced by the process defined by claim 1 .
13. The process defined by claim 1 wherein the consolidated formation is subsequently hydraulically fractured.
14. A well treatment process comprising injecting into a gravel pack an aqueous pumpable system comprising an insoluble silica source and a source of calcium hydroxide, that forms particles of silica and particles of calcium hydroxide each small enough to enter the pores of the gravel pack, and in an amount sufficient to allow the system to form a calcium silicate hydrate gel within the pores of the gravel pack.