Drilling fluids and methods of use
Drilling fluid compositions and methods of using them are described. The drilling fluid compositions comprise nanocomposites comprising core-shell morphology, wherein the core material comprises a nanoparticle having an average particle size of about 5 nm to 100 nm, and the shell material comprises a crosslinked polymer comprising acrylamide repeat units. The nanocomposites are effective fluid loss control agents when the drilling fluids are employed in mud drilling operations.
1. A drilling fluid comprising:
a water source;
a bridging agent; and
a fluid loss additive comprising a nanocomposite, the nanocomposite comprising a core-shell wherein the core-shell comprises a core and a shell, wherein the core comprises an inorganic nanoparticle having an average particle size of about 5 nm to 500 nm and wherein the inorganic nanoparticle is selected from silica, treated or partially treated fumed silica, colloidal silica, or silica-alumina composite particles, or titania and the shell comprises a crosslinked polymer comprising acrylamide repeat units, acrylic acid repeat units or a salt thereof, 2-acryloylamino-2-methylpropane-1-sulfonic acid repeat units or a salt thereof, or a combination thereof, wherein the crosslinking polymer is from about 0.1 wt % to 1 wt %,
wherein fluid loss of the drilling fluid is less than the fluid loss with only the shell.
2. The drilling fluid of claim 1 wherein the bridging agent is calcium carbonate.
3. The drilling fluid of claim 1 wherein the nanoparticle comprises silica or titania.
4. The drilling fluid of claim 3 wherein the nanoparticle is hydrophobically modified.
5. The drilling fluid of claim 1 wherein the crosslinked polymer comprises an N,N′-methylenebisacrylamide crosslinker.
6. The drilling fluid of claim 1 wherein the weight ratio of nanoparticle to polymer is about 1:100 to 50:50.
7. The drilling fluid of claim 1 wherein the nanocomposite is present at about 0.5 wt % to 5 wt % of the fluid weight.
8. The drilling fluid of claim 1 wherein the nanocomposite comprises two or more nanocomposite sources.
9. The drilling fluid of claim 1 wherein the nanocomposite comprises two or more nanoparticle sources.
10. The drilling fluid of claim 1 wherein the nanocomposite is thermally stable up to 250° C.
11. The drilling fluid of claim 1 wherein the nanocomposite does not gel.
12. The drilling fluid of claim 1 wherein the fluid loss of the drilling fluid is less than about 10 mL at 149° C.
13. The drilling fluid of claim 1 wherein the nanocomposite is in a water in oil latex form.