Solid-free recyclable micro-foamed drilling fluid and preparation method thereof

The invention discloses a solid-free recyclable micro-foamed drilling fluid which is prepared from the following raw materials, added in per liter clear water, by weight: 1-2g of NaOH, 3-5g of xanthan gum XC, 3-5g of polyanionic cellulose PAC, 10-20g of modified starch, 1-6g of foaming agent BZ-MBS-1, 1-6g of foam stabilizer BZ-MBSF-1, and 60-80g of lubricant. The drilling fluid is low in density, good in shielding effect, obvious for leakage prevention effect of a low-pressure and easily-leaked layer, simple to prepare, adjustable in density, applicable to low-pressure, easily-leaked and multi-pressure system stratums, the foaming agent has excellent oil resistance, and after the drilling operation is finished, the defoaming can be conducted, and the density can be restored to the density of a base fluid.