Micro Porosity of High Expansion Tuff and Its Application

Abstract

The pore size, distribution, connectivity and pore change of Lancang Lead Ore’s tuff were studied by means of SEM, AFM, nitrogen adsorption at low temperature and mercury injection at high pressure. And the pore research results were applied to the development of anti-collapse drilling fluid. The results show that the high expansion tuff of Lancang Lead Ore has the typical lamellar microstructure of clay. The pore diameter is most concentrated in the range of 1 - 20nm, the pore size is widely distributed, the throat is developed. It is known from pore research that chemical anti-sloughing can be used in the development of Lancang anti-collapse drilling fluid because of the similar size of tuff’s main pore and hydrate ions, and nano-plugging materials should be used as the main material when physical plugging materials are used, which explains why ordinary bentonite cannot prevent sloughing. And under the guidance, the application of alkaline soluble starch plus NaCl and KBr solution was successfully achieved.