Process for preparing alkaline flooding solutions that avoid silica dissolution

Claim 1

A process for preparing an aqueous alkaline solution to be injected into a relatively hot subterranean reservoir to displace relatively acidic oil within pores of the reservoir without dissolving a significant proportion of siliceous solids from within the borehole or reservoir comprising: determining the reservoir temperature and the minimum pH needed to convert most of the petroleum acids in the reservoir oil to alkali metal soaps; determining the alkalinity required to satisfy the consumption of alkalinity due to chemical reactions with the reservoir oil, brine and mineral materials in the reservoir exclusive of the consumption due to silica dissolution; determining the concentration and alkali metal oxide to silicon dioxide ratio of alkali metal silicate needed to (1) provide said minimum pH, (2) satisfy said consumption of alkalinity due to reactions other than silica dissolution, and (3) reduce silica dissolution at the reservoir temperature; and preparing an aqueous solution to be injected into the reservoir which consists essentially of water and said determined alkali metal oxide to silicon dioxide ratio of alkali metal silicate.