Compatibility of Acid Precursors and Solvents with Sandstone Formations

摘要

Organic acids and their precursors have been used to remove filter cake created by water or oil-based drilling fluids. Solvent and emulsifying surfactants are incorporated in the fluid recipe to solubilize oil residue and water-wet the surface of filter cake. Acids lost into the formation may interact negativity sandstone formation minerals and clays. The objective of this study is to assess fluid/rock interactions using high permeable sandstone core plugs. Oil-based drilling fluids were used to create the filter cake. Formic and acetic acids-based fluid recipes were used at concentrations below their solubility limits. Mutual solvents and microemulsifying surfactants were added to the acid recipes to dissolve the oil residue and water-wet the filter cake. Compatibility, HT/HP fluid loss and coreflooding experiments, were conducted using the acid/solvent based recipes. Experiments were conducted at 250°F and 3,000 psi. XRD analysis was conducted to analyze solids generated after the reaction of sandstone core plugs with injected fluids. Acetic acid-based fluid recipes were compatible with sandstone core plug. A Formic acid-based recipes showed a significant decrease in core plug permeability. XRD results showed presence of iron-based and calcium formate precepitations. Filtercake removal recipes showed effective removal efficiencies (e.g., 80-100 wt%).