PERFORMANCE PREDICTION OF ACIDS ON SANDSTONE ACIDIZING

*Mian Umer Shafiq, Aung Kyaw, and Muhannad Talib Shuker

Department of Petroleum Engineering, Universiti Teknologi PETRONAS, Malaysia.

Accepted 22 July 2013

The aim of this research study is to find the suitable acid for sandstone acidizing. Stimulation of sandstone formations is a challenging task, which involves several chemicals and physical interactions of the acid with the formation. Mud acid has been successfully used to stimulate sandstone reservoirs for a number of years.It is a mixture of hydrofluoric (HF) and hydrochloric (HCl) acids designed to dissolve clays and siliceous fines accumulated in the near-wellbore region. Matrix acidizing may also be used to increase formation permeability in undamaged wells. In this case, the permeability of the formation is less and acidizing is done to increase the permeability and porosity. The change may be up to 50% to 100% with the mud acid. For any acidizing process, the selection of acid (Formulation and Concentration) and the design (Pre-flush, Main Acid, After-flush) is very important. Different researchers are using different combinations of acids with different concentrations to get the best results for acidizing. Mainly the common practice is combination of Hydrochloric Acid – Hydrofluoric with Concentration (3% HF – 12% HCl). This paper presents the results of a laboratory investigation of Orthophosphoric acid instead of hydrochloric acid in one combination (HF: H3PO4) and the other combination is Fluoboric and formic acid (HBF4: HCOOH). The results are compared with the mud acid (HF: HCl) and the results analyzed are porosity, permeability, color change, solubility, strength and FESEM Analysis. Both of these new combinations shows that these have the potential to be used as acidizing acids on sandstone formations in future.

Key words: Stimulation, Sandstone, Mud Acid, Phosphoric Acid.

Full Text PDF (577KB)