How High-Resolution Visualisations and Quantifications Gave Insight into Damaging Mechanisms and Treatment Fluid Performance in Omani Carbonate Reservoirs

Abstract

A study was carried out to examine Formation Damage mechanisms caused by drilling and completion fluids in onshore wells in Oman. A specific understanding of what caused any damage was important, as this data would be used to help select treatment fluid options and assess their suitability. Two phases of corefloods looked at the compatibility of drilling mud and displacement fluid with reservoir core, and two further phases considered a range of treatment options. Treatment fluids included different strengths of hydrochloric acid, with and without solvent. The initial phases showed moderate to very high levels of permeability reduction, predominantly caused by the nature of the drilling mud-cakes and incomplete clean-up during drawdown. 15% HCl was successful in removing much of the operational fluid damage but was typically not forming wormholes. Including a solvent seemed to aid in wormhole development but left some of the operational fluid damage at the wellbore. Using only traditional metrics such as permeability measurement, filtrate loss volumes, and electron microscopy, it was difficult to see differences between the treatment options; when adding in the visualisations and quantifications there were clear variances in behaviour. Taking this integrated approach was therefore key to gaining a proper understanding of damaging mechanisms, how they could be removed or bypassed, and whether treatment fluids worked as intended.