Use of 3D Images to Evaluate Formation Damage Induced by Montmorillonite Fines in Porous Media Systems

Abstract

Formation damage costs oil and gas industry $140 billion/year in lost productivity, this is a key challenge to Qatar, the world's largest LNG exporter. During production from a well, multiphase flow foster drag forces to mobilize fine particles from within the subsurface. Fine' migration can alter the gas flow, clogging pores and disconnecting gas pathways. Understanding fines influence is a complex challenge due to the reservoirs' porous media heterogeneity. Microtomography of sand sediments provides a standardized approach to study the fines impact. X-Ray microtomography of two repacked sand cylinders was carried at Argonne National Lab synchrotron. Rounded silica sand was mixed with hydrophilic swelling montmorillonite clay. High and low fines concentrations were mix--ed with the sand then deposited into five layers. Initially, samples were fully saturated, then gas was injected, the sediments were scanned before and after injection. At first, fines were suspended in the brine, but after injection were retained on the gasbrine interface, and their concentration in the brine increased. Gas injection divided pores and throats, reducing their average size. Contrarily, main gas pathways increased in size but were disconnected in the sediment with high fines concentration. Fines caused increased capillary pressure and lowered the sediment permeability.