Blocking a Flow Conductive Inter-well Fault by Fines Detached by a Low-Salinity Water Slug

Abstract

Fines detachment, migration and pore clogging are important processes in diverse problems in underground formations. Recent works have analyzed the idea of employing fines detached by low-salinity water injection to modify water trajectories in a rock formation. In oil and geothermal reservoirs, fines can play, in this context, a beneficial role in water production control. In underground pollution processes, fines can serve as a potential mechanism for isolating soil or water contaminants. In this work, a new application to block the fluid flow in a conducting fault that directly links the injection well with extraction wells by using a slug of low-salinity water is explored. This technique could bear significant relevance, particularly in scenarios where water is injected to displace oil or soil contaminants from the formation into extraction wells. The existence of this type of highly conductive pathways can significantly reduce the efficiency of oil or contaminant sweeping. To analyze the problem, we consider here a low-salinity water slug that is introduced in the injection stream of a standard inverse five-spot well array, in which a high-permeability fault-like streak directly connects the injector with two of the four extraction wells. The mathematical model to describe fines detachment, migration, pore clogging and permeability impairment is revisited and adapted. The nonlinear coupled equation set for single-phase fluid flow, salinity transport and fines dynamics is numerically solved by a finite element method. The efficiency of the low-salinity fines detaching method to block water flow in conductive faults is discussed in terms of slug injection period, slug salinity and flow injection rate. The most sensitive parameters are injection period and injection rate. It was found that fines are equally effective at obstructing broad or narrow faults.