Experimental and theoretical investigation of clogging processes near production wells using X-ray tomography

Formation damage in production wells has been less studied than in injection wells. In injection wells, decline in well injectivity can occur, due to fine particles suspended in the water. These particles are deposited in the reservoir, blocking the pores, causing reduction in the permeability of reservoir rock near the well. Thus, the decline is due to injected water quality and reservoir properties. In production wells, particles can be transported through the reservoir and cause formation damage. The damage is caused by deposition near the wellbore as a result of the converging flow geometry. As is briefly discussed, it is a common problem in the water industry, where water production wells suffer from productivity decline due clogging of the aquifer near the wellbore. The accumulation of particles causes plugging of pores and decreases the permeability creating a damaged zone near the well. This results in extra, expensive cleaning operations and early shut-in of producers. This paper reports on an investigation on particle deposition in converging flow geometry, modeling oil and water production wells. Parameters are varied to study the effect on particle deposition of flow rate, particle concentration and particle/grain aspect ratio. The experiments use a converging-flow unconsolidated sand-pack. A hematite particle suspension is injected into the sand pack to observe clogging effects. With the aid of a CT-scanner (X-ray tomography), deposition profiles in time are obtained. Effluent particle concentrations and pressure profiles are also measured in real time. The results of the experiments are interpreted using deep bed filtration theory in converging flow geometry. The experiments show a clear effect of converging flow geometry on particle deposition.