Injectivity during PWRI and Disposal in Thick Low Permeable Formations (Laboratory and Mathematical Modelling, Field Case)

Abstract

Produced water management is a growing challenge for oil and gas industry. Over the last decade, the scale of produced water re-injection (PWRI) and disposal in petroleum industry has increased tremendously. PWRI is an important economic and environmental-friendly option to convert waste to value with waterflooding. Nevertheless, drastic decline of injectivity, widely reported in the literature, restricts the project efficiency. In the present work, laboratory coreflood test using low permeable core sample is performed to investigate the impedance (normalised reciprocal of injectivity) behaviour. Analytical model for well impedance growth, along with probabilistic histograms of injectivity damage parameters, is applied to the well injectivity decline prediction during produced water disposal in a thick low permeable formation (Völkersen field). Unusual convex form of impedance curve is observed in both laboratory coreflooding and well behaviour modelling. Impedance grows slower during external cake formation compared to that during deep bed filtration. This is due to low reservoir permeability and consequent high values of filtration and formation damage coefficients causing fast impedance growth during deep bed filtration; while external cake build-up yields relatively slower impedance growth during cake formation. Risk analysis method using probabilistic histograms of injectivity damage parameters is applied to well behaviour prediction under high uncertainty conditions.

Mathematical Modelling of Non-Uniform External Cake Profile in Long Injection Wells

“…Drastic decline of well injectivity is a widespread phenomenon which has been widely reported for fresh and hot water storage in aquifers, for industrial waste disposal, during well drilling and completion, for seawater and produced-water injection into oilfields and geothermal reservoirs (Schechter, 1992;Khilar and Fogler, 1998;Cheng et al, 2000Cheng et al, , 2004Abou-Sayed et al, 2007;Civan, 2011;Rosenbrand et al, 2014). The phenomenon is explained by deep-bed filtration of solid and liquid particles associated with the injected fluids, causing permeability decline (Oliveira et al, 2014;Kalantariasl et al, 2014bKalantariasl et al, , 2015b. Besides, the formation of external filter cake on the sand-face wall causes additional hydraulic resistance to the injected water.…”