INHIBITION OF PARTICLE MIGRATION: A KEY FACTOR IN INTENSIFYING INFLOW FROM THE VALANGINO RESERVOIRS

Abstract

A group of Valazhin formations, located in Russia’s Arctic region, makes up highly productive oil, gas and condensate fields, which generally do not require any flow stimulation technologies at the initial stages of their development. However, their development history has shown that the wells’ productivity index decreases over time. The reasons for the increase in the skin factor had remained disputable for a long time before they were finally identified while optimizing flow stimulation fluids. One should keep in mind the extreme reactivity of mud acid systems, which may cause a decrease in the productivity of the formations treated with them, unless sufficient study is done. The highly sensitive formations in these fields require careful attention to the study of acid systems, which should be done on core samples, since the formations have a heterogeneous lithological structure and reservoir properties. These formations also demonstrate significant facies variation, interlayering of different thickness and pinching-out. Seven productive formations are distinguished within the horizon, separated by shale layers up to 5–7 meters thick. This paper is devoted to the discovery of factors that reduce the filtration properties of the formation after acid treatments with various types of acid compositions and urges the oil and gas community to pay attention to the importance of full range of laboratory studies prior to acid system implementation. The paper describes methods for preventing the precipitation of insoluble chemical compounds and preventing the occurrence of migration of fines and suspended particles after acid treatments. The optimal acid composition was selected for treating the near-wellbore formation zone based on laboratory experiments. And two treatments were performed in oil wells with increase in productivity index in 3 times and above.