Research and application of biological enzyme as plug remover for stimulation

In order to remove the formation blockage resulted from heavy component pollution and drilling fluid pollution, this paper studies the plug removal performance of two kinds of enzyme (Apollo and SUN) now widely used. Through the appearance analysis, stability study, analysis experiments about bacteria content, protein, sugar component and bio surfactant and interfacial tension measurement, we recognize the roles of two enzymes in improving rock wettability and sweeping oil, and their ability to emulsify crude oil and plug removal mechanism. Simulation experiment results demonstrate that two enzyme can release the heavy component blockage in different degree, especially the Apollo enzyme solution prepared with formation water can remove the formation blockage resulted from drilling fluid. The paper introduces the well selection principle of plug removal with biological enzyme, field operation technique scheme, operation scheme and effect evaluation. Plug removal operation was implemented in 2 oil wells of offshore oilfield in terms of 1.8m treatment radius of and 4% mass fraction of Apollo solution and the results of the reservoir stimulation are successful giving a reference to similar oilfield.