Finite element forward modeling of scattering characteristics of carbonate cavern reservoirs

Abstract

Abstract: Mitigation of reservoir damage during water flooding is critical for efficient development of offshore oil fields. In this paper, analysis of reservoir sensitivity and SEM analysis of suspended solids and scale samples were conducted for the water flooding process in a block, the Bohai Oilfield, during which some problems like higher injection pressure and insufficient injection exist. The experiment results indicate that the reservoir is susceptible to moderate-stronger water-sensitive damage, or plugging due to swelling and dispersion of smectite and illite/montmorillonite interlayer to various degrees. The content of suspended solids in injected water is up to 16.7 mg/L, which is much higher than the standard requirement. The size of particles in injected water are chiefly about 30 μm, which may easily cause plugging in the reservoir. After water flushing, a large amount of carbonate particles scatter in the pores and throats of the reservoir, decreasing the reservoir permeability. On the basis of the defined reservoir damage mechanism, some protective measures (e.g. optimization of doping way and acidification) were put forward. In practical operations, injection pressure at the wellhead of water flooding well dropped by 7 MPa, and daily water-injection volume increased by 6 times, revealing the obvious unplugging effect by acidification.

Key words: carbonate rock, scattering effect, forward modeling, finite element, heterogeneity, wave equation

Duan Zhongyu, Guo Hongwei. Finite element forward modeling of scattering characteristics of carbonate cavern reservoirs[J]. China Petroleum Exploration, 2016, 21(5): 103-109.

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