碳酸盐岩洞穴型储层散射特征有限元正演模拟

摘要/Abstract

摘要： 碳酸盐岩储层的非均质性增加了该类油气藏的勘探开发难度，是目前研究热点之一。不同孔洞大小和分布密度的非均质性洞穴型储层具有不同的地震波散射特征，根据散射波场的特征可以对地下储层的非均质性进行评价，因此研究非均质储层的地震波散射波场特征对于解决复杂地质问题具有广泛的实用价值。基于非均匀随机介质，采用可以模拟任意地质体形态的有限元波动方程正演模拟技术，对碳酸盐岩洞穴型储层中不同的孔洞尺度和分布密度产生的散射波场进行了正演模拟与分析。正演模拟结果表明，孔洞越大造成的非均质性越强，产生的尾波能量越强；孔洞越多非均质性越强，分布密度足够大时表现出弱非均质性；孔洞分布越均匀非均质性越弱，分布越不均匀其非均质性越强。

关键词: 碳酸盐岩, 散射效应, 正演模拟, 有限元, 非均质性, 波动方程

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

段中钰, 郭宏伟. 碳酸盐岩洞穴型储层散射特征有限元正演模拟[J]. 中国石油勘探, 2016, 21(5): 103-109.

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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