火驱过程中注气压力对储层岩石的影响

Impacts of gas-injection pressures on reservoir rocks during fireflooding

针对新疆油田火驱试验中存在的问题,为筛选出合理的火驱区块,运用一维火驱物模实验模型,在固定注气流量和预热温度条件下,采用砂岩和砂砾岩岩心开展不同注气压力对储层岩石的低熔点物质分流和矿物组成影响的基础实验。研究表明:随注气压力增加,砂岩和砂砾岩中的Fe、S、Mg等元素含量降低,Si、K、Na含量升高,S、Fe元素含量在燃烧区明显增大,而在待燃区Fe、S等元素含量沿火驱方向逐渐增加,表现出明显的元素分流;根据各主要成分变化分析可知,S、Fe元素含量变化反映了黄铁矿的氧化,K、Na、Mg元素含量变化反应了长石及黏土矿物之间的转化;燃烧过程中,长石发生变化析出石英。该项研究对筛选火驱区块具有理论指导意义。

With consideration to problems encountered during fireflooding tests in the Xinjiang Oilfield, and to i- dentify suitable blocks for fireflooding operations, 1 D fireflooding physical simulation models have been constructed to determine impacts of different gas-injection pressures on flow of materials with low melting points and mineral composition of reservoir rocks by using sandstone and glutenite cores under constant gas-injection flow rate and pre -healing conditions. Research results show contents of Fe, S, Mg and other elements in sandstone and glutenite may decrease with increase of gas-injection pressures. On the other hand, St, K, Na contents may increase. Con- tents of S and Fe are high in combustion zones, whereas contents of Fe, S and other elements in waiting-for-com- bustion zones yet may increase gradually along the direction of fireflooding. Such conditions may reflect flow of ele- ments ; Analyses for changes in all these key elements show changes in contents of S and Fe may reflect oxidization of pyrite, whereas changes in contents of K, Na and Mg may reflect conversion among feldspar and clay minerals ; During combustion, feldspar may be changed to extract quartz. Relevant research results may provide valuable guid- mace for identification of favorable blocks for fireflooding operations.