致密砂岩储层可动流体赋存规律及制约因素研究:以鄂尔多斯盆地华庆油田长6段储层为例

Distribution and Controlling Factors of Movable Fluid in Tight Sandstone Reservoir: Taking Chang 6 Formation of Huaqing Oilfield in Ordos Basin as An Example

可动流体能相对独立地表征储层流体流动性质及采收率,但关于致密砂岩储层可动流体赋存规律及制约因素方面的研究仍然存在不足。为了提高致密砂岩储层勘探开发效果,明确可动流体赋存及控制因素,以鄂尔多斯盆地华庆油田长6段储层为例,采用物性分析、薄片鉴定、X射线衍射、压汞及核磁共振等实验手段,在储层基础性质研究的基础上,挑选典型样品对可动流体含量及其影响因素进行了详细研究。结果表明:华庆油田长6段储层孔隙度平均值为9.42%,渗透率平均值为0.38×10^-3μm^2,为典型的致密砂岩储层。利用离心法测定的T2截止值推算出的可动流体饱和度平均为31.22%,较经验法所得结果准确;储层物性、黏土矿物质量分数、成岩演化及孔喉参数对储层可动流体饱和度有不同程度的影响。其中,孔隙度与可动流体饱和度的关系较渗透率密切,黏土矿物质量分数越低可动流体饱和度下降趋势越明显;压实作用导致可动流体饱和度明显减少,早期胶结通过保存孔隙、晚期胶结通过封闭优势通道扩大波及面积来提升可动流体饱和度;孔喉参数中,主流喉道半径是控制可动流体饱和度的最关键的参数,可动流体饱和度<30%的样品其饱和度随着孔喉配置关系变差而急剧降低。对比结果表明,利用离心法能够对储层可动流体饱和度进行更准确的评价,储层主流喉道半径及压实作用对可动流体分布具有明显的控制作用。

Movable fluid can represent fluid characteristics and recovery rate of a reservoir. However, the study of distribution and controlling factors of movable fluid is not enough. In order to understand the distribution of movable fluid and its influence factor and improve the development of tight sandstone reservoir, this paper takes Chang 6 Formation of Huaqing Oilfield in Ordos Basin as an example to identify the distribution and controlling factors of movable fluid in tight sandstone reservoir. Characteristics of reservoir and movable fluid have been studied based on various experiments such as physical property analysis, casting thin sections, X-ray diffraction, and MIP. The results show that Chang 6 Formation of Huaqing Oilfield is a typical tight sandstone reservoir which can be induced by the data gained by physical property analysis.This formation shows an average porosity of 9.42% and the average permeability of 0.38×10^-3 μm^2.The movable fluid saturation gained by centrifugation is 31.22% in average, lower than empirical value.The movable fluid is influenced by various elements such as physical property and diagenetics.The correlation between movable fluid saturation and porosity is better than permeability and the content of clay minerals also has a positive impact on movable fluid saturation.The compaction process can significantly decrease the content of movable fluid and the cementation process which can be divided into two phases improve the movable fluid in the reservoir.The key factor which controls movable fluid is mainstream throat radius and the saturation of movable fluid decreasing dramatically when movable fluid saturation is <30%.The results show that the measure of movable fluid with centrifugation is more precisive than empirical method and the movable fluid saturation is controlled by compaction and mainstream throat radius.