加拿大麦凯河油砂含油性差异的形成机理

Mechanism of oil content difference in Mackay River oil sands,Canada

油砂作为一种重要的非常规油气资源逐渐受到全世界的重视,但油砂储层通常存在非均质性强,含油性差异大等缺点,导致开发效率受限。本文基于岩心、铸体薄片和扫描电镜观测、测井数据、储集岩热解和可溶有机质色谱质谱分析结果,研究了加拿大阿萨巴斯卡地区麦凯河区块白垩系上麦克默里组油砂含油性差异的形成机理。麦凯河油砂成岩作用弱,基本不存在胶结物,岩石特征主要由粒径、分选和杂基含量3个参数决定,岩石类型可划分为杂砂岩、粉砂岩、细砂岩和极细砂岩。根据测井和岩心含水饱和度数据可以将麦凯河油砂储层评估为气、水、油和差油层4类,油水层由岩性和生物降解程度决定。生物标志物特征显示沥青属于同一族群且没有成熟度的差异,形成油砂含油性差异的原因可能是岩性差异导致降解程度和早期充注量不同。细砂岩连通性较好,受到水洗、氧化等降解作用严重,通常形成水层;粉砂岩致密程度较高,早期原油难以完全充注,通常形成差油层;杂砂岩物性介于二者之间,在不影响原油充注的前提下,受到降解程度也相对较低,通常形成油层。

As an important unconventional oil and gas resource,oil sands have been paid more and more attention all over the world.However,oil sands usually have some disadvantages such as strong heterogeneity and large differences in oil content,which leads to limited development efficiency.Based on the results of core,casting thin section and SEM observations,logging data,reservoir rock pyrolysis and soluble organic matter gas chromatography–mass spectrometry analysis,the mechanism of the oil content difference in the Cretaceous Upper McMurray Formation oil sands in the Mackay River area,Athabasca,Canada was studied.The diagenesis of the Mackay River oil sands is weak and there is no cement.The rock characteristics are mainly determined by three parameters:grain size,sorting and matrix content.The rock types are divided into extremely fine sandstone,fine sandstone,greywacke and siltstone.According to logging and core water saturation data,the oil sands reservoir can be evaluated as the gas,water,oil and poor oil interval,which are mainly composed of extremely fine sandstone,fine sandstone,greywacke and siltstone,respectively.The biomarker characteristics show that bitumen derives from the same source kitchen and there is no difference in maturity.Therefore,the main reason for the difference in oil content may be the difference in degradation degree and the amount of oil charged due to the diversity in reservoir petrological.Fine sandstone has good connectivity and is easy to be affected by degradation such as washing and oxidation,and usually forms the water interval.The siltstone is dense,and the early oil charging has difficulty reaching completion and this usually forms the poor interval.The properties of greywacke lie somewhere in between,the degree of degradation is relatively low and without affecting the early charging of oil,so it usually forms the oil interval.