绝大部分重油和油砂都是由生物降解作用所形成,准确预测生物降解作用程度,能大大降低勘探风险并优化石油开发。由于微生物仅生活在水中,所以生物降解主要发生在油水界面附近。控制生物降解程度及速度的主要因素是油藏热史、地层水进入油藏的难易程度、养分供给、油藏充注史、降解与未降解油的混合作用及油水界面大小与油藏体积的关系。温度是油藏生物降解作用的最关键控制因素,生物降解的终止温度大约为80℃,但油藏温度低于约30℃后,降解通量会大大降低。养分是原油生物降解的最终控制因素,在没有明显地层水活动的区带,底水存在与否及底水层厚度大小就成了生物降解的另一个重要控制因素。由生物降解和充注混合造成原油组成和物性在盆地范围内大规模侧向梯度及油藏范围内小规模垂向梯度变化在重油区非常普遍,在一个连续充注的油柱上,原油所遭受的生物降解程度差异非常大,底部和顶部原油的组成和性质完全不同,这主要是因为未降解油向油柱顶部充注,而生物降解发生在油柱底部,充注强度与生物降解速度的相对大小决定了原油的最终组成面貌,原油物性变化与油藏温度(史)密不可分。通过地质因素对流体物性变化控制的定量描述,根据岩心或岩屑抽提物的地球化学分析获取高分辨率地球化学信息,根据统计方法可以建立地球化学参数与实测黏度间的对比关系,快速获取原油黏度或API重度,并将结果运用到油藏描述和定量模拟中,为产能预测和优化管理提供更有效的工具。 Most of the heavy oil and oil sands are formed by the role of biodegradation, accurate prediction of the degree of biodegradation, can greatly reduce the exploration risk and optimize the oil development. Since microbes live only in water, biodegradation occurs mainly near the oil-water interface. The main factors that control the degree and speed of biodegradation are the thermal history of reservoirs, the difficulty of formation water entering into reservoirs, the supply of nutrients, the history of reservoir filling, the mixing of degraded and undegraded oils and the size of oil-water interface and reservoir volume Relationship. Temperature is the most critical controlling factor for reservoir biodegradation. The final temperature of biodegradation is about 80 ℃. However, when the reservoir temperature is lower than about 30 ℃, the degradation flux will be greatly reduced. Nutrient is the ultimate controlling factor of crude oil biodegradation. The presence or absence of bottom water and the thickness of bottom aquifer are another important controlling factor for biodegradation in zones without obvious formation activity. Crude oil composition and physical properties caused by biodegradation and charge mixing Large-scale lateral gradients in the basin and small-scale vertical gradients in the reservoir range are very common in heavy oil zones. On a continuously charged oil column, crude oil The degree of biodegradation suffered was very large and the compositions and properties of the bottom and top crude oil were completely different, mainly due to the fact that undegraded oil was charged to the top of the oil column while biodegradation occurred at the bottom of the column, filling strength and biodegradation rate The relative size of the crude oil determines the final composition of the face, physical changes in oil and reservoir temperature (history) are inseparable. According to the quantitative description of the control of fluid physical changes by geologic factors, high-resolution geochemical information can be obtained according to the geochemical analysis of the core or cuttings extract. According to the statistical method, the correlation between the geochemical parameters and the measured viscosity can be established and quickly obtained Crude oil viscosity or API severity, and the results applied to reservoir description and quantitative simulation, to provide more effective tools for capacity prediction and optimization management.