苏丹Muglad盆地下白垩统原油破坏作用及黏度变化规律——以Fula凹陷Jake south油田Bentiu油藏为例

The degradation of petroleum in Lower Cretaceous of Muglad basin and the variation regularity of its viscosity:a case of Bentiu reservoir in Jake south oilfield,Fula sag,Sudan

苏丹Muglad盆地Fula凹陷Jake south油田在生产过程中发现下白垩统Bentiu油藏原油性质差异较大,且原油性质变化机理不清,为油藏开发带来较大困难。综合测井、试油、原油性质、原油全烃色谱、质量色谱等资料,对Bentiu油藏原油破坏作用及黏度变化规律进行了研究,结果表明,Bentiu油藏原油性质变化的主要因素为生物降解作用,水洗作用影响较弱,氧化作用影响最弱。在各种原油破坏作用影响下,由油藏油水界面处至油藏顶部,原油破坏作用逐渐减弱,破坏作用逐渐变小,API重度值逐渐升高,黏度逐渐降低。通过数理统计方法建立了Bentiu油藏50℃脱气原油黏度与其距油水界面的垂直距离、地层深电阻率、密度曲线的线性关系式,计算结果可为油藏数值模拟提供数据支持。

In daily production, the oil from Lower Cretaceous Bentiu Formation of Jake south oilfield in Fula sag of Muglad basin has large variation in physical properties including API gravity and viscosity. The mechanisms of these phenomena are not clear, which causes serious problems in production. With comprehensive analyses of well logging, well testing, physical property and geochemistry data, the petroleum degradation mechanisms and the variation regularity of oil viscosity are studied. Results show that the main cause of the variation of oil physical properties is biodegradation, while water washing effect is weak and the oxidization is the weakest. Controlled by these degradation processes, degree of petroleum degradation decreases from the oil-water contact to the top of the reservoir, thus the oil turns lighter and less viscous. With mathematical statistic method, the linear relation is es-tablished among 50°C degas oil viscosity and the vertical distance to the oil-water contact, deep resistivity and den-sity curve. The result can provide data support for reservoir numerical simulation.