南海西部北部湾区域地层原油黏度预测方法

目前海上油田受多方面因素制约,地层流体取样少或无取样,而南海西部北部湾区域油藏流体性质变化较大,导致地层原油黏度难以准确预测。针对上述问题,通过收集北部湾区域已开发油藏地面及地层流体性质资料,分析影响原油黏度的主控因素,从主到次依次为含硫量、胶质含量、沥青质含量、含蜡量,其中胶质含量、沥青质含量和含硫量组合因素对原油性质影响显著,原油黏度对温度敏感,原油脱气前,压力对其影响小;运用数理统计学原理,建立了地面原油参数团、原油密度、地面脱气原油黏度与地层原油黏度间的3种评价方法,经乌石油田群15个样本点检验,平均绝对误差在0.5 mPa·s左右。该预测方法可为流体评价和油藏开发提供较为科学可靠的地层原油黏度资料。

A method for crude oil viscosity prediction in the Beibu gulf region,western South China Sea

Formation fluid sampling in the Beibu gulf region,western South China Sea is rare or absent restricted by many factors of offshore oilfields.However,the reservoir fluid properties vary widely in this region,which makes it difficult to accurately predict.In view of these problems,the surface and the formation fluid properties of the developed reservoirs are collected to analyze the main factors which affecting the viscosity of crude oil.The main influencing factors are sulfur content,colloid content,asphaltene content and wax content,among which the combination of colloid content,asphaltene content and sulfur content has significant influence on the properties of crude oil.The crude oil viscosity is sensitive to temperature and the pressure has little effect for undegassed crude oil.Three empirical equations to forecast the viscosity of crude oil between crude oil viscosity and the combination of surface oil properties,oil density and degassed surface oil viscosity are established using the theory of mathematical statistics.The absolute errors of those three methods to forecast crude oil viscosity are less than 0.5 mPa·s for 15 samples from Wushi oilfield group.It could provide scientific and reliable formation oil viscosity for fluid evaluation and reservoir development.