白云凹陷原油气洗作用

Study on gas washing of crude oils in Baiyun sag

白云凹陷天然气资源丰富,同时产出一定量轻质原油和凝析油.其天然气成熟度高于原油的,具有油气同源不同期、早油晚气的特征,后期充注的天然气对早期形成的油气藏进行气洗分馏改造,导致原油轻组分正构烷烃大量损失并形成次生凝析气藏.基于全油气相色谱数据,计算原油正构烷烃损失量,研究白云凹陷原油气洗作用强度及成因.结果表明,研究区原油多具有气洗分馏作用残留油特征,原油气洗作用主要发生在珠江组储层,且东部流花—荔湾构造带气洗的广度和强度大于北部番禺低隆起构造带的;东区LH3构造正构烷烃损失量最大,达到90%以上;北部番禺低隆起构造带气洗程度差异较大,与该区断裂发育程度及与油气源距离有关.该结果为寻找富含轻质烷烃、贫芳烃的凝析油气藏提供指导.

Natural gas is the main product in Baiyun sag,while there is a certain number of light olis and condensates.The maturity of gas is higher than crude oil,and gas charged into reservoir later than oil.The oil pools formed in early stage has experienced intensive gas invasion,and the process of gas washing can deplete the n-alkanes of the oil and produce the subsequent condensates.Based on the whole oil gas chromatograms,through calculating the mass depletion of oil in n-alkanes relative to an unfractionated oil,it shows that the Zhujiang reservoir experienced progressive fractionation by gas washing,and the scale and intensity of gas washing in east are greater than north.The crude oil in LH3 has the highest level of n-alkanes loss,with as much as 90%of original n-alkanes have been removed.There is muchdifference in northern because of the development of fault and the distance from gas source.The crude oils founded in present mostly show the characteristic of residual oils by gas washing,so it is the possible direction to search the condensates with high concentration of light n-alkanes and poor aromatic.