环渤中凹陷挥发性原油特征及其主控因素

Characteristics and main controlling factors of volatile oil in the surrounding areas of Bozhong Sag

为研究环渤中凹陷挥发性原油特征、成藏主控因素和有利区带,利用原油族组分、原油物性、PVT高压物性实验分析等技术手段,对渤中凹陷及围区多个油田和含油气构造的原油组分和物性特征进行了统计分析,明确了渤中凹陷挥发性原油“五高三低”的特征以及各特征的数值范围。基于多组分相态变化的机理分析认为,渤中凹陷易于发育挥发性原油油藏的主控条件有3个:①优质烃源岩经过较高的热演化能够为挥发性原油提供轻质烃类组分;②渤中凹陷埋深较大,高温高压能够满足挥发性原油赋存的条件;③渤中凹陷快速沉降形成的区域泥岩盖层是挥发性原油能够保存的有利条件。基于渤中凹陷的温压梯度,推测渤中凹陷及围区埋深在2.5~4.3 km且有区域泥岩封盖的地层中易于发现挥发性油藏。

To investigate the characteristics,main controlling factors,and favorable zones of volatile crude oil in the Bozhong Sag and surrounding areas,we analyzed statistically the data of crude oil composition characteristics and physical properties of many oilfields and oil-bearing structures in Bozhong Sag and its surrounding areas by means of crude oil group composition analysis,crude oil physical property analysis,experimental analysis of PVT high-pressure physical property and other technical means.Then,the characteristics of"five high and three low"of volatile oil in Bozhong Sag and the numerical range of each characteristic are defined.Based on the mechan-ism of multicomponent phase change,we determined three main controlling conditions on the development of volatile crude oil in Bozhong Sag.The first,after high thermal evolution,high-quality source rocks could provide light-hydrocarbon components for volatile crude oil.The second,the buried depth of Bozhong Sag is large,and the high-temperature and-pressure conditions could satisfy the storage conditions of volatile crude oil.And the third,the regional mudstone caprock formed by rapid subsidence in Bozhong Sag was an important condition fa-vorable for the preservation of volatile crude oil.Based on the temperature pressure gradient of Bozhong Sag,we suggested that the strata in burial depth of 2.5~4.3 km with regional mudstone capping in Bozhong Sag and its surrounding areas shall be targeted for volatile oil reservoirs.