歧口凹陷埕海高斜坡低饱和度油藏形成机制与开发实践——以刘官庄油田馆陶组三段为例

Formation mechanism and development practice of low saturation oil reservoir in Chenghai high slope in the Qikou sag:a case study of Ng_(3) oil reservoir in Liuguanzhuang Oilfield

位于歧口凹陷南缘埕海高斜坡的刘官庄油田,低饱和度油藏分布规律认识不清,具有原油密度高、黏度大及含油饱和度低的特点,热采和化学降黏效果不理想,难以开发动用。通过详细分析低饱和度油藏的形成机制,明确油气远源运移、储层非均质性强、构造幅度宽缓是刘官庄油田馆陶组三段低饱和度油藏形成的主要因素;并结合刘官庄油田低饱和度油藏富集特征,指出埕海高斜坡发育的馆陶组不整合面与其上底砾岩层配置,既是油气输导的主要通道,也是低饱和度含油“箱体”的载体;在刘官庄油田形成以低饱和度油藏为主,常规构造、岩性油气藏为辅,沟槽内“立体含油,整体连片”的油气富集模式。探索“水平井+CO_(2)吞吐”开发实践,累计实施水平井10口,单井平均产量由2t左右,最高上升到50t,采收率提高7.9%,大幅度改善了刘官庄油田低饱和度油藏的开发效果。

Liuguanzhuang Oilfield,located in the Chenghai high slope area in the southern margin of Qikou sag,is characterized by high density,high viscosity and low saturation of crude oil.The distribution law of low saturation oil reservoir is not clear.This type of oil reservoir is difficult to recover and utilize due to the effect of measures such as thermal recovery and chemical viscosity reduction is unsatisfactory.Taking Liuguanzhuang Oilfield as an example,this paper analyzes the formation mechanism of the low saturation oil reservoir in detail.The main controlling factors of the low saturation oil reservoir in Ng_(3)member include:long distance migration of hydrocarbon away from the source,strong heterogeneous of the reservoir,and wide and gentle structures.Combining with the enrichment characteristics of low saturation oil reservoir in the Liuguanzhuang Oilfield,it is pointed out that the configuration of Guantao formation unconformity developed in the high slope in the Chenghai area and above basal conglomerate is not only the main channel for hydrocarbon transport,but also the carrier layer of low saturation oil-bearing“box”.The oil and gas accumulation mode in the Liuguanzhuang area is dominated by low saturation oil reservoir,supplemented by conventional structural and lithologic oil and gas reservoir,and“stereoscopic oil-bearing and integrated as a whole”in the trench.Development practice of“horizontal well+CO_(2) huff and puff”was implemented in 10 horizontal wells totally,with the average production of a single well rising from about 2 t to 50 t at maximum,and the recovery factor improving by 7.9%,which greatly enhanced the development effect of low saturation oil reservoir in Liuguanzhuang Oilfield.