裂缝性油藏精细裂缝表征及渗流机理研究  

Study on fine fracture characterization and percolation mechanism of fractured reservoirs

作　　者：朱志强 王永平 孟智强 刘斌 邓景夫 ZHU Zhiqiang;WANG Yongping;MENG Zhiqiang;LIU Bin;DENG Jingfu(Tianjin Branch of CNOOC Ltd.,Tianjin 300459,China)

机构地区：[1]中海石油(中国)有限公司天津分公司,天津300459

出　　处：《非常规油气》2023年第5期121-126,共6页Unconventional Oil & Gas

基　　金：“十三五”国家科技重大专项“渤海油田加密调整及提高采收率油藏工程技术示范”(2016ZX05058-001)。

摘　　要：针对裂缝性油藏渗流规律复杂,目前暂无有效的方法进行描述这一问题,以实际露头为原型开展裂缝精细描述,得到不同尺度裂缝符合幂函数分布规律,且裂缝尺度越小,数目越多。在此基础上建立裂缝精细表征地质模型,开展裂缝油藏渗流规律研究。结果表明:开采初期油藏中大裂缝优先得到动用,产油比例95%以上来自大裂缝,此阶段油藏含水率一般不超过20%,生产特征表现为产能高和递减快;随着注入水沿大裂缝窜流,油藏含水上升,中裂缝在大裂缝的带动下控制油藏整个渗流场和剩余油的分布,裂缝出油比例仍占70%以上,油藏含水率为20%~40%;当大、中裂缝水淹后,油藏含水率超过40%,在渗吸作用下小裂缝及基质成为产油的关键,占比达50%以上,这一阶段油藏采油速度低但持续时间长。根据不同阶段的渗流规律制定合理的注水开发策略,以减缓裂缝水窜和增大基质出油,具体为初期阶段降压开采延长无水采油期,中期阶段脉冲注水减缓裂缝水窜,后期阶段周期注水增加基质出油。该注水策略在渤海KAT油田现场应用,实践效果较好,单井含水率下降10%~60%,日增油10~90 m^(3),提高采收率超过6%,可为类似裂缝性油藏注水开发提供指导和借鉴。The existence of fractures leads to complicated percolation characteristics in fractured reservoirs.In order to describe this percolation mechanism,the actual outcrop was used to carry out the detailed fracture description.The results show that in the initial stage of exploitation,large fractures are prioritized for utilization,with over 95%of oil production coming from large fractures.At this stage,the water content of the reservoir generally does not exceed 20%,and the production characteristics are high production capacity and rapid decline;As the injected water flows along the large fractures,the water content in the reservoir increases.The medium fractures,driven by the large fractures,control the entire seepage field and remaining oil distribution in the reservoir.The proportion of oil produced by the fractures still accounts for over 70%,and the water content in the reservoir is between 20%and 40%;When large and medium fractures are flooded,the water content of the reservoir exceeds 40%.Under the action of infiltration,small fractures and matrix become the key to oil production,accounting for over 50%.At this stage,the oil recovery rate of the reservoir is low but the duration is long.Develop reasonable water injection development strategies based on the seepage patterns of different stages to slow down fracture water channeling and increase matrix oil production.Specifically,these strategies include extending the anhydrous oil recovery period during the initial stage of depressurization mining,slowing down fracture water channeling through pulse water injection in the mid-term stage,and increasing matrix oil production through periodic water injection in the later stage.This water injection strategy has been applied on-site in the KAT oilfield in Bohai,and the practical effect is good.The water content of a single well has decreased by 10%to 60%,the daily oil increase is 10~90 m^(3),and the oil recovery rate has increased by more than 6%.It can provide guidance and reference for the water injection develo

关 键 词：裂缝性油藏 精细油藏数值模拟 渗流机理 注水策略 

分 类 号：TE312[石油与天然气工程—油气田开发工程]