昆北油田切12井区基岩油藏产能主控因素及高效开发实践

Main controlling factors on the productivity of the basement oil reservoir and the practice of efficient development for Well Block Qie12 in Kunbei Oilfield

柴达木盆地昆北油田切12井区纵向上发育基岩油藏和不整合面上覆E_3~1砂砾岩油藏(简称E_3~1油藏)2种类型油藏,但彼此间不发育稳定隔夹层,具有统一油气系统。该区开发初期主要对E_3~1油藏进行注水开发,基岩油藏以试采评价为主。为实现对E_3~1油藏产能的有效接替,在基岩储层特征认识的基础上,归纳总结出岩性、裂缝发育程度和上覆油藏注水特征3个基岩油藏产能的主控因素,以此来确定该区水平井开发方式,并在开发实践中建立了块状油藏地质模型、制定了井位部署方案和形成了随钻跟踪技术。研究证实板岩与花岗岩均是有利储层,基岩顶部风化程度高、裂缝最发育,E_3~1油藏的注水开发实际上对基岩油藏完成了超前注水,产能主控因素的分析奠定了水平井高效开发的理论基础,从近3 a基岩油藏开发效果来看,在低油价背景下实现了少井高产,在柴达木盆地首次完成了针对基岩油藏的规模开发。

There are two types of oil reservoir in the Well Block Qie12 in Kunbei Oilfield of the Qaidam Basin,which are the basement oil reservoirs at the bottom and the E_3~1 glutenite reservoir above the unconformity surface. There are no stable intercalations between them and they are a unified oil and gas system. Water flooding was done in E_3~1 oil reservoir and oil test evaluation was made in the basement oil reservoir at the beginning of development in this area. In order to achieve effective production replacement of E_3~1 oil reservoir,three main controlling factors of the basement oil reservoir productivity were summed up from the aspects of lithology,the degree of fracture development and the water flooding characteristics based on the understanding of the characteristics of the basement oil reservoir. And then the development mode of horizontal wells in this area was determined. The geological model of massive oil reservoir was established,and the well deployment plan was made and the tracking-while-drilling technology was formed. The research proved that both slate and granite are favorable reservoirs which have high weathering degree and well-developed fractures at the top of the basement. The water flooding in the E_3~1 oil reservoir indicates advanced water injection in the basement oil reservoir. The analysis of the main controlling factors on the productivity is the theoretical basis of the efficient development in horizontal wells. Development results of the basement oil reservoir in the recent two years show that high efficient production with less wells has been realized under the background of low oil price,and large-scale development has been carried out in the basement oil reservoir for the first time in the Qaidam Basin.