油页岩原位开采井筒结构设计

在油页岩原位开采过程中,需要300℃以上高温持续对地层加热数月甚至数年,造成井筒密封完整性失效。目前国内外关于油页岩原位开采的研究集中于加热方式的实验介绍,没有可参考的实钻井筒结构设计。依据吉林松南青一段油页岩的实际情况,设计电加热、注热氮气加热两种不同开发方式下的井筒结构,利用有限元软件对加热体、套管、水泥环、围岩组合体密封完整性模型进行模拟分析。结果表明,采用600℃电加热方式进行开采时,热量传入地层迅速衰减,有效开发半径仅2. 0 m,难以适用于油页岩的开采;采用注热氮气加热开发时,有效开发半径仅5. 0 m,考虑后期压裂,热氮气可通过裂缝有效加热地层,适用于油页岩的开采;套管在加热段热应力可达1 094 MPa,需选用偏梯扣TP110H抗高温套管。

Discussion on Design of Wellbore Structure for Oil Shale in Situ Mining

In the in-situ mining process of oil shale, high temperature above 300 °C is required to continuously heat the formation for several months or even years, resulting in failure of the wellbore seal integrity. At present, the research on in-situ exploitation of oil shale at home and abroad focuses on the experimental introduction of heating mode, and there is no physical drilling tube structure design that can be referred to. According to the actual situation of oil shale in the Nanqing section of Jilin Songnan, the wellbore structures under two different development modes, electric heating and nitrogen injection heating, are designed respectively, and the heating element, casing, cement ring and surrounding rock are used by finite element software. The combined seal integrity model was simulated. The results show that when mining with 600 °C electric heating, the heat is transferred to the formation and decays rapidly. The effective development radius is only 2.0m, which is difficult to apply to the exploitation of oil shale. When using the heating nitrogen heating, the effective development radius is only 5.0m. Considering the late fracturing, the hot nitrogen can effectively heat the formation through the crack, which is suitable for the exploitation of oil shale; the thermal stress of the casing in the heating section can reach 1094 MPa, and the TP110H anti-high temperature casing is required.