基于多相渗流理论的环空气窜机理及应用基础研究

Gas migration has became a frequent threaten to well safety with the development of natural gas exploration. Due to time variant characters of cement setting process, cement slurry would experience a plastic state which fluid could easily invade into cement slurry and interfacial transition zone of cement slurry/filter cake. Actually, it should be a replacement percolation process for multiphase flows, but, so far none of current theory could describe it in an accurate way. This research plans to build a equipment to simulate and test the migration of multiphase flows to plastic state cement slurry/filter cake/formation, and then take use of SEM, XRD, XRF, TGA, MRI to analysis the time variant characters of plastic cement slurry at HTHP and the impacts of phase behavior change of fluids on annular channeling. Based on these tests and analyses, the percolation theory of multiphase flow in the time-varying cement matrix and the interfacial transition zone and the mechanism of energy exchange, transfer, dissipation during annular channeling are explored. These analysis results and mechanisms could provide specific technical ideas for controlling the annular channeling and guidance for the development of new technology, new material and new product. The results of this research could safeguard the operational security of oil & gas wells during cementing and extend the lifetime of oil & gas wells.

随着我国天然气勘探开发的快速发展，固井环空气窜问题频发，气井安全越来越受到重视。由于水泥浆凝结具有时变特性，当水泥浆处于塑性态时，井下流体极易侵入水泥浆基体及钻井液滤饼-水泥浆界面过渡带，其实质应为多相流体在水泥浆时变结构基体及过渡带中的置换渗流过程，但目前尚无相应理论描述这一机理。研究拟建立多相流体在塑性态水泥浆-滤饼-地层中的侵入窜流模拟测试装置，结合SEM、XRD、XRF、TGA、MRI等测试手段，分析高温高压条件下塑性态水泥浆时变特性及环空流体相态变化对环空气窜的影响，开展多相流体在时变结构基体及过渡带中的置换渗流理论研究，并探索环空气窜过程中的能量交换、转移、耗散机理，提供固井环空气窜综合控制技术思路，指导固井防气窜新技术、新材料及新产品开发，有助于保障油气井固井作业安全，延长油气井生产寿命。

随着我国天然气勘探开发的快速发展，固井环空气窜问题频发，气井安全越来越受到重视。由于水泥浆凝结具有时变特性，当水泥浆处于塑性态时，井下流体极易侵入水泥浆基体，其实质应为多相流体在水泥浆时变结构基体中的置换渗流过程。通过调研国内外水泥浆早期气窜研究现状，采用室内实验研究和理论分析，建立多相流体在塑性态水泥浆-滤饼-地层中的侵入窜流模拟测试装置，结合SEM、XRD等测试手段，分析高温高压条件下塑性态水泥浆时变特性及环空流体相态变化对环空气窜的影响，开展多相流体在时变结构基体及过渡带中的置换渗流理论研究，并探索环空气窜过程中的能量交换、转移机理，提供固井环空气窜综合控制技术思路，指导固井防气窜新技术、新材料及新产品开发，有助于保障油气井固井作业安全，延长油气井生产寿命。