深水导管架平台外加电流阴极保护优化设计Ⅰ:单座辅助阳极

目的 以南海某200 m深水导管架平台为原型，研究外加电流单座辅助阳极在静态和动态海水条件下的导管架阴极保护电位分布及其变化规律。方法 采用一定比例缩小的导管架模型，对其施加外加电流阴极保护，研究不同条件下的阴极保护电位分布，以及电位分布的变化规律。结果 辅助阳极距离导管架模型越远，模型整体的阴极保护越均匀，反之，则越不均匀。导管架距离辅助阳极最近的区域，阴极保护电流密度最大，易出现过保护风险，而平台内部屏蔽严重区域和距离辅助阳极较远的水面附近导管架结构，阴极保护电位负移程度最小，易出现欠保护风险，这2个典型区域应当是阴极保护监测的重点位置。在相同保护电流密度和保护距离下，从静态到动态转换时，整座导管架表面的电位均呈现上升趋势，电位差值更大，分布更不均匀。随着阴极保护时间的延长，代表沉积层形成质量和覆盖程度的表观电阻率Rsr呈现初期快速增加、后期缓慢升高的趋势。海水流动会导致沉积层变薄，甚至脱落，使得动态海水环境中Rsr较同时期静态环境下的小。结论 在导管架模型的一侧放置一套辅助阳极，可实现整个模型的有效阴极保护。

Optimization Design of Impressed Current Cathodic Protection for Offshore Oil Jacket Platform I:Single Seat Auxiliary Anode

The work aims to study the cathodic protection potential distribution and change law of jacket with impressed current and single seat auxiliary anode under static and dynamic seawater conditions by taking an offshore jacket platform in the South China Sea as the prototype. A jacket model with a certain scale reduction was adopted and impressed current cathodic protection was applied. The cathodic protection potential distribution under different conditions and the change law of potential distribution were studied. The farther the auxiliary anode was from the jacket model, the more uniform the cathodic protection of the whole model was, otherwise, the more uneven it was. The area closest to the auxiliary anode outside the jacket was prone to over-protection risk due to the high protection current density. However, the negative shift of cathodic protection potential was the least in the severely shielded area inside the platform and the jacket structure near the water surface farthest from the auxiliary anode, which was prone to the under-protection risk. These two typical areas were the key locations for cathodic protection monitoring. Under the same protection current density and protection distance, the potential of the whole jacket surface presented an upward trend during the transition from static state to dynamic state, and the potential difference was larger and the distribution was more uneven. With the extension of cathodic protection time, the surface resistivity Rsr representing the formation quality and coverage degree of the sedimentary layer increased rapidly in the initial stage and slowly in the later stage. Seawater flow could lead to thinning and even shedding of sediments, so Rsr in dynamic seawater environment was smaller than that in static environment at the same time. Placing an auxiliary anode on one side of the jacket model can realize the effective cathodic protection of the whole model.