水基钻井液硫酸铝污染处理工艺

KS19井三开φ311.2 mm井眼在钻至6243~6387 m井段时，使用的高密度KCl-聚磺水基钻井液被含有硫酸铝的清洁化生产用工业废水污染，流变性每日不断呈现上涨趋势至发生突变，一是φ6与φ3读值、初切值、动切力均上涨较高，而其他参数均比较正常；二是上水罐、过渡槽钻井液表面粗糙，大量针眼型气泡包裹其中，流态缓慢；三是循环系统加重泵上水困难、泥浆泵抖动严重，泵冲泵压变化较大，钻进期间被迫使用灌注泵辅助泥浆泵上水。分别在套管鞋、井底分2次进行循环调整处理，采用稀释置换、气泡界面张力改变、提高碱度进行中和、流变性改变、提高油含量等至恢复正常钻进，上水罐、过渡槽钻井液仅包裹有少量针眼型气泡，泥浆泵、加重泵上水正常。

Treatment of Aluminum Sulphate Contamination to Water Base Drilling Fluids

A high density KCl-polymer sulfonate drilling fluid was used to drill the third interval (φ311.2 mm) of the well KS-19. When drilling between 6243 m and 6387 m, the drilling fluid was contaminated by industrial waste water containing aluminum sulphate. The drilling fluid was experiencing rheology increase every day, or abrupt change sometimes. Several changes can be seen of the drilling fluid after being contaminated. First, the φ6 and φ3 readings, 10s gel strength and yield of the drilling fluid were increased to higher values, other drilling fluid parameters remained normal. Second, the mud in the suction pit and mud ditches had coarse surface and plenty of pinhole bubbles were trapped in the mud, making the mud flow very slowly. Third, the mud became difficult to pump, the mud pump trembled seriously, and the pump strokes per minute and pump pressure were unstable, changing in wide ranges. Charging pumps had to be used during drilling to pump the mud. To resolve these problems, the mud was circulated when the drill bit was at the casing shoe and the bottom of the hole to adjust its properties. Several measures, such as dilution and displacement, changing of the surface tension of the bubbles, neutralization with high pH value, changing rheology and increasing oil content of the mud, were taken to improve the properties of the mud. Drilling was then resumed and there were only small amount of bubbles found in the suction pit and ditches. Circulation was resumed to normal condition.