塔河油田盐膏层钻井液技术

Drilling fluid technology for drilling the gypsum salt bed in Tahe Oilfield

塔里木盆地石炭系盐膏层埋藏深,温度为110～130℃。钻井过程中,盐岩、软泥岩的塑性变形,硬石膏的吸水膨胀.高压低矿化度的盐水层对高密度钻井液的污染,盐岩、石膏的溶解使井径扩大,造成井壁垮塌;含膏盐泥页岩吸水膨胀和塑性变形,造成缩径和垮塌,易导致粘卡事故的发生。采用聚磺欠饱和盐水钻井液体系。经现场应用表明,聚磺欠饱和盐水钻井液性能稳定,抑制泥页岩水化分散能力强,携岩能力强,井壁稳定,井径扩大率低,流变性好,FCLS可有效控制钻井液的流变性;钻盐层前把聚磺钻井液转换为聚磺欠饱和盐水钻井液,控制Cl-含量大于160000 g/L,钻井液具有良好的抗盐性,有效抑制膏盐层的塑性流动和盐岩的溶解;该钻井液滤失量低,具有良好的造壁性能,能够有效防止井眼扩大;该钻井液体系钻井液排放量少,处理维护工艺简单,满足了塔河油田盐膏层钻井的要求。

The gypsum salt bed is located deep in the Carboniferous system of Tarim Basin, and its temperature is 110-130 ℃. During field drilling, there are many potential problems, i. e. , the plastic deforma tion of salt rock and soft shale, the hydrating inflation of hard gypsum, and the contamination of high pressure low salinity salt water on high density drilling fluid; the dissolving of salt rock and gypsum enlar ges borehole and causes hole collapse, and the hydrating inflation and plastic deformation causes hole shrinkage and collapse, and leads to pipe sticking. The polysulfonated under-saturated saltwater drilling fluid system is used, and the field using of it displays its stability, strong shale inhibition, good cuttings transportation and wellbore stability, small hole enlargement rate, and good rheology. The rheology of the drilling fluid can be adjusted by using FCLS. Before penetrating the salt bed, modify the polysulfonated drilling fluid into polysulfonated under-saturated saltwater drilling fluid, and control the content of Cl o-ver 160,000 g/L, to effectively inhibite the plastic flow of gypsum zone and the dissolving of slat bed. This drilling fluid has low filtration and good wall building capability, which can effectively prevent the hole enlargement; furthermore, this drilling fluid system has a small discharge amount and its field maintenance is easy and convenient.