新型封堵剂FDJ-EF封堵特性及其作用机理

Characteristics of novel sealing agent FDJ-EF and its sealing mechanism

封堵近井壁微裂缝是避免硬脆性泥页岩地层井壁失稳的有效手段之一。在分析各类型水基钻井液防塌封堵剂的基础上,优化研制出一种新型热塑性聚酯类封堵剂FDJ-EF;通过具有模拟微裂缝金属缝板的高温高压封堵仪,评价FDJ-EF的封堵效果,证明其在较宽的温度范围(80～140℃)内具有优异的封堵性能,且其封堵能力强于目前常用的防塌封堵剂(聚乙二醇、乳化石蜡、乳化沥青);通过荧光光度计分析,FDJ-EF无荧光显示;通过封堵特征微观观察及粒度分布测量等实验手段,探讨了FDJ-EF的封堵机理。结果表明,其封堵机理主要为:在软化温度范围内,FDJ-EF封堵粒子在压差作用下软化变形,与其他固相颗粒一同挤入微裂缝内,在短时间内形成致密的封堵层,一方面阻碍了压力和滤液传递,一方面增强了黏土矿物的胶结强度。

Sealing of the microfractures near wellbore is one of effective measures of preventing sidewall instability in hard-brittle clay shale formation. A novel thermoplastic sealing agent FDJ-EF was developed on the basis of the evaluation of various anti- sloughing sealing agents for water-based drilling fluid. It is proved that the sealing agent FDJ-EF has the most significant blockingfunction within a wide temperature range（80-140 ~C） through the analysis of FDJ-EF sealing effect with HTHP sealing instrument, which can model the microfactures in hard-brittle clay shale formation. The sealing capacity is better than the common anti- sloughing sealing agents now, such as polyethylene glycol, emulsified wax and emulsified bitumen. FDJ-EF has not fluorescent display through the analysis of fluorophotometer. The sealing mechanisms of novel sealing agent were studied through theexperiments including microstructures observation and particle size distribution measuring. It is concluded that main sealing mechanisms within softening temperature range are that FDJ-EF sealing partieles, deformed by softening under pressure difference, and other particles are squeezed into the microfractures and the tight sealing layer is created in a short time. On the one hand, the transmission of pressure and filtrate is slowed down, and on the other hand, the cementing strength of clay mineral is strengthened.