新型纳米材料在页岩气水基钻井液中的应用研究

针对页岩气钻探中水基钻井液携岩、封堵纳米孔径、抑制页岩分散等方面需求，研制了一种直径约为30 nm的纳米层状材料LDP。在流变方面，120℃老化后，2% LDP悬浮液比6%钠膨润土具有更高的弹性模量、屈服应力和剪切稀释性，与0.5% PAC-LV溶液复配实验表明，1% LDP的增黏提切性能优于4%钠膨润土；同时，周期震荡应变扫描实验表明，LDP悬浮液在高低应变转换时具有更好的凝胶结构恢复和拆散性能；粒径分析、透射电镜分析表明，LDP比钠膨润土在水溶液和PAC-LV溶液中更容易形成明显的网状结构；在封堵方面，利用N₂吸附分析了页岩在不同溶液浸泡后的孔隙，结果表明，LDP比纳米二氧化硅、钠膨润土具有更明显的封堵效果，扫描电镜分析揭示了LDP材料能够封堵页岩狭长纳米孔道。在页岩抑制方面，2% LDP抑制黏土线性膨胀率较清水降低45%，优于7% KCl，100℃页岩滚动回收率约为59.6%，与7% KCl基本一致，土块浸泡在2% LDP溶液96 h形貌完整。整体而言，LDP纳米材料在增黏提切、纳米孔隙封堵和页岩抑制方面有良好的效果，在页岩气高性能水基钻井液中有一定的应用前景。 

Research on Application of a Novel Nanophase Material in Water Base Drilling Fluids for Shale Drilling

A layered Nanophase material LDP of 30 nm in particle sizes has been developed to satisfy the needs of shale drilling such as cuttings carrying, plugging nanometer-sized fractures and inhibiting the dispersion of shale formations. Laboratory experiments showed that a 2%LDP suspension, after aging at 120℃, had higher elastic modulus, yield stress and better shear thinning ability than a 6% sodium bentonite suspension. In 0.5%PAC-LV solution, 1%LDP shows better ability in increasing the viscosity and gel strengths of the solution than 4% Na-bentonite. Periodic oscillatory strain scanning demonstrated that LDP suspension showed better ability to restore and break down its gel structure at the switch of high strain and low strain. Particle size measurement and transmission electron microscopy indicated that, compared with Na-bentonite, it is much easier for the LDP to form network structure both in water and in PAC-LV solution. To evaluate the plugging performance of LDP, shale samples rinsed in different solutions were measured for their pore sizes using N2 adsorption method. The measurement showed that LDP has better plugging capacity than nano SiO2 and Nabentonite. SEM scanning showed that LDP can plug the long and narrow nano-sized holes in shale. In clay swelling test, the percent core swelling caused by 2%LDP solution was 45% of the percent core swelling caused by fresh water, better than 7%KCl solution. The percent shale cuttings recovery of LDP in hot rolling test at 100℃ was 59.6%, equivalent to 7%KCl solution. Clay clod rinsed in 2% LDP solution for 96 h still kept its integrity. In general, LDP nanophase material is beneficial to viscosity and gel strength enhancement, plugging of nanometer-sized pores and inhibiting shale formations, and is thus prospective in formulating high performance water base drilling fluids for shale drilling.