Graphene oxide (GO) nano-sheets were synthesized using a modified Hummers' method from graphite powder. The Raman spectrum of GO displayed a D-band at 1359 cm -1 and a G-band at 1594 cm -1 . The I D /I G value of GO was calculated to be 0.97, suggesting the formation of new sp 2 clusters upon reduction. A method was designed to investigate the assembly of the GO/montmorillonite (MMT) composite. After the addition of GO, the typical peaks of montmorillonite in FT-IR spectra shifted, indicating the assembly between GO and MMT. The D-band and G-band reduced sharply in the GO/MMT composite. More importantly, the D-band (1344 cm -1 ) and G-band (1574 cm -1 ) shifted significantly and the I D / I G value of the GO/MMT composite was calculated to be 1.13, showing a change in the GO structure. In the addition of 0.04 wt% GO to MMT, the value of interlayer space (d) was up to 13.0 Å measured by XRD due to the insertion of GO into MMT. The evident increases in contents of carbon atoms (26.59%) and nitrogen atoms (3.44%) indicate that GO was successfully combined with MMT. The nano-pores and clay sheets were not observed in the SEM image of GO/clay, but obvious wrinkles, while flexible sheets were observed in the typical scanning electron microscopy images of GO. This further proves that GO was combining with clay. The TEM image shows that the GO nano-sheets were tiled on the surface of MMT sheets. This observation suggests that a stable assembly structure was formed between GO sheets and MMT sheets. The change in particle size of MMT with the addition of GO shows that interaction occurred between GO sheets and MMT sheets, which was further confirmed by the results of zeta potential. Adsorption and insertion were the main mechanisms to assemble GO and MMT.

Deep earth exploration plays an important role in studying our planet for more information about geological data and mineral resources,,oil and gas. It is a great challenge to develop geodrilling technology facing a deep well depth, high temperature, great pressure, and complicated geological conditions. Lost circulation is a common and difficult problem especially in deep wells, which costs great loss.In this paper, a new kind of acrylamide copolymer/phenolic resin gel is introduced. The gel's molecular skeleton is cellulose which graft copolymerized by water-soluble acrylamide monomer. Phenolic resin is a crosslinking agent. The viscosity of the polymer solution is low and shows excellent shear thinning properties, and the solution is easy to be injected into the well and enters into rock fractures and pores. The crosslinking time can be controlled by changing the crosslink ratio and the amount of catalyst. After the gel is crosslinked, it will completely lose mobility, which has a high strength as plugging agent with high temperature (up to 200 °C) and pressure resistance. The polymer gel has good properties of flushing fluid resistance, high salinity brine resistance and crude oil resistance. The sand pack experiments, permeability tests of cores treated with the gel and other tests about plugging material all shows the intelligent gel has good plugging performance. The intelligent gel can be mixed with other solid plugging agents to enhance plugging effects without affecting its properties. It has good application prospect in lost circulation control, workover operation, and water plugging. Figure 1. 1.5 inch steel pipe and sand pack with intelligent gel.Intelligent gel is crosslinked in the sand pack which can bear the pressure of 20Mpa at 180 °C with the length of 1.2 meters. This experiment shows that the acrylamide copolymer/phenolic resin gel has excellent plugging performance.