关键词: 纳米胶乳, 半透膜, 隔离层, 钻井液, 网络结构

Abstract:

The formation of high efficiency semi-permeable membranes at the interface of drilling fluids and borehole walls is a new approach to prevent formations from water. On the principle of activity control, a semi-permeable membrane can control the flow orientation of water, and provided transformed to an isolation layer via membrane contamination, semi-permeable membranes can prevent formations from the invasion of extraneous substances, playing a role in stabilizing borehole walls and safeguarding formations. The present study prepared a kind of  nanometer drilling fluid using the self-made nano-latex NM-1 (65 nm in mean grain size) and inorganic nano-powder (NMTO) as the host and tested the semi-permeable membrane efficiency of this drilling fluid via the osmotic pressure method, which was 65%. The study also evaluated the effect of the drilling fluid as an isolation layer through the API filtration loss method, and the result showed that the incremental of the API filtration loss with time decreased nearly to 0 after 120 minutes and the bearing resistance to pressure increased up to 3.5 MPa. The scanning electron microscopic examination of sliced cores after membrane formation indicated that microstructures inside this semi-permeable membrane were network structures formed through the interaction of nano-latex with polymers in the drilling fluid, while isolation layers with an average thickness of 50~60μm were thermally felted through the deformation, filling and cementation of latex particles based on semi-permeable membranes.

Key words: nano-latex, semi-permeable membrane, isolation layer, nanometer drilling fluid, network structure