耐温抗盐微纳米环保降滤失剂的性能

针对国内环保型抗高温抗盐降滤失剂种类较少，分子结构过于单一的现状，以1-溴代十二烷为引发剂，对羟乙基纤维素进行改性，使其与纳米碳酸钙接枝共聚，使接枝共聚物大分子链间产生分子内或分子间的缔合作用，形成了不同形态的超分子网络结构，并与纳米颗粒相互作用形成稳定结构以增强其相关性能，合成了一种新型的耐温抗盐的微纳米环保型降滤失剂MND-1。该降滤失剂体积小，比表面积大，表面活性羟基多，可形成以氢键和范德华力连接的空间网架结构，这种空间结构的强度有限，在高剪切作用下容易被破坏，溶液的黏度下降，当剪切速率降低后，大分子间的缔合作用形成的交联网络结构重新形成，黏度恢复，空间网架结构的破坏和恢复形成了动态平衡，体现了优异的剪切稀释性，可有效封堵滤饼和微纳米空隙，起到降滤失作用。通过对MND-1性能评价结果得出，MND-1有优异的降滤失作用，在淡水、盐水、饱和盐水中降滤失性能良好，在180℃、16 h下的饱和盐水基浆中的API滤失量仅为6.8 mL，易生物降解，EC₅₀为4.3×104mg/L，环保性能良好，可用于高温高盐且对环保性要求较高的地层。 

The Properties of an Environmentally Friendly High Temperature Salt Resistant Micrometer and Nanometer Filter Loss Reducer

Presently there are fewer environmentally friendly high temperature salt resistant filter loss reducers available in China, and the molecular structure of the filter loss reducers are also quite simple. In our studies, MND-1, a new environmentally friendly high temperature salt-resistant micrometer and nanometer filter loss reducer, was developed by the modification of hydroxyl ethyl cellulose (HEC), with 1-bromododecane as the initiator for the reaction. Graft copolymerization of HEC and nanometer CaCO₃ produced a product of macro molecules. Association among the macro molecules or among the different molecular chains of a single macro molecule produced supramolecular network structure of different morphologies. The interaction between the graft copolymer and the nanometer CaCO₃ helped stabilize the molecular structure of the final product and also enhanced the relevant properties of the final product. The filter loss reducer developed has small molecular volume and high specific area. The molecules of MND-1 can form a spatial network structure through hydrogen bonds and Van der Waal’s force among the hydroxyl groups in the molecules. The strength of this spatial network is not strong enough to resist high shear rates, and the viscosity of the MND-1 solution is thus decreased at high shear rates. When shearing stops, MND-1 regains its spatial network structure formed through the association forces among the molecules of MND-1, and the MND-1 solution resumes its viscosity. This is the so-called shear thinning effect formed through a dynamic equilibrium between the destruction and recovery of the spatial network structure. With this excellent shear thinning effect, MND-1 can effectively seal the voids in mud cakes, thereby reducing the rate of filtration. Laboratory evaluation experiment showed that MND-1 has excellent filtration control capacity in freshwater, saltwater and saturated saltwater drilling fluids. The API filter loss of an MND-1 treated saturated saltwater base drilling fluid aged at 180 ℃ for 16 h was only 6.8 mL. MND-1 is environmentally friendly and easy to biodegrade, it has an EC₅₀ of 4.3×104 mg/L.MND-1 can be used in drilling high temperature salt formations in environmentally sensitive areas.