The Study Of Foam Fracturing Fluid Based On Associative Polymers

Foam fracturing fluid is based on conventional water-base fracturing fluid mixing high concentrations liquid nitrogen or carbon dioxide that gas as internal phase, liquid as external pHase. Foam fracturing fluid with good shear properties, strong carrying capacity, low loss, low damage and rapid flowback is considered to be the most comprehensive of reservoir fluids. But traditional foam fracturing fluid system is still based on cross-linking technique for water-base fracturing fluid, the shortcomings of the cross-linking technique on foam fracturing fluid is still there. Existing cross-linking technique by varying the pH to change the time and temperature tolerance, pH increases will harm to alkali-sensitive reservoir, itself of acidic carbon dioxide foam fracturing fluid, we had to seek new thickener and crosslinker. The cross-linking technique will bring more water-insoluble, affecting the effectiveness of stimulate.There is also a series of questions, such as friction to reduce hard, shear resistance to raise hard, temperature resistance to further breakthrough hard. In recent years, the emergence of a series of novel non-crosslinked fracturing fluids which represented by the viscoelastic surfactant fracturing fluid, that fracturing fluid of non-crosslinked technique has gradually become an important direction of development.The thesis based on the problems of traditional foam fracturing fluid and the development direction of fracturing fluid technology to study, through theoretical research, laboratory experiment and field application acquired main results and awareness as the following:(1) Application of supramolecular chemistry and supramolecular structure solution theory and practice, used a combination of micro and macro research methods and technical means, through a series of different hydrophobic associating polymer of the monomer content, the different of degree of associating polymer studies, was established interactions between the molecular structure of polymers and the viscoelasticity of polymer solution, and interactions between the viscoelasticity of solution and stability of foam.(2) Using environmental scanning electron microscopy, fluorescence probe method and electric conductivity method confirmed the network structure of associating polymer solution and polymer solution in a gas-liquid interface of separation of foam stability plays a very active role.(3) Through the study of rheological property of polymer solution, it is found that the special molecular structure of associating polymer caused polymer solution with shear-thickening and shear-thinning two special properties. When the shear rate is small, as the shear rate increases the viscosity of polymer solution increased sharply. When the shear rate exceeds a certain value, as the shear rate increases the viscosity of polymer solution fell sharply. The particular rheological behavior can be favour of the foam generated, but also favor to stabilize foam. Associating the network structure of associating polymer solution so that it does not need to be cross-linked with the rheology of required for foam fracturing fluid.(4) Based on the rheology of foam fracturing fluid study found that the viscoelasticity of associating polymer solution and, under the shear action the geometric topological variation of the plato passage structure in foam endow with the new viscoelasticity of foam. When associating polymer solution turn into foam, the foam storage modulus increases triple, over than the elastic base on single pHase fluid or gas, elastic greatly enhanced means more carrying capacity.(5) By filtering the single chemical and laboratory evaluation of comprehensive performance of foam fracturing fluid, formed the associating polymer foam fracturing fluid system. The system has good viscosifying action, strong carrying capacity, low damage to matrix permeability. Based on the results of experimental and theoretical research, breaking the traditional understanding of the cross-linking technique of water base fracturing fluid, using intermolecular association technique to obtain non-crosslinked associative structure of foam fracturing fluid system with good functional.(6) Homemade flow circuit friction measuring device was developed, through the evaluation of the device shows that associating polymer foam fracturing fluid with low friction, good shearing resistance. Laboratory tests confirmed the idea of associating polymer foam fracturing fluid is fully justified and feasible.(7) The foam fracturing fluid system was successfully carried out in oilfield. This is the first time for the associative polymer foam fracturing fluid system for application in shale gas developmen in China. Field construction showed that associating polymer foam fracturing fluid with excellent performance, fully able to meet this kind of formation fracturing requirements, low damage on shale formation, measure response quickly, then produce gas after flowback liquid is 80m in total. The blowout ignit is 3mm glib, the pressure above 11MPa, open flow capacity up to 10×104m3/d. The result of the fracturing construction shows that increase production of associative polymer foam fracturing is obvious.Based on theory, laboratory study and field application demonstrated that the associating polymer fracturing fluid system principle is correct and technique is feasible, enriched our foam fracturing fluid types, widened the scope of application of associating polymer, improved the level of efficiency development of low permeability fields, and provided the necessary theoretical and experimental foundation.