Research On The Technology Of Low-carbon Alkane Hydrofracturing Fluids

The reserves of unconventional oil and gas resources in China are very abundant,but they are generally faced with the difficult problem of exploitation.Fracturing is an important technical measure for the effective development of unconventional reservoirs.Unconventional oil and gas reservoirs are very complex and sensitivity,fracturing fluids are of great importance as an important working fluid in the fracturing process.Taking shale gas as an example,although shale gas reservoirs in China have large reserves,most of them are located in the Sichuan-Yunnan mountain area.While large-scale hydraulic fracturing consumes a large amount of water resources,the backflow of fracturing fluid can also pollute the environment,destroy the ecological environment.Therefore,the study of waterless fracturing technology has very important strategic significance for the development of unconventional oil and gas reservoirs in China.In this paper,the low carbon hydrocarbon non-aqueous fracturing fluid was studied and the following results were obtained:(1)A single alcohol phosphate gelling agent and a mixed alcohol phosphate gelling agent were synthesized.The viscosity of two gelling agents was evaluated,and the synthesis conditions were optimized.The two kinds of gelling agents under the conditions of excellent synthesis were characterized by infrared spectroscopy and nuclear magnetic resonance spectroscopy,confirming that the main structures of the two samples as expected.(2)Select iron ion cross-linking agent with main agent ferric sulfate,cross-linking accelerator C2,complexing agent ethanolamine and phase-transfer catalyst cetyl trimethyl ammonium chloride;Select the novel,high-efficiency,low-cost aluminum ion cross-linking agent with aluminum sulfate as main agent and propanolamine as complexing agents,and its optimum preparation conditions are obtained by optimizing two cross-linking agent systems.(3)The optimal ratio of the iron-ion and aluminum-ion low-alkane anhydrous fracturing fluid system was optimized,and the performance of the anhydrous fracturing fluid system under two optimal conditions was evaluated.Experiments show the heat-resistant capacity of iron-ion and aluminum-ion anhydrous fracturing fluids are 160? and 150? respectively.The viscosity of iron ion and aluminum ion fracturing fluids is maintained around 200mPa·s and 100mPa·s,under the condition of continuously sheared at 120? and 170s-1 for 120 minutes;both fracturing fluid systems have good sand carrying properties,breaking properties,and very low core damage rates.(4)The rheological of two low-carbon alkane anhydrous fracturing fluid systems based on iron ion and aluminum ion were tested and analyzed.It was found that both fracturing fluid systems have good viscoelasticity and shear thinning properties and thixotropy;The new low carbon hydrocarbon non-aqueous fracturing fluid system studied in this paper is a major step forward for the technology of waterless fracturing fluid,providing a solid foundation for promoting the large-scale application of low-carbon hydrocarbon non-aqueous fracturing fluids.