Research And Application Of Clean Fracturing Fluid For Yangchang Gas Field

Yangchang gas fields is typical low permeability reservoir, it was characterized by the low holes, low permeability, low pressure, low degree of richness and low production. Based on the current situation, Yangchang gas field still has large development space, but the degree of technology dependence is increasing rapidly. Basing on the geological characteristics of Yangchang gas field, a new clean fracturing fluid system was developed for solving the problems of fracturing fluid.Firstly, the core porosity, permeability and components were analyzed. The results showed that the reservoir are low holes, low permeability and tight gas sands, the cores are mainly composed of quartz, calcite, chlorite and kaolinite. According to the geological characteristics and mechanism of clean fracturing fluid, ammonium Gemini surfactants(C18-4-C18·2Br- and C18-6-C18·2Br-) were synthesized from N,N-Dimethyloctadecylamine and 1,4-Dibromobutane(1,6-dibromohexane). The surfactants were characterized via IR spectra, 1H NMR spectra and elemental analysis,and the results prove that they are all the objective products.The clean fracturing fluid were identified by system experiment, in which Octadearyl dimethyl ammonium chloride(1831), C18-4-C18·2Br-, C18-6-C18·2Br- and supramolecular surfactant(LQ-1) are based agents. The comprehensive performance of these clean fracturing fluids are evaluated according to SY/T 5107-2005 "Water-based Fracturing Fluid Performance Evaluation Method" and SY/T 6376-2008 "General Technical Conditions of Fracturing Fluid". The results show that the 1831 Clean fracturing fluid system is not suitable for high temperature(80℃~120℃) according to viscosity-temperature curve. Gemini surfactants and supramolecular surfactant clean fracturing fluids system have good heat resistance performance, and can used under 110 ℃. The comprehensive performance of Gemini surfactants and Supramolecular surfactant clean fracturing fluids are evaluated, in which include viscosity-temperature, rheological properties, shear resistance, suspended sand performance and broken plastic performance. The results showed that the performance indicators are in line with SY/T 6376-2008 " General Technical Conditions of Fracturing Fluid ". Core damage experiments show that formation damage is small of these clean fracturing fluid systems, and they can be used for Yangchang gas fiel. Fracturing design was developed according to the geological conditions of 340 S. LQ supramolecular surfactant clean fracturing fluid system was tested in gas field, and the results show that the fracturing progressed successfully and the performance met the design requirements.