The Study On Laboratory Evaluation Of Recyclable Fracturing Fluid Of Low Temperature And Low Permeability Reservoirs

The Chang 3 oil reservoir of Weibei in North Branch Company,which has shallow buried depth,thick sand body,good properties,bad fracture development,big difference in plane distribution and physical properties,and almost has no natural capacity.It must carry out fracturing operation.So fracturing is the key technology of the reservoir development.Fracturing technology for fracturing fluid requires a lot of water,but Weibei oil field is in mountainous area,in which traffic is unconvenient and water resource is lack.On the other hand,sand fracturing can generate a lot of waste water,but the processing ability is limited.So the flowback fluid treatment causes great environment pressure and cost pressure.To carry out recyclable fracturing fluid research based on these two aspects,and recycle waste water,save waterto its fullest extent,reduce the treatment cost of waste water greatly.In addition,use waste water,change waste into valuable.This paper studies the present situation of flowback fracturing fluid in Weibei oil field,and analyzes the water quality characteristic of flowback fluid mainly from the residual guanidine gum,residual additives,residual gelout and so on.By optimizing some additives such as the metal balance regulator,gel breaker to remove adhesive,molecular reconstructed additives through a lot of indoor experiments,choosing pretreatment equipment and processing technology of flowback fluid,and testing recycled fracturing fluid formula according to the compatibility of fracturing fluid and reservoir,we can make comprehensive performance evaluation of flowback fluid based on China’s oil and gas industry standards SY/T5107 2005 The Performance Evaluation of Water-based Fracturing Fluid,and put suggestions and conclusions of fracturing construction site on risk control of construction,economic evaluation,and environment requirement finally.By optimizing the conventional fracturing fluid formula of Weibei blocks,the paper designs the basic formula for the first time:0.1%formaldehyde+0.5%KCl+0.35%⁰.30%modified melon glue+0.5%clay stabilizer+0.5%platoon aid;Crosslinking ratio:100:0.3;Breaker:0.12%ammonium persulfate+0.3%activator at low temperature.The pH value of base fluid is 6.5⁷.5,and the viscosity is about27.6mPa·s.Forming a set of reuse fracturing fluid formula system of low temperature and low permeability reservoirs which is a base fluid-reuse fluid integration research:gel breaking fluid+0.1%formaldehyde+0.05%⁰.15%gel breaker to remove adhesive+0.3%⁰.8%metal balance regulator+0.30%⁰.28%modified melon glue+0.1%platoon aid;Crosslinked ratio:100:0.2⁰.1,0.3%⁰.4%molecular reconstructed additives at the same time.Under the condition of 65℃,170s^-1,the fluid keeps shearing for 2 hours and its viscosity remains at about120mPa·s.The surface tension of gel breaking fluid is at about 24.26mN/m,and the viscosity is between 3.7mPa·s to 4.8mPa·s.The residue content is about 265mg/L and its expansion rate is higher.The gel performance is stable and the heat resistance is up to 65℃.The comprehensive performance of the system is good totally.