A Study On Degradable Temporary Plugging Agent And Its Perfromance Under High Temperature In Oilfield Exploitation

With the progress of society, the demand of people for energy is increasing, which has promoted the development of oil and gas industry.Many oil fields have no nature productivity and begin to use the water flooding to promote oil exploration. The constant water injection has led to the high water content in reservoir, the oil well seriously producing water, the poor horizontal andvertical homogeneity, low production efficiency and a series of problems. In order to solve these problems, the researchers constantly study plugging agent, changing the reservoir heterogeneity, sealing the high permeability layer to ensure the oil production. However, with the increasing exploitation, the shallow reservoirs have been developed completely, many conditions, such as temperature, pressure, salinity increase with the mining depth. The existing temporary plugging agent can only meet the salt resistance, while the thermal resistance is below 135°C. The temporary plugging agent will degrade or dissolve after injection and has no effect to plugging a lot of deep reservoir. The use of temporary plugging agent should combine oil and environmental protection, to avoid the pollution of temporary plugging agent caused by residues in formation. In conclusion, a new temporary plugging agent with good thermal resistance, salt tolerance, shear resistance and degradability should be synthesized to increase the exploitation of deep oilfields.This paper summarizes the previous data and choose the aqueous solution polymerization by changing the monomer and ratio to compound the gel. The viscoelasticity, thermal resistance and degradability has been improved through the temperature experiment. After the synthesis, the solubility, expansibility, compatibility, portability, plugging ability, harmfulness and other performance of the temporary plugging agent were evaluated. The characteristics of the synthetic temporary plugging agent with different ratio were discussed as well, then concluded the temporary plugging agent for different reservoir condition.Temporary plugging agent reach the following standards:(1) It is able to withstand temperature of 120~180°C;(2) It could be expanded 20~30 fold in residual acid and water;(3) The degradation rate could be more than 95% within 48 hours;(4) It has a good suspension in fracturing fluid and it’s easy to carry;(5) The degradation has a good compatibility with the residual acid and a strong plugging ability to pore throat and the cracks less than 300μm and its resilience of the core is greater than 88%;(6) The synthesis process is simple, economical and feasible.