Filtrate loss reducer and application thereof to non-tackifying pure liquid-state CO2 sand fracturing

The invention discloses a filtrate loss reducer. The filtrate loss reducer is prepared from the following raw materials in parts by weight: 10-25 parts of 5# white oil, 0.5-2 parts of NP-1, 0.1-1 part of TX-4, 1-10 parts of n-caprylic acid, 1-10 parts of KCl, 4-15 parts of a carboxymethyl guanidine gum solution with the concentration of 1%. According to the filtrate loss reducer, the sand carrying capability of pure liquid-state CO2 fracturing liquid can be improved and the loss of the fracturing liquid is effectively reduced. Meanwhile, the invention further provides application of the filtrate loss reducer to a pure liquid-state CO2 sand fracturing process; the filtrate loss reducer is pumped into a stratum before pure liquid-state CO2 fracturing is constructed, and the sand fracturing is carried out; the filtrate loss reducer has the advantages of rapid backflow, increased backflow rate, shortened period of putting into production and the like; and water-based fracturing liquid does not need to be prepared in the process and backflow liquid does not need to be treated, so that the environment pollution degree is reduced, and the filtrate loss reducer has relatively good practical significance on regions with lacked water resources and regions with fragile ecological environments.