Abstract: In the test of exploration wells in offshore fault-block oilfields, there are large differences in oil production indexes under different chokes, well deviation and partial perforation effects. Although the field productivity estimation method is simple and quick, it cannot solve the above problems. In view of the above problems, taking the X oilfield in South China Sea as an example, after applying the formula calculation and the pressure build-up test interpretation methods to obtain the partial skin, the corrected oil production index and the specific oil production index under low pollution conditions are calculated, and the specific oil production index correction chart is formed to realize the rapid correction of the specific oil production index. The critical sanding production pressure difference of sand layer is calculated by using the inflection point in the relationship diagram of pollution skin and production pressure difference, and the critical sand production pressure difference of non-sand layer is determined by using the relationship diagram of permeability and critical sand production pressure difference. The correction of oil production index and the determination of critical production pressure difference provide a basis for the productivity evaluation of loose sandstone reservoirs in this area. This method can quickly obtain the productivity calculation parameters of exploration wells in loose sandstone reservoirs, and has reference significance for productivity evaluation of similar reservoirs.