工业品级 meaning in English

commercial grade

But during long time , it is very difficult for the exploration and development of sandstone oil layers on the upper part of the fouth member of shahejie formation . it is mainly represented as it ca n ' t be got the optimum production test effect and ca n ' t keep long term rate - maintenance
该区深层沙四上段砂岩油层的勘探开发一直存在较大的难度，集中体现于不能有效获得最佳试采效果并长期稳产，产量有时在短短几天内可由数十吨降至工业品级之下。