Most core measurement analyses done on shales are currently performed with a crushed rock sample following the procedure established in the GRI (Gas Research Institute) study on shales .

following the procedure为现在分词短语作方式状语，established...为过去分词短语作定语修饰procedure。following从来不引导从句，当然你查不到后接从句的用法了。你忽略了procedure和established之间的被动关系，因而误将过去分词当作过去式作谓语了。注意句子逻辑就能避免类似误解。