1. CNPC Tubular Goods Research Institute, Xi’an, Shaanxi, P. R. China
2. Linfen Branch of PetroChina, Coalbed Methane Co., Ltd, Linfen, Shanxi, P. R. China
3. Petroleum Research and Development Center, Petrochina Tuha Oilfield Co., Ltd, Turpan, Xinjiang, P. R. China