Fuyan Zhang

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Panjin, CN

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Patents Grantslast 30 patents

Information Patent Grant
Downhole cut-off valve used for cementing
- Patent number 5,957,197
- Issue date Sep 28, 1999
- Liaohe Petroleum Exploration Bureau of Xinglongtai
- Xianchang Xia
- E21 - EARTH DRILLING MINING