In the traditional method of well completions in gas fields of gas dissloved in water type, the steel casing pipes were utilized in almost cases. The steel pipes had feen corroded quickly by producing water from gas wells. For the two purposes, the prolongation of well lives and the low cost of well completions, writers had researched and tested about the utilization of plastic pipes. (poly vynil chloride pipe) And writes suceeded in completion of many natural gas wells using plastic pipes in Mobara gas field, Chiba prefecture. From the experiences of actual works of well completion, writers shall explain about the following itens in the report. (1) On the characters of PVCP (poly vynil chloride pipe) utilized in casing pipes. (2) On the economy of well completion with PVCP casing. (3) On the practices of utilization of PVCP. (4) On the results of the test of strength of PVCP.