Is this what you are trying to do?
xfile = OpenWrite["C:\\Users\\xyz\\Desktop\\file.txt", FormatType -> StandardForm];
For[i = 0, i < 11, i++,
For[j = 0, j < 11, j++,
WriteString[xfile,
StringJoin@Map[ToString, #] &@{11111111111, " ", 11111111111, " ",
11111111111, " ", 11111111111, " ", 11111111111, " ",
11111111111, " ", 11111111111, " ", 11111111111, " ",
11111111111, " ", 11111111111, " ", 11111111111, " ",
11111111111, "\n"}]]]
Close[xfile]
