Complex sentence: He took many chances and came up dry on nine different ventures until the tenth, which he drilled in Anderson County, Texas in 1941, which brought on the discovery of the East Long Lake field, all of which was now owned by the Harvey Company.
Split into simpler sentences: He took many chances and came up dry on nine different ventures until the tenth, which he drilled in Anderson County, Texas in 1941. This latest drilling brought on the discovery of the East Long Lake field, all of which was now owned by the Harvey Company.