Complex sentence: From 1927 to 1934 he operated his own business as a consulting geologist, and from 1934 until his death as a research geophysicist for the Humble Oil and Refining Company was a pioneer in the application of geophysical principles in the exploration for petroleum.
Split into simpler sentences: From 1927 to 1934 he operated his own business as a consulting geologist, and from 1934 until his death as a research geophysicist for the Humble Oil and Refining Company. He was a pioneer in the application of geophysical principles in the exploration for petroleum.