Stephens was born March 8, 1938, in De Leon, Texas, the fourth of five children to Martin Elmore Stephens, a watermelon and peanut farmer, and Hazel Lila Stephens (née Johnson; 1905–2011).[1][2] His father owned a dealership that sold Massey Ferguson tractor equipment.[3] He graduated from De Leon High School in 1956; while in high school, he worked on a peanut farm.[1] After a major drought that year, with the advice of his father, he decided to pursue a career other than farming; his love of the outdoors and exotic locations led him to major in petroleum engineering.[4] He enrolled in Tarleton State College but transferred to the University of Texas at Austin in 1958.[1]
He received a Bachelor of Science in 1961 and a Master of Science in 1962, both in Petroleum engineering from the University of Texas at Austin.[5]
In 1962, he began his career as a petroleum engineer for Humble Oil.[1] That year, he took a leave of absence to fulfill his duties to the Reserve Officers' Training Corps outside of Paris.[4][1] He returned to Humble Oil in 1964 in Monahans, Texas.[1]
In 1969, he took a job with First National Bank of Midland as a petroleum engineer and loan officer, where he worked for 10 years completing appraisals of properties for petroleum exploration.[4][1]
In 1979, he founded a petroleum consulting firm to estimate reserves for financial disclosures but was fired by his major client after it disagreed with his valuations.[4] That year, Stephens used his life savings to acquire 80 acres of land on which he drilled his first well, McClintic B-30 #2, in the Spraberry Trend.[6][3]
In 1996, he founded Big Dog Drilling.[4]
In 2000, he founded Endeavor Energy Resources as the successor to his sole proprietorship.
Stevens defaulted on debt in 1999 and lost a lot in both 2008 and 2014 when oil prices crashed.[3]
After Stephens was diagnosed with prostate cancer, he sold the company to provide liquidity for his family.[7][8][9][10]
After an auction process, in September 2024, one month after Stevens died, Diamondback Energy acquired the company for $26 billion, including $8 billion in cash and the remainder in stock.[11][12][13]