8. Commitments and Contingencies At December 31, 2015, we had outstanding employment agreements with all four of our executive officers that contained automatic renewal provisions providing that such agreements may be automatically renewed for successive terms of one year unless the employment is terminated at the end of the term by written notice given to the employee not less than 60 days prior to the end of such term. Our maximum commitment under the employment agreements, which would apply if the employees covered by these agreements were each terminated without cause, was approximately $6.3 million at December 31, 2015. This estimate assumes the maximum potential bonus for 2016 is earned by each executive officer during 2016. We lease our office space in Fort Worth, Texas, under a non-cancelable agreement that expires on March 31, 2020. We also have non-cancelable operating lease commitments related to office equipment that expire by 2019. The following is a schedule by years of future minimum rental payments required under our operating lease arrangements as of December 31, 2015 (in thousands): 2016 $ 957 2017 967 2018 975 2019 976 2020 246 Total $ 4,121 Rent expense under our lease arrangements amounted to $1,002,000, $717,000 and $734,000 for the years ended December 31, 2015, 2014 and 2013, respectively. Litigation We are involved in various legal and regulatory proceedings arising in the normal course of business. While we cannot predict the outcome of these proceedings with certainty, we do not believe that an adverse result in any pending legal or regulatory proceeding, individually or in the aggregate, would be material to our consolidated financial condition or cash flows. Environmental Issues We are engaged in oil and gas exploration and production and may become subject to certain liabilities or damages as they relate to environmental clean up of well sites or other environmental restoration or ground water contamination, in connection with drilling or operating oil and gas wells. In connection wi