b'Estimated proved reservesUnless otherwise specifically identified in this report, the summary data with respect to ourestimated net proved reserves for the years ended December 31, 2018, 2017 and 2016 has beenprepared by Ryder Scott Company, L.P. (RSC), our independent reserve engineering firm for suchyears, in accordance with the rules and regulations of the Securities and Exchange Commission(SEC) applicable to companies involved in oil and natural gas producing activities. These rulesrequire SEC reporting companies to prepare their reserve estimates using reserve definitions andpricing based on 12-month historical unweighted first-day-of-the-month average prices, rather thanyear-end prices. For a definition of proved reserves under the SEC rules, see the Glossary andSelected Abbreviations. For more information regarding our independent reserve engineers, please seeIndependent petroleum engineers below.Our estimated proved reserves and related future net revenues, PV-10 and Standardized Measurewere determined using index prices for oil, without giving effect to derivative transactions, and wereheld constant throughout the life of the assets.Future net revenues represent projected revenues from the sale of proved reserves net ofproduction and development costs (including operating expenses and production taxes). Suchcalculations at December 31, 2018 are based on costs in effect at December 31, 2018 and the 12-monthunweighted arithmetic average of the first-day-of-the-month price for the year ended December 31,2018, adjusted for anticipated market premium, without giving effect to derivative transactions, and areheld constant throughout the life of the assets. There can be no assurance that the proved reserves willbe produced within the periods indicated or prices and costs will remain constant.Independent petroleum engineersRyder Scott Company, L.P.RSC, our independent reserve engineers for the years ended December 31, 2018, 2017 and 2016,was established in 1937. For over 80 years, RSC has provided services to the worldwide petroleumindustry that include the issuance of reserves reports and audits, appraisal of oil and gas propertiesincluding fair market value determination, reservoir simulation studies, enhanced recovery services,expert witness testimony, and management advisory services. RSC professionals subscribe to a code ofprofessional conduct and RSC is a Registered Engineering Firm in the State of Texas.For the years ended December 31, 2018, 2017 and 2016, we engaged RSC to prepare independentestimates of the extent and value of the proved reserves of certain of our oil and gas properties. Thesereports were prepared at our request to estimate our reserves and related future net revenues andPV-10 for the periods indicated therein. Our estimated reserves at December 31, 2018, 2017 and 2016and related future net revenues and PV-10 at December 31, 2018, 2017 and 2016 are taken fromreports prepared by RSC, in accordance with petroleum engineering and evaluation principles whichRSC believes are commonly used in the industry and definitions and current regulations established bythe SEC. The December 31, 2018 reserve report was completed on January 13, 2019, and a copy isincluded as an exhibit to this report.In connection with the preparation of the December 31, 2018, 2017 and 2016 reserves report, RSCprepared its own estimates of our proved reserves. In the process of the reserves evaluation, RSC didnot independently verify the accuracy and completeness of information and data furnished by us withrespect to ownership interests, oil and gas production, well test data, historical costs of operation anddevelopment, product prices or any agreements relating to current and future operations of the fieldsand sales of production. However, if in the course of the examination something came to the attentionof RSC which brought into question the validity or sufficiency of any such information or data, RSCdid not rely on such information or data until it had satisfactorily resolved its questions relating thereto27'