Exhibit 99

DeGolyer and MacNaughton

5001 Spring Valley Road

Suite 800 East

Dallas, Texas 75244

February 16, 2021

ConocoPhillips 

925 N. Eldridge Parkway

Houston, Texas 77079

Re: SEC Process Review 

Ladies and Gentlemen:

Pursuant to your request, DeGolyer and MacNaughton has performed a process review of the

processes and controls used by ConocoPhillips in preparing its internal estimates of proved reserves,

as of December 31, 2020. This process review, which is contemplated by Item 1202 (a)(8) of

Regulation S–K of the United States Securities and Exchange Commission (SEC), has been performed

specifically to address the adequacy and effectiveness of ConocoPhillips’ internal processes and

controls relative to its estimation of proved reserves in compliance with Rules 4–10(a) (1)–(32) of

Regulation S–X of the SEC.

DeGolyer and MacNaughton has participated as an independent member of the internal

ConocoPhillips Reserves Compliance Assessment Team in reviews and discussions with each of the

relevant ConocoPhillips business units relative to SEC proved reserves estimation. DeGolyer and

MacNaughton has participated in the review of all major fields in all countries in which

ConocoPhillips holds proved reserves worldwide. ConocoPhillips has indicated that these reserves

represent over 90 percent of its estimated total proved reserves as of December 31, 2020. 

The reviews with ConocoPhillips’ technical staff involved presentations and discussions of a) basic

reservoir data, including seismic data, well-log data, pressure and production tests, core analysis,

pressure-volume -temperature data, and production history, b) technical methods employed in SEC

proved reserves estimation, including performance analysis, geology, mapping, and volumetric

estimates, c) economic analysis, and d) commercial assessment, including the legal basis for the

interest in the reserves, primarily related to lease agreements and other petroleum license agreements,

such as concession and production sharing agre

ements.

ConocoPhillips 

February 16, 2021 

Page 2 of 2

A field examination was not considered necessary for the purposes of this review of ConocoPhillips’

processes and controls.

It is DeGolyer and MacNaughton’s opinion that ConocoPhillips’ estimates of proved reserves for the

properties reviewed were prepared by the use of recognized geologic and engineering methods

generally accepted by the petroleum industry. The method or combination of methods used in the

analysis of each reservoir was tempered by ConocoPhillips’ experience with similar reservoirs, stage

of development, quality and completeness of basic data, and production history. It is DeGolyer and

MacNaughton’s opinion that the general processes and controls employed by ConocoPhillips in

estimating its December 31, 2020, proved reserves for the properties reviewed are in accordance with

the SEC reserves definitions.

This process review of ConocoPhillips’ procedures and methods does not constitute a review, study,

or independent audit of ConocoPhillips’ estimated proved reserves and corresponding future net

revenues. This process review is not intended to indicate that DeGolyer and MacNaughton is offering

any opinion as to the reasonableness of the reserves estimates reported by ConocoPhillips.

DeGolyer and MacNaughton is an independent petroleum engineering consulting firm that has been

providing petroleum consulting services throughout the world since 1936. Neither DeGolyer and

MacNaughton nor any employee who participated in this project has any financial interest, including

stock ownership, in ConocoPhillips. DeGolyer and MacNaughton’s fees were not contingent on the

results of its evaluation. 

Very truly yours,

 /s/ DeGolyer and MacNaughton

 DeGOLYER and MacNAUGHTON

 Texas Registered Engineering Firm F-716

/s/ Charles F. Boyette

Charles F. Boyette, P.E.

President and COO

DeGolyer and MacNaughton