Exhibit 15.3









1800
West Loop South, Suite 1000, Houston, Texas 77027, USA



T+1 713 586 5950 F +1 281 586 5955 W www.rpsgroup.com



January 31, 2017



CNOOC Limited



No. 25, Chaoyangmenbei
Dajie



Dongcheng
District



Beijing 100010,
P.R. China



Gentlemen:



As per your
request, RPS has prepared an estimate of the proved reserves, future production and income attributable to certain leasehold interests
owned by CNOOC Limited as of December 31, 2016. The reserves and income data were estimated based on the definitions and disclosure
guidelines of the United States Securities and Exchange Commission (SEC) contained in Title 17, Code of Federal Regulations, Modernization
of Oil and Gas Reporting, Final Rule released January 14, 2009 in the Federal Register, including all references to Regulation
S-X and Regulation S-K (SEC regulations). Our third party revision, completed on January 27, 2016 and presented herein, was prepared
for public disclosure by CNOOC Limited in filings made with the SEC in accordance with the disclosure requirements set forth in
the SEC regulations. The estimated reserves and future net income amounts presented in this report, as of December 31, 2016, are
based on the reserve estimate review that RPS performed for PAE’s year-end 2016 reserve report. In our opinion, the assumptions,
data, methods, and procedures used in the preparation of this report are appropriate for such purpose.



CNOOC Limited
holds 50% interest in Bridas Corporation and Bridas Corporation holds 40% interests in PAE. Therefore CNOOC Limited, through Bridas
Corporation, owns 20% of participating interests in PAE.



The subject
properties are located in Argentina and Bolivia, South America. The properties evaluated by RPS account for a portion of CNOOC
Limited’s total net proved reserves as of December 31, 2016.













Based on
information provided by CNOOC, the third party estimate conducted by RPS addresses 6.3 percent of the Total Proved reserves of
CNOOC on a barrel oil equivalent basis (BOE).



The estimated
reserves and future net income amounts presented in this report, as of December 31, 2016, are related to hydrocarbon prices. The
hydrocarbon prices used in the preparation of this report are based on the average prices during the 12-month period prior to
the ending date of the period covered in this report, determined as the unweighted arithmetic averages of the prices in effect
on the first-day-of-the-month for each month within such period, unless prices were defined by regulatory or contractual arrangements,
as required by the SEC regulations. Actual future prices may vary significantly from the prices required by SEC regulations; therefore,
volumes of reserves actually recovered and the amounts of income actually received may differ significantly from the estimated
quantities presented in this report. The results of this study are summarized in the following table.



















Note: Hydrocarbon
liquids are crude oil, condensate and gasoline which are reported in thousands (103) stock tank barrels (Mbbl). The
Condensate and Gasoline estimates are volumes captured during field separation and gas plant processing in the field. The natural
gas reserves reported include gas sales and fuel gas. These volumes are reported in million (106) cubic feet (MMcf)
at standard conditions of 14.7 psia and 60° Fahrenheit.



In this report,
the revenues, deductions and income data are expressed as thousands of U.S. dollars (M$).



Note: Values
by property are shown in Table 1 included in the report.



Note:The
future gross revenue is after the deduction of royalty and turnover taxes in Argentina.



The deductions
also account for the joint venture (JV) terms PAE has with Petrominera del Chubut









S.E. (PMC),
new JV partner in the Anticlinal Funes field, in which PAE carries all the investments and cost, in return receives a greater
share of the production until reimbursed. In Bolivia royalty IDH and YPFB part has been also subtracted.



The deductions
incorporate the normal direct costs of operating the wells, recompletion costs, development costs, certain abandonment costs,
which are shown as “other” deductions. The future net income is before the deduction of foreign government income
taxes and general administrative overhead, and has not been adjusted for outstanding loans that may exist, nor does it include
any adjustment for cash on hand or undistributed income.



The discounted
future net income shown above was calculated using a discount rate of 10 percent per annum compounded monthly. Future net income
was discounted at four other discount rates which were also compounded monthly. These results are shown in summary form as follows:







The results
shown above are presented for your information and should not be construed as our estimate of fair market value.



Reserves
Included in This Report



The proved
reserves included herein conform to the definition as set forth in the Securities and Exchange Commission’s Rules and Regulations
Part 210.4-10(a). An abridged version of the SEC reserves definitions from Part 210.4-10(a) entitled “Petroleum Reserves
Definitions” is included as an attachment to this report.



The various
proved reserve status categories are defined under the attachment entitled “Petroleum Reserves Definitions” in this
report. The proved developed non-producing reserves included herein consist of the shut-in and behind-pipe categories.



Reserves
are “estimated remaining quantities of oil and gas and related substances anticipated to be economically producible, as
of a given date, by application of development projects to known accumulations.” All reserve estimates involve an assessment
of the uncertainty relating the likelihood that the actual remaining quantities recovered will be greater or less than the estimated
quantities determined as of the date the estimate is made. The uncertainty depends chiefly on the amount of reliable geologic
and engineering data available at the time of the estimate and the interpretation of these data. The relative degree of uncertainty
may be conveyed by placing









reserves
into one of two principal classifications, either proved or unproved. Unproved reserves are less certain to be recovered than
proved reserves, and may be further sub-classified as probable and possible reserves to denote progressively increasing uncertainty
in their recoverability. At CNOOC Limited’s request, this report addresses only the proved reserves attributable to the
properties evaluated herein.



Proved reserve
estimates will generally be revised only as additional geologic or engineering data become available or as economic conditions
change. For proved reserves, the SEC states that “as changes due to increased availability of geoscience (geological, geophysical,
and geochemical), engineering, and economic data are made to the estimated ultimate recovery (EUR) with time, reasonably certain
EUR is much more likely to increase or remain constant than to decrease”. Moreover, estimates of proved reserves may be
revised as a result of future operations, effects of regulation by governmental agencies or geopolitical or economic risks.



Therefore,
the proved reserves included in this report are estimates only and should not be construed as being exact quantities, and if recovered,
the revenues therefrom, and the actual costs related thereto, could be more or less than the estimated amounts.



For Cerro
Dragón, Piedra Clavada and Koluel Kaike areas there are volumes of Proved Undeveloped Reserves associated with Proved Locations
that have been booked for more than 5 years. PAE's continued development activities over the years have created new opportunities
that have delayed drilling some of the existing Proved locations. All Proved locations are planned to be drilled in the following
5 years in each area.



The proved
reserves reported herein are limited to the period prior to expiration of current contracts providing the legal rights to produce,
or a revenue interest in such production, unless evidence indicates that contract renewal is reasonably certain. Furthermore,
properties in the different countries may be subjected to significantly varying contractual fiscal terms that affect the net revenue
to CNOOC Limited for the production of these volumes. The prices and economic return received for these net volumes can vary significantly
based on the terms of these contracts.



Estimates
of Reserves



The estimation
of reserves involves two distinct determinations. The first determination results in the estimation of the quantities of recoverable
oil and gas and the second determination results in the estimation of the uncertainty associated with those estimated quantities
in accordance with the definitions set forth by Part 210.4-10(a). The process of estimating the quantities of recoverable oil
and gas reserves relies on the use of certain generally accepted analytical procedures. These analytical procedures fall into
three broad categories or methods: (1) performance-based methods; (2) volumetric-based methods; and (3) analogy. These methods
may be used singularly or in combination by the reserve evaluator in the process of estimating the quantities of reserves. Reserve
evaluators must select the method or combination of methods which in their professional judgment is most appropriate given the
nature and amount of reliable geoscience and engineering data available at the time of the estimate, the established or anticipated
performance characteristics of the reservoir being evaluated and the stage of development or producing maturity of the property.









These performance
methods include, but may not be limited to, decline curve analysis and material balance which utilized extrapolations of historical
production and pressure data available through December 31, 2016 in those cases where such data were considered to be definitive.
The volumetric method, analogy or a combination of methods were used where there were inadequate historical performance data to
establish a definitive trend and where the use of production performance data as a basis for the reserve estimates was considered
to be inappropriate. The volumetric analysis utilized pertinent well and seismic data supplied to RPS by PAE that were available
through December 31, 2016. The data utilized from the analogues as well as the well and seismic data incorporated into our volumetric
analysis were considered sufficient and appropriate for the purpose thereof.



In many cases,
the analysis of the available geoscience and engineering data and the subsequent interpretation of this data may indicate a range
of possible outcomes in an estimate, irrespective of the method selected by the evaluator. When a range in the quantity of reserves
is identified, the evaluator must determine the uncertainty associated with the incremental quantities of the reserves. Therefore,
it is the classification of reserve quantities as proved, probable and/or possible that addresses the inherent uncertainty in
the estimated quantities reported. All quantities of reserves within the same reserve class must meet the SEC definitions.



To estimate
economically recoverable proved oil and gas reserves and related future net cash flows, we consider many factors and assumptions
including, but not limited to, the use of reservoir parameters derived from geological, geophysical and engineering data that
cannot be measured directly, economic criteria based on current costs and SEC pricing requirements, and forecasts of future production
rates.



PAE has made
all of the material accounts, records, geological and other data required for this investigation available to us. In preparing
our forecast of future proved production and income, we have relied upon data furnished by PAE, CNOOC ́s Limited joint venture
partner. RPS considers the factual data used in this report appropriate and sufficient for the purpose of preparing the estimates
of reserves and future net revenues herein.



Estimates
of reserves quantities and their associated reserve class and categories may be revised in the future as additional geoscience
or engineering data become available. Furthermore, estimates of reserves quantities and their associated reserve class and categories
may also be revised due to other factors such as changes in economic conditions, results of future operations, effects of regulation
by governmental agencies or geopolitical or economic risks as previously noted herein.



In summary,
we consider the assumptions, data, methods and analytical procedures used in this report appropriate for the purpose hereof, and
we have used all such methods and procedures that we consider necessary and appropriate to prepare the estimates of reserves herein.
The proved reserves included herein were determined in conformance with SEC regulations. In our opinion, the proved reserves presented
in this report comply with the definitions, guidelines and disclosure requirements as required by the SEC regulations.









Future
Production Rates



For wells
currently on production, our forecasts of future production rates are based on historical performance data. If no production decline
trend has been established, future production rates were held constant, or adjusted for the effects of curtailment where appropriate,
until a decline in ability to produce was anticipated, in which case an estimated rate of decline was then applied to depletion
of the reserves. If a decline trend has been established, this trend was used as the basis for estimating future production rates.



Test data
and other related information were used to estimate the anticipated initial production rates for those wells or locations that
are not currently producing. For reserves not yet on production, sales were estimated to commence at an anticipated date furnished
by PAE. Wells or locations that are not currently producing may start producing earlier or later than anticipated in our estimates
due to unforeseen factors causing a change in the timing to initiate production. Such factors may include delays due to weather,
the availability of rigs, the sequence of drilling, completing and/or recompleting wells and/or constraints set by regulatory
bodies.



The future
production rates from wells currently on production or wells or locations that are not currently producing may be more or less
than estimated because of changes including, but not limited to, reservoir performance, operating conditions related to surface
facilities, compression and artificial lift, pipeline capacity and/or operating conditions, producing market demand and/or allowable
or other constraints set by regulatory bodies.



Hydrocarbon
Prices



The hydrocarbon
prices used herein are based on SEC price parameters using the average prices during the 12-month period prior to the ending date
of the period covered in this report, determined as the unweighted arithmetic averages of the prices in effect on the first-day-of-the-month
for each month within such period, unless prices were defined by regulatory and contractual arrangements. For hydrocarbon products
sold under contract, the contract prices, including fixed and determinable escalations, exclusive of inflation adjustments, were
used until expiration of the contract. Upon contract expiration, the prices were adjusted to the 12-month unweighted arithmetic
average as previously described.



The product
prices that were actually used to determine the future gross revenue for each property reflect adjustments to the benchmark prices
for gravity, quality, local conditions, gathering and transportation fees and/or distance from market, referred to herein as “differentials.”
The differentials used in the preparation of this report were furnished by PAE and reviewed by RPS for their reasonableness.



Costs



Operating
costs for the leases and wells in this report are based on the operating expense reports of PAE and include only those costs directly
applicable to the leases or wells. The operating costs include a portion of general and administrative costs allocated directly
to the leases and wells. The operating costs furnished to us were accepted as factual data and reviewed by us for their reasonableness;
however, we have not conducted an independent verification of the operating









cost data
used by PAE. No deduction was made for loan repayments, interest expenses or exploration and development prepayments that were
not charged directly to the leases or wells. Development costs were furnished to us by PAE and are based on authorizations for
expenditure for the proposed work or actual costs for similar projects. The development costs furnished to us were accepted as
factual data and reviewed by us for their reasonableness; however, we have not conducted an independent verification of these
costs. The estimates of the net abandonment costs furnished by PAE were accepted without independent verification. Current costs
used by PAE were held constant throughout the life of the properties.



Standards
of Independence and Professional Qualification



RPS is a
multi-disciplinary consultancy, providing technical, commercial and project management support services in the fields of operations,
geoscience, engineering and health, safety and environment to the energy sector worldwide. RPS’s clients around the world
include governments, national oil companies, integrated majors, independents, and start-ups, legal and financial institutions.



RPS USA is
part of the larger UK based RPS Group plc that employs nearly 5,000 staff based in offices located in the UK, Ireland, the Netherlands,
USA, Canada, Australia and Brazil.



As an independent
and experienced consultancy company with a global capability, RPS is well qualified to provide both technical and economic assessments
of reserves/resources, prospect evaluation, field discoveries and producing fields. In the Oil and Gas Sector, RPS personnel have
provided Competent Persons reports for inclusion in both public and private circulars for funding purposes. We have provided investors
with confidential valuations and assessments during mergers and acquisitions. Asset appraisal and valuation have always been a
core element of RPS consulting business.



As indicated
above, this study was based on data supplied by PAE. The supplied information was reviewed for reasonableness from a technical
perspective. As is common in oil field situations, basic physical measurements taken over time cannot be verified independently
in retrospect. As such, beyond the application of normal professional judgment, such data must be accepted as representative.



The opinions
and interpretations presented in this report represent our best technical interpretation of the data made available to us. However,
due to the uncertainty inherent in the estimation of all sub-surface parameters, we cannot and do not guarantee the accuracy or
correctness of any interpretation and we shall not, except in the case of gross or willful negligence on our part, be liable or
responsible for any loss, cost damages or expenses incurred or sustained by anyone resulting from any interpretation made by any
of our officers, agents or employees.



Except for
the provision of professional services on a fee basis, RPS does not have a commercial arrangement with any other person or company
involved in the interests that are the subject of this report.









RPS personnel
who prepared this report are degreed professionals with the appropriate qualifications and experience to complete the estimate
work. RPS and its staff do not claim expertise in accounting, legal and environmental matters, and opinions on such matters do
not form part of this report.



Terms
of Usage



The results
of our third party study, presented in report form herein, were prepared in accordance with the disclosure requirements set forth
in the SEC regulations and intended for public disclosure as an exhibit in filings made with the SEC by CNOOC Limited.



Very truly
yours,



RPS







/s/ Victor
Wayne Taylor



Victor Wayne
Taylor



PE License#
71417



Principal
Engineer