UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

Form 6-K

REPORT OF FOREIGN PRIVATE ISSUER

PURSUANT TO RULE 13a-16 OR 15d-16

UNDER THE SECURITIES EXCHANGE ACT OF 1934

October 22, 2014

Indicate by check mark whether the registrant files or will file annual reports under cover of Form 20-F or Form 40-F:  x Form 20-F    ¨ Form 40-F

Indicate by check mark if the registrant is submitting the Form 6-K in paper as permitted by Regulation S-T Rule 101(b)(1):  ¨

Indicate by check mark if the registrant is submitting the Form 6-K in paper as permitted by Regulation S-T Rule 101(b)(7):  ¨

Indicate by check mark whether the registrant by furnishing the information contained in this Form is also thereby furnishing the information to the Commission pursuant to Rule 12g3-2(b) under the Securities Exchange Act of 1934:  ¨ Yes    x No

If “Yes” is marked, indicate below the file number assigned to the registrant in connection with Rule 12g3-2(b): n/a

NEWS RELEASE

BHP BILLITON OPERATIONAL REVIEW

FOR THE QUARTER ENDED 30 SEPTEMBER 2014

BHP Billiton Chief Executive Officer, Andrew Mackenzie, said: “Robust operating performance across our diversified portfolio in the September 2014 quarter delivered a nine per cent increase in production² with records achieved for eight operations and four commodities. With production guidance maintained across all operations and businesses, we remain on track to generate Group production² growth of 16 per cent over the two years to the end of the 2015 financial year.

“Our relentless focus on productivity continues to yield strong results. At Western Australia Iron Ore, we have completed our major supply chain investments and, for the first time in a decade, we have no major projects in execution. With our focus now on maximising the value of existing infrastructure, we plan to reduce costs and invest judiciously in very low capital cost debottlenecking initiatives. These plans are expected to increase total supply chain capacity to 290 Mtpa³ by the end of the 2017 financial year and reduce unit costs⁴ by at least 25 per cent to less than US$20 per tonne⁵. When combined with other initiatives across our portfolio we are very well positioned to reduce cash costs⁶ by more than US$2.3 billion and deliver volume-related productivity gains⁶ of at least US$1.2 billion by the end of the 2017 financial year.”

Note: Unless specified otherwise: variance analysis relates to the relative performance of BHP Billiton and/or its operations during the September 2014 quarter compared with the September 2013 quarter; production volumes, sales volumes and capital and exploration expenditure from subsidiaries (which include Escondida, Jimblebar, BHP Billiton Mitsui Coal and our manganese operations) are reported on a 100 per cent basis; production volumes, sales volumes and capital and exploration expenditure from equity accounted investments (which include Antamina, Samarco and Cerrejón) and other operations are reported on a proportionate consolidation basis. Abbreviations referenced in this report are explained on page 11.

Summary

Operational performance

Robust operating performance across our diversified portfolio in the September 2014 quarter delivered a nine per cent increase in production² with records achieved across eight operations and four commodities. Group production² growth of 16 per cent is expected over the two years to the end of the 2015 financial year.

Metallurgical coal production increased by 25 per cent in the September 2014 quarter to 13 Mt as Queensland Coal achieved record production and sales volumes. The new Caval Ridge mine operated at capacity during the period while the Daunia and South Walker Creek mines also produced at a record rate. Total metallurgical coal production is forecast to increase by four per cent in the 2015 financial year to 47 Mt, consistent with prior guidance.

Western Australia Iron Ore (WAIO) achieved record production of 62 Mt (100 per cent basis) as the ramp-up of Jimblebar continued ahead of schedule and we improved the availability, utilisation and rate of our integrated supply chain. WAIO production guidance for the 2015 financial year remains unchanged at 245 Mt (100 per cent basis) while Samarco production is expected to grow by 29 per cent to 28 Mt (100 per cent basis).

Petroleum production increased by seven per cent in the September 2014 quarter to 67.4 MMboe as Onshore US liquids volumes rose by 49 per cent to a record 11.5 MMboe. Guidance for the 2015 financial year remains unchanged at 255 MMboe with strong performance at Onshore US expected to underpin a 16 MMboe increase in total liquids production.

Escondida copper production decreased by three per cent in the September 2014 quarter to 269 kt as strong operating performance was offset by a 12 per cent decline in ore grades, industrial activity and a power outage throughout Northern Chile. The temporary reduction in ore grades was anticipated, ensuring production guidance for Escondida remains unchanged at 1.27 Mt of copper for the 2015 financial year. Total copper production¹ is forecast to increase by five per cent to 1.8 Mt, consistent with prior guidance. A US$361 million increase in the budget of Escondida Organic Growth Project 1 to US$4.2 billion was approved during the period. The project remains on schedule for completion in the first half of the 2015 calendar year.

Energy coal production decreased by nine per cent in the September 2014 quarter to 18 Mt as adverse weather constrained production at both Cerrejón and New South Wales Energy Coal. Total energy coal production of 73 Mt is expected for the 2015 financial year, consistent with prior guidance.

Production guidance for the 2015 financial year is summarised in the table below.

Corporate update

On 16 October 2014, BHP Billiton confirmed that it will pursue a Standard listing on the UK Listing Authority’s Official List and admission to trading on the London Stock Exchange for the new company it plans to create via demerger. This is in addition to the proposed primary listing on the Australian Securities Exchange and secondary inward listing on the Johannesburg Stock Exchange. The Group continues to work towards completion of the demerger in the first half of the 2015 calendar year, subject to receipt of the necessary third party, Board and shareholder approvals.

On 2 September 2014, legislation to repeal the Minerals Resource Rent Tax (MRRT) in Australia received the support of both Houses of Parliament. The MRRT was applicable until 30 September 2014. At 30 June 2014, the Group carried a MRRT deferred tax asset (net of income tax consequences) of US$698 million. An income tax charge approximating this amount is expected to be recognised as an exceptional item in the 2015 financial year and the adjusted effective tax rate guidance⁷ of 30 per cent to 34 per cent for the period remains unchanged.

On 15 August 2014, the Group redeemed all outstanding Petrohawk Energy Corporation 7.25 per cent Senior Notes due August 2018 and 6.25 per cent Senior Notes due June 2019 at the applicable call prices. The aggregate principal value of the notes redeemed was approximately US$1.8 billion.

Petroleum and Potash

Production

Total petroleum production – Total petroleum production increased by seven per cent in the September 2014 quarter to 67.4 MMboe. Guidance for the 2015 financial year remains unchanged at 255 MMboe as strong performance at Onshore US is expected to underpin a 16 MMboe increase in total liquids production. Total conventional volumes for the 2015 financial year are forecast to remain broadly unchanged, consistent with prior guidance.

Crude oil, condensate and natural gas liquids – Crude oil, condensate and natural gas liquids production increased by 19 per cent in the September 2014 quarter to a record 30.9 MMboe.

Onshore US liquids volumes rose by 49 per cent in the September 2014 quarter to a record 11.5 MMboe. This strong performance was underpinned by continued momentum in the Black Hawk and Permian where liquids production increased by 53 per cent and 141 per cent, respectively. We remain confident that shale liquids volumes will rise by approximately 50 per cent in the 2015 financial year.

In our Conventional business, liquids production at Atlantis increased by 38 per cent in the September 2014 quarter as the operation benefited from the completion of two production wells in the June 2014 quarter. At Pyrenees, production increased by 24 per cent in the September 2014 quarter following the completion of five new production wells in the second half of the 2014 financial year.

Natural gas – Natural gas production of 219 bcf was unchanged in the September 2014 quarter.

A two per cent increase in natural gas production from the June 2014 quarter reflected higher seasonal demand at Bass Strait and stronger uptime performance at North West Shelf following a period of planned maintenance. This was partially offset by natural field decline at our Onshore US dry gas assets.

Projects and Onshore US capital expenditure

Onshore US drilling and development expenditure totalled US$895 million in the September 2014 quarter. The Company’s operated rig count increased to 25 during the period, with an additional rig now operating in the Permian. At the end of the period, 17 operated rigs were in action in the Eagle Ford, five were in the Permian and three were in the Haynesville. We expect Onshore US drilling and development expenditure of approximately US$4.0 billion for the 2015 financial year, consistent with prior guidance.

Petroleum exploration

Exploration and appraisal wells drilled during the September 2014 quarter are summarised below.

Petroleum exploration expenditure for the September 2014 quarter was US$154 million, of which US$146 million was expensed. A US$750 million exploration program, largely focused on the Gulf of Mexico, Western Australia and Trinidad and Tobago is planned for the 2015 financial year. The seismic acquisition program in Trinidad and Tobago is progressing on schedule.⁹

Following recent economic reforms in Mexico, BHP Billiton and Petroleos Mexicanos (Pemex) signed a memorandum of understanding and cooperation (MOU) on 25 September 2014 to exchange technical knowledge, information, experiences and practices in activities related to the oil and gas industry.

Potash

Copper

Production

Copper – Total copper production¹ decreased by one per cent in the September 2014 quarter to 389 kt. Guidance for the 2015 financial year remains unchanged at 1.8 Mt.

Escondida copper production decreased by three per cent in the September 2014 quarter to 269 kt as strong operating performance was offset by a 12 per cent decline in ore grades, two days of industrial action and a power outage throughout Northern Chile. As a result of increased throughput, water restrictions are anticipated during the December 2014 quarter which may result in the partial deferral of production to the March 2015 quarter. The Escondida Water Supply project, which involves the construction of a new 2,500 litre per second sea-water desalination facility, will ensure continued water supply over the long term. Production guidance for Escondida remains unchanged at 1.27 Mt of copper for the 2015 financial year.

At Pampa Norte, copper production increased by 28 per cent in the September 2014 quarter to 56 kt, as Spence benefited from higher grades and recoveries. An increase in pad height at Cerro Colorado to optimise longer-term leaching stability and tertiary crusher maintenance at Spence contributed to the weaker performance relative to the June 2014 quarter. Production at Pampa Norte for the 2015 financial year is expected to be broadly unchanged from the prior year, as higher grades and recoveries at Spence offset declining grades and recoveries at Cerro Colorado.

While Olympic Dam copper production increased by 41 per cent in the September 2014 quarter to 39 kt, the completion of planned smelter maintenance led to a 28 per cent decline in production from the June 2014 quarter. Production at Olympic Dam in the 2015 financial year is expected to remain broadly unchanged from the prior year.

Antamina copper production declined by 39 per cent in the September 2014 quarter to 26 kt as the mine plan progressed through a zone of lower grade ore. Average copper grades at Antamina in the 2015 financial year are expected to remain at a similar level to the September 2014 quarter, consistent with the mine plan.

Lead/silver – Lead and silver production¹ increased by seven per cent and five per cent, respectively, in the September 2014 quarter as higher mill throughput more than offset lower average ore grades at Cannington.

Zinc – Total zinc production increased by 42 per cent in the September 2014 quarter and primarily reflected higher grades at Antamina, consistent with the mine plan. Strong performance at Cannington was underpinned by higher grades and increased mill throughput.

Uranium – Uranium production decreased by 11 per cent in the September 2014 quarter as lower mill throughput was only partially offset by higher grades.

Projects

A US$361 million increase in the budget of the Escondida Organic Growth Project 1 to US$4.2 billion was approved during the period and reflected challenges associated with contractor progress which have now been addressed. The project remains on schedule for completion in the first half of the 2015 calendar year.

Iron Ore

Production

Iron ore – Iron ore production increased by 17 per cent in the September 2014 quarter to a record 57 Mt. Total iron ore production is forecast to increase by 11 per cent in the 2015 financial year to 225 Mt, consistent with prior guidance.

Western Australia Iron Ore (WAIO) production increased by 15 per cent in the September 2014 quarter to a record 62 Mt (100 per cent basis) as the ramp-up of Jimblebar continued ahead of schedule and we improved the availability, utilisation and rate of our integrated supply chain. In addition to the strong operational performance achieved at our mines, a higher proportion of direct to ship ore increased outflow capacity at the port and facilitated record sales volumes of 63 Mt (100 per cent basis).

WAIO production guidance for the 2015 financial year remains unchanged at 245 Mt (100 per cent basis) with the tie-in of shiploader 2 expected to be completed during the December 2014 quarter. Further growth in supply chain capacity to 270 Mtpa (100 per cent basis) is expected to be achieved without the need for additional fixed plant investment. Beyond that, the Inner Harbour Debottlenecking and Jimblebar Phase 2 projects³ have the potential to increase total capacity to 290 Mtpa (100 per cent basis) by the end of the 2017 financial year at very low capital cost.

As production grows we will maintain a relentless focus on costs. We expect unit cash costs⁴ of less than US$20 per tonne⁵ in the medium term, a reduction of more than 25 per cent on the average achieved in the 2014 financial year. Sustaining capital expenditure guidance of approximately US$5 per tonne over the next five years reflects the size and quality of our major operating hubs and highly concentrated resource.

Samarco production increased by 12 per cent from the June 2014 quarter to 7 Mt (100 per cent basis). The ramp-up of the fourth pellet plant to 30.5 Mtpa (100 per cent basis) is expected before the end of the 2015 financial year.

Coal

Production

Metallurgical coal – Metallurgical coal production increased by 25 per cent in the September 2014 quarter to a record 13 Mt. Total metallurgical coal production is forecast to increase by four per cent in the 2015 financial year to 47 Mt, consistent with prior guidance.

Record production at Queensland Coal was underpinned by strong operational performance across the business and continued improvement in truck and wash-plant utilisation. The new Caval Ridge mine operated at capacity during the period while the Daunia and South Walker Creek mines also produced at a record rate.

Illawarra Coal production increased by 64 per cent in the September 2014 quarter to 2.3 Mt as a series of productivity initiatives enabled the mine to achieve record run-of-mine production. Volumes in the September 2013 quarter were affected by an extended outage at Dendrobium.

Energy coal – Energy coal production decreased by nine per cent in the September 2014 quarter to 18 Mt. As anticipated, a drought in the La Guajira region of Colombia constrained production volumes at Cerrejón given the need to manage dust emissions. At New South Wales Energy Coal, adverse weather and unplanned wash plant outages resulted in a 12 per cent decline in production during the period. Navajo Coal production also declined following the permanent closure of three of the five power units at the Four Corners Power Plant.

Total energy coal production of 73 Mt is expected for the 2015 financial year, consistent with prior guidance.

Projects

Aluminium, Manganese and Nickel

Production

Alumina – Alumina production was broadly unchanged in the September 2014 quarter at 1.2 Mt, supported by record production at the Alumar refinery. While a series of calciner outages constrained Worsley production during the September 2014 quarter, volumes are expected to recover as the refinery processes stockpiled hydrate in future periods.

Aluminium – Aluminium production decreased by 16 per cent in the September 2014 quarter to 261 kt. Lower volumes primarily reflected the cessation of smelting activities at Bayside in June 2014 and the suspension of capacity at the Alumar smelter during the 2014 financial year. This was partially offset by record production at Mozal during the period.

Manganese ores – Manganese ore production increased by 10 per cent in the September 2014 quarter to a record 2.3 Mt as an improvement in ore recovery at Mamatwan and an increase in plant availability at Wessels resulted in record quarterly production at Hotazel.

Manganese alloys – Manganese alloy production increased by 25 per cent in the September 2014 quarter to 171 kt as smelter reliability improved at both Metalloys and TEMCO.

Nickel – Nickel production declined by 12 per cent in the September 2014 quarter to 36 kt, primarily as a result of the closure of the Perseverance underground mine at Nickel West in November 2013. Consistent with prior guidance, we expect saleable nickel production at Nickel West to decline by four per cent in the 2015 financial year to 95 kt. Ferro-nickel production at Cerro Matoso is expected to decline by three per cent to 43 kt as a result of lower grades and recoveries.

Minerals exploration

Minerals exploration expenditure for the September 2014 quarter was US$79 million, of which US$58 million was expensed. Greenfield minerals exploration is predominantly focused on advancing copper targets within Chile, Peru and the South-West United States.

This report represents the Interim Management Statement for the purposes of the UK Listing Authority’s Disclosure and Transparency Rules. There have been no significant changes in the financial position of the Group in the quarter ended 30 September 2014.

The following abbreviations may have been used throughout this report: barrels (bbl); billion cubic feet (bcf); cost and freight (CFR); cost, insurance and freight (CIF); dry metric tonne unit (dmtu); free on board (FOB); grams per tonne (g/t); kilograms per tonne (kg/t); kilometre (km); metre (m); million barrels of oil equivalent (MMboe); million cubic feet per day (MMcf/d); million tonnes (Mt); million tonnes per annum (Mtpa); ounces (oz); pounds (lb); thousand barrels of oil equivalent (Mboe); thousand ounces (koz); thousand standard cubic feet (Mscf); thousand tonnes (kt); thousand tonnes per annum (ktpa); thousand tonnes per day (ktpd); tonnes (t); and wet metric tonnes (wmt).

Further information on BHP Billiton can be found at: www.bhpbilliton.com.

Members of the BHP Billiton Group which is headquartered in Australia

BHP BILLITON PRODUCTION SUMMARY

Throughout this report figures in italics indicate that this figure has been adjusted since it was previously reported.

BHP BILLITON PRODUCTION

Refer footnotes on page 16.

BHP BILLITON PRODUCTION