Let me start by saying I'm pleased with our achievements in 2021 as our $200 million -- $211 million of adjusted EBITDA slightly exceeded the top end of the adjusted EBITDA guidance range provided at the beginning of the year, exceeding the guidance midpoint by 14%.
We delivered robust free cash flow in 2021, which supported our ability to repurchase $100 million of our 2024 senior notes and increased our cash position by $86 million during the year to $538 million on December 31, 2021.
Today, I'll focus my comments on our performance for the fourth quarter and full year of 2021, our market outlook for 2022, Oceaneering's consolidated 2022 outlook, including our expectation to generate positive free cash flow of between $75 million and $125 million, and EBITDA in the range of $225 million to $275 million, and our segment outlook for the first quarter and full year of 2022.
For the fourth quarter of 2021, our consolidated adjusted earnings before interest, taxes, depreciation, and amortization or adjusted EBITDA was $46.7 million.
Fourth quarter 2021 consolidated adjusted operating income of $17 million, was $1.2 million higher than in the third quarter on the strength of increased throughput and margins in our manufactured products segment, which more than offset the decline in our ad tech segment and higher unallocated expenses.
We generated $140 million of cash from operating activities.
And after deducting $14.4 million of capital expenditures, our free cash flow was $126 million for the quarter.
We made additional progress with debt reduction during the fourth quarter with $37 million of open market repurchases of our 2024 senior notes, bringing total repurchases to $100 million for the year.
Good operating cash flow, working capital efficiencies, and capital expenditure discipline allowed us to increase our cash position by $90.4 million during the fourth quarter of 2021.
As of December 31, 2021, our cash balance stood at $538 million.
As a result, we recorded a net loss of $30 million in connection with these Evergrande contracts in our fourth-quarter financial results.
In conjunction with these terminations, we reclassified $20 million of contract assets into saleable inventory.
SSR EBITDA margin of 31% during the fourth quarter improved as compared to the 29% achieved during the third quarter of 2021 and was consistent with the average margin achieved during the first nine months of 2021.
The SSR revenue split was 77% from our remotely operated vehicle or ROV business and 23% from our combined tooling and survey businesses compared to the 79-21 split, respectively, in the immediate prior quarter.
Fleet utilization declined to 55% in the fourth quarter 2021 from 63% in the third quarter 2021 and our days on hire decline for both drill support and vessel-based services.
Our fleet use during the quarter was 62% drill support and 38% in vessel-based services, compared to 57% and 43%, respectively, during the third quarter.
Fourth quarter 2021 average ROV revenue per day on hire of $8,162, was 4% higher than in the third quarter of 2021.
Days on hire were 12,747 in the fourth quarter or 12% lower as compared to 14,474 in the third quarter.
We ended the quarter and the year just as we began with a fleet count of 250 ROV systems.
At the end of December, we had ROV contracts on 75 of the 137 floating rigs under contract or 55%, a slight decrease from September 30, 2021, when we had ROV contracts on 77 of the 133 floating rigs under contract or 58%.
Our fourth quarter 2021 revenue of $103 million was 37% higher than in the third quarter of 2021.
Adjusted operating income and adjusted operating income margin of 9% were substantially higher sequentially primarily due to better absorption of fixed costs and a favorable project mix.
Our manufactured products backlog on December 31, 2021, was $318 million, compared to our September 30, 2021, backlog of $334 million.
The backlog decline in the fourth quarter of 2021 reflects a $38 million reduction associated with the Evergrande contract terminations.
Our book-to-bill ratio was 1.1 for the full year of 2021 as compared with the trailing 12-month book-to-bill of 1.0 on September 30, 2021.
Revenue declined 11% due to seasonality in the Gulf of Mexico and the third quarter completion of the Angola riserless light well intervention project.
Fourth quarter 2021 operating income margin of 8% remained consistent with the third quarter 2021 as improved margins from intervention, maintenance, and repair or IMR activity positively offset the fixed cost margin effect of lower revenue.
Operating income margin improved to 10% in the fourth quarter of 2021 from 9% in the third quarter of 2021 as the business continues to benefit from operational improvements implemented since the beginning of 2020.
Our Aerospace and Defense Technologies, or ADTech, fourth quarter 2021 operating income declined from the third quarter of 2021 on a 6% decline and rapid decrease in revenue.
Operating income margin declined as expected to 13% due to changes in project mix.
Fourth quarter 2021 unallocated expenses of $36.7 million, were sequentially higher due to a combination of increased accruals for incentive-based compensation higher-than-expected healthcare costs, and increased information technology costs.
Adjusted operating income in our energy segments improved by $57.3 million and operating income margin improved by 376 basis points over 2020 results to 9%.
Compared to 2020, our 2021 consolidated revenue increased 2% to $1.9 billion with revenue increases in our SSR, OPG, IMDS, and ADTech segments being partially offset by a decline in our manufactured products revenue.
Consolidated 2021 adjusted operating income and adjusted EBITDA improved by $51.4 million and $26.3 million, respectively, led by our OPG and SSR segments.
Overall, we generated adjusted EBITDA of $211 million, a 14% increase over 2020.
we generated $225 million in cash flow from operations and invested $50.2 million in capital expenditures.
Significant free cash flow of $175 million, allowed us to repurchase $100 million of our 2024 senior notes while also increasing our cash balance by 86% -- $86 million, excuse me, to $538 million.
Our OPG business achieved the most significant improvement of our five operating segments growing revenue by 31% in 2021.
Adjusted operating income improved by almost $37 million and operating income margin improved to 8% as compared to an adjusted operating loss margin of 2% and in 2020.
Our Subsea Robotics business, a recognized leader in world-class ROV services, continue to achieve best-in-class drill support performance with a 99% plus uptime achieved during the year.
We continue to see significant improvement in our IMBS business with adjusted operating income improving by more than $12 million as compared to 2020.
Our AdTech business grew its revenue by 8% while maintaining its operating income margin over 16%, leading to a new record annual operating income and EBITDA performance.
Our total recordable incident rate, or TRIR, of 0.4 for 2021 remained comparable to the record performance achieved in 2020.
Revenue of $1.9 billion was modestly higher than the $1.8 billion achieved in 2020.
Adjusted EBITDA of $211 million exceeded the top end of the guidance range from the beginning of the year and was 14% higher than the $184 million generated in 2020.
Positive free cash flow of $175 million significantly surpassed the $76 million generated in 2020.
We maintained our commitment to capital discipline by reducing capital expenditures for a second year to $50 million as compared to $61 million in 2020.
Cash increased by $86 million to $538 million.
Outstanding debt decreased to $700 million, following $100 million of open market repurchases of our 2024 senior notes.
Net debt-to-adjusted EBITDA ratio decreased from 1.9 on December 31, 2020, to 0.8 on December 31, 2021.
Consolidated adjusted EBITDA margin of 11% improved from the 10% margin achieved in 2020.
Brent pricing of about $70 per barrel, sustained a modest level of offshore project sanctioning and good IMR activity in 2021.
The forecast of nearly $90 per barrel in 2022 and anticipated higher prices in the out years, should support increased levels of E&P, opex, and capex spending in 2022.
There were approximately 200 tree awards in 2021 and Rystad forecasts a 55-plus percent increase in 2022 to around 320 and remaining near 300 into 2023.
Rystad had -- also forecasts 317 tree installations in 2022 to be essentially flat to 2021.
Rystad estimates that offshore wind capex and opex spending will average around $50 billion per year in 2022 and 2023, an 85% increase from the average annual spend between 2016 and 2020.
Rystad also sees continued double-digit growth through the end of the decade with spending projected to increase to $126 billion by 2030.
We are projecting our 2022 consolidated revenue to grow more than 10% with increased revenue in each of our operating segments, led by manufactured products.
For the year, we anticipate generating $225 million to $275 million of EBITDA with increased contributions from each of our segments.
At the midpoint of this range, our EBITDA for 2022 would represent an 18% increase over 2021 adjusted EBITDA.
We anticipate our full year 2022 to yield positive free cash flow of $75 million to $125 million.
For 2022, we forecast our organic capital expenditures to total between $70 million and $90 million.
This includes approximately $40 million to $45 million of maintenance capital expenditures and $30 million to $45 million of growth capital expenditures.
In 2022, interest expense net of interest income is expected to be approximately $38 million, and our cash tax payments are expected to be in the range of $40 million to $45 million.
Survey results are projected to improve on higher survey and positioning activity, and we expect revenue growth in the high single-digit range and EBITDA margins to average in the low 30% range for the full year.
For ROVs, we expect our 2021 service mix of 60% drill support and 40% vessel services to generally remain the same through 2022.
Our overall ROV fleet utilization is expected to be in the mid-60% range for the year with higher seasonal activity during the third -- excuse me, the second and third quarters.
We expect to generally sustain our ROV market share in the 55% to 60% range for drill support services.
At the end of 2021, there were approximately 23 Oceaneering ROVs on board 20 floating drilling rigs with contract terms expiring during the first six months of 2022.
During the same period, we expect 39 of our ROVs on 33 floating rigs to begin new contracts.
For 2022, we anticipate unallocated expenses to average in the mid-$30 million range per quarter as we foresee higher information technology expense and higher cost due to inflation as compared to 2021.
For our first quarter 2022 outlook, sequentially, as previously noted, we forecast our first quarter 2022 EBITDA to be significantly lower on lower revenue.

Summary:
For our first quarter 2022 outlook, sequentially, as previously noted, we forecast our first quarter 2022 EBITDA to be significantly lower on lower revenue.