The picture from the Q1 reporting season is emerging. While the growth rate for revenues quarter over quarter has dipped into the red, the year over year comparison shows continued growth in the oilfield service industry.
In Q1 2018, the blended quarterly growth in revenue for service companies exposed to upstream oil and gas activities was down 3% quarter over quarter (QoQ), representing the first negative QoQ growth rate since Q1 2017. The first quarter is known to be slow for oilfield service companies, and we see improving market conditions despite the QoQ decline. Adjusted for seasonality, we see an aggregated revenue increase of 10% year over year (YoY). The PHLX Oil Service Index (OSX, modified market weighted index composed of companies involved in the oil services sector) is up 11.83% (as of publication) since the last year following the recovery in oil prices worldwide. Year to date, the OSX index is up 0.5%.
By breaking down the aggregated numbers for more than 220 companies that have reported first quarter 2018 figures into service segments, we see that all segments deliver negative QoQ growth. However, adjusting for seasonality, all service segments except EPCI, Subsea and Drilling Contractors deliver positive growth YoY. Well Services and Commodities are the service segment with the highest growth YoY, followed by Maintenance and Operations, and Seismic.
Well Services revenue grew 26% YoY, mainly driven by service companies delivering drilling and completion services to North America shale players. In North America alone, Well Services and Commodities revenue grew 46% YoY. Furthermore, Halliburton, Schlumberger and Baker-Hughes (BHGE) are among the service companies with the highest contribution to the blended growth rate of 26% YoY. In Q1 2018, we saw a 5% increase in US land rigs compared to the trailing quarter. During BHGE's earnings call CFO Brian Worrell pointed out that the completed well count in the US slumped compared to the fourth quarter due to industry-wide supply chain challenges, leading to an increase in drilled uncompleted wells. The supply chain challenges were also discussed by Halliburton's CEO, Jeff Miller, during the company's first earnings call in 2018. He pointed out that Halliburton experienced significant challenges in North America related to rail disruptions. Both companies are optimistic in their projections for the full year and confident in their ability to navigate the supply change obstacles experienced in the first quarter. For the full year, Halliburton expects to see growth in both revenue and margins in North America. BHGE expects to see an increase in completion activity in North America for the second quarter given good oil price fundamentals.
Maintenance and Operations revenue grew 9% YoY, mainly driven by increased activity in Asia, the Middle East and Europe. Seismic revenue grew 4% YoY, mainly driven by increased activity in Asia, North America and Europe. Within the seismic segment, PGS, Spectrum and TGS Nopec are among the service companies with the highest contribution to the blended growth rate of 4% YoY.
If we break down the numbers geographically, we see that all continents show a QoQ decline but a YoY increase. North America comes in at the top with a 27% growth followed by the Middle East and Africa, and Asia/Pacific with growth rates of 6% and 3%, respectively. Revenues grew YoY for service companies exposed to service segments such as Maintenance and Operations, EPCI and Well Services and Commodities in the Middle East and Africa, whereas revenues declined for service companies exposed to Subsea- and Seismic services and drilling. In Asia/Pacific, Maintenance and Operations, Well Services and Commodities and Seismic grew by 3% (blended growth rate), while EPCI, Subsea services and drilling declined.
In summary, the oilfield service industry continues to show a positive trajectory despite a negative though unsurprising decline this quarter. As a result of strong oil market fundamentals, we estimate shale investment to grow at around 20% rate in 2018 and we now foresee 100 offshore FIDs in 2018. We expect that the improved market fundamentals will translate into better performance for oilfield service players in the coming quarters. In 2018, we expect the oilfield service market to grow by 3.8% compared to 2017. For the full year, Well Services and Commodities is expected to grow 12%. Seismic- and drilling services is expected to grow around 7%. Maintenance and Operations and Subsea are expected to grow 2.5% and 2%, respectively. EPCI is expected to decline around 10% YoY.