Segment Revenue Segment Operating Income Segment Operating Income Margins  (1) Reservoir Description Production Enhancement (1) “Corporate and other” represents those items that are not directly relating to a particular segment. “NM” means not meaningful. (1)  Calculated by dividing “Operating Income” by “Revenue.” Revenue for our Reservoir Description segment increased, by 5.4%, to $522.3 million in 2013 compared to $495.5 million in 2012,  an increase of 5.5% compared to $469.8 million in 2011. This segment’s operations, which focus on international crude-oil related  products, continued to benefit from an increasing number of large-scale core analyses and reservoir fluids characterization studies in  the Asia-Pacific areas, offshore West and East Africa, the eastern Mediterranean region and the Middle East, including Iraq, Kuwait and  the United Arab Emirates. Operating income increased to $146.3 million in 2013 from $144.5 million in 2012 and $116.2 million in 2011. This segment empha- sizes technologically demanding services on internationally-based development and production-related crude oil projects over the  more cyclical exploration-related projects. These increases are a result of higher sales, including a better mix of projects aimed at more  complex reservoirs, over the fixed cost structure. Revenue for our Production Enhancement segment increased by $48.6 million, or 12.0% in 2013 compared to 2012, primarily due to the continued successful introduction of Core’s new FLOWPROFILER $_{ }$™ service and our new completion diagnostic services for opti- mizing completions and stimulations of horizontal wells. Revenue for our Production Enhancement segment increased 8.7% in 2012  compared to 2011 primarily due to demand for our stimulation diagnostic services both for fracture diagnostics in North America and  field flood diagnostics internationally. 22 For the Years Ended December 31, (dollars in thousands) 2013 % Change 2012 % Change 2011 Reservoir Description $ 522,251 5.4% $ 495,529 5.5% $ 469,775  Production Enhancement 452,415 12.0% 403,792 8.7% 371,449  Reservoir Management 98,842 20.9% 81,759 23.1% 66,424 Total Revenue $1,073,508 9.4% $ 981,080 8.1% $ 907,648 For the Years Ended December 31, (dollars in thousands) 2013 % Change 2012 % Change 2011 Reservoir Description $ 146,338 1.3% $ 144,502 24.3% $ 116,244  Production Enhancement 154,715 20.3% 128,602 14.2% 112,576  Reservoir Management 31,555 19.4% 26,428 20.7% 21,887  Corporate and other (1) 811 NM (2,252) NM 47 Operating Income $ 333,419 12.2% $ 297,280 18.6% $ 250,754 For the Years Ended December 31, 2013 Margin 2012 Margin 2011 Margin Reservoir Description 28.0% 29.2% 24.7% Production Enhancement 34.2% 31.8% 30.3% Reservoir Management 31.9% 32.3% 33.0% Total Company 31.1% 30.3% 27.6%