In 2017, newly-added probable oil reserves reached 160 million tonnes and possible oil reserves 210 million tonnes. As for natural gas, newly-added probable reserves amounted to 251.1 billion m3 and possible reserves 265.6 billion m3. Throughout the year, we produced 35.054 million tonnes of crude oil. Natural gas production was 25.74 billion m3, an increase of 4.148 billion m3, up by 19.2%. Newly-built crude oil production capacity was 2 million tonnes, up by 920 thousand tonnes and newly-built natural gas production capacity was 4.12 billion m3, up by 780 million m3.
We focused on making strategic breakthrough, scaling up new reserves and developing economical reserves. Aiming at “Six Major Enhancements”, we rolled out verification of traps by class and reinforced basic research and standard basic work. The designated fund for risk exploration was set up to encourage 3D seismic and risk exploration, which contributed to 3 important discoveries, 14 new discoveries and 20 commercial discoveries. Success rates for drilling prospecting wells and appraisal wells increased by 9.8 and 10.2 percentage points respectively. Finding cost for probable reserves was 3.8 yuan per tonne lower than planned.
Remarkable achievements include the following. Both of the 2 exploratory wells in Shunbei No. 5 faulted zone of Tarim Basin obtained high oil yield over 100 tonnes/day, which added another 100 million tonnes of probable reserves to Shunbei No. 1 zone and prepared a base for one million tonne/year production; we explored new types and new areas of buried hill reservoir of Jiyang and shallow water area, of which 8 exploratory wells all generated high oil yield and added another 13.5 million tonnes of probable reserves, blazing a new path to increase scaled reserves in mature exploratory zone under the low oil price scenario; new shale gas discoveries were made in the Weirong negative tectonic zone of Sichuan Basin below 3500 meters where all 5 appraisal wells harvested high gas yield with newly-added probable reserves of 120.6 billion m3, ready to be another big scale shale gas capacity building base after Fuling; the appraisal wells deployed for the phase Ⅱ of Fuling shale gas project all had high gas yield with newly-added proven reserves at 220.2 billion m3 and 2 commercially developed zones, Jiangdong and Pingqiao would be in place, due to which total proven reserves of Fuling shale gas filed reached 600.8 billion m3.
In shale gas, we made concrete measures to optimize and implement the capacity building plans for Jiangdong and Pingqiao for Fuling phase Ⅱ and built new production capacity of 3 billion m3. The total production capacity for Fuling shale gas field has reached 10 billion m3. We strengthened precision management for Fuling phase I by optimizing development technology, providing supporting measures like cleaning pipes and reducing transmission pressure, and proceeding with well pattern infilling pilot trials and upper gas layer development appraisal. Annual production reached 6 billion m3, up by 1 billion m3.
In conventional gas,we made great efforts to construct the production capacity of Hangjinqi and Dongpo of west Sichuan. Pilot production appraisal went well. We actively tapped the potential of gas fields in Puguang, Daniudi, Yuanba, Songnan and Yakela. We stepped up dynamic analysis and single well tailor-made management. Dewatering gas production and systematic pressure boosting were used to enhance recovery while controlling water erosion and decline rate to prolong stable production period. Newly-built production capacity for the year was 1.45 billion m3. Total conventional gas production was 19.43 billion m3 with an increase of 3.06 billion m3.
In coal bed methane,we continued with the precision dewatering gas production in the South Yanchuan coal bed methane field, producing 300 million m3, up by 120 million m3.
We grasped the opportunity of the rising oil price and implemented a variety of measures to guarantee profit and keep stable production. We finetuned the production plan, intensified operation management, and enhanced the efficiency of well production and drilling.
For the new capacity,we focused on building profitable production capacity, carried out rolling exploration and reservoir assessment, and accelerated the set-up of commercial development bases. We highlighted the profit-gaining ability and cut development cost. We accentuated the integrated optimization of reservoir, process and engineering as well as the whole-process optimization of design, operation and construction. Capacity building projects in Shunbei, Jiyang and Subei progressed smoothly with new capacity standing at 920 thousand tonnes. New wells produced 1.71 million tonnes, up by 730 thousand tonnes.
For the existing capacity,we endeavored to raise the quality and efficiency of mature fields and enhanced precision reservoir characterization which covered 250 million tonnes of reserves. We applied low cost technologies and reduced energy and resources consumption during oil production. Annual natural decline rate was 10.8% and comprehensive decline rate 6.5%, down by 2.2 and 2.5 percentage points respectively, the best record since 2011. In terms of water-flooding reservoir technology, we upgraded it in integrated pilot zone and leveled up water quality, subdivisional water injection and fine-tuned balance between injection and recovery. Natural decline rate and operating cost both dropped. For Tahe carbonate cavern type reservoir, we unleashed reservoir potential and expanded the scale to utilize water and gas flooding EOR technologies, with the natural decline rate below 16%. For heavy oil reservoir, we well managed the thermal efficiency throughout steam production, transmission and injection. We also optimized the combination of huff and puff, separate layer injection and sealing technologies. Thermal recovery is stabled at over 4.8 million tonnes/year and oil to steam ratio over 0.55. For chemical flooding reservoirs, we had individualized adjustment for each well cluster and paid close attention to the quality of the oil-flooding agent along with the optimization of flooding plugs and parameters, producing another 1.26 million tonnes for the year. Oil flooded by each tonne of polymer was up by 1.1 tonnes.