Oil and gas with high flow rate is produced at Niudong1 well, and this is PetroChina's another great breakthrough in exploration of buried hill in Jizhong Depression of the Bohai Bay Basin, after the discovery of Renqiu buried hill in 1976. Exploration for oil and gas in deeply buried hill of Niudong1 well took 33 years and experienced six exploration stages. Several generations of explorationists kept on striving to make technological breakthrough in geophysical exploration, continuously built and improved geological structure of buried hill, finally confirmed buried hill morphology after processing of the second 3D seismic data acquisition and prestack depth migration, and calibrated Niudong1 well. The deepest high-yield oil and gas reservoir in the Bohai Bay Basin and even East China was discovered then, opening up new dimension in exploration of deeply buried hill in Jizhong Depression. This is of milestone significance to promoting deep exploration of the Bohai Bay Basin.

Many new achievements and new progress in natural gas exploration had been made by PetroChina during the "11th Five-Year Plan" period, the growth of natural gas reserves had entered into a new stage of development, and a group of target areas with large-scale reserves had been found and carried out, forming six main areas of natural gas exploration. Analysis of PetroChina's newdomains of large gas field exploration in the future indicates that the large-area sandstone lithology, marine carbonate rocks, thrust belts of foreland basin, and volcanic gas reservoirs of Ordos, Sichuan, Tarim, Songliao, Qaidam, and Junggar Basins are the main realm to find large gas fields in the future. Biogenic gas and unconventional gas are important realm to find large gas fields in the future

South China has experienced intense reconstruction from multiple structural movements and caused complex Mesozoic-Palaeozoic hydrocarbon evolvement, resulting in the formation of oil and gas reservoirs with diversified origin and complex regular pattern. Based on genetic analysis, the reservoirs could be divided into primary reservoirs, secondary reservoirs, and regenerated reservoirs. There are pore reservoir (oolitic beach and organic reef), fractured reservoir, fracture- pore reservoir and pore-fracture reservoir. All reservoir types were mainly controlled by special sedimentary-diagenetic facies and structures. Effective preserving conditions and good match of key elements for reservoir formation in time and space were very important to the reservoir formation of Mesozoic-Palaeozoic marine facies carbonate rock. This paper pointed out the future exploration orientation, i.e. looking for the secondary porosity reservoir leached by fresh water or the dolomization reservoir created by the mixture of sea water and fresh water and microfracture reservoir, looking for the area with the combination of thick source bed, reservoir strata and capping.

There is a dispute between two options---"Shallow T8" and "Deep T8" for data interpretation of Xiqiu structural belt, Kuqa Depression. Determination of different geological horizons of seismic horizons resulted in the huge difference in interpretation options, trap property and size, and burial depth of highs of subsalt structure. So the oil and gas exploration idea and deployment of Xiqiu structural belt were altered completely. Synthesizing seismic, geological and logging data showed that seismic reflection layers were not the reflection of Cretaceous sandstone and mudstone, but the gypsum mudstone inside the Palaeogene salt bed of Xiqiu structural belt. Therefore, no large subsalt structural traps were likely to exist in the structural belt. Overall deployment should be carried out for oil and gas exploration in subsalt traps, based on the recognition that "the subsalt structure of Xiqiu structural belt is low-amplitude structural trap at the monoclinic belts tilting to the north

BZ28-2S Oilfield is located at central structural ridge of Huanghekou Sag south of Bohai Sea. It is a high quality and middle size scale oilfield with reserves of 4500×104m3 that was found by CNOOC in 2006. Oilfield was produced in 2009 and had an annual production of 180 × 104m3. The main produced oil layer is lower Minghuazhen Formation. The burial depth of oil layers is about 900~1600m. The sourcereservoir- seal assemblage of lower Minghuazhen Formation is good and belongs to shallow water delta. The discovery of BZ28-2S was devious. Exploration about this structure was terminated because the shallow targets of adjacent structure failed in 1980s. BZ28-2S Oilfield was found after 24 years later till the recognitions about the model of migration and accumulation was got during the evaluating of BZ34-1 Oilfield in 2005. These recognitions of fault of migration, transfer station model and high-amplitude in oil which were analyzed before drilling were verified during evaluating of BZ28-2S Oilfield. BZ28-2S Oilfield's discovery process inspired explorers again that new discovery could be got in old exploration field only the new thinking was taken.

The Triassic Lower Oil Formation in Akeyasu of Tahe Oilfield is a nice thick reservoir-cap combination featuring in upper mud and lower sand, where shallow braided river delta and shore-shallow lacustrine sediments developed. The braided channel and mid channel of the delta plain intrafacies and the debouch bar of the front intrafacies constitute the main sand body of the Formation. Practical exploration indicated that thick massive channel sand body and debouch bar were main carriers of underground aquifer, oil and gas was mainly generated from the thin mid-channel sand body on the top and constituted local low-amplitude secondary oil and gas reservoirs characterized by upper oil and lower water. Investigating the cause showed that firstly oil and gas that migrated along the fault mainly accumulated in the channel sand body of Upper and Lower Oil Formations on the top, and the Lower Oil Formation had lower filling degree. Secondly, oil and gas was easily migrated and transported and difficult to be accumulated, due to the development of channel sand bodies of strong connectivity in Lower Oil Formation. Oil and gas could only be accumulated in mid-channel pinchout sand body that developed in low-amplitude structures, in addition, the distance of migration and transportation was so long that only low-amplitude structural-lithologic oil and gas reservoirs developed. Therefore, to determine the distribution range of mid-channel sand body and its superimposition relations to low-amplitude structures, and to make clear the time-space matching relation between channel sand and faults were critical to further exploration in Triassic Lower Oil Formation of Akeyasu

To accurately predict the velocity of a favorable target before drilling has always been a dream pursued by geophysics workers. For the more mature blocks, the velocity could be predicted more accurately, and smaller prediction error could be achieved, using a variety of VSP velocity, and combined with fine velocity processing results. However, there was huger error in predicting results with regards to exploration of offshore exploration wells or new areas. Such errors may arise from no exploration wells or no exploration wells at all, and the misunderstandings and problems existing during the process of velocity prediction. For instance, imaging velocity used for time-depth conversion and pressure prediction to establish velocity body could improve the accuracy of time-depth conversion. Several common problems urgently to be solved were got by analyzing some typical cases in Ying-Qiong Basin, i.e. how to judge the accuracy of re-processing velocity and how to fulfill reprocessing; there existed systematic error between logging rate and velocity spectrum velocity; velocity spectrum data were limited by its own accuracy.

By core observation and data analysis of conventional well logging and electric imaging logging in the oilfields west of South China Sea, it was revealed that low resistivity of oil and gas reservoirs was not only caused by the deep mud invasion and thin oil and gas reservoir, but also by the sedimentary environment. Some effective evaluation methods were summarized. Good exploration results have been obtained in the oilfields in South China Sea, based on laying emphasis on core analysis, integrating regional geology sedimentary and diagenesis study, and selecting appropriate logging methods and series.

Logging evaluation of new overseas oil and gas projects involves all types of reservoirs in exploration and development. Oil and gas reserves are core assets of oil &gas resource investment. The logging technology exerts great effect on reserves evaluation. In reserves calculation, the influence of logging calculation error on reserves could be eliminated, by analyzing the influence of the accuracy of such main parameters as the reservoir porosity, average saturation, and effective thickness needed for reserves calculation on the uncertainty of reserves. Subsequently, the reserves could be evaluated accurately and objectively, fulfilling logging evaluation of new overseas oil and gas projects

Oriente-Maranon Basin has undergone multiple development stages since Late Palaeozoic. Using geotectonic and Palaeogeographic methods, and combined with palaeotectonic stress field analysis, it was thought that the Oriente-Maranon Basin was a superimposed one started to come into being since Late Palaeozoic, including four development stages, i.e. the stage of Late Palaeozoic passive continental margin basin, the stage of Triassic-Jurassic continental fault basin, the stage of Cretaceous marginal sea basin, and the stage of Cenozoic foreland basin

Great Unity Oilfield, one of the main productive ares of Sudan 1/2/4 project, lies on the central uplift belt in Muglad Basin. Structure of Great Unity is a large-scale faulted anticline, with 3 trap patterns developing on it, i.e., anticline, fault-nose and fault-block. The Great Unity structure has large amount of traps with 29 structural traps on top Aradeiba A. Abu Gabra formation source rock and multiple sets of reservoirs including Bentiu, Aradeiba, Zarqa, Ghazal and Baraka, etc, form the multi-oil-water system called "stacked plate pattern" reservoirs which have many oil-bearing formations and long oil-bearing well sections. Most are layered reservoirs. Analysis of key factors of reservoir accumulation indicated that the major faults are the vertical migration pathways of hydrocarbons. Oil and gas accumulated along the major faults. The lateral sealing condition was crucial to form an effective fault-block trap.

Distinctive CBM generation law determines that to generate CBM by adequate desorption needs longer production time. So it is difficult to obtain productivity data in a short time, affecting reserves submission. This paper used practical production data to probe into CBM generation law and discuss the characteristics and suitable conditions of various reserves estimating methods. On this basis, it proposed the application of analogy technology, and conducted analogy analysis from geological background, reservoir control and sufficient data recording, electrical property of coal bed, thickness of coal bed producing CBM, CBM content, reservoir property, and the ratio of critical desorption pressure to coal reservoir pressure, so as to comprehensively verify reserves parameters, recovery ratio, productivity potential, and reserves estimation, and make the results more rational, scientific, and accurate. The analogy technology has been applied well in practice and achieved good results.

This paper analyzed the geothermal resources characteristic of PetroChina, as well as the superiority of developing geothermal resources, summarized three basic types about the geothermal resources in oil regions, and proposed four modes for developing the geothermal resources, i.e. themode for developing conventional geothermal water resources, themode for developing oilfield production water type geothermal resources, the mode for developing shallow geothermal resources, and mode of utilizing mid-low temperature geothermal resource for power generation. According to domestic energy conditions and national policies as well as our own superiority, this paper looked forward PetroChina's prospect for developing geothermal resources. For PetroChina, geothermal resources were rich, and the development & utilization of geothermal resources should rely on oilfields and comprehensive utilization, taking advantage of abandoned wells and oilfield produced water, which could improve working and living environment in oil regions and reduce energy consumption. At the same time, the geothermal resources could be used to generate power in some areas of higher temperature geothermal resources. PetroChina consumed huge energy, owned large space to save energy, and had broad prospect for development and utilization of geothermal resources