Effects of Fracture Seepage on the Stability of Landslide during Reservoir Water Level Fluctuation

The hydraulic conductivity function of fractures is a key scientific question to describe and reveal the process and the role of water seepage reasonably. In this paper, the generation technology of random fracture network and the latest numerical computation method for equivalent permeability tensor of fracture network are applied to analyze the landslide located at Wangjiayuanzi in Wanzhou District of Chongqing by simulating the changes of the seepage field caused by the running of the Three Gorges Reservoir. The influences of the fracture seepage on the seepage field and stability of the landslide were discussed with emphasis. The results show that the fractures existing in the soil increase the permeability coefficient of the landslide body and reduce the delay time of the underground water level in the landslide which fluctuates relative to the water level of reservoir，that causes the safe coefficient of the slope changes more gently than that of the same slope without fractures. It means, if only water level fluctuating condition is concerned, the fractures existing in the soil plays a positive role to the stability of slopes.

Study on Water Resources Regulation and Reservoir Operating Prediction for Suppression of Salt Water Intrusion in the Pearl River Estuary

Salt water intrusion occurred frequently during dry season in Modaomen waterway of the Pearl River Estuary. With the development of region's economy and urbanization, the salt tides affect the region's water supply more and more seriously in recent years. Regulation and allocation of freshwater resources of the upper rivers of the estuary to suppress the salt tides is becoming important measures for ensuring the water supply security of the region in dry season. The observation data analysis showed that the flow value at the Wuzhou hydrometric station on the upper Xijiang river had a good correlation with the salinity in Modaomen estuary. Thus the flow rate of Wuzhou has been used as a control variable for suppression of salt tides in Modaomen estuary. However, the runoff at Wuzhou mainly comes from the discharge of Longtan reservoir on the upper reaches of Xijiang river and the runoff in the interval open valley between Longtan and Wuzhou sections. As the long distance and many tributaries as well as the large non-controlled watershed between this two sections, the reservoir water scheduling has a need for reasonable considering of interaction between the reservoir regulating discharge and the runoff process of the interval open watershed while the deployment of suppression flow at Wuzhou requires longer lasting time and high precision for the salt tide cycles. For this purpose, this study established a runoff model for Longtan - Wuzhou interval drainage area and by model calculations and observation data analysis, helped to understand the response patterns of the flow rate at Wuzhou to the water discharge of Longtan under the interval water basin runoff participating conditions. On this basis, further discussions were taken on prediction methods of Longtan reservoir discharge scheduling scheme for saline intrusion suppression and provided scientific and typical implementation programs for effective suppression flow process at the Wuzhou section.

Application Of (CS)-C-137 fingerprinting technique to interpreting sediment production records from reservoir deposits in a small catchment of the Hilly Loess Plateau；China

IEECAS SKLLQG

Identifying paleoflood deposits archived in Zhongba Site, the Three Gorges reservoir region of the Yangtze River, China

IEECAS SKLLQG

Petroleum System in Deepwater Basins of the Northern South China Sea

The northern South China Sea margin has experienced a rifting stage and a post-rifting stage during the Cenozoic. In the rifting stage, the margin received lacustrine and shallow marine facies sediments. In the post-rifting thermal subsidence, the margin accumulated shallow marine facies and hemipelagic deposits, and the deepwater basins formed. Petroleum systems of deepwater setting have been imaged from seismic data and drill wells. Two kinds of source rocks including Paleogene lacustrine black shale and Oligocene-Early Miocene mudstone were developed in the deepwater basin of the South China Sea. The deepwater reservoirs are characterized by the deep sea channel rill, mass flow complexes and drowned reef carbonate platform. Profitable capping rocks on the top are mudstones with huge thickness in the post-rifting stage. Meanwhile, the faults developed during the rifting stage provide a migration path favourable for the formation of reservoirs. The analysis of seismic and drilling data suggests that the joint structural and stratigraphic traps could form giant hydrocarbon fields and hydrocarbon reservoirs including syn-rifting graben subaqueous delta, deepwater submarine fan sandstone and reef carbonate reservoirs.

Seismic characteristics of a reef carbonate reservoir and implications for hydrocarbon exploration in deepwater of the Qiongdongnan Basin, northern South China Sea

Our analysis of approximately 40,000 km of multichannel 2-D seismic data, reef oil-field seismic data, and data from several boreholes led to the identification of two areas of reef carbonate reservoirs in deepwater areas (water depth >= 500 in) of the Qiongdongnan Basin (QDNB), northern South China Sea. High-resolution sequence stratigraphic analysis revealed that the transgressive and highstand system tracts of the mid-Miocene Meishan Formation in the Beijiao and Ledong-Lingshui Depressions developed reef carbonates. The seismic features of the reef carbonates in these two areas include chaotic bedding, intermittent internal reflections, chaotic or blank reflections, mounded reflections, and apparent amplitude anomalies, similar to the seismic characteristics of the LH11-1 reef reservoir in the Dongsha Uplift and Island Reef of the Salawati Basin, Indonesia, which house large oil fields. The impedance values of reefs in the Beijiao and Ledong-Lingshui Depressions are 8000-9000 g/cc x m/s. Impedance sections reveal that the impedance of the LH11-1 reef reservoir in the northern South China Sea is 800010000 g/cc x m/s, whereas that of pure limestone in BD23-1-1 is > 10000 g/cc x m/s. The mid-Miocene paleogeography of the Beijiao Depression was dominated by offshore and neritic environments, with only part of the southern Beijiao uplift emergent at that time. The input of terrigenous sediments was relatively minor in this area, meaning that terrigenous source areas were insignificant in terms of the Beijiao Depression: reef carbonates were probably widely distributed throughout the depression, as with the Ledong-Lingshui Depression. The combined geological and geophysical data indicate that shelf margin atolls were well developed in the Beijiao Depression, as in the Ledong-Lingshui Depression where small-scale patch or pinnacle reefs developed. These reef carbonates are promising reservoirs, representing important targets for deepwater hydrocarbon exploration. (C) 2008 Elsevier Ltd. All rights reserved.

Typhoon effects on DOC dynamics in a phosphate-limited reservoir

To explore typhoon effects on dissolved organic carbon (DOC) dynamics, field investigations (tributary and dam site) and laboratory experiments (bioassay and DOC consumption) were conducted in a subtropical reservoir. A tributary survey indicated that after typhoon disruption, upstream areas were the sources of phosphate (P) but not DOC for the dam site located downstream. Bioassay experiments verified P-limitation on bacteria and phytoplankton during summer stratification, and bacteria showed a faster response than algae to added P. Experiments indicated that DOC consumption was determined by the availability of P. The 4 yr typhoon period (June-September) data of the dam site denoted that DOC concentration (27 to 270 mu M C) and its rate of change (-13 to 24 mu M C d(-1)) varied more dramatically in the weak (2006 and 2007) than in the strong (2004 and 2005) typhoon years. The negative correlation of DOC with the ratio of bacterial production (BP) to primary production (PP) in the euphotic zone (0 to 10 m) signified the interactive effects of auto- and heterotrophic processes on DOC variation. In the aphotic zone, the variation of DOC could be ascribed to the change of BP, which showed a positive correlation with P concentrations. This study documents that DOC concentration in the studied system varied at multiple time scales. Such variation can be explained by the decoupling between BP and PP, which is believed to be a function of the limiting nutrient's availability. More importantly, this study suggests that the P supply introduced by strong typhoons might have substantiated a tighter coupling between BP and PP, so that the amplitude of DOC oscillation during the summer period was effectively reduced.

鄂尔多斯盆地上古生界低渗透砂岩有效储层识别与预测

Sulige Gasfield, with a basically proven reserve as high as one trillion cubic meters, is one giant gas field discovered in China. The major gas -bearing layers are Upper Paleozoic strata with fluvial-lacustrine sedimentary facies. Generally, gas reservoirs in this field are characteristic by "five low" properties, namely low porosity, low permeability, low formation pressure, low productivity and low gas abundance. Reservoirs in this field also feature in a large distribution area, thin single sandbody thickness, poor reservoir physical properties, thin effective reservoir thickness, sharp horizontal and/or vertical changes in reservoir properties as well as poor connectivity between different reservoirs. Although outstanding achievements have been acquired in this field, there are still several problems in the evaluation and development of the reservoirs, such as: the relation between seismic attributes and reservoir property parameters is not exclusive, which yields more than one solution in using seismic attributes to predict reservoir parameters; the wave impedance distribution ranges of sandstone and mudstone are overlapped, means it is impossible to distinguish them through the application of post-stack impedance inversion; studies on seismic petrophysics, reservoir geophysical properties, wave reflection models and AVO features have a poor foundation, makes it difficult to recognize the specific differences between tight sandstone and gas-bearing sandstone and their distribution laws. These are the main reasons causing the low well drilling success rate and poor economic returns, which usually result in ineffective development and utilization of the field. Therefore, it is of great importance to perform studies on identification and prediction of effective reservoirs in low permeable sandstone strata. Taking the 2D and 3D multiwave-multicomponent seismic exploration block in Su6-Su5 area of Sulige field as a study area and He 8 member as target bed, analysis of the target bed sedimentary characteristics and logging data properties are performed, while criteria to identify effective reservoirs are determined. Then, techniques and technologies such as pre-stack seismic information (AVO, elastic impedance, wave-let absorption attenuation) and Gamma inversion, reservoir litological and geophysical properties prediction are used to increase the precision in identifying and predicting effective reservoirs; while P-wave and S-wave impedance, ratio of P/S wave velocities, rock elastic parameters and elastic impedance are used to perform sandstone gas-bearing property identification and gas reservoir thickness prediction. Innovative achievements are summarized as follows: 1. The study of this thesis is the first time that multiwave-multicomponent seismic data are used to identify and predict non-marine classic reservoirs in China. Through the application of multiwave-multicomponents seismic data and integration of both pre-stack and post-stack seismic data, a set of workflows and methods to perform high-precision prediction of effective reservoirs in low permeable sandstone is established systematically. 2. Four key techniques to perform effective reservoir prediction including AVO analysis, pre-stack elastic wave impedance inversion, elastic parameters inversion, and absorption attenuation analysis are developed, utilizing pre-stack seismic data to the utmost and increasing the correct rate for effective reservoir prediction to 83% from the former 67% with routine methods. 3. This thesis summarizes techniques and technologies used in the identification reservoir gas-bearing properties using multiwave-multicomponent seismic data. And for the first time, quantitative analysis on reservoir fluids such as oil, gas, and/or water are carried out, and characteristic lithology prediction techniques through the integration of pre-stack and post-stack seismic prediction techniques, common seismic inversion and rock elastic parameters inversion, as well as P-wave inversion and converted wave inversion is put forward, further increasing the correct rate of effective reservoir prediction in this area to 90%. 4. Ten seismic attribute parameters are selected in the 3D multi-wave area to perform a comprehensive evaluation on effective reservoirs using weighted-factor method. The results show that the first class effective reservoir covers an area of 10.08% of the study area, while the second and the third class reservoirs take 43.8% and 46% respectively, sharply increasing the success rate for appraisal and development wells.

高邮凹陷陈堡及陈堡东地区油气成藏规律研究

With the development of petroleum exploration in Gaoyou Depression, both old and new areas have been the active exploration targets, so the study of petroleum accumulation is significant to the petroleum exploration in the study area and the integrated oil and gas accumulation theory. Based on hydrocarbon accumulation theory and systematical research methods and combined with the structural characteristics of Gaoyou Depression, Chenbao and East of Chenbao were selected as the study areas in this dissertation, oil and gas migration pathways, accumulation periods, as well as accumulation models were studied, and favorable exploration targets were proposed. There develop three sets source rocks, which are Tai-2 Member, Fu-2 Member and Fu-4 Member respectively. Tai-2 Member is the predominant source rock in the eastern part. Fu-2 Member mainly occurs in the northern slope, while Fu-4 Member develops in the deep depression. In the study area, oil mainly comes from Fu-2 Member of Liuwushe subsag. The lower limit of TOC is 0.4%, and active source rock mostly distributed in the south fault-step zone. The source rock in Liuwushe subsag began to generate hydrocarbon in the late of Dainan depositional stage and the threshold was 2300m. The macro and micro characteristics of reservoirs and the reservoir heterogeneity characteristics of the Fu-1 Member were studied systematicly. The results show that Fu-1 Member, which has better reservoir properties, are medium porosity-medium permeability reservoir. The reservoir permeability has good correlation with porosity connectivity. The reservoirs have strong dissolution, pores are mainly thin to medium throat, and throat radii are distributed concentratedly, the sorting is good and pore structures are homogeneous. Sandstone reservoirs whether in the plan view, interlayer or in layers have a certain degree of heterogeneity, in particular, the heterogeneity in layers directly affect and control the oil and gas migration and accumulation. By analyzing the lithology correlation of the fault walls, shale smear, cross section stress, the configuration of fracture active periods and hydrocarbon generation and expulsion periods and fuzzy comprehensive evaluation, the main faults sealing were evaluated. The results show that the faults in Chenbao and East of Chenbao had poor sealing properties in Sanduo period and could be used as the migration pathways at that time. After Sanduo period, the tectonic stress fields in the area changed largely, and, consequently, the fault properties converted from tensional shear to compressive shear, the faults changed progressively from close to open, so the faults sealing became better and were conducive to the preservation of oil and gas reservoirs. According to the seismic event suspension modes and profile configurations above and under the unconformities, combined with tectonic evolutions of the study areas, the unconformity types can be classified into truncation unconformity, overlapped unconformity and parallel unconformity and the distribution characteristics of unconformities in the plan view was also studied. The unconformity structure was divided into basal conglomerate, weathered clay and semi-weathered layer vertically in the study area and this kind of structure make unconformities to be effective oil and gas migration pathways and is significant to hydrocarbon accumulation in a parts of areas. With the analyses of typical oil and gas reservoirs in the study area, combined with the research results of pathway systems, hydrocarbon accumulation models were established and the oil and gas accumulation laws in Chenbao and East of Chenbao analyzed. The oil and gas came from Liuwushe subsag and Liuliushe subsag. The oil and gas from Liuwushe subsag mainly migrated from the structural high parts into the fault-step zone along strata in northeast direction, a part of them migrated upward into the fault-step zone and the Wubao low uplift along Wu-1 Fault in northeast direction. The oil and gas from Liuliushe subsag mainly migrated into the upper reservoirs through Wu-2 fault, and lesser oil and gas migrated into the fault-step zone because of the controls of cross-section orientation, depression center and the hydrocarbon formation tendency. The favorable exploration targets in Chenbao and East of Chenbao have been concluded: the southern fault-step zone is a favorable oil and gas accumulation zone of Liuwushe subsag, and they are fault block reservoirs where fault acted as the barriers, the main target intervals are Fu-1 Member and Fu-3 Member in palaeocene; Oil and gas in the middle and northern fault-step zone mainly laterally migrated from the south areas, and the main target interval is Fu-3 Member in palaeocene; Fu-1 Member and the reserviors above the Wubao subsag are still the focuses in future explorations. The results of this study have important guiding significance for the future oil and gas exploration.

东海陆架盆地复杂天然气藏地震勘探判别技术研究

Exploration study proves that East sea shelf basin embeds abundant hydrocarbon resources. However, the exploration knowledge of this area is very low. Many problems in exploration are encountered here. One of them is that the gas reservoir of this area, with rapid lateral variation, is deeply buried. Correlation of Impendence between sandstone, gas sand and shale is very poor. Another problem is that the S/N ratio of the seismic data is very low and multiples are relatively productive which seriously affect reservoir identification. Resolution of the seismic data reflected from 2500-3000 meter is rather low, which seriously affects the application of hydrocarbon direct identification (HDI) technology. This research established a fine geological & geophysical model based on drilling、well logging、geology&seismic data of East sea Lishui area. A Q value extraction method from seismic data is proposed. With this method, Q value inversion from VSP data and seismic data is performed to determine the subsurface absorption of this area. Then wave propagation and absorption rule are in control. Field acquisition design can be directed. And at the same time, with the optimization of source system, the performance of high resolution seismic acquisition layout system is enhanced. So the firm foundation is ensured for east sea gas reservoir exploration. For solving the multiple and amplitude preserving problems during the seismic data processing, wave equation pre-stack amplitude preservation migration and wave equation feedback iteratively multiple attenuation technologies are developed. Amplitude preservation migration technology can preserve the amplitude of imaging condition and wave-field extrapolation. Multiple removing technology is independent of seismic source wavelet and velocity model, which avoiding the weakness of Delft method. Aiming at the complicated formation condition of the gas reservoir in this area, with dissecting typical hydrocarbon reservoir, a series of pertinent advanced gas reservoir seismic identification technologies such as petrophysical properties analyzing and seismic modeling technology、pre-stack/post-stack joint elastic inversion, attribute extraction technology based on seismic non-stationary signal theory and formation absorption characteristic and so on are studied and developed. Integrated analysis of pre-stack/post-stack seismic data, reservoir information, rock physics and attribute information is performed. And finally, a suit of gas reservoir identification technology is built, according to the geological and geophysical characteristics of this area. With developed innovative technologies, practical application and intergrated interpretation appraisal researches are carried out in Lishui 36-1.The validity of these technologies is tested and verified. Also the hydrocarbon charging possibility and position of those three east sea gas exploration targets are clearly pointed out.

海上时移地震综合解释技术研究与应用

The practical application and development of the time-lapse seismic reservoir monitor technology has indicated which has already become one of most important development technologies in seeking the surplus oil distribution and improving the reservoir recovering. The paper, first obtained the rock physics experiment analysis data according to the Bohai Sea loose sandstone in-situ measure technical, and determined the feasibility research of the S oil-field on the time-lapse seismic reservoir monitoring combining with the time-lapse numeric simulation technology, which was used to analyze the time-lapse seismic respond raw of the reservoir parameters change and pointed out the attentive problems during the real time-lapse seismic processing and interpretation. Next, simply introduced the technical link and the effect of the time-lapse mutual constrained fidelity and match processing aiming at the local complex gathering condition, geological condition, development engineering condition. Third, introduced the time-lapse integrated interpretation and the technical system with the innovative key technology that includes the time-lapse difference explanation technology, the time-lapse seismic multi-attributes integrated interpretation technology, and the time-lapse constrained reservoir parameters inversion technology, and so on. Using the time-lapse difference direct explanation technology, directly obtained the surplus oil macroscopic distribution through the difference seismic data; Using the presenting 8 big principles of the sublayer isochronisms comparison, carried on the time-lapse integrated interpretation analysis on the fine sublayer comparison and the thin oil-layer(group) contrast and the oil layer (group); The paper putted up the research, contrast, applications of the multi-sides sensitive attribute analysis and the RBF nerve network on the nearest study algorithm, and predicted the reservoir parameters and the surplus oil distribution with them; Combining with innovative researches and the time-lapse seismic constrained reservoir parameters inversion technology realized the good combination of the seismic and the reservoir engineering. Fourth, under fully analyzing the geology condition, the reservoir condition, the exploit dynamic data, and the seismic data of the S oil-field, and analyzing the time-lapse difference factors with reservoir dynamic exploit data, calibrated the oil-gas saturation change, the pressure change, the water saturation change, and determined the rationality of the time-lapse seismic difference, and finally obtained the surplus oil distribution, the water flood characteristic understanding, reservoir degasification, and pressure drop raw, and so on, which had been used in the well pattern tightening plan proof of the S oil-field development adjustment plan. Finally, the paper summarized the knowledge and understanding of the marine time-lapse seismic integrated interpretation, also had pointed out the further need researched question.