Seasonal changes in weight and body composition of yak grazing on alpine-meadow grassland in the Qinghai-Tibetan plateau of China

Forty-five male yaks (born April 2001) were studied to determine how seasonal changes on the Qinghai-Tibetan plateau affected BW and body composition. Thirty yaks were weighed monthly from birth to 26 mo of age to determine seasonal changes in BW. The remaining 15 yaks were allocated randomly to five groups (three yaks per group), designated for slaughter at 13, 15, 18, 22, and 25 mo to measure seasonal effects on body chemical composition. All yaks were grazed on the alpine-meadow grassland of the plateau without any supplementation. All BW and body composition data were calculated on an individual basis. Body weight and body composition data were both compared across seven growth periods spanning 2 yr and defined by season. From April (birth) to December 2001 of the first growing season, yak BW increased (P < 0.01); however, during the subsequent cold season (December 2001 to May 2002), BW decreased (P < 0.01). The second growing season ran from May 2002 (13 mo of age) to October 2002 (18 mo of age), and the second live weight-loss season ran from October 2002 until May 2003. The weight loss experienced by yaks during the first weight loss season was 25.64% of the total weight gain in the first growing season. The weight loss experienced by yaks during the second weight-loss season was 29.73% of the total weight gain in the second growing season. Energy retention in the second growing season was 291.07 MJ, 50.8% of which was consumed during the subsequent cold season. Energy accumulation in the summer (from May to July) and fall (from July to October) of the second growing season did not differ (5.01 and 6.30 MJ/kg of EBW gain, respectively; P = 0.63). The energy mobilized during the second winter (from October 2002 to February 2003) was 16.49 MJ/kg of EBW, and in the second spring (from February to May 2003), it was 9.06 MJ/kg of EBW. These data suggest that the decrease in grazing yak BW during the first cold season is much less than during the second cold season, and that the energy content per unit of BW mobilized is greater (P = 0.02) in winter than in spring. Results from this study demonstrate highly efficient compensatory growth in grazing yaks following the first weight loss period during the first cold season. This benefit could be exploited by herders to improve yak production. Yaks may have developed a type of self-protection mechanism to overcome the long cold seasons in the Qinghai-Tibetan plateau.

鄂尔多斯盆地陇东地区长8段砂岩输导体定量表征研究

Migration carriers act as the “Bridges” connecting source rock and traps and play important roles in petroleum migration and accumulation system. Among various types of carriers, sandstone carrier constitutes the basis of carrier system consisting of connected sandstone bodies, of sand-bodies connected with other carriers, such as faults and/or unconformities. How do we understand sandstone carrier beyond the traditional reservoirs concept? How could we characterize quantitatively this kind of carriers for petroleum migration? Such subjects are important and difficult contents in dynamic studies on hydrocarbon migration and accumulation. Sandstone carrier of Chang 8 member in Longdong area of Ordos Basin is selected as the research target in this thesis. Through conducting integrated reservoir analysis on many single wells, the correlation between single sandstone thickness and oil thickness seems good. Sketch sandstone is defined in this thesis as the principal part of carrier based on systematical analysis on lithology and sandstone thickness. Geometry connectivity of sandstone bodies was identified by the spatial superposition among them and was proved by the oil property features in oilfields. The connectivity between sandstone carriers is also hydrodynamically studied by observing and analyzed various diagenetic phenomena, especially the authigenic minerals and their forming sequence. The results were used to characterize transporting capability of sandstone carriers during the key petroleum migration periods. It was found that compaction and cementation are main causes to reduce pore space, and resolution may but not so importantly increases pore space after the occurrence of first migration. The cements of ferrocalcite and kiesel seem like the efficient index to demonstrate the hydraulic connection among sandy bodies. Diagenetic sequence and its relationship with petroleum migration phases are analyzed. Sandstone carrier of Chang 8 member was then characterized by studying their pore space and permeable properties. The results show an average porosity and permeability of Chang 8 carriers are respectively 8% and 0.50md, belongs to low porosity - low permeability reservoirs. Further, the physical properties of Chang 81 member are commonly better than those of Chang 82 member. Methods to reconstruct property of sandstone carrier during petroleum migration phase (late Jurassic) are built based on diagenetic sequence. Planal porosity, porosity and permeability of sandstone carrier in this period are statistically analyzed. One combining index - product of thickness and ancient porosity - is selected as the idea parameter to characterize sandstone carrier of late Jurassic after contrast with other parameters. Reservoirs of Chang 8 member in Longdong area are lithological reservoir controlled by sand body in which oil layers in middle part are clamped with dry layers in upper and lower parts, in a sandwich way. Based a newly proposed “migration-diagensis-remigration” model in low permeability sandstone of Chang 8 member in Longdong area, oil migration and accumulation processes during different periods are simulated with the reconstructed sandstone carriers system. Results match well with current reservoir distributions. Finally, suggestions for next favorable exploration areas are given based on all research achievements.

济阳坳陷陡坡带砂砾岩体发育特征及油气成藏规律研究

Jiyang depression is one of the most important petroleum production basins in China. The petroleum pools, found easier, have been densely explored and developed. At present, the subtle traps are becoming the main exploring aims. A lot of Tertiary sand-conglomerate body petroleum pools, as one of the important subtle pools, have been discovered recently. It is necessary and urgent to study deeply the developing characteristics and petroleum pool distribution of Tertiary sand-conglomerate bodies in Jiyang Depression. The present dissertation has concluded the main developing characteristics of the Tertiary sand-conglomerate bodies in Jiyang Depression, and studied the sand-conglomerate bodies in Chengnan Fault Zone in detail. Depending on the synthesized studies of geology, geophysics and logging data, the following conclusions have been arrived at. Four criterion layers in Member 3 of Shahejie Formation, according to the depositional cycle analyses, have been established for the subdivision of different layers of sand-conglomerate bodies and the correlation of different sand-conglomerate bodies. It indicated that the alluvial delta, delta-fan, alluvial fan, shallow water fan , deep water turbidite , fan-front turbidite are the six kinds of sand-conglomerate bodies, which have been distinguished in Jiyang Depression with the study of genetic types, characteristics and distribution of sand-conglomerate bodies. The shallow water fan, steep slope deep water turbidite and fan-front turbidite were the main types of sand-conglomerate bodies developed in Chengnan steep slope. Their identification and distribution have been described in detail. The development and distribution of sand-conglomerate bodies were resulted by fault depressing, palco-climate change and channel or trough on the uplift. The fault depressing is the most important-factor to the episodic developing of sand-conglomerate bodies. An episodic developing genetic mode has been established by the contrast analyses between episodic fault depressing and climate change cycles. The hydrocarbon accumulation in the sand-conglomerate bodies in the steep slope was correlated with fan types, depositional phases, fault depressing and diagenesis. Sand-conglomerate wedge out (include up-oblique and onlap), lithological wedge out, mud screen (for anticline), fault plugging (by mud opposite sand, mud daubing) are the 5 possible mechanisms of oil accumulation. Lithological pool, stratigraphic pool and tectonic pool and lithologic-tectonic complex pool, and 9 subtypes of petroleum pools have been detected. It is easy for different pools to be combined as a complex reservoir, which was distributed along the syn-depositional fault slopes. The sand-conglomerate bodies in deep sag were usually evaluated as pore zone for hydrocarbon accumulation before. In fact, they are potential. Because of fan-front turbidite sands were especially developed in these zones, the sands have a close connection with the oil mud, and lithological pools can be expected to find in these zones. Chengnan fault slope was main channel of oil migration, and mud screen is the principle key for the oil accumulation in the sand-conglomerate bodies. If there was no mud between the sand-conglomerate bodies or on the top of sand-conglomerate bodies, the sand-conglomerate bodies would connect each other and there would be no dense material to hold up the oil migration along the slope. As the sand-conglomerate bodies could not been taken as a screen, the mud screen is the key for developing pool in this slope. According to this principle, about 6 potential traps, such as C915 block, C913 block, C916 block, south of Y109 well block, Y104 block and Y153 block, were selected for exploration and development.

克拉2异常高压气藏地质特征及开发技术研究

Kela-2 gas field in Tarim Basin is the main supply source for West-to-East Pipeline project, also the largest abnormally-pressured gas field discovered in China currently. The geological characterization, fine geological modeling and field development plan are all the world-class difficult problems. This work includes an integrated geological and gas reservoir engineering study using advanced technology and approaches, the scientific development plan of Kela-2 gas field as well as the optimizations of the drilling, production and surface schemes. Then, it's expected that the Kela-2 gas field can be developed high-efficiently.Kuche depression is one part of the thrust belt of the South Tianshan Mountains, Kela-2 field is located at the Kelasu structural zone in the north of Kuche depression. The field territory is heavily rugged with deeply cut gullies, complex geological underground structure, variable rock types, thrust structure development. Therefore, considerable efforts have been made to develop an integrated technique to acquire, process and interpret the seismic data in complicated mountain region. Consequently a set of seismic-related techniques in the complicated mountain region has been developed and successfully utilized to interpret the structure of Kela-2 gas field.The main reservoir depositional system of Kela 2 gas field is a platform - fan delta - braided river system. The reservoir rocks are medium-fine and extremely fine grained sandstones with high structure maturity and low composition maturity. The pore system structure is featured by medium-small pore, medium-fine throat and medium-low assortment. The reservoir of Kela-2 gas field is characteristic of medium porosity and medium permeability. The pay zone is very thick and its lateral distribution is stable with a good connection of sand body. The overpressure is caused mainly by the strongly tectonic squash activities, and other factors including the later rapid raise and compartment of the high-pressure fluid, the injection of high-pressure fluid into the reservoir.Based on the deliverability tests available, the average binomial deliverability equation is provided applicable for the overall field. The experimental results of rock stress-sensitive tests are employed to analyze the change trend of petrophysical properties against net confining stress, and establish the stress-based average deliverability equation. The results demonstrate the effect of rock deformation on the deliverability is limited to less than 5% in the early period of Kela-2 gas field, indicating the insignificant effect on deliverability of rock deformation.In terms of the well pattern comparisons and development planning optimizations, it is recommended that the producers should be located almost linearly along the structural axis. A total of 9 producers have a stable gas supply volume of 10.76 BCMPY for 17 years. For Kela-2 gas field the total construction investment is estimated at ￥7,697,690,000 RMB with the internal earning rate of 25.02% after taxation, the net present value of ￥7,420,160,000 RMB and the payback period of 5.66 years. The high profits of this field development project are much satisfactory.