Differences of Hydrocarbon Enrichment between the Upper and the Lower Structural Layers in the Tazhong Paleouplift

The Tazhong paleouplift is divided into the upper and the lower structural layers, bounded by the unconformity surface at the top of the Ordovician carbonate rock. The reservoirs in the two layers from different parts vary in number, type and reserves, but the mechanism was rarely researched before. Therefore, an explanation of the mechanism will promote petroleum exploration in Tazhong paleouplift. After studying the evolution and reservoir distribution of the Tazhong paleouplift, it is concluded that the evolution in late Caledonian, late Hercynian and Himalayan periods resulted in the upper and the lower structural layers. It is also defined that in the upper structural layer, structural and stratigraphic overlap reservoirs are developed at the top and the upper part of the paleouplift, which are dominated by oil reservoirs, while for the lower structural layer, lithological reservoirs are developed in the lower part of the paleouplift, which are dominated by gas reservoirs, and more reserves are discovered in the lower structural layer than the upper. Through a comparative analysis of accumulation conditions of the upper and the lower structural layers, the mechanism of enrichment differences is clearly explained. The reservoir and seal conditions of the lower structural layer are better than those of the upper layer, which is the reason why more reservoirs have been found in the former. The differences in the carrier system types, trap types and charging periods between the upper and the lower structural layers lead to differences in the reservoir types and distribution. An accumulation model is established for the Tazhong paleouplift. For the upper structural layer, the structural reservoirs and the stratigraphic overlap reservoirs are formed at the upper part of the paleouplift, while for the lower structural layer, the weathering crust reservoirs are formed at the top, the reef-flat reservoirs are formed on the lateral margin, the karst and inside reservoirs are formed in the lower part of the paleouplift.

Study on the Plugging System of the Lower Ancient High Loss Zone in Changqing Gas Field

At present, in the workover operations of old gas wells in the Changqing Gas Field, due to years of exploitation in the production layer, pressure deficits, and general leakage during the well killing, the well must be plugged before the well can be killed. In particular, the fracture-cavity type fractures of the lower paleocarbonate reservoirs have serious leakage. Traditional plugging materials and traditional plugging materials and methods have some limitations in dealing with leakage problems. Therefore, a composite plugging system using polymer solution as the base carrier fluid, multi-particle size rigid particles, expandable particles and modified fibers is developed. Its formula is: water + 2% polyacrylamide + 0.1% N, N-methylene bisacrylamide polymer gel is the base carrier fluid;the formulation of the particle plugging agent was continuously optimized through the CDL-II high temperature and high pressure dynamic and static plugging ability to plug the core. The final formulation of the plugging agent is: 1) 20% rigid particles (5 mm, 1 mm, 0.5 mm CCP-3 ratio 4:2:1) + 1% 3 mm expanded particles SMK-1 + 1% 1 ~ 2 mm fiber SRXW-10;2) 20% rigid particles (3 mm, 0.1 mm, 0.05 mm CCP-3 ratio 3:2:1) + 1% 3 mm expanded particles SMK-1 + 1% 1 ~ 2 mm fiber SRXW-10. The water swelling multiples of the granular plugging agent in salt water are all above 7 times, which meets the requirements of leak-proof plugging operations under high salinity;3% HCl is selected as the gel breaker, and the plugging system has a gel breaking rate of 95%;through the water plugging and profile control experimental system, the sand-filled pipe is used to simulate the plugging effect under high temperature and high pressure, and the plugging system can be sealed for 5 days at a high temperature of 110°C and a high pressure of 20 MPa to achieve a good plugging of the formation. It is expected that the developed plugging system has a good application prospect in future workover operations.

Characteristics of karst groundwater system in the northern basin of Laiyuan Spring area

Guided by the theory of groundwater system, based on the groundwater level data from the northern basin of Laiyuan Spring area, the authors took into account factors such as the lithology, geological structure and topography to study the relationship between groundwater recharge, runoff and drainage in this area. It was concluded that the infiltration of atmospheric precipitation is the main source of groundwater supply in this area; the upper layer of the Spring area is distributed with the Cambrian-Lower Ordovician karst water, and the lower layer is filled with the Jixian system karst water. The upper layer of karst water supplies to the lower layer of karst water or the pore water in loose strata through the fault while the lower layer of karst water runs to the three strong runoff belts from the east and west sides of the watershed, southwards into the basin, partially replenishing the pore water in loose strata, or forming fault Springs(e.g. Nanguan Spring, Beihai Spring) when dolomite movement encounters faults. Replenished by atmospheric precipitation and the upper and lower layers of karst waters, the pore water in loose strata joins the groundwater in the southern basin and then flows eastwards, in the end it flows out of the system in Shangfanpu. Through the analyses of groundwater level data and hydrogeological drilling data, based on groundwater D and ^(18) O isotope test results, the karst groundwater circulation system in the northern basin of Laiyuan Spring area is further verified, which provides hydrogeological basis for water resources development and utilization as well as protection in this area.

Thermo-Flow Performances for the Main-Auxiliary Integrated Natural Draft Dry Cooling System

Recently,natural draft dry cooling system with the main-auxiliary integrated air-cooled heat exchangers in the up and lower layers,has drawn attention to the electric power industry.This research firstly develops two physical models for the integrated cooling system,namely Case A and Case B.In Case A,the main air-cooled heat exchanger is arranged in the upper layer and the auxiliary air-cooled heat exchanger arranged in the lower layer,while in Case B,the two heat exchanger systems are arranged in the opposite way.And then,directing at the engineering TMCR and TRL 1 working conditions,the unit-local-overall thermo-flow characteristics of Case A and Case B are obtained and compared by numerical simulation.The findings show that,for the auxiliary air-cooled exchanger,Case A has obviously higher cooling performances than Case B,with the difference varying from 5.46%to 7.55%.Whereas,for the main air-cooled exchanger,Case B shows the recovered cooling performances,with the difference changing from 1.15%to 2.99%.Case A is preferably recommended to the engineering application in consideration of more strict cooling demand of the auxiliary cooling system.Conclusively,this research will provide some theoretical guidelines for the design and construction of the main-auxiliary integrated natural draft dry cooling system.

Characteristics of the lower layer of sandstorms in the Minqin desert-oasis zone

By measuring the sand-dust flux,vertical deposition,and the wind velocity throughout 19 sandstorms in the Minqin region,we quantitatively analyzed the horizontal distribution and vertical variation in sandstorm characteristics under different land cover conditions.The effect of different land cover on mitigating sandstorms was also investigated.The results indicated that,in the surface layer ranging from 0-50 m,the intensity of sand-dust horizontal flux and concentration of sand-dust decreased with the increase of the height in the desert and the edge of oasis,whereas the two physical quantities increased slightly with the increase of the height in the oasis.The two physical quantities obey power function well under all three cover conditions.Moreover,in the desert and at the edge of oasis,the sand-dust vertical deposition decreased with the increase of the height.But a partial unimodal distribution at the oasis site and the maximum deposition occurred at the height of 9 m,which corresponds to the middle height of farmland protection forest.The annual flux that passed through a section of 1 m in width and 50 m in height was 9169 kg in the desert,5318 kg at the edge of oasis,and 2345 kg in the oasis.And the annual fluxes at the edge of oasis and in the oasis are 42% and 74% less,respectively,than that in the desert.This implies that the wind break forest significantly reduced the intensity of sandstorms.

SEASONAL VARIATION OF LIDAR-DERIVED AEROSOL CONTENT IN THE LOWER LAYERS OF THE ATMOSPHERE

Results of the study of seasonal variation of total column content of aerosols in the 50—1100 m height region are presented,The columnar content of aerosols is computed by integrating the height profiles of nighttime aerosol number density estimated from the Argon ion lidar observations collected at the ⅡTM, Pune for the one year period from October 1986 to September 1987.The results of the study indicated that the aerosol content was higher during winter than during monsoon months by over 78% with an annual mean columnar aerosol content of 1.66×10~8 cm^(-2).The observed seasonal variaticn of aerosol content was found to be associated with that of surface wind,temperature,relative humidity(R.H.)and rainfall data recorded for the above one year period at the station.

Paleogene geological framework and tectonic evolution of the central anticlinal zone in Lufeng 13 sag,Pearl River Mouth Basin

The Paleogene geological framework and evolution process in the central anticline zone in the Lufeng 13 sag in Pearl River Mouth Basin is well analyzed through seismic data and drilling data,and control of tectonic evolution on hydrocarbon accumulation is also discussed.The results show that the central anticline zone in the Lufeng 13 sag develops the upper deformation layer and lower deformation layer.The“arched graben system”is developed in the upper deformation layer,and the magmatic diapir structure and flowing deformation of plastic strata is developed in the lower deformation layer.The evolution process of the central anticline zone can be divided into four stages,i.e.fault block uplifting stage,prototype stage,strengthening stage and finalization stage.The geological framework and tectonic evolution of the central anticline zone control Paleogene hydrocarbon accumulation.The Paleogene twolayer geological framework is favorable for development of structural traps and composite traps;the paleostructure highs are the direction of hydrocarbon migration,and the gravitational gliding faults are the main carrier bed for vertical hydrocarbon migration;the tectonic uplift is a key factor for reservoir diagenesis improvement and preservation of primary pores,and also controls distribution of high-quality reservoirs.