Tectonic Deformation Characteristics And Structural Stress Simulation In Meso-Cenozoic Era In Northern Qaidam

The northern fringe of Qaidam Basin(abbr. northern Qaidam ) is one of the three principal oil-gas bearing provinces in Qaidam Basin. However, due to the complicated geological structure and poor quality of seismic materials, as well as high elevation and bad natural environment, there exist large divergence with the geological structure in this region, and the rule of hydrocarbon generation, migration and accumulation is not well understood, which make the proven reserves unbalanced with its resource potential. Therefore, the thesis starts from the tectonic deformation characteristics and structural stress measurement in Meso-Cenozoic era in northern Qaidam, and analyzes the stress field character of this region by means of simulation, and further discusses the relationship between the stress field and the exploration and development of the oil-gas bearing provinces.In contrast with other basins, the ground structural features in the mid-west region of Qaidam Basin are well developed. The thesis discusses the developing characters of the fault and fold in the region, and makes an emphasis on the northern Qaidam fault zone by field investigations and dating techniques. Moreover, based on the analysis of tectonic characteristics in mid-west region, the author introduces the tectonic style and neotectonic development characters, and further discusses the relationship between tectonic characters and the oil-gas.With regard to the tectonic stress study, making use of many methods, such as magnetic fabric, acoustic emission and hydraulic fracture, and combining with focal mechanism solution, GPS data and tectonic analysis, the thesis discusses the Meso-Cenozoic stress field characteristics in this region. Based on the stress measurement data and geological materials, the geological structure models are set up for T2 and T4 seismic reflection layers of the mid-west region of Qaidam Basin. Photoelastic simulation and plastic-elastic numerical simulation were carried out in terms of those two models. The results comparison between photoelastic and numerical simulations indicate that those two methods have certain comparability, and consequently prove that numerical simulation is appropriate to tectonic stress field analysis. However, because the numerical model takes the material influence into account, the later results in difference to some extent of those two models in details.In order to further understand the stress distribution conditions in northern Qaidam Basin, the three-dimensional stress simulation is carried out in Kunteyi depression where the tectonics is relatively simple. The simulation results indicate that the spacial distribution characteristics of each reflection layer and the fault strike make relatively remarkable emphasis on the stress. In the research area, the vertical stress resulting from the gravity becomes the maximal principal stress in the section more than 4600 meters in depth scope, while in the section less than 4600 meters in depth scope, the maximal principal stress is horizontal and takes place interchange with the minimal principal stress in the direction. In the depth scope ranging from 400 meters to 700 meters, the direction of the minimal principal stress is vertical. In the depth scope ranging from 1100 meters to 3500 meters, the direction of the middle principal stress becomes vertical.The simulation result, from the modelling of the Kun 2# drill and its vicinities, suggests that the vertical stress variation is relatively small in the place 3 to 7 times of the drill diameter from the well wall, but the horizontal stress varies in some trend. Moreover, the direction of the minimal stress component and the remote loading pressure take place large deviation in southeast direction. Lastly, utilizing the simulation result, the author tries to analyze the distributional characteristics of fluid potential, fracture development, sealing of Kun 1# fault and the drill wall stability of Kun 2# well. The analysis result shows that Kun 2# well and its vicinities is the beneficial oil-gas bearing province in Kunyite depression, and the sealing of Kun 1# fault zone is well, and the well wall in Kun 2# well region is relatively stable.