Research On 3-D Simulation Of Tectonic Stress Field Based On Corner-point Grid Data Model

Tectonic stress plays an important role in process of structure,migration and accumulation of oil gas,and formation of petroleum reservoir. Some research results and practice shows that the development and evolution of tectonic stress field not only control the formation of OGB and the formation and distribution of tectonic in basins,but also affect the development of birth,store,cap rock and the generation, migration, accumulation process of oil-gas. It is mainly for two aspects. On the one hand, tectonic stress provide energy for generation,migration and accumulation of oil-gas; On the other hand, tectonic stress is the main motivation of driving oil and gas migration,it is also the important factors of the formation of abnormal pressure, which can affect the flowing state and rate of oil-gas in rocks, etc; In different evolutionary stages, geological events happened are changed with tectonic stress field. These geological events are mutual connection and reciprocal causation,that are very important with the variation of hydrocarbon migration, fluid potential and abnormal pressure. So it is need to do tectonic stress field simulation with different geological periods.At present, research on stress field is mainly based on planar 2-D. With the development of 3-D simulation of hydrocarbon accumulation process,3-D numerical simulation of tectonic stress field is becoming more and more important. This article analyzes from space of 3-D, based on corner-point grid data model that is constitute of irregular hexahedron units, analyzes and studies 3-D finite element method based on elastic mechanics,and it was applied to the numerical simulation of 3-D tectonic stress field. Finite element method is analysed and researched and calculation methods have been put forward. From the innovative speaking, existing 3-D stress field numerical simulations are realized mostly based on existing stress simulation software,and they are not be the real 3-D,that all are combined with surface model. This article realized 3-D numerical simulation coding based on the corner-point grid data model,which is real 3-D volume model.This function can draw a full 3-D space stress field through the simulation,that includes all information of the magnitude and direction of the principal stress in horizontal and vertical direction.Corner-point grid model has the unique advantage of the characteristics of the data model is stand-alone to some extent, that can occur broken and plain between adjacent cells. Z coordinates of each node will store up to eight times, the eight values can reflect the connection between adjacent cells, such as fault exists or closely linked. So it can reflect the geological structure of the study area, including the faults and cracks. It is more in line with geological conditions. This ensures that the simulation results can reflected the actual situation more accurately. Generally, the 2-D simulation of tectonic stress field ignored the vertical stress and the strain analysis, without considering the interaction between stratums. However, These factors are fully taken into account in this article with the realization of 3-D numerical simulation of tectonic stress field. More comprehensive information on the stress field are obtained to ensure the integrity and usefulness of the simulation results.Finally, the features of the numerical simulations of tectonic stress field are programmed based on the above principles and algorithms, including 2-D and 3-D. And they are applied to the Niuzhuang-Wangjiagang area of the Dongying Depression. The 3-D numerical simulation of tectonic stress field is applied to this area, including the corner grid model, the simulation and the storage of the results and the display and the analysis of the tectonic stress field. The Niuzhuang sag is the secondary sag in the southern part of the Dongying depression. The analyses of the simulation results tell us that the simulated stress field is consistent with the actual deformation of the Niuzhuang sag. Therefore it proves that the method and model can be well applied to the field of the simulation of oil and gas accumulation for the three-dimensional tectonic stress field.