Description And Quantitative Predication Of Reservoir Tectoclase

Low permeability reservoir composed of siltstone, silt-fine sandstone and fine sandstone represents intensive brittleness. Tectoclase is the dominant in this kind of reservoir in comparison with other kinds of fractures. Relevant with tectonic stress field, tectoclase is the outcome of the paleo-ground stress field which resulted from the overlay of geo-static field and tectonic stress field. The present ground stress field is unfavorable for the forming of fractures and it just reconstructs the fractures that came into being in early era. If the reservoir possesses of a relatively simple structural attitude and bears relatively weak tectonic movement, the reservoir tectoclase aperture, density, porosity and permeability can be predicted by numerical simulation of the tectonic stress field. Nowadays, fracture research chiefly involves in three aspects: the identification of underground fracture, the prediction of fracture spatial distribution and the quantitative characterization of fracture parameter. The developmental law, conformation, spatial distribution and flow law of tectoclase is under control of tectonic stress field and reservoir petrophysical property. Therefore, many scholars from home and abroad predict tectoclase by tectonic stress field and research on fracture reservoir flow law by the tectoclase parameter produced hereby. Since fine and close reservoir mainly contains tectoclase, it is a certain tendency to quantitatively characterize fracture by the numerical simulation of tectonic stress field with the geomechanics theory and methods. On the basis of predecessors'achievements, this paper proposes fracture description and quantitative research method by considering the paleo and present ground stress field simultaneously. First of all, a rock burst law fitting for low permeability sand reservoir was set up by the combination of rock mechanics after a survey and study on relevant papers. Then, a relation between stress field and the fracture aperture and density of brittle reservoir was built up by experiment and theoretical modeling. A quantitative relation between stress field and fracture porosity and permeability was set up with the conjunction of fracture aperture and density. Finally, according to the thought that fracture was formed under paleo-stress field and reworked under present stress field, the distribution of fracture parameters in different periods were predicted on the basis of the numerical simulation of paleo, present and future stress field in conjunction with the abovementioned rock burst law and quantitative relation between stress field and fracture porosity and permeability in Di'na Gas Field. On one hand, this paper offers clue and method for research on fracture in low permeability reservoir in other areas. On the other hand it settles the foundation for developing the second biggest gas pool efficiently, steadily and safely in the project of transporting the natural gas from the west to the east, which is also the call for this paper.