3D PRESSURE TRANSIENT ANALYSIS MODEL OF FRACTURED-CAVED RESERVOIR BASED ON SEISMIC CHARACTERIZATION

Large-scale fractures and cavities cause difficulties of geological modeling, which in turn makes the fluid flow simulation difficult. In this paper, a geological modeling process based on three-dimensional (3D) seismic characterization is proposed to model real reservoirs, and then a 3D pressure transient analysis model is developed to model the fluid flow in the fractured-caved reservoirs. In this model, the reservoir is characterized as three types of media explicitly: cavities simplified as irregular polyhedrons, fractures represented by slabs, and the matrix of the rest. A finite-element method is implemented to obtain the solutions of the governing equations. Two idealized cases of fractures and cavities are presented using the model. The results show fractures and cavities play the dominant role in the fluid flow. In the fractures case, the log-log type curves can be divided into six stages, and the bilinear flow is the main feature. A larger permeability of fractures causes a longer period of bilinear flow. The log-log type curves of the cavity case are also divided into six stages. The larger permeability of cavities, the lower the horizontal line of the pressure derivative, but the influence of cavities not connected with the wellbore is limited. Comparison with the radial-composite model shows that the radial-composite model gets a volume-equivalent radius of the cavity, but a higher permeability and a negative skin factor. The developed model is also applied for the well test analysis of a field case, which shows a significant ability to characterize the fluid flow of fractured-caved reservoirs.