Simulation Study of Block to Block Interaction Effect in Naturally Fractured Reservoirs under the Gas-Oil Gravity Drainage Mechanism

In fracture reservoirs with gas cap, oil production and pressure reduction lead to gas cap expansion and downward movement of gas/oil contact. In fracture system gas with high mobility, moves faster than oil and above the oil zone, form a new zone named gas invaded zone. In this zone, gravity drainage is the major mechanism that helps for oil production, in this mechanism density difference between oil and gas cause gas to push into the matrix blocks and oil to drain from them. In a system that consists of matrix blocks, some of the oil drained from upper matrix block can reinfiltrate into the lower block from the top or lateral surfaces. This study was divided in two parts, firstly using a single porosity simulator a fine grid was built in the space occupied by the stack of matrix blocks and fractures allocating the particular characteristics and properties of each medium to the different portions that these systems occupy in the grid, in this part the effect of fracture and matrix capillary pressure and matrix permeability on the each block oil recovery is considered Secondly, using the dual porosity simulator , a coarse grid is built of the same dimensions of the single porosity fine grid and the gravity drainage is simulated and results of dual porosity and single porosity have been compared. The main conclusion drawn from this work is that reinfiltration causes a reduction in the production rate; however, it has no effect on ultimate recovery.

Keywords:

Fractured Reservoir , Gravity Drainage , Single Porosity , Dual Porosity , Reinfiltration