Pressures and Pressure Derivatives of Vertical and Horizontal Wells Located Within Intersecting Sealing Fault and Constant Pressure Boundary

Abstract

Abstract The optimization of the performance of oil and gas wells (whether vertical or directional) as well as well location from external reservoir boundaries or faults has been a major concern of the reservoir engineer over the years. This work presents an accurate method for evaluating the performance of both the vertical and horizontal wells each located within an intersecting sealing/no-flow boundary and a constant-pressure boundary. The main aim of this study was to investigate the transient pressure behaviour of a vertical well as well as a horizontal well located within an intersecting sealing fault and a constant pressure boundary. The methods employed in computing the dimensionless pressures and dimensionless pressure derivatives for both well types include the method of images and principle of superposition. The computations were also made using Microsoft Excel, Python and MATLAB software. The results obtained show that for the selected parameters; 1) the models give accurate estimation of distances between active and image wells, PD and PD’, 2) at 30 hours of production, both wells completely overcome the effects of the boundaries at 2000 ft. equidistant to faults, 3) for the infinite-acting reservoir, a characteristic values of PD’ for the vertical and horizontal wells are 0.5 and 0.2 respectively, 4) for both well types, the effect of the upper boundary is greatly felt between distances of 5.00ft. and 10.00 ft., and beyond this region, the effect of the lower boundary becomes gradually felt and then, greatly felt beyond 15.00 ft. The relationship between the pressures and unequal faults distances has no maximum or minimum points, 5) the point with the least effect of either or both boundaries as well as longest transient period is point 3 (equal distance of 15.00 ft. from both boundaries). This is the point of optimal productivity, 6) for a given distance, both PD and PD’ decrease as horizontal well length L increases, 7) for all the cases considered and dimensionless time tD, both PD and PD’ decrease with increasing horizontal well length. The longer the well length, the lower the drawdown required to give same effects, as would shorter lengths, on the well performance at a given time of production thereby prolonging production over time, and 8) for a given distance, the horizontal well length has no impact on the flow periods. The type curves can be used for matching of actual pressure drawdown data and determining the drainage area and relative well location with respect to physical boundaries. Worthy of future research are similar works on; 1) anisotropic reservoir, 2) larger values of faults distances, and 3) angles other than basic angles.