Abstract

High-gravity solids (HGS) invasions via microfractures and large openings is known to cause a severe formation damage. A HGS invasion model is presented by using unsteady-state mass transfer as its basis for calculations for inclined and horizontal wells. Results are compared to previously published studies for an invasion that is limited to vertical wells.

The model developed considers wells inclination, mud rheology, filtration rate, effective contact area, pore sizes, effective pore reduction, solids particle size and the nature of formation pore throat. This model created to determine the effect of inclination, invasion impact, penetration length, magnitude of the productivity loss that is related to some particular scenarios with high accuracy and stability.

The HGS invasion model is compared to the similar earlier models or studies that are published or commercially available, which is limited to the vertical well system. Five wells at the same observation depth and similar formation characteristics are simulated, with different inclinations of 0°, 30°, 45°, 60°, and 90°. The most significant new finding is that the invasion depth and the damage is increased consistently with the increase of inclination, and the invasion impact is strictly limited to the size of the openings such as pore throat and fractures. This is important because the higher solids invasion rate leads to higher formation damage, PI reduction, completion problems, insoluble solid plugging, and formation testing difficulties. Minimizing solids invasions are important because it always increases the formation damage to the pay-zone. The HGS invasion model is capable to solve solids invasion calculations for entire sections of an inclined well as well as the damage that accompanies in the simplest way possible with better visualization.

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