Invasion around a horizontal wellbore

Abstract

A mathematical model is developed for mud cake growth and fluid invasion around a horizontal wellbore during drilling. The non-axisymmetry of the invasion front is addressed for the case of water based drilling mud and isotropic rock formation. It is shown that the invasion profile may lose convexity due to gravitation even though the filtrate density is the same as that of the pore fluid in the rock.

Ionic Fracture Fluid Leak-Off

“…It was proved in [19,20] that the invasion front can be determined by the method of characteristics from the following equation for the position vector ξ = (ξ 1 , ξ 2 ) at the (x, y)-plane:…”

Geodynamics of the zone close to a borehole during drilling

“…We can consider that in the case of a ver tical borehole, the mud cake is symmetrical. If we neglect the variations in the mud cake along the bore hole, the growth of the mud cake obeys equation [3]:…”

“…Parameter Λ is determined by the properties of the drill fluid and porous matrix. The method for calculating Λ is given in [3].…”

“…The problem of the penetration zone was previ ously considered in [1][2][3] without account for the mechanical stresses in the rocks surrounding the bore hole. However, when deep boreholes are drilled, the stresses in the rocks can increase significantly owing to the high pressure, which in turn leads to variations in the porosity, permeability, and penetration dynamics.…”

“…Therefore, it is necessary to take into account the variation in the thickness and permeability of the mud cake to determine the porous pressure, the stresses in the hard mud cake matrix, and the equation for the dynamics of the permeability front. The most general equations for the growth of the mud cake in the pro cess of drilling vertical and horizontal boreholes were obtained in [3]. In this work, we consider the drilling process of vertical boreholes when the mud cake front and permeability front have axial symmetry.…”