Stability of horizontal oil well - A Jointed Rock model approach

Abstract

Advancement in technology has paved different ways for the extraction of oil. Drilling of wells, production and injection of fluids results in the alteration of pre-existing stress field in a reservoir. The current study is undertaken to analyze the stability of horizontal oil wells with the change in radius of the well, Poisson's ratio, saturation density, permeability and also to find stress distribution around horizontal oil wells drilled in different reservoir conditions, stress distribution before and after production and also to assess the effect of stress distribution on the stability. The knowledge of stress distribution and its redistribution with change in reservoir conditions can help in selecting well locations and orientations for maximum sweep in reservoirs. Displacement of the particles gives the direction of fracture propagation. As the particle size increases, fracture propagation increases. The stability analysis has been done using Jointed Rock method of Numerical Modeling. Numerical models are mathematical models that use numerical time-stepping procedure to obtain the models behavior over time. The results of the model are shown to agree qualitatively with field observations. The extent of stress distribution is dependent on radius of the well, pore pressure in the reservoir, fracture density of the reservoir and drilling direction. Horizontal wells drilled in highly fractured reservoirs will be less stable. In case of anisotropy, since the stability is very less we must reduce the radius of the well in order to increase the FOS and hence the stability. © 2011 CAFET-INNOVA TECHNICAL SOCIETY.