Investigation of production depletion rate effect on the near-wellbore stresses in the two Iranian southwest oilfields

Abstract

Effect of depletion rate on wellbore stability due to production of oil from hydrocarbon-bearing reservoirs is important and can result in a reduction of the reservoir pore pressure. A reduction in the reservoir pressure, in turn, results in a change in the stresses acting within the reservoir. If these changes are not well analyzed and applied in future calculations, we may be unsuccessful in some cases such as drilling infill wells or extended wells, forecast of sand production and optimum flow rate, preventing of casing collapse, etc. Therefore, knowing the stresses around the well at every stage of production is fundamental to the next calculations. In this paper, we recognized these changes in near-wellbore stresses using data from logging (image log, dipole sonic, full set log, mud log), production data, information from kick, blow out, loss etc. and determined it using Techlog software and theoretical calculations. Three wells of two huge oilfields of SW Iran were investigated after depletion or production for long years. In each well, state of stresses were calculated in cases of safe drilling mud weight using log data and theoretical equations. At the end effect of depletion rate on wellbore stability was investigated in these three wells.

Keywords

• Depletion rate
• Wellbore stability
• Pore pressure
• Sand production
• Near-wellbore stress