A Method for Estimating Capacity Increases from Acidizing Mud-Damaged Reinjection Wells

Abstract

Acid stimulation of mud damaged wells involves a great deal of time and resources. In fasttrack, time constrained geothermal development such as that current& undertaken by PNOC-Energy Development Corp. (PNOC-FDC), every capacity gained from acidizing is an essential input to the overall development plan and strategy. Thus, aside fiom identijication of candidate wells for acidzing, there is a need to predict possible gains that would result fiom such undertaking. This paper presents a method for evaluating the capacity increases to be expected by acidizing mud damaged reinjection wells. The method is based on including a zero data point in the injectivity test plot. An offset between the extrapolated injectivity line and the zero flow pressure indicates a "skin pressureö or flow initiation pressure ÆÆ due to viscous mud. The pressure difference (dp) is the available pressure that can be removed by acid stimulation. This can then be used to determine an estimate of the reinjection capacity increase from acidizing. This method however is not applicable to high permeability wells sufering skin damage caused by mineral deposition or cement slugging.The method gives good agreement with actual results for wells MNI, 5R70 and 4R6D.