Formation Plugging While Testing a Steam Well at The Geysers

Abstract

During testing of a steam well at The Geysers steam field in Sonoma County, California, rate suddenly dropped by 17,500 lb/hr and wellhead pressure simultaneously increased by 30 psi. There was no evidence of plugging in any of the surface facilities downstream of the wellhead. Pressure buildup tests before and after the incident show that there was a 15% reduction in permeability-thickness. Analysis of pressure losses in the wellbore due to friction showed that all of the rise in wellhead pressure could be explained by the reduction in mass flow that occurred as a result of the 15% reduction in kh. The change in wellhead enthalpy from 1200 Btu/lb and 4O-5'F superheat prior to the incident to 1197 Btu/lb and 0-1.4OF superheat after the incident indicates the well became slightly wet. One possible explanation for this reduction in kh is that movement of free water caused a plugging action or a reduction of mobility to steam in one or more steam entries.