| Popis: |
Cleanup operations of gas wells are conducted when the well is kicked off and tested the first time. During cleanup, the drilling and completion fluids come out of the well along with the produced gas and associated liquids. The phenomena is transient in nature and minimum gas rate and time required for cleanup are key questions to be answered before embarking on the cleanup and subsequent well test operation. The knowledge of minimum gas rate and time required for cleanup can assist the engineer in deciding the well test package and make best use of the available time. In the current study, transient simulations of cleanup and MRT of three horizontal gas wells are conducted using a commercial multiphase transient simulator. Before the actual cleanup operations, simulations were conducted to estimate the cleanup time and to arrive at optimum beanup procedure to achieve best cleanup for a maximum gas rate constraint of 60 MMscf/D which is dictated by the size of well test package. After the cleanup and MRT operations were conducted, the operational data was used to tune the model. It was observed that the predicted temporal variations of gas rate and gauge temperature and pressure from the tuned model were in very good agreement with the measured values. The tuned model was then used to ascertain the degree of cleanup achieved from the actual cleanup and MRT operations and the model predictions showed that except the last 60 metres from the toe, the wells were completely cleaned of completion fluid. The poor cleanup in the last 60 metres was possibly because of 60 MMscf/D gas rate limit imposed by the size of well test package or resulting from poor contribution from the near-toe area. The study brings forth the significance of dynamic simulations in predicting and history matching gas well clean up operations and how dynamic simulations can provide an insight into the pressure and flow transients during cleanup. The knowledge gained from dynamic simulations can assist the engineer in deciding the well test package for gas wells to be cleaned up and in quantifying the cleanup achieved from an already conducted cleanup operation. |
