PREDICTIONS OF CRITICAL GAS RATES IN HORIZONTAL AND DEVIATED WELLS

Abstract

The author’s intent through this work is to shed light on the current methods of predicting the onsets of liquid loading and to clarify that there is a difference in critical gas rate predictions between horizontal and vertical wells. A new model that predicts the critical gas rates for horizontal and deviated wells is presented. Literature data comprised of 69 horizontal and deviated wells reported in various studies in addition to experimental data from two horizontal wells are used to test the accuracy of the model and compare it to currently available models. Results using literature data show that the new model is capable of predicting the critical gas flow rates in horizontal wells within 15.7% of the actual values, a 2–6% improvement over the currently available horizontal well models, and 8–20% improvement over the currently available vertical well models. Results from the experiment tend to support the finding from literature comparison with a deviation of 5% from actual observed rates, an 18-24% improvement over the current horizontal well models, and 23-35% improvement over the current vertical well models. The New model yield best results for rates less than 10,000 Mscf/d and BUR’s between 4 and 30o/100 ft. The Conventional models (such as the Turner and Coleman) are not suitable for usage in horizontal wells and should only be used for vertical wells. The new model accounts for the effect of geometry on flow especially particle impact with the flow conduit wall as a result of change in geometry present in horizontal wells. When this effect is accounted for, as in the new model, the estimation of the critical gas rate is more accurate and yields optimized production performance from horizontal wells.