| Abstract |
This work undertakes an evaluation of the production decline and the reservoir pressure decline of the load-varying well, ULB-2, which is the only well supplying steam to the power plant. The generating units supply electricity directly to the 20 kV distribution line which is coupled with a Diesel Power Plant, the plant operating scheme often have to follow the local load demand pattern. The plant cannot be operated in a constant load. Increase opening and throttling the well alternately at the peak load time, and vice versa, is part of the well operator daily routine job. Two numerical methods, i.e. Decline-Lumped Parameter Model and Inflow Performance Relationship (IPR) Model are used to analyze well productivity. The result of the work will be used to forecast the plant generation capacity until the steam from a make-up well is ready. It will be approximately one year after the drilling campaign for the development of a new unit is commenced, considering the time requirement for FEED process and construction of steam pipelines. Analysis from the production data suggests that from Decline-Lumped Parameter Model, the overall production decline rate is 5.4% and 3.8% per annum, assuming an exponential and harmonic decline, respectively. Some analysis distinguishing the decline on the field when only two units were in operation (July 2012 – September 2014) versus four units (September 2014-afterwards), were also performed resulting lower decline rate for fewer plant units in operation, i.e. 2.04% versus 6.24% (exponential decline) and 2.78% versus 7.15% (harmonic decline). In addition, the forecasted plant generation capacity by the time a make-up well is ready in January 2022, is approximately between 4.5-6.5 MWe, depending on the operation scenario. The IPR model results maximum flow rate and reservoir pressure decline rate of 3.24 kg/s and 0.47 bar per annum, respectively. Furthermore, by using IPR model, it can be observed that between 2004 and 2011 productivity index (PI) decreases due to formation damage (wellbore skin), while between 2011 and 2016 PI deteriorates mainly as a result of reservoir pressure decline. It can be observed that Decline-Lumped Parameter and IPR model pressure decline results are in good agreement, thus confirm the applicability of both methods. |