Integrated Production Model for Offshore Victorian Fields
Haydn Axon and Saehaneul Moon - 2014
Australian School of Petroleum
University of Adelaide
Integrated production modelling (IPM) is a computational, analytical modelling process which simulates oil or gas fields by integrating the tank, well and surface facility models developed using various Petroleum Experts (PETEX) IPM programs. The following project involved the development of a fully functional, history matched integrated production model of the Santos owned and operated fields within the Gippsland Basin.
Upon completion of the model an extensive history matching process was undertaken, ensuring the model is representative of the historical field behaviour. This process involved the matching of simulated gas flow rates and wellhead pressures against historical data, spanning the entire life of the field, provided by Santos Ltd. In order to match the production history as close as possible to the simulated data, two new history matching processes were adopted for Well-C1 and Well-C2. The methods were based on changes in pressure drop and skin factor across the wellbore using GAP. Although these methods allowed an accurate production match between the historical and the simulated data, the validity within the forecasting has been questioned during the project. Therefore factors altered as a result of the two history matching methods have been offset during production forecasting.
Production forecasting until the beginning of 2028 has indicated that Well-C1 and Well-C2 will cease production on 01/06/2020 and 01/09/2016 respectively. Appropriate shut-in dates for Wells C1 and C2 have been considered using the modified turners equation, where the minimum rate to lift liquid (MRTLL) was calculated to be 5 MMscf/day for each well. Considering the MRTLL for Wells C1 and C2, appropriate shut-in dates were determined to be 01/07/2015 and 01/03/2018, where a cumulative gas production of 1.15 Bscf and 14.79 was predicted.
In-addition to production forecasting of the existing wells, various case studies using the Gippsland Basin models have been analysed. Future Santos Ltd expansion plans of the Gippsland Basin including the introduction of new development wells; Well-D1 and Well-C3 have been studied. Well-D1 is expected to begin production on 01/01/2018 and a cumulative gas production of 209.67 Bscf over 9.5 years has been predicted. Well-C3 is predicted to produce 35.8 Bscf over 8.5 years; no specific first gas time has been identified for Well-C3. The two future wells are expected to have negligible impact upon the existing production wells of the Gippsland Basin. Gas flow from 3rd party gas into the existing pipelines has the potential to completely backout Well-C1 and Well-C2; therefore it is recommended that 3rd party gas is allowed to flow into the system after the abandonment of Wells C1 and C2. Production predictions indicate that recompleting Wells C1 and C2 to 4.5 inch tubes can result in an increase in 4.94 Bscf of cumulative gas production. While wells A1 and B1 show no indication of gas flow within the forecast timeframe.