Abstract
Across the Cooper Basin (on-shore South Australia) historical trends of developed reserves have shown annual growth. This highlights the understated potential in the area and the under-lying difficulty in quantifying the true value of a tight gas well early in its life. This difficulty generally arises from the challenge of forecasting multi- layered reservoirs with variable surface conditions using traditional decline curve analysis. This conservatism impacts significantly on a company's value through underestimation of developed reserves thus magnifying the negative impact on the accounting depletion rate and profitability of an asset.
This paper details a process of organisation change designed to stabilise this ‘reserve growth’ by defining an "unchanging" best estimate of developed Estimated Ultimate Recovery (EUR). This process involved an improved technical workflow which utilises advanced Production Data Analysis (PDA) rolled out and applied across a large technical department.
This revised process was successfully implemented within three months in a resource constrained department involving an intensive training phase and an external audit. The process resulted in improved technical understanding of the department in advanced PDA, well models on over 70 wells and, most importantly, a gain of over 115 Bcf of 2P developed reserves.
In addition to these immediate reserve estimations and asset profitability improvements, the development of these analytical well models has allowed the asset teams to develop a greater understanding of field and well performance, has overcome surveillance gaps and allowed teams to discover further opportunities.
This technique is not a perfect solution but a significant step forward. With the process now standard within the department it is expected that decline forecasts will continually improve for these complex reservoir systems, which in turn will more closely reflect the value ascribed to these assets.
