Incremental production analysis in acidized fractures.
Engineering Honours Degree 2008
University of Adelaide
Acid fracturing is a stimulation technique which has been widely used in the oil industry for several decades. However compared to other techniques such as hydraulic fracturing, acid fracturing has not received the same level of interest in the literature. Acid fracturing by nature has unique challenges, especially in modelling. Issues can include reaction kinetics, fluid loss and successful conductivity creation. This report combines widely used geometry, mass transport and conductivity models in acid fracturing to investigate impact of design parameters on conductivity.
Initially, sensitivity analysis on dimensionless conductivity was investigated. This enabled a greater understanding of how design parameters impact conductivity. The sensitivity analysis highlighted the importance of efficient acid transport, and the impact of fracture length and width.
Following the sensitivity analysis a forward production model was created. This method calculated production for transient and pseudo steady state flow periods. The aim of such a model was to realise the value of the fracture over a long period of time, rather than the more widely used productivity ratio. This model was used to calculate the cumulative production of acid fractures from a variety of fracture designs and compared over a ten year period. The production model proposed shows a strong correlation to the productivity ratio.
There are several distinct benefits to using the new cumulative production parameter. The first is that it provides the engineer with a concept that is quite tangible, that is the incremental production can be compared to the unstimulated case. Secondly, this method allows fracture designs from different fields to be analysed quantitatively and compared. Two fractures designs in different fields with the same productivity ratio may not show the same production increment in terms of ultimate recovery. Lastly, understanding the production behaviour of a fractured well could aid financial analysis.