Abstract

There are several methodologies to model post-acid fracturing well performance such as implementing negative skin factor and stimulated reservoir volume local grid refinement (SRV LGR). However, the first method is too simplified to be applied in numerical simulation and the second method is too complex and time consuming. Therefore, to bridge the two methods, this paper will discuss the application of a grid virtual connection to model the well performance of acid fractured wells.

Grid virtual connection is the planar of fracture that alters the deliverability of the penetrated grid. In this study, series of analyses are performed, such as: (i) Data input quality check (QC) and validation (reservoir model and fracture model); (ii) Simulation running using the skin factor method, SRV LGR, and grid virtual connection; (iii) Comparison between the three methods regarding the streamline result and simulation running time; (iv) Model calibration (history matching) using post-fracturing data; (v) QC the result of history matching. Post-fracturing production data from two wells (X-6 & X-8) are used as the calibration point. From these analyses, the advantages and limitations of the virtual connection method will be examined.

The input for this study is the history matched simulation model (up to the period before acid fracturing) and the 2D fracturing model from the fracturing simulator, from which the fracturing parameters will be taken forward to numerical simulation. Details as follow: (i) the skin factor method is generated from the analytical model which results in equivalent skin of −5.6 and −5.9 for the X-6 and X-8 wells, respectively; (ii) Input parameters for the SRV LGR and grid virtual connection methods use the output from the fracturing simulator. There are several findings from these three methods: (i) The simulation running time for the grid virtual connection is similar to the skin factor method, while SRV LGR takes longer to finish; (ii) Streamline simulation shows the grid virtual connection method provides a sensible approximation of the physics behind the reservoir – fracture – wellbore flow which fully represents by SRV LGR method, meanwhile skin factor method only makes changes in the wellbore; (iii) The history matching process shows that the grid virtual connection and SRV LGR method could be matched with the actual production data, however the SRV LGR method is a highly non-unique solution due to the limited data input from the fracture simulator. Meanwhile, the skin factor method could not be matched with the actual data using a sensible skin. Based on these analyses, the grid virtual connection is shown to be the best (?) method to model the post-acid fracturing well performance.

This paper shows that the grid virtual connection is a technically sound method to perform a first order approximation of post-acid fracturing well performance. This method is beneficial to assessing the production gain on an acid fracturing job with sensible physical approximation and fast computational times.

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