Abstract

Vaca Muerta is an organic shale and one of the main source rocks for conventional reservoirs in the Neuquen Basin in Argentina. According to the 2013 United States Energy Information Administration (EIA) report, Vaca Muerta could produce 16 billion barrels of liquids and 308 TCF of gas (EIA, 2013). Up to the time of writing, only about 200 wells have been drilled to test Vaca Muerta, over 90% of them vertical.

Multiple wells drilled by Pluspetrol in different Neuquen basin locations were selected for this paper to explore and test Vaca Muerta productivity. A wide range of data was gathered. Some examples are: a full set of logs, wet samples, petrophysic and geomechanic tests in cores, geochemistry in cut samples and PVT fluid samples. Most of the wells were completed with two fracture stages while some others had only one stage in order to test the most prolific horizons individually.

During the production testing, a careful and detailed oriented surveillance program was designed to gather high quality data. Between 14 and 20 months of daily rates and pressure information is available. Additionally, several pump in/flow back tests and extended build ups (more than 40 days) were performed on these wells. Some of these wells flow naturally while others had an artificial lift installed providing information on different production conditions.

This information was combined to make a full reservoir characterization. A full rate transient analysis workflow was carried out in six wells. This includes straight line plots, type-curve analysis, analytical model history matching and probabilistic forecasting. In addition, pressure dependent permeability and average reservoir pressure increase due to fracture injection fluids effects on well performance will be discuss in this paper. Finally, a set of conclusion with the findings are presented. The aim of this paper is to summarize the analysis and findings to characterize Vaca Muerta as an unconventional reservoir.

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