--> Unconventional Hydrocarbon Potential of the Weald Basin, Southern England, United Kingdom

AAPG ACE 2018

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Unconventional Hydrocarbon Potential of the Weald Basin, Southern England, United Kingdom

Abstract

Petroleum in the Weald Basin has been produced since the late 19th century from conventional sandstone and carbonate reservoirs sourced from Jurassic marine source rocks. These source rocks include the Kimmeridge Clay, the Lower Oxford Clay, and the Liassic Shale intervals. To date 13 small oil fields have been discovered and all of them are located on the basin margins, while only gas shows and seeps have been recorded in the basin centre. The exploration success and production have undergone a major downturn in the last 30 years as existing production has declined and exploration has ceased. Our view of the Weald Basin hydrocarbon potential changed radically in 2014 following the Horse Hill 1 oil discovery. This well successfully tested two previously unknown naturally fractured Kimmeridge Limestone horizons. Dry-oil flowing at rate of around 400 and 900 bopd were recorded from the Lower and the Upper Kimmeridge Limestone horizons respectively.

In this study a regional 3D basin and petroleum systems model has been built using 70 available boreholes data and composite 2D seismic lines. The research is focused on gaining a better understanding of how the Weald Basin petroleum system has developed through time, taking into account its complex tectonic evolution and erosion/uplift history. Furthermore, some of the outcomes of the model are used to address some key questions such as: why are the conventional oil fields limited to the basin margins? Why do we find only gas shows in the basin centre? Is there a basin centre petroleum system preserved in tight rocks?