Geological factors controlling Early Carboniferous carbonate platform development in the Netherlands

Abstract

AbstractA deep pre‐Silesian carbonate play has recently come into focus in the Netherlands and poses some real opportunities and challenges to the explorationist. Underneath the very thick cover of Westphalian and Namurian clastic sediments, which cover almost the entire Netherlands, a yet undiscovered petroleum system may be present in Dinantian carbonates. However, lack of well control and the significant depth involved has caused pre‐Silesian formations to be under‐explored. Furthermore, seismic definition below the widespread Permian Zechstein evaporites is often very poor. Nevertheless, recent discoveries in the Caspian Sea area have shown that during the Lower Carboniferous very thick carbonate bioherms can develop. These giant reservoirs related to large build‐ups can provide the required size for deep pre‐Silesian prospects in the southern North Sea area and Dutch onshore. From the sparse well control and extrapolation of limited geological data in the Netherlands, the United Kingdom, Belgium and Germany, it is suggested that thick Dinantian platform carbonates may be present at the northern fringe of the London‐Brabant Massif. For realistic reservoir models of these platforms, areas outside the Netherlands have to be studied, for example the UK Midlands, and south of the London‐Brabant Massif, in eastern and southern Belgium. Although, the latter area has been affected by the Variscan Orogeny, the Dinantian‐aged rocks at outcrop provide a good model for the understanding of the frequency of the major depositional cycles, solution collapse, erosion and dolomitization processes.Dolomitization may be one of the most important processes that can provide good reservoir quality, and primary porosity related to reef growth, the second important process. Reservoir studies show, that significant reef growth, with associated grainstone facies on the windward side, is an important factor, to understand Dinantian‐aged reservoirs in the Caspian Sea area. Similarly, a dominant east to west wind direction may explain, the development of build‐ups and grainstone facies as an eastern fringe to the Dutch Dinantian platforms, but not on the leeward‐side of the London‐Brabant Massif in southern Belgium. Copyright © 2007 John Wiley & Sons, Ltd.