Shale Plays in The Netherlands

Bouw, Sander S. (EBN) | Lutgert, Jan (Energie Beheer Nederland BV)

OnePetro 


The Netherlands is a mature hydrocarbon province. EBN, the Dutch state participant for hydrocarbon exploitation and exploration, has identified shale plays as one of the contributors to add reserves and to maintain production at the current level. The main source rock for the limited amount of oil accumulations in The Netherlands are the Lower Jurassic (Toarcian) oil-prone shales. Lower Carboniferous (Namurian) hot shales have often been suggested as possible contributor to oil and gas Formation in The Netherlands as well, but this has not been proven to date. Recent discoveries of gas in the time-equivalent Bowland shales in the UK have encouraged interest in the production potential of these shales in North-western Europe. In this paper the geological and geomechanical properties of the Lower Jurassic and Lower Carboniferous are presented in a shale play context. The assessment methodology is subdivided in three sections: 1) the overall geology of the play, 2) the type and quantification of hydrocarbons present and 3) the production characteristics. New and specific measurements
on core and cutting material include pyrolysis, methane adsorption, mineralogy, texture, porosity, permeability, static and dynamic geomechanical properties, hardness and fracture conductivity.

The two identified plays show very distinctive properties. The Lower Jurassic samples indicate to be mostly thermally immature for dry gas implying that liquids can be expected. The Lower Carboniferous samples show areas that are overcooked. Mineralogical and geomechanical data suggest that different stimulation strategies may be necessary for these two plays to produce hydrocarbons effectively. The source rocks of Lower Jurassic age qualify as relatively soft while the Lower Carboniferous shales with high TOC content classify as very hard. Comparing the results of the assessment to known shale plays in the US, the plays position themselves in the opposite extremes of the productive shale play spectrum.

Introduction

The resource base of the Netherlands is maturing rapidly. The current portfolio of producing gas fields shows that approximately 75% have produced more than half of their initial reserves volume (EBN, 2010). In order to maintain the current high production levels, enhanced recovery from existing fields is required as well as portfolio rejuvenation by increased exploration activities. In North America the gas production from organic rich shales have proven to be a game changing concept for the gas industry. This success sparked a worldwide interest in other shale basins with similar characteristics. In order to assess the
production potential of this type of unconventional resource, The Netherlands are currently investigating their prospective shale resources.