Broad fourteens basin

Netherlands Journal of Geosciences / Geologie en Mijnbouw 82 (1): 71-90 (2003)

History of petroleum systems in the southern part of the Broad Fourteens Basin

J.M.Verweij1, H.J. Simmelink1, R.T.Van Balen2 & P. David1
1

2

Netherlands Institute of Applied Geoscience TNO - National Geological Survey, P.O. Box 80015, 3508TA Utrecht, the Netherlands; E-mail: j.verweij@nitg.tno.nl Facultyof Earth and Life Sciences,Vrije Universiteit, De Boelelaan 1085, 1081HV Amsterdam, the Netherlands

Manuscript received: January 2002; accepted: January 2003

Abstract
2D Basin modelling was used to evaluate the response of source rock maturation, and of petroleum expulsion, migration, accumulation and preservation to the evolution of the southern part of the inverted Broad Fourteens Basin.Modelling results show that the temperature, maturation and petroleum generation history as well as migration characteristics of both the Jurassic oil systems and the Carboniferous gas systems vary over short distances relative to the differences in burial history of the basin. Model results indicate that no major gas accumulations are preserved in the Slochteren Formation along the cross-sectionat present-day. Gas accumulations are predicted in sandstone-dominated Triassic units in the southern part of the section. Present-day oil accumulations predicted in the Vlieland Sandstone Formation sealed by the Vlieland Claystone Formation (in P9 and Q1 crestal structures) are in accordance with known oil accumulations. Additional oil accumulations are predicted in the sandstone-dominated MiddleWerkendam Member, and in sandstones of the Delfland Subgroup. The modelling offers an explanation for the different geochemical compositions of the accumulated oils in the P9 and Q1 areas. Modelling implies, that the oils in the Q1 oil field were sourced by remigrated oils expelled over time, from early mature to mature source rocks of the Posidonia Shale Formation. The biodegraded andwater-washed nature of the Q1 oil is explained by the concentrated topography-induced groundwater flow through the Vlieland Sandstone Formation during the Late Cretaceous inversion of the basin. The oils accumulated in the P9 area were sourced from an early mature part of the Posidonia Shale Formation and were probably not affected by water washing and biodegradation because of post-inversion charging of thereservoir. Keywords: petroleum systems, basin modelling, Broad Fourteens Basin, North Sea Basin

Introduction This paper presents results of a 2D basin modelling study along a cross section in the southern part of the Broad Fourteens Basin (Fig. 1). The modelling study was part of an integrated basin study of the Broad Fourteens Basin (Verweij et al., 2000; Verweij & Simmelink, 2002; Verweij,2003). The research presented here aimed to increase the understanding of and provide a time framework for petroleum generation, migration, accumulation and preservation in the basin. The Broad Fourteens Basin, located in the Dutch
Netherlands Journal of Geosciences / Geologie en Mijnbouw 82(1) 2003

part of the southern North Sea, has been extensively studied since the first successfulexploration well in 1968 (Oele et al., 1981; Van Wijhe, 1987; RRI, 1984, 1985, 1988, 1990; Lee et al,. 1989; Van der Poel, 1989; Hastings et al., 1991; Roelofsen & De Boer, 1991; Nalpas et al., 1995; Goh, 1996; Gauthier et al., 2000; Wong et al., 2001). As a consequence, there is a wide range of information and data – geological, geophysical, thermal and geochemical – available on it (both from publishedsources and public wells). We have used these data to obtain an a priori understanding of the past geological, hydrogeological, geother71

geologic history as the nearby West Netherlands Basin (Fig. 1).Van Balen et al. (2000) studied this basin, using similar modelling techniques. Geological setting The Broad Fourteens Basin is a northwest-southeast trending Mesozoic basin, approximately 120...