High-resolution stratigraphic correlation of the Upper Carboniferous of the Anglo-Dutch basin

A proposal for a non-exclusive study

INTRODUCTION

ENRES International and associates propose to carry out a non-exclusive study of the Upper Carboniferous of the Anglo-Dutch Basin, with data from onshore and offshore United Kingdom, Netherlands, Belgium and Germany.

Hydrocarbon exploration and production of the Upper Carboniferous has a long history, a number of onshore fields dating from the Second World War. Although Carboniferous production was eclipsed by the early Rotliegend discoveries in the Netherlands and North Sea, discoveries and significant production levels have continued, and there is renewed interest in Carboniferous plays in the Southern North Sea now that the Rotliegend play is reaching maturity.

Exploration and development of the Carboniferous play requires tight stratigraphic control, but this is not generally available from seismic (which has significant imaging problems), or from biostratigraphy, especially as parts of the succession are barren of fossils. Conventional wireline log stratigraphy also has limitations and may even fail to reliably pick the all-important base-Permian unconformity.

Using new techniques of analysis coupled with new approaches available through the discipline of cyclostratigraphy, it is possible to arrive at a near-synchronous correlation that can be applied at both local and regional scale. Spectral analysis of facies-sensitive logs reveals the climate-driven cycles in the rock record; analysis of spectral changes and spectral trends leads to the characterisation of individual sequences and hence to a detailed framework for correlation, often at a resolution better than 10m. These methods are available through ENRES’ proprietary software tool, CycloLog®, which will be used throughout the study.

The proposed study aims to establish a regionally significant, near-synchronous, high-resolution correlation extending from the northwestern part of the basin, onshore UK, to its southeastern limits in Belgium and western Germany. The stratigraphic boundaries and intervals comprising this framework will be identified in as many as possible of the participating wells, resulting in detailed and objective correlations across the basin. This will represent a significant and basin-wide advance in the search for reliable ways of identifying and predicting sand-prone reservoir intervals in the Upper Carboniferous.

DATABASE

We aim to use between 120 and 140 wells, access to which is dependent on the companies sponsoring the project. The majority of the wells are expected to be from the UK offshore and Netherlands (offshore and onshore) sectors, but we hope for a significant contribution of wells from onshore UK, onshore Belgium, and onshore Germany.

Wells should penetrate as much as possible of the Westphalian, ideally with TD in or below the Namurian. The basic suite of logs required is GR, sonic, density, neutron and caliper. If available, additional logs such as DRHO, PEF, resistivity and spectral GR can also be very useful. Data should be made available in LAS format if possible (if not, please discuss alternatives with project personnel).

If core descriptions can be made available to the study, they will be used to calibrate the electrofacies/lithofacies analyses, and the false-colour imaging of logs.

OBJECTIVES

• Using CycloLog, to establish a regionally applicable high-resolution correlation framework in the study area.
• To identify the newly established stratigraphic horizons and intervals, as far as possible, in all wells included in the study.
• To construct a correlation in the time-domain for a selection of wells.
• To correlate the cyclostratigraphic framework with existing biostratigraphic and other standard schemes, with appropriate commentary on the similarities and differences.
• Drawing on experience gained from ENRES’ previous study on the Rotliegend, to define rigorous criteria for identification of the base-Permian unconformity.
• To recognise and comment on patterns of vertical and lateral lithofacies change, using methods of electrofacies analysis available in CycloLog.
• To propose criteria for recognition and correlation of sand-prone intervals, with commentary on the implications for future exploration in the Carboniferous play.

REPORTING

1. Status meeting nine months into the study
2. Final report in digital format
3. In-house presentation (on request only and at subscriber’s expense)

DELIVERABLES

The study deliverables will comprise a final report entirely in digital (PDF) format, on CD-ROM. This will include the following elements:

Report text, including explanation of methodology

Well composite logs showing all new stratigraphic picks

Correlation panels

Well data in CycloLog format, together with a run-time version of CycloLog

Tables of wells used

Tables of new stratigraphic picks in all wells

The correlation panels will additionally be presented as paper copies, and data tables will be available as Excel files.

TIMING

Please contact us for information.

PERSONNEL

The study will be carried out by senior exploration geologists each with a minimum of 15 years experience in the industry. Each has substantial experience with a major E&P company, as well as current experience in the application of cyclostratigraphy in consulting work. The following principals will be supported by technical associates where appropriate:

Dr S. Djin Nio         Project Leader, Enres International

Dr Mat De Jong     Senior Geologist

Dr David Smith      Senior Geologist and Independent Consultant

PRICING

Companies pre-committing to the study will pay a reduced price, while those contributing data will enjoy a further reduction, as follows:

• Standard purchase price,
  without pre-commitment or contribution to data:   € 35,000
• Special price,
  no contribution to data:                                             € 25,000
• Special price,
  and contributing data to the study:                          € 20,000

For details on the special price please contact us.

Affiliates and partners of subscribing companies may purchase their own copies of the study at 50% of the above prices.

Although the study is non-exclusive, individual subscribers can request the addition of exclusive parts, at extra cost, if they wish.

TO SUBSCRIBE TO THIS PROJECT, AND FURTHER INFORMATION, PLEASE CONTACT

ENRES International		For the United Kingdom
Mat De Jong		David Smith
Ruysdaellaan 3		25 Fisher Close
3712 AP Huis ter Heide		Walton on Thames, Surrey
T: +31.30.693 1922 / +31 23 532 2645		T: +44 (0)1932 42940
F: +31 30 693 2149 / +31 23 551 7044		F: +44 (0) 1932 700831
Mobile: +31 (0)6 12 946 837		Mobile: +44 (0) 7765 656086
E-mail: mdejong@enres.nl		E-mail: smithdg@ntlworld.com