The age of illite cement growth, Village Fields area, Southern North Sea: Evidence from K-Ar ages and [sup 18]O/[sup 16]O ratios

Journal Article · Fri Jan 01 00:00:00 EST 1993 · AAPG Bulletin (American Association of Petroleum Geologists); (United States)

OSTI ID:6809651

Robinson, A G; Coleman, M L; Gluyas, J G ^[1]

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1. BP Research, Sunbury on Thames (United Kingdom)

In this paper we describe K-Ar radiometric ages and oxygen isotope ratio measurements of illite cements from eolian sandstone samples of the Permian lower Leman Sandstone Formation (Rotliegen-des Group). The samples come from a large (about 100 [times] 100 km) part of the Southern North Sea basin (Village Fields area) and from a range of burial depths (2.8-3.4 km subsea bed). Mean illite ages in the gas fields of Ravenspuran North (164 Ma [+-] 20.1 [2[sigma]], n = 11), Hyde (161 Ma [+-] 12.3 n = 7), Cleeton (155 Ma [+-] 20.2, n = 3), and Hoton (152 Ma [+-] 14.0, n = 14) fields, and in two wells located in Block 47/5A (162 Ma [+-] 16.1, n = 4) are all in the Middle to Late Jurassic, apart from two Early Cretaceous ages considered to represent unreliable analyses. The mean for all ages is 158 Ma [+-] 18.6 [2[sigma]], n = 39. We largely avoided contamination with (old) detrital K-bearing minerals by careful sample selection and monitoring. To a first approximation, the assumptions of K-Ar dating appear to be fulfilled, so the measured ages are likely to date illite cement precipitation. Oxygen isotope ratios measured on the dated illite samples show small but significant variations among fields and a weak correlation with depth during the Middle jurassic when illite grew. Both K-Ar dating and oxygen isotope ratios are compatible with a region Middle to Late Jurassic phase of illite growth during which the mineral precipitated over a large area and over a range of temperatures governed by the depth of the formation at that time. The age of illite cementation coincides with rifting, which ultimately may have caused illite growth by driving pore-water flow. 18 refs., 17 figs., 2 tabs.

• OSTI ID: 6809651
• Journal Information: AAPG Bulletin (American Association of Petroleum Geologists); (United States), Vol. 77:1; ISSN 0149-1423
• Country of Publication: United States
• Language: English

Related Subjects

03 NATURAL GAS
58 GEOSCIENCES
NATURAL GAS DEPOSITS
EXPLORATION
RESOURCE ASSESSMENT
NORTH SEA
RESERVOIR ROCK
ISOTOPE DATING
ARGON
GEOCHEMICAL SURVEYS
ILLITE
ISOTOPE RATIO
OXYGEN 16
OXYGEN 18
POTASSIUM
RADIOMETRIC ANALYSIS
AGE ESTIMATION
ALKALI METALS
ATLANTIC OCEAN
CHEMICAL ANALYSIS
CLAYS
ELEMENTS
EVEN-EVEN NUCLEI
FLUIDS
GASES
GEOLOGIC DEPOSITS
ISOTOPES
LIGHT NUCLEI
METALS
MINERAL RESOURCES
NONMETALS
NUCLEI
OXYGEN ISOTOPES
QUANTITATIVE CHEMICAL ANALYSIS
RARE GASES
RESOURCES
SEAS
STABLE ISOTOPES
SURFACE WATERS
SURVEYS
030200* - Natural Gas- Reserves
Geology
& Exploration
580000 - Geosciences