Micro rhombic calcite of a giant barremian (Thamama B) reservoir onshore Abu Dhabi - Clumped isotope analyses fix temperature, water composition and timing of burial diagenesis

V. Vahrenkamp, J. Barata, P. J. Van Laer, P. Swart, S. Murray

Research output: Chapter in Book/Report/Conference proceedingConference proceeding contribution

6 Citations (Scopus)

Abstract

Micro porosity associated with micro-rhombic calcite provides volumetrically the largest pore volume in Middle Eastern Cretaceous carbonate reservoirs. With progressing reservoir development and depletion of macro-pore systems the low permeability micro pores have ever increasing importance as host to remaining hydrocarbons and for reservoir performance. A new technique is presented - Clumped Isotope Thermometry - which yields significant new insights on burial depth, timing of diagenesis and the nature of the diagenetic fluids. This in turn helps to better understand the widespread distribution of micro porosity in Abu Dhabi reservoirs. The genesis of micro-rhombic calcite has previously been placed into the shallow burial realm under the influence of meteoric or marine pore waters (Budd, 1989; Moshier, 1989) using oxygen stable isotopes and petrographic observations. However, the interpretation of oxygen isotope data is limited by the fact that the isotopic composition of calcite minerals is determined by two independent factors: the isotopic composition and the temperature of the precipitating water. The new analytical technique of clumped isotopes has established a way to independently determine one of the variables (temperature) thus allowing the other (water composition) to be fixed. The new technique has been applied to 15 samples from three cores of a giant Abu Dhabi reservoir. Samples are from the Barremian Thamama B reservoir unit. Stable isotope data exhibit a normal range for Thamama B calcite (δ13C: 2.8%o to 3.9%o; δ180: 4.6%o to 5.9%o). Clumped isotope analyses indicate a most likely precipitation temperature of 65°C to 72°C and an isotopic composition of precipitating waters of 3.3%o to 4.9%o δ180. Using a well calibrated basin model the temperature range places the depth of diagenesis between 0.65 km and 1.1 km and the timing of diagenesis into the Late Cretaceous (Turonian to Campanian). This coincides with the subsidence of the eastern Arabian plate margin caused by the opduction of oceanic crust (Semail ophiolite and associated marine sediments). The heavy oxygen isotopic composition of the diagenetic water of 3.3%o to 4.9%o δ18 corroborates a burial setting for diagenesis. Results imply that diagenesis was driven by a regional east to west burial flow system driven by compaction and convection with likely significant implications for the regional distribution of porosity & permeability.

Original languageEnglish
Title of host publicationAbu Dhabi International Petroleum Exhibition and Conference, 10-13 November, Abu Dhabi, UAE
Subtitle of host publicationproceedings
Place of PublicationTexas
PublisherSociety of Petroleum Engineers
Number of pages12
ISBN (Electronic)9781613993385
DOIs
Publication statusPublished - 2014
Externally publishedYes
Event30th Abu Dhabi International Petroleum Exhibition and Conference: Challenges and Opportunities for the Next 30 Years, ADIPEC 2014 - Abu Dhabi, United Arab Emirates
Duration: 10 Nov 201413 Nov 2014

Conference

Conference30th Abu Dhabi International Petroleum Exhibition and Conference: Challenges and Opportunities for the Next 30 Years, ADIPEC 2014
CountryUnited Arab Emirates
CityAbu Dhabi
Period10/11/1413/11/14

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