Quick Search:    advanced search

GSW Home   GeoRef Home   My GSW Alerts   Contact GSW   About GSW   Journals List   Help

Petroleum Geoscience

This Article Figures Only Full Text Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Taghavi, A. A. Articles by Emadi, M. A. Search for Related Content GeoRef GeoRef Citation

Sequence stratigraphically controlled diagenesis governs reservoir quality in the carbonate Dehluran Field, southwest Iran

¹ Department of Geology and Mineral Resources Engineering, NTNU, Norwegian University of Science and Technology,S. Sælands vei 1, No-7491, Trondheim, Norway (e-mail: ali.taghavi@geo.ntnu.no)
² SINTEF Petroleum Research, S. P. Andersens vei 15B, No-7465, Trondheim, Norway
³ Research and Development (R &D) Department, National Iranian Oil Company (NIOC), No. 27, Valiasr Sq., Tehran, Iran

The Sarvak Formation (late Albian–early Turonian) is one of the major oil and gas reservoir units in southwestern Iran and was deposited in a wide carbonate ramp marine setting. Three major transgressive–regressive sequences are interpreted in the upper part of the Sarvak Formation in the Dehluran Field. Sequence boundaries are recognized from facies shifts and diagenetic effects related to sea-level fall, whereas maximum flooding episodes are indicated by deep-water facies characterized by abundant bioturbation and high gamma-ray log responses.

Diagenesis is the main controlling factor on reservoir quality and plays both a constructive and a destructive role. Permeability is decreased by cementation, which fills primary porosity and disconnects pore throats, while compaction decreases porosity by establishing tighter intergrain contacts. Conversely, the dissolution of unstable minerals (mainly aragonite) is the major process that improves porosity and then permeability by enlarging pores and pore throats. Dolomitization, when associated with dissolution, creates the best reservoir intervals in the Sarvak Formation, although this is not a widespread phenomenon.

These diagenetic processes are controlled by sea-level fluctuations, and thus the sequence stratigraphic development. Dissolution, early cementation and exposure-related dolomitization took place during falling sea-levels, mainly in the uppermost, regressive parts of the major sequences. Dolomitization is recognized in the transgressive and in the regressive systems tracts. Stylolitization and fracturing are independent of sea-level fluctuations and are most likely to have formed through a combination of compaction and tectonic events.

KEYWORDS: carbonate reservoirs, diagenesis, sequence stratigraphy, Cretaceous, Iran