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AAPG Bulletin

Abstract

AAPG Bulletin, V. 99, No. 9 (September 2015), PP. 16491669

Copyright copy2015. The American Association of Petroleum Geologists. All rights reserved.

DOI: 10.1306/03091514148

A new borehole temperature adjustment in the Jeffara Basin (southeast Tunisia): Inferred source rock maturation and hydrocarbon generation via one-dimensional modeling

Achraf Bouaziz,1 Amina Mabrouk El Asmi,2 Ahmed Skanji,3 and Khaled El Asmi4

1Faculty of Sciences of Tunis, Department of Geology, University of Tunis El Manar, 2092 Tunis, Tunisia; [email protected]
2Faculty of Sciences of Tunis, Department of Geology, University of Tunis El Manar, 2092 Tunis, Tunisia; [email protected]
3ETAP, 54, Avenue Mohamed V, 1002 Tunis, Tunisia; [email protected]
4Faculty of Sciences of Bizerte, Department of Geology, University of Carthage, 7021 Zarzouna, Tunisia; [email protected]

ABSTRACT

In Tunisia, most borehole temperatures used to constrain the thermal histories of sedimentary basins were previously corrected using various methods, set to best-fit domains other than the Tunisian basins. This study aimed to propose a new method of borehole temperature correction suitable for the Jeffara Basin, southeastern Tunisia. A total of 92 temperature values including bottomhole temperatures (BHTs) and drill stem test (DST) temperatures were collected from 11 boreholes in the area. The correction method consists of plotting BHT versus DST. The derived equation BLTN14148eq1BLTN14148eq2 generates corrected temperatures close to formation temperatures.

An error temperature curve following the equation BLTN14148eq3 was calculated (x = depth in meters and y = temperature error in °C). The error varies from BLTN14148eq4 to BLTN14148eq5 (BLTN14148eq6 to BLTN14148eq7) at depths below −274 m (−898 ft). A temperature error (BLTN14148eq8) is proposed according to depth, and to the time elapsed since mud circulation ceased intervals.

To test the method consistency, the Silurian Tannezuft hot shales Formation thermal history is simulated using the BasinMod 1-D™ software program. Two runs were tested based on the new method: (1) noncorrected BHT and (2) corrected BHT.

The first run indicates that the Silurian source rock is at an early stage of the oil window. The second run shows that the source rock is mature and even at a late mature stage toward the north. Oil expulsion has occurred even at an oil saturation expulsion threshold of 5%. The results explain gas condensate production in the study area.

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