The Gabes Gulf located in the South Mediterranean Sea (Southeastern part of Tunisia) is a prolific petroleum-producing area with several oil and gas fields and it's the subject of significant discoveries. The area is affected by intense tectonic events and several stages of hydrothermal activities. During drilling at the MX area in NE of the Gabes Gulf, a magmatic intrusion has been encountered within a reservoir rock (i.e., Douleb Formation). The objectives of the present study are (1) to investigate the impact of the hydrothermal activities on this magmatic intrusion and (2) to characterize the potential modifications in its mineralogy and petro-physical properties that can affect the migration/accumulation of hydrocarbons. To do so we combine optical microscopy, X-ray diffraction, scanning electron microscopy, energy dispersive X-ray spectrometry, micro-Raman spectroscopy, electron microprobe analyses, and petro-physical measurements.

Our results show that the initial magmatic intrusion (dolerite) is composed mainly of plagioclase, clinopyroxene, and olivine. Based on petrographic observations, this intrusion subjected to several stages of hydrothermal fluid alterations that modified the primary texture and mineralogy. Albite, calcite, ankerite, dolomite, pyrite, quartz, anatase, kaolinite, and chlorite are the main secondary mineral products. During this alteration process, carbonates, pyrite, and quartz precipitated in vesicles, forming amygdules structure with enveloped zones indicating a fluctuation of fluid chemistry during their formation. In addition, petrographic observations indicate an interaction between feldspars exsolution and metasomatic processes in the studied area.

The dissolution mechanisms, as well as the textural modifications in the dolerite induced by the hydrothermal activity, are underlined by the presence of spherulites, pores, and micropores. Such modifications significantly improved the porosity of the dolerite body. Conversely, the new mineralization that filled the fractures and micro-fractures, have reduced the inter-pore connections, and thus reduced its permeability. The present work demonstrates the important role of hydrothermal activity on the petro-physical properties of magmatic intrusions and how it could facilitate the migration/accumulation of hydrocarbons. Our results open the door for further investigations to check the potential presence of hydrocarbons within this doleritic intrusion.

位于地中海南部（突尼斯的东南部）的加布斯海湾是一个多产的石油产区，有多个油气田，这是重大发现的主题。该地区受强烈的构造事件和热液活动的几个阶段的影响。在加贝斯湾东北部的MX地区进行钻探时，在储层岩石（即，杜勒布组）中遇到了岩浆侵入。本研究的目的是（1）研究热液活动对该岩浆侵入的影响，以及（2）表征其矿物学和岩石物理性质的潜在变化，这些变化会影响烃类的运移/聚集。为此，我们将光学显微镜，X射线衍射，扫描电子显微镜，能量色散X射线光谱法，显微拉曼光谱法，电子显微探针分析和石油物理测量相结合。

我们的研究结果表明，最初的岩浆侵入（辉母岩）主要由斜长石，斜辉石和橄榄石组成。基于岩相学观察，这种侵入经历了热液流体改变的几个阶段，这些阶段改变了原始的质地和矿物学。主要的次要矿物产品有： bit石，方解石，方铁矿，白云石，黄铁矿，石英，锐钛矿，高岭石和绿泥石。在这种变化过程中，碳酸盐，黄铁矿和石英在小泡中沉淀，形成杏仁状结构，其包膜区表明其形成过程中流体化学的波动。此外，岩石学观察表明长石之间存在相互作用研究领域中的解脱和变元过程。

球墨石，孔隙和微孔的存在突显了水热活动在白云石中引起的溶解机理以及结构改变。这样的改性显着改善了白云石体的孔隙率。相反，充满裂缝和微裂缝的新矿化作用减少了孔间连接，从而降低了渗透率。本工作证明了热液活动对岩浆侵入岩的岩石物理性质的重要作用，以及它如何促进烃类的运移/聚集。我们的结果为进一步研究以检查这种白垩纪侵入岩中碳氢化合物的潜在存在打开了大门。