In altered wall-rock, there is such a potential porosity that could store an accumulation of hydrocarbon. The wall-rock alteration could be performed by chemical mechanism or physical mechanism. The (hydrothermal) fluid in chemical mechanism run along the fracture and altered whatever they could be. Every rock could be altered as long as it met the condition of being altered, such as an exact pressure and temperature, or wall-rock chemical and mineralogy condition, and many more condition for us to get an attention. In this paper we try to link between fracture, wall-rock, and alteration to reservoir porosity in the term of petrography, and chemically. We study the basement reservoir in southern Sumatra basin. We use the analytical study based on previous reference and petrography of thin section based on the related rock in outcrop or in coring. The result of our analysis is a range data of alteration in wall-rock related to porosity and mineralization type in microscopic, or in a term of chemically. There are several alteration create new type of mineralization that opened new porosity or closed the last porosity generated by fracture along its basement. By this paper, we introduce a better understanding about fracture and alteration concept. It’s important for geologist to know what happened in their fracture. It’s generated porosity in wall-rock or closed the fracture itself. The altered fractured basement reservoir will opened our idea about secondary porosity by alteration, for opening a good porosity or on the other hand, it will closed our porosity by fractured. It obtains profits and rise the production by knowing that our fracture is crystallize growth.
Author : Stefenson Alfa, Ahmadi Afandi, Agata Vanessa, Gita Ayu Srikandini, M. Ikhwan Ariph