General model for the calculation of geological probability associated with new gas discoveries in the northern Adriatic with an example of the Ika gas field : master’s thesis

Plinsko polje Ika je jedino polje u Jadranu gdje je plin nakupljen i u karbonatima. Do danas na tom području izrađene su dvije proizvodne platforme Ika A i Ika B te 5 bušotina iz kojih se pridobiva plin. Razradba plinskog polja Ika započela je 2004. godine i moguća je rentabilna eksploatacija. Polje sadrži četiri ležišta, od kojih se najdublje nalazi u karbonatima. Najdublje ležište uvjetovano je tektonsko - erozijskom diskordancijom koja se nalazi na dodiru mezozojskih stijena s pliocenskim taložinama, a plin je nakupljen ispod te diskordancije. Radi se o „burried hill“ strukturi koja je podjeljena u tri strukturna uzvišenja. Ostala tri plića ležišta izgrađena su od pleistocenskih rahlih pijesaka. Cilj ovoga rada bila je procjena vjerojatnosti uspjeha „POS“ (engl. Probability of Success) pronalaska novih otkrića plina unutar rubnog područja spomenutog polja, tj. u mezozojskim karbonatima i pleistocenskim pijescima. Procjena je učinjena nadogradnjom ranije objavljenog hrvatskog modela procjene POS-a, uz pomoć Microsoftovog programa „Excel“ i programa „GeoProbe Modeling 1.1“ koji je se koristi za računanje geološke vjerojatnosti pojave ugljikovodika na području HPBS-a.Abstract: Ika Gas Field is the only field in the Adriatic with gas reservoir in carbonate rocks. Today in that gas field there are two production platforms, Ika A and Ika B, and five production wells. The development of Ika gas field started in 2004 and production is profitable. Ika Field consists of four reservoirs, the deepest of which is in carbonates. The deepest reservoir is defined with tectonic-erosional discordance which is located at the point of contact of Mesozoic rocks with Pliocene deposits and gas is located below the unconformity. The structure is one of a buried hill with three structural tops. Three other reservoirs are composed of Pleistocene loose sands. The aim of this thesis is to assess the ‘’Probability Of Success’’ (abbr. POS) of finding new gas discoveries within the marginal area of the both mentioned fields, that is in Mesozoic carbonates and Pleistocene sands. The assessment is completed using the Microsoft Excel and GeoProbe Modeling 1.1 program, which is originally used to calculate the geological probability of hydrocarbon discoveries in the Croatian part of the Pannonian Basin System