University of Zagreb. Faculty of Mining, Geology and Petroleum Engineering. Department of Petroleum Engineering.
Abstract
U nekonvencionalnim ležištima struktura pornog sustava, oblik pora i kapilaritet bitno utječu na račun protoka i pada tlaka, a protok je često neopisiv Darcyevom jednadžbom. Proračun propusnosti kod slabo propusnih stijena (propusnosti manje od 10-15 m2) osobito je osjetljiv na efekte proklizavanja fluida te na efekte protočnih puteva koji nastaju radi heterogenosti propusnosti. U radu su izrađena tri modela nekonvencionalnog plinskog ležišta te su praćeni dnevna proizvodnja plina u periodu crpljenja (engl. Field gas production rate, FGPR), dnevna proizvodnja vode u periodu crpljenja (engl. Field water production rate, FWPR) te pad tlaka tijekom proizvodnje (engl. Field average pressure, FPR). Simulacija je izvedena korištenjem ležišnog simulatora Eclipse tvrtke Schlumberger. Razmotren je slučaj proizvodnje prije i nakon frakturiranja, definiravši tanki proslojak povećane propusnosti (koja predstavlja efektivnu propusnost frakture). Kao rezultat dobiven je veći iscrpak plina nakon frakturiranja, a izrađeni model može poslužiti pronalaženju najoptimalnijih parametara stimulacije, prije svega smještaja bušotina u prostoru, te optimalnih parametara (visina, duljina, propusnost) frakture.Abstract: Pore system structure in unconventional reservoirs, shape of the pores and capillary essentialy influence calculation of fluid flow and pressure drop, but fluid flow sometimes cannot be described by Darcy's equation. Flow through low permeability rocks (with permeability less then 10-15 m2) is affected by fluid slippage effect and effects of flow streams that occur due to permeability heterogeneity. In this work three cases of simulation models of unconventional gas reservoirs were made to observe field gas production rate (FGPR), field water production rate (FWPR) and field average pressure (FPR). Simulation is performed using Eclipse, reservoir simulator developed by Schlumberger company. Results before and after fracturing were compared, by defining a thin layer with higher permeability (which is the effective permeability of the fracture). This resulted in a increased production of gas after fracturing. The model can be used as a template to find the optimal stimulation parameters, first of all of wells spacing and placement, and then to find optimal fracture parameters (height, length, permeability)
