State-Of-The-Art of Carbonate Pore Type and Permeability Modelling: An Approach of Petro-Acoustic Modelling by Using Lucia Rock Fabric Number (RFN) in Central Luconia, Offshore Sarawak

Abstract

Abstract Central Luconia province is located in South China Sea, Sarawak with development of more than 250 carbonate pinnacles and platform in Middle Miocene to Late Miocene. The study proposes a methodology that has been successfully applied and calibrated to 20 exploration or appraisal wells in both carbonate pinnacles and platform with the objective to model pore types from compressional velocity and subsequently used it for permeability prediction based on Lucia's rock fabric number (RFN). Porosity, permeability, petrography and mercury injection pressure (MICP) data of more than 2000 core plugs and sidewall core samples were analyzed to establish functions in between compressional velocity, pore types and permeability. This paper is established based on two concepts by many authors in the past, but no publication to date has linked these two concepts together. The first concept is the poroelastic behavior of carbonate rock under constant pressure and 100% water saturation is controlled primarily by a combination of porosity and pore geometry (Wyllie et. al., 1958; Anselmetti & Eberli, 1993; Anselmetti et. al. 1997; Eberli et. al., 2003). High aspect ratio pores sample such as molds and vugs, typically has higher pore throat size. The sonic velocity of this sample will plot above Wyllie-time-average (WTA) equation. Low aspect ratio pores such as interparticle and intercrystalline pores, typically has lower pore throat size. The sonic velocity of this sample will plot below WTA equation. The second concept is the Lucia rock fabric number (RFN) which described porosity – permeability relationships for various particle- size groups in non-vuggy or interparticle porosity rocks only. However, our MICP dataset conclude that Lucia RFN number is inversely proportional to dominant pore throat size in carbonate rock with little to no presence of primary porosity. The dominant pore throat size was determined based on the apex of curve in the crossplot of mercury saturation divided by injection pressure to mercury saturation.