Characterization of carbonate reservoir by using nuclear magnetic resonance (NMR) logging analysis at hydrocarbon field C South Sumatera

Abstract

Carbonate reservoirs are known to have very complex petrophysical parameters compared to sandstone reservoirs. This is due to the porosity and permeability of rocks that are often heterogeneous and unconnected. Nuclear Magnetic Resonance (NMR) is a well logging method that can characterize the reservoir by using porosity parameters including pore distribution and fluid type determination in pores. Determination of rock porosity is important for predicting the quality of the reservoir. The T2 cutoff value is reflected in the valley values between peaks of the T2 distribution data due to the proton movement in the rocks. The permeability prediction using NMR is strongly influenced by the value of T2 cutoff. This is because the pore state is affected by porosity-permeability. Interpretation to characterize reservoir is influenced by determination of T2 cutoff value. Porosity as the main result of NMR processing will result in an estimation of the permeability value. The hydrocarbon field C is located in the basin of South Sumatra and produces gas. Based on an earlier petrophysical analysis, the Baturaja formation is a production zone. The NMR yield on the well M4 has a T2 cutoff value of 92 ms and R1 well has a value of 100 ms. This value is compared with conventional core and petrophysical samples. The NMR response results in this study support NMR behavior on carbonate samples, which sensitive to NMR measurements on porosity. A small T2 cutoff value would represent a small porosity compared to a large T2 cutoff that would represent a large porosity. The NMR product analysis is used for the evaluation of rock formations.