Fuzzy Logic In The Simulation Of Sonic Log Using As Input Combinations Of Gamma Ray, Resistivity, Porosity And Density Well Logs From Namorado Oilfield

Abstract

The main premise of this work is to consider that any geophysical well log may be derived from combinations of two other logs measured at the same depth, even if its physical principles are very different. Thus, our proposal is to simulate the sonic log (DT), because it is not always present on the set of logs, it may present problems in its measurement and it is very useful in the oil industry activities. To achieve these objectives, the basic suite of well logs from Namorado Oilfield was analyzed: DT, gamma ray (GR), resistivity (RT), porosity (NPHI) and density (RHOB). The results show a high correlation between DT-GR, DT-NPHI, DT-RHOB, GR-NPHI, RT-RHOB and NPHI-RHOB pairs, meanwhile, low correlations between DT-RT, GR–RT, GR-RHOB and RT-NPHI couples. The couples DT-NPHI and DT-RHOB reveal linear relationships, potential relationship for DT-GR, GR-NPHI, GR-RHOB and NPHI–RHOB pairs, and logarithmic ones for the couples RT – RHOB, RT – NPHI, GR – RT and DT- RT. In the simulation, it was found low fit errors regarding real data ranging between 5% to 7% for all the pairs, showing this that the utilized approach functioned very well, even in the presence of low correlations and non linear relationships between logs, caused by a clayey sandstone reservoirs present in Namorado Oilfield.