ESTIMATION OF SPONTANEOUS POTENTIAL USING PETROPHYSICAL WELL LOGS: THE ASMARI RESERVOIR OF AHVAZ OILFIELD, IRAN

Spontaneous potential is one of the old types of logs which are used in the petroleum industry for determining lithology, bed thickness, and the salinity of formation water. SP does not measure in some wells; for example in holes filled with nonconductive muds such as oil-based muds, SP curve cannot be recorded. In this article a new model for estimating spontaneous potential using multiple regression technique are constructed with data from three wells of Ahvaz oilfield. The model is successfully tested with coefficient of determination of 0.84 for another well in Ahvaz oilfield. Our studies are demonstrated a good agreement between our multiple regression model prediction and actual SP log.The model is also applied to another three wells in the studied oilfield without SP log which the results are then successfully validated with their gamma ray logs. The results show the constructed SP log displays good agreement with GR log. The aim of this article is to introduce a model able to estimate SP using other conventional logs (such as sonic interval transit time, gamma ray, neutron porosity, bulk density and formation resistivity logs) in wells without SP log. The results of this article are promising and can be easily extended in other similar neighboring reservoirs.

Keywords:

Spontaneous potential , Multiple regression technique , Synthetic well log , Regression analysis , Ahvaz oilfield