Newly developed rock physics studies currently used along with other oil and gas studies methods. One major application of rock physics is determination of lithology. In this paper, lithology of Fahliyan Formation (carbonate reservoir) of two wells, from two neighboring oil fields in southwest of Iran have been determined for first time. This method uses rock physics and relations between acoustic impedances and compression wave module with porosity and density. The results end up with lithology determination.
There are several methods like petrophysical methods based on log data or core analysis and cutting studies based on sampling data, which can help us to predict lithology. There is a big question mark when we want to know what happen far from well. That how we can predict lithology when we have not well data? Seismic data are good data that cover all of study area. However, what is the relation between well data and seismic data? How can we make a connection between this two useful data? Rock physics methods can answer these questions. Nowadays rock physics methods are used in oil and gas studies as new methods that we can used it to connect between this two data. Rock physics methods are connection between seismic, petrophysic and geology. One major of rock physics application, is a lithology prediction that use from compression wave, porosity and density. Acoustic impedance and compression wave module are parameters which come from compression wave (p V), density and fluid saturation condition. Gamma ray log and neutron porosity logs are used for help to analyze data and compare our results. In this study, we compare followings cross plots:
Acoustic impedance vs. Porosity
Acoustic impedance vs. Density
Compression wave module vs. Porosity
Compression wave module vs. Density
We predict lithology of Fahliyan formation based on rock physics studies in two wells from two neighbor oil fields. We compared our results with cutting samples and they confirm our results. We studied Fahliyan Formation on A1 and A2 two wells. Figure.1 illustrates location and figure.2 shows stratigraphy column of these two wells, which Fahliyan formation is reservoir rock, in two major oil fields of southwest of Iran. In these basins, Fahliyan formation divided in two members (upper and lower members). The upper member belongs to part of Early Cretaceous (Barremian) age and is poor reservoir and lower member of Fahliyan is related to Neocomian and it is a The Fahliyan Formation has a thickness of 542m in A well#1, which starts at depth of 3980m and ends at depth 4522m. As you can see on figure.2, the upper member of this formation consists of alternative limestone and shale in this well. There is complete well logging that we used neutron porosity, density and compression wave logs, in this study (figure.3). This data are used to calculate fluid saturation and bulk module.