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The purpose of the present study is to investigate the effect of sedimentary environments and diagenesis processes on the reservoir quality of the Asmari Formation in Kupal field by combining the results of seismic sequence stratigraphy, petrophysical evaluation, seismic attributes and the inversion of threedimensional seismic data to determine more precisely the process of changes in the reservoir properties of zones 1 to 5 of the sequences of the carbonate part of the Asmari Formation. In this study, the inversion method was used to extract acoustic impedance from 3D seismic data by Hampson Russell software. There are different methods of inversion of seismic data, according to the available data and the conditions of the Kupal field, in this study, model-based inversion is chosen due to its higher accuracy and separation power. The special aim of this article is to determine the changes in the reservoir properties of the Asmari formation by combining the results of the inversion of seismic data and seismic indicators with the results of sedimentological studies, sequence stratigraphy. According to sequence of stratigraphic studies, Asmari Formation has three sequences. The lower sequence is in the sandstone section and the middle and upper sequences are in the carbonate section. According to petrophysical studies, Asmari reservoir has 7 main zones. Zones 1 to 5 are in the upper and middle sequences of the carbonate section, zones 6 and 7 are in the lower sequence of the sandstone section. After matching the results of inversion with the results of sedimentology, the stratigraphic sequence was identified as the middle sequence, which includes zones 3, 4, and 5. It settled in a carbonate platform sedimentary environment. This sedimentary sequence is influenced by digenesis factors after deposition and the conditions of the sedimentary environment during deposition. Zones 3, 4, and 5 have sporadic changes in acoustic impedance indicators, layer thickness, and porosity. The most important factor of these changes can be due to the presence of mounds and reefs in these sediments. According to the dissolution or cementation of reefs, these zones may have high porosity and low impedance (dissolution) or low porosity and high impedance (cementation) in reefs. The final sequence of the Asmari formation, which includes zones 1 and 2, was deposited in the Sabkhai environment. This condition has caused primary or secondary porosity between the dolomite crystals. The changes in porosity and acoustic impedance and the amplitude of zones 1 and 2 are very small. Due to the low depth of the sedimentary basin, we see the activity of river systems in some places, which have caused erosion and deposition. The sediments of these rivers can have high porosity and low acoustic impedance. These sediments have high reservoir quality. The implications of this study suggest that in Maron and Aghajari fields are adjacent to the Kupal field and they have three-dimensional seismic data. Coincidentally, they can indicate a interpretation of threedimensional seismic data and stratigraphic seismic sequence in these fields. [ABSTRACT FROM AUTHOR]

Shear wave velocity is a key factor to estimate the elastic and petrophysical parameters of the hydrocarbon reservoir. However, shear wave velocity is rarely logged at wells due to the imposition of high costs. Therefore, it is usually attempted to estimate this parameter by different methods from the available and related data. Describing the elastic parameters of reservoir rock, including shear modulus, bulk modulus and Poisson's ratio, requires the measurement of density and compressional and shear wave velocities of the reservoir formations. Direct measurement of the shear wave velocity is done by drilling cores and DSI (Dipole Shear Sonic imager) tools, which are unfortunately very time-consuming and expensive. In this study, a practical method for estimating shear wave velocity in a sandstone oil reservoir is presented. In the studied reservoir, from seven existing wells, the shear wave velocity has been measured by DSI tools in only one of them (well #7). The shear wave velocity log in the location of the other wells was estimated using a petrophysical equation, defined for the location of well #7. The correlation of other logs (i.e. acoustic, density, porosity, resistivity, gamma ray, dolomite volume, quartz volume, and water saturation logs) with the shear wave velocity was investigated in well #7. We found that the compressional wave velocity, density, porosity, dolomite volume and quartz volume logs were more correlated with the shear wave velocity log in well #7. Thus, these logs were selected as input for estimating shear wave velocity log and the experimental equation using the multivariable linear regression method was calculated. The estimated shear wave velocity log using the obtained relationship has a 90% correlation with the measured shear wave velocity log in well #7. Using this petrophysical relationship, the shear wave velocity were estimated in the other wells (blind wells). The main goal in this study, was to produce the volume of the shear wave velocity information at the sandstone reservoir. To obtain 3D volume of shear wave velocity distribution in the reservoir, the seismic and well data are integrated. To achieve this goal, the model-based seismic inversion technique has been performed to obtain the acoustic impedance volume for the sandstone reservoir. The calculated acoustic impedance volume using model-based algorithm has an average of 99% correlation and 15% error with the real acoustic impedance log. The results of the seismic inversion were fed into the cross validation method to derive the optimal number of seismic attributes relevant to shear wave velocity information. The cross validation method shows that the attributes of the filter 20/25-30/45, the cosine instantaneous phase, the acoustic impedance and the instantaneous frequency have the reasonable correlation with the shear wave velocity information respectively, and are selected as the input attributes for the estimation of shear wave velocity volume in the sandstone reservoir. Our results show a good agreement between the real shear velosity log and the predicted shear velocity from the seismic attributes in the place of well #7. The obtained shear wave velocity volume accompanied by the compressional wave velocity information can be used to infer more robust petrophysical parameters in the reservoir. [ABSTRACT FROM AUTHOR]