Porosity is one of the most important petrophysical parameters, studied in the subject of reservoir characterization. Determining porosity and how it changes in hydrocarbon reservoirs is an important issue that has been addressed in various researches. In this research, Poro-Acoustic IMPEDANCE (PAI) is introduced as an extended form of Acoustic IMPEDANCE (AI). The difference between PAI and AI is related porosity that is directly involved in the PAI. The inclusion of porosity data in the PAI formula made porosity effective in forward modeling and INVERSION of seismic data. The use of PAI in the forward modeling of synthetic models increases the contrast between the subsurface layers, and the contrast increases twice as compared to the AI. Band Limited Recursive INVERSION (BLRI) algorithm is used for INVERSION of synthetic seismograms and model-based algorithm is used for real seismic data INVERSION. For real data, due to the existence of well data, seismic horizons and geological information, using the basic model method for INVERSION is more accurate. The main difference between INVERSION using PAI and AI is that changes in porosity can be seen directly in the results of PAI INVERSION. The correlation of porosity with PAI and AI is -0.93 and -0.85, respectively, which shows that porosity has a stronger relationship with PAI. The use of PAI can be a quick and simple solution to understand porosity changes in hydrocarbon reservoirs and increase the accuracy of porosity determination in reservoirs to a great extent.

Oil companies are trying to increase production rate by improved recovery methods. Typically, oil and gas fields have been penetrated by lots of wells. The seismic INVERSION method is a powerful technique. This project is about INVERSION of 3-D seismic data to acoustic IMPEDANCE in one of the south-west oil field of Iran. In this study we checked other different INVERSION methods such as sparse spike and model based. We applied model based INVERSION method in the studied area. The input data includes seismic data, well log data, and structural interpreted data. Knowledge of the seismic wavelet is also necessary. In this study we integrated available information from seismic data, well logs and the knowledge of regional and local geology to produce detailed, spatially consistent, 3-D IMPEDANCE models. The results of this study reveal that there are several reefal structures in the main reservoirs.

This paper examines the work of Immanuel Kant in the light of a new theory on the nature of truth, knowledge and falsehood (the INVERSION Theory of Truth). Kant’s idea that knowledge could be absolutely certain, and that its truth must correspond with reality, is discredited by a dissection of the Correspondence Theory of Truth. This examination of the nature of truth, as well as knowledge and falsehood, is conducted with reference to Sir Karl Popper’s writings on regulative ideas, the criterion of demarcation and the principle of falsifiability. It is argued that if truth is to be regarded as certain, it should be used to describe objects and events in the objective (noumenal) state, and that subjective knowledge must contain (and is improved by) falsehood. Perceptions and knowledge are obtained by the biological and evolutionary process of Active Subjectivism. Ideas we have knowledge of can be metaphysical or scientific, according to Popper’s Criterion of Demarcation. Kant’s “Copernican revolution” claim that our intellect imposes absolutely true laws on nature could not allow for the possibility that ideas might be constructed from fallible perceptions, and hence that all knowledge is uncertain. Instead, he developed a Critique of Practical Reason in which religion, though not provable through logical reasoning, could be proved by our innate moral sense, giving us a Categorical Imperative that could lead to perverse results. By rejecting the absolute certainty of a priori knowledge, and admitting a degree of essential falsehood, we arrive at a more reasonable grounding for moral behavior.

The prestack seismic INVERSION converts seismic data to the physical properties of a rock such as sonic and shear IMPEDANCE and density. It provides accurate information for predicting lithology changes and fluid types. In this paper, well logging data is used to construct synthetic seismogram. In the final stage, by transforming offset domain to angle domain and using the well information to the prestack seismic INVERSION, the extracted petro-physical parameters are discussed. The applied average wavelets of 7 wells in prestack INVERSION were in the angles of 5-9, 9-13, 13-17, 17-21 and 21-25 degrees. After wavelet extraction, low frequency acoustic IMPEDANCE models and shear IMPEDANCE and density were made as one of the INVERSION inputs. We built these, low frequency initial models using sonic log, shear IMPEDANCE log and density log from well data. There are two techniques for doing the pre-stack seismic INVERSION: simultaneous and elastic INVERSION. These technics require wavelets and background model. Simultaneous pre-stacking INVERSION is defined by seismic trace angle, logarithms of P-IMPEDANCE and S-IMPEDANCE, and extracted wavelet but Elastic INVERSION uses a transformation of the Zeoppritz equations In other words, by performing the prestack INVERSION, the sonic and shear IMPEDANCE and density are calculated using above mentioned equations. In this paper, prestack seismic INVERSION method was carried out in one of Iranian oil fields in Ghar-Asmari Reservoir and Jahrum Reservoir formations. The results showed that the presence of oil and gas in the Ghar-Asmari zone caused the reduction of the sonic and shear IMPEDANCE and density. From Ghar-Asmari zone to Jahrum, the amount of the sonic and shear IMPEDANCE and density increased. Also, the results of sonic IMPEDANCE cross-plots versus the ratio of sonic-to-shear wave velocity were determined based on porosity variations and water saturation changes. In Ghar-Asmari zone, porosity is high and water saturation is low because of the presence of gas and oil in this section. From Ghar-Asmari zone to Jahrum, water saturation increases and porosity decreases. Hence, using simultaneous INVERSION, the hydrocarbon reservoir was identified.

The deep internal structure of the crust can be determined using appropriate seismic and electromagnetic methods. The natural source magneto telluric (MT) method is the most suitable electromagnetic technique for probing into the deep crust. A long period magneto telluric data set obtained in the Southern Chilean Andes is investigated in this paper. Dimensionality analysis shows that the data may be regarded as with a strike 2D direction aligned to the N-S direction. Results of a joint INVERSION of different MT data types indicate relatively high conductive structures in the middle to deep crust beneath the volcanic arc.

The direct way to access the petrophysical property of hydrocarbon reservoir is based on well data but due to its high cost, the seismic data has been used to obtain these parameters. For this purpose, many different methods are available and each has its own advantages and limitations. From these methods the seismic INVERSION is the best tool to study the reservoir characterization. The outcome of the seismic INVERSION is the transformation of seismic reflection data to pseudo-IMPEDANCE logs at each CMP. It is therefore, the seismic INVERSION results facilitate better estimations of reservoir properties such as porosity. In this study the results of two different post-stack INVERSION methods on seismic data will compared. These are sparse-spike and model-based methods. These results were used for acoustic IMPEDANCE construction based on 2D seismic data in the Saraje Gas Field. By using this model and creation of linear regression the estimated porosity model has been achieved.

Poststack seismic INVERSION generally transmutes seismic amplitude to P-wave acoustic IMPEDANCE, which lacks low-frequency component due to the stacking process. This component should be compensated using well logs as a priori constraint. If this low-frequency trend is known with adequate accuracy, poststack INVERSION could produce precise results. Nevertheless, in most cases, the mentioned information are far from the true model. In such cases, poststack INVERSION results could have high uncertainty. Because there is no mode conversion at normal incidence, postsatck INVERSION is completely acoustic, hence P-wave IMPEDANCE is the only information which can be extracted from poststack INVERSION of P-wave data. In simulations prestack INVERSION, in addition to the P-wave acoustic IMPEDANCE, S-wave information, density, and Poisson’ s ratio can also be derived from prestack data. Thus, prestack INVERSION can be used to get more information than poststack INVERSION. The two-step process of acoustic IMPEDANCE and shear IMPEDANCE by model-based INVERSION is replaced by one-step pre-stack simultaneous INVERSION. In order to apply simultaneous INVERSION method to our prestack seismic data, the data should be transformed from offset domain to angle domain as the first step. A useful approach is to calculate offset as a function of incidence angle, using Snell’ s Law to follow the ray path through the layers if velocity information is available. The next step is to build initial models of acoustic IMPEDANCE, shear IMPEDANCE, and density. We built these initial models using sonic log, Delta-Time Shear (DTSM) log and RHOB log which were available in the interest area. There are two relationships that should hold for these wet rocks. The first relationship uses this fact that in wet clastics the ratio of the s-wave velocity over p-wave velocity should be constant within a rock layer. After reformulation of the mentioned trend, one can understand that the natural logarithm of shear IMPEDANCE has a linear relationship with the natural logarithm of acoustic IMPEDANCE. The second fact uses Gardner equation. After reformulation of the Gardner relation, it is understandable that the natural logarithm of density has a linear relationship with the natural logarithm of acoustic IMPEDANCE, too. We determined k, kc, m and mc which respectively are slope of the natural logarithm of shear IMPEDANCE against natural logarithm of acoustic IMPEDANCE, intercept of the natural logarithm of shear IMPEDANCE against natural logarithm of acoustic IMPEDANCE, slope of the natural logarithm of density against natural logarithm of acoustic IMPEDANCE, intercept of the natural logarithm of shear IMPEDANCE against natural logarithm of acoustic IMPEDANCE. Besides, we need a set of angle-dependent wavelets which are derived from angle stacks. Hence, we built three angle stacks; near-angle stack (0 to 11 degrees), middle-angle stack (11 to 20 degrees) and far-angle stack (20 to 29 degrees). Using these angle stacks, we built three statistical angle-dependent wavelets from three angle stacks. Finally, with log information, we built an initial model for acoustic IMPEDANCE and tried to solve the INVERSION matrix using conjugate gradient method. Solving the equation, we can derive acoustic IMPEDANCE, shear IMPEDANCE, and density sections simultaneously from prestack data. Using simultaneous INVERSION, we identified hydrocarbon reservoir.

During this project we tried to show high capability of the SIS scheme for 1D magneto telluric (MT) sounding data INVERSION. The scheme transforms the nonlinear problem of estimating layer resistivities and thicknesses into a linear problem of estimating the coefficients of power series of the new response function. We have used this scheme for prospecting conductive structures in southeastern shore of the Caspian Sea. This area is located in the Golestan Province in northeastern part of Iran at the border with Turkmenistan. Detecting conductive sediments in this area, which are supposed to bear iodine is economically of interest. We provided data from three MT sites and inverted the data by the SIS scheme. According to our results there is a conductive layer in the depths deeper than 600 m at all three sites. We have compared our results with the previous results, also compared the results with the geological witnesses, which accordingly existence of a conductive layer has been proved at about 700 m depth. This conductive layer is proposed to bear iodine in economic meanings.