As the extraction of information about petrophysics and fluid content from near-field versus far-field variations has gained more importance in recent years, understanding the effect of shale anisotropy in near-field versus far-field is essential. The layered structure of clay minerals causes elastic anisotropy. Shales (even conventional shale samples) are often elastically anisotropic due to the alignment of anisotropic clay minerals with the bedding plane. This research aims to address this issue by presenting a method based on rock physics modeling and the use of Thomsen parameters for AVO analysis in VTI environments. In this study, the impact of shale anisotropy on amplitude versus offset (AVO) analysis at the gas sand/shale interface in the Kerman Formation has been examined. This issue is important because accurate AVO analysis can be effective in identifying hydrocarbon areas, but in many previous studies, isotropy in environments has been assumed, which may lead to errors. In this study, the amplitude versus offset analysis in a vertically transverse isotropic (VTI) medium has been examined. For this purpose, Thomsen's anisotropy parameters were calculated. Since the anisotropy of shale affects the results of amplitude versus offset analysis at the gas sand/shale contact in the Kerman Formation, we have evaluated the impact of shale on amplitude versus offset analysis in the Kerman Formation. The results showed that in an anisotropic environment, Class 1 AVO is identifiable, indicating the presence of hydrocarbons, whereas in an isotropic environment, no distinct trend is observed in the AVO class. Additionally, it was observed in synthetic models that the effect of anisotropy is more pronounced at larger angles. The innovation of this study lies in presenting a combined analytical approach based on rock physics modeling and Thomsen parameters for AVO analysis in an anisotropic environment, which goes beyond classical isotropy assumptions and can aid in improving the location of new drilling areas.

Maximum Likelihood (ML) estimation of the frequency offset between the transmitter and the receiver from known transmitted preambles is the dominant technique for the estimation of Carrier Frequency Offset (CFO) in OFDM systems. A general formulation of ML detection problem for OFDM systems is provided in this paper and it is described how different ML techniques can be treated as special cases. In addition, major newly proposed ML techniques are compared in unified simulation framework in the presence of AWGN and their performance in term of estimation range and complexityis compared. Furthermore, we proposed two new preamble structures which have comparable complexity to the simplest available methods while their estimation ranges are fairly large, comparable to the largest achieved ranges.

AVO as a known methodology is used to identify fluid type and reservoir lithology in subsurface exploration. Method discussed in this paper, consists of three stages, including: Direct modeling, Inverse modeling and Cross plot interpretation. By direct modeling we can clarify lithology or fluid dependent attributes. Analysis performed using both P-P and P-Sv attributes. Inverse modeling deals with real data and is fed by the results of direct modeling to identify the light hydrocarbon (gas) zones. The main role of cross plot interpretation is to confirm the inverse modeling results and consequently increasing validity of performed analysis. Using Hodogram – cross plot, makes possible to identify hydrocarbon zone even in small scales. This methodology was applied in Gorgan Plain Southeast Caspian, northern Iran. It was concluded that: fluid factor, SIGN, and Poisson reflectivity are fluid dependent attributes. It was also defined that normal incidence reflectivity and P-wave impedance reflectivity are lithology dependent.Inverted sections of fluid-dependent attributes defined the existence two light hydrocarbon accumulation under the Tertiary-Cretaceous unconformity in the North Gorgan Plain. Two wet and gaseous zones are also confirmed by cross plot.

Shear wave information plays a valuable role in the interpretation of seismic data and reservoir characterization studies. Due to the high cost and technical difficulties in data recording of full elastic seismic data (3D-9C), using converted waves can be helpful to extract valuable S-wave information. Analysis of the amplitude and phase variations of converted waves with offset would be useful in better identification of converted reflections in the seismic sections and uncertainty reduction in the processing and interpretation of these data. In this regard, by using Zoeppritz equations, the energy distribution of different seismic modes (P-P, S-S, P-Sv, and Sv-P) on the interface of the layers with different acoustic impedances at various incidence angles has been studied. Then, by using forward modeling and ray tracing methods, it should be obtained that how converted waves propagate in isotropic and anisotropic media. Besides, the effect of the Vp/Vs variations in the travel time and amplitude of the converted modes are inspected. For data recorded by receivers oriented in the same direction as the seismic source (both vertical or both horizontal), the polarity of converted waves is the same in the positive and negative offsets. However, if the direction of receivers is perpendicular to the seismic source, the converted waves will have opposite polarities on different sides of the source. Moreover, for primary P-Sv reflections, the largest P-to-S conversion occurs beyond the critical angle that is related to large source-receiver offsets. In contrast, S-to-P conversion significantly appears before the critical angle. However, it should be noted that for the same takeoff angle, the Sv-P and P-Sv waves will be recorded in the same offset, because the P-Sv incidence angle equals the Sv-P reflection angle and vice versa. For example, the synthetic models show that in seismic layers with Vp/Vs = and horizontal reflector, maximum P-Sv conversion occurs at an incidence angle of about 64° and reflection angle of about 31° , while maximum Sv-P conversion occurs around 31° angle of incidence and around 64° angle of reflection. This means that from the viewpoint of source-receiver distance, depending on the intended depth, mid and far offsets data are necessary for good recording of the conversion mode reflections. Moreover, according to Snell law and Zoeppritz equations, in the case of converting Sv to P, the transmitting converted P-wave would have a small amplitude. Hence, in Sv-P studies, only the converted waves with purely Sv incoming and purely P reflection are considered.

In this paper reflection data obtained from a seismic line located in the south of Gheshm Island in the Persian Gulf region were processed. Seismic section showed weak amplitudes for deeper reflectors due to energy decay of reflections. To retrieve the weak amplitudes to their true values, the AVO attributes were applied. For this purpose, CDP angle gathers in the incident angle domain were performed. To suppress multiples and noises with high amplitudes, mute windows with different incident angles in the x-t domain were applied. Mute windows with the angles between30 and 35 degrees resulted considerable effects on the noise elimination. To study the amplitude variations versus offset, the AVO gradient section of reflection data was performed. In this stage a negative gradient anomaly was determined in the middle part (1600 - 1800 ms TWT) of the seismic section. The mentioned anomaly with due attention to the geological information was attributed to a gas reservoir. In this study, application of the AVO attributes on seismic data showed that, amplitude due to energy decay that was not present on the routine seismic section could be simulated.

Reservoir geophysics studies have playeda significant role in exploration and production activities during the last decades. These techniques often try to identify the lithology and fluid content of the reservoir by utilization of pre-stack seismic data. The most effective type of these studies is performed in sandstone reservoirs, in which shear sonic logs increase the quality of the results. In this study, Amplitude Versus Offset (AVO) technique is applied in one of the sandstone reservoirs in the Persian Gulf. The applied methodology is based on modeling of seismic responses with different scenarios of fluid saturations in order to identify, using rock physics models, theseismic behavior of the reservoir in wells lacking shear logs. To achieve this goal, petrophysical interpretations of well data and reservoir parameters were integrated into a rock physics model, which eventually helped to recognize the seismic attributes sensitive to fluid content of the reservoir. In addition, calculation of pre-stack seismic attributes data led us to discriminate accurately the gas-oil contact. The comparison of the AVO study results with petrophysical evaluation results shows that AVO method results are very reliable and precise in the study area.

Offset agreements are legal trade practices, common in the aerospace and military industries. The international names for these commercial practices are various: industrial compensations, industrial cooperation, offsets, industrial and regional benefits, balances and equilibrium. An offset agreement is an agreement between two parties whereby a supplier agrees to buy products from the party to whom it is selling, in order to win the buyer as a customer and offset the buyer's outlay. Generally the seller is a foreign company and the buyer is a government that stipulates that the seller must then agree to buy products from companies within their country. Indeed, industrial compensation practices required as a condition of purchase in either government-to-government or commercial sales of articles and/or services. Often, the aim of this process is to even-up a country's balance of trade. Although the offset agreement is so significant, it has been rarely known for inner academic associations; in this work, after brief introducing of the mechanism, variations and compensatory obligations of these contracts, we discuss about the structure of them and the tendency of their parties to bind independent contracts related to each other throughout a document called the protocol.

This research used prestack seismic data in Penobscot to detect gas-bearing layers using AVO analysis. AVO technique is not easy based on Zoeppritz equations then this work applied Shuey approximation to calculate gradient (G) and intercept (Rp) parameters using least square and Tikhonov solutions. Model covariance matrix was calculated for least square and Tikhonov technique to obtain the variance of estimation of Rp and G. The variance of estimation of least square method is 0. 24 and 15. 08 for RP and G, respectively. Also, it is equal to 0. 08 and 0. 14 for Rp and G in Tikhonov solution. Therefore, the results of Tikhonov are more reliable than least square solution. Multiplication of intercept and gradient showed the strong and positive values in gas layers. The reflection coefficient of shear wave identified gas-bearing layers by a positive value. The difference of P-wave and S-wave profile appeared relatively high negative values in time range of 2000 to 2020 ms. L30 well which was drilled in cross line 1153 showed that there is gas accumulation in time range of 2000 to 2036 ms. Therefore, AVO attributes could identify gas-bearing layers.

Relying on the observation that language – “langage” or logos – has a questioning essence and its existence depends on the “problematological difference”, Michel Meyer proposes the couple “question/answer” as the basic unity of linguistic studies. His analysis of the contrastive blend of these two elements leads to some problematological triangle with hermeneutic/semantic, rhetoric/ argumentative and dialectic/dialogic as sides, and which includes any speech act, i. e. any kind of interaction between question and answer, in both intra- and intersubjective areas. Between this triangle and what Meyer calls the “classic model of syntax/semantics/pragmatics”, there is no side by side opposition, especially since the semantic dimension is common in both models. However, Meyer insists on their division, because he considers the classic model as the very manifestation of “propostionalism” in language sciences. In the problematological conception of language, the critique of linguistic propostionalism and the one of philosophical propositionalism are melded. They join the critique of positivism which, says Meyer, is the radical form of propostionalism.