The Gulf of Mexico (GOM) represents a challenge for exploration and production. Most of the sediments coming from North America has bypassed the shelf margin into Deep Water. In an Attempt to attack this challenge this thesis pretends to break the GOM's false bottom, mainly comprised by diverse salt structures and growth fault families. In this attempt, geological and geophysical data are integrated to find clues to potential hydrocarbons indicator (PHI) that could be of Reservoir Quality (RQ). 3D Pre stack depth migrated data comprised of Mississippi Canyon blocks, were interpreted: Top and base of salt, leading to the identification of a PHI represented by a consistent Amplitude Anomaly (AA) below and towards a salt structure. This AA may be of RQ and feasibility evaluation for further decisions may be taken. Following the structural sequences that Govern central GOM during Oligocene through out Miocene was important to support the results.

The North Caspian Basin (NCB) contains a significant number of major oil fields, some of which are yet to be put into production. The reason why some of these fields are not yet put into production is the exploration challenge that the NCB poses. In particular, the complex geological structure of this region makes it quite difficult to image its oil fields with conventional seismic techniques. This thesis sheds more light on difficulties associated with acquiring and processing seismic data in the NCB. The two central tools for investigation of these imaging challenges were the construction of a geological model of the NCB and the use of an accurate elastic wave-propagation technique to analyze the capability of seismic to illuminate the geological structures of the NCB. Using all available regional and local studies and my knowledge gained with oil companies, where I worked on subsalt and suprasalt 2D and 3D seismic data from the North Caspian Basin, I constructed a 2D elastic isotropic 10-by-6 km geological model of a typical oil field located on the shelf of the Caspian Sea in the southeastern part of the North Caspian Basin, which has the largest oil fields. We have propagated seismic waves through this model. The technique we used to compute wave propagation is known as the Finite-Difference Modeling (FDM) technique. Generating 314 shot gathers with stationary multicomponent OBS receivers that were spread over 10 km took two weeks of CPU time using two parallel computers (8 CPU V880 Sun Microsystems and 24 CPU Sun Enterprise). We have made the data available to the public. The dataset can be uploaded at http://casp.tamu.edu in the SEGY format. The key conclusions of the analysis of these data are as follows: - Combined usage of P- and S-waves allows us to illuminate subsalt reef, clastics and complex salt structures despite the 4-km overburden. - Free-surface multiples and guided waves are one of the key processing challenges in NCB, despite relatively shallow (less than 15 m) shelf water.

Nowadays, subsalt oil and gas exploration is drawing more and more attention from the hydrocarbon industry. Hydrocarbon exploitation requires detailed geological information beneath the surface. Seismic imaging is a powerful tool employed by the hydrocarbon industry to provide subsurface characterization and monitoring information. Traditional wave-equation migration algorithms are based on the one- way-in-depth propagation using the scalar wave equation. These algorithms focus on downward continuing the upcoming waves. However, it is still really difficult for conventional seismic imaging methods, which have dip limitations, to get a correct image for the edge and shape of the salt body and the corresponding subsalt structure. The dip limitation problem in seismic imaging can be solved completely by switching to Reverse-Time Migration (RTM). Unlike old methods, which deal with the one-way wave equation, RTM propagator is two-way and, as a result, it no longer imposes dip limitations on the image. It can also handle complex waveforms, including prismatic waves. Therefore it is a powerful tool for subsalt imaging. RTM involves wave extrapolation forward and backward in time. In order to accurately and efficiently extrapolate the wavefield in heterogeneous media, I develop three novel methods for seismic wave modeling in both isotropic and tilted transversely isotropic (TTI) media. These methods overcome the space-wavenumber mixed-domain problem when solving the acoustic two-way wave equation. The first method involves cascading a Fourier Transform operator and a finite difference (FD) operator to form a chain operator: Fourier Finite Differences (FFD). The second method is lowrank finite differences (LFD), whose FD schemes are derived from the lowrank approximation of the mixed-domain operator and are represented using adapted coefficients. The third method is lowrank Fourier finite differences (LFFD), which use LFD to improve the accuracy of TTI FFD mothod. The first method, FFD, may have an advantage in efficiency, because it uses only one pair of multidimensional forward and inverse FFTs (fast Fourier transforms) per time step. The second method, LFD, as an accurate FD method, is free of FFTs and in return more suitable for massively parallel computing. It can also be applied to the FFD method to reduce the dispersion in TTI case, which results in the third method, LFFD. LFD and LFFD are based on lowrank approx- imation which is a general method to handle mixed-domain operators and can be easily applied to more complicated mixed-domain operators. I show pseudo-acoustic modeling in orthorhombic media by lowrank approximation as an example. / text

There are many complications associated with abnormally high fluid pressures in overpressured formations. Pore pressure can directly influence all parts of operations including drilling, geological studies, completion, and production. Accurate predictions of pore pressure and fracture pressure are vital aspects to the production and completion of safe, time efficient, and cost efficient projects. Knowledge of pressure distribution in the formation can greatly reduce complexities associated with drilling and completing a well. A three-method pore pressure and fracture pressure study was performed on two prospect deepwater wells located in the Gulf of Mexico. More than thirty offset wells in the greater region were initially analyzed for similarities with the two prospect wells. In the final analysis, only six wells were used to create pore pressure and fracture pressure models due to inconsistencies in similarities or lack of usable data in many of the offset wells. Pore pressure and fracture pressure models were constructed for the offset wells, and then applied and calibrated for the two prospect wells using drilling data such as mud weights, MDTs (Modular Dynamic Testing), and LOTs (Leak-off Test). Three types of pore pressure and fracture pressure models were used in the study: Eaton’s deep resistivity method; Eaton’s acoustic sonic method; and Bower’s interval seismic velocity method. Pore pressure and fracture pressure prediction was complicated by abnormal pressure in the formation due to undercompaction and seals. Both prospects were located in a deep subsalt environment. Low permeability and traps prevents fluid from escaping as rapidly as pore space compacts thus creating overpressure. Drilling through salt in deep water is expensive and risky. Elevated pore pressure and reduced fracture pressure underneath salt seals can create very tight mud weight windows and cause many drilling problems, as seen in the results of the offset wells’ pore pressure and fracture pressure models. Results indicate very small pore pressure and fracture pressure windows, or mud weight windows, because of overpressures in the formation caused by such a deep subsalt environment. Many casing points were needed in the final casing design of prospect wells to accommodate the smaller mud weight windows. Pore pressure has the most significant increase immediately below the salt, while the mud weight window remained constant or decreased with depth. The average mud weight window ranged between 1 to 2 pounds per gallon below the salt. / text

Made available in DSpace on 2016-08-02T21:42:38Z (GMT). No. of bitstreams: 1 Gilson Mendes Pinto.pdf: 1055309 bytes, checksum: 93ab378715ac04a19eabcebc7510db41 (MD5) Previous issue date: 2014-08-19 / The main objective of the research is seeking lifting, analyze, quantify and sort by levels of competences which professionals were recruited by Petrobras after the discovery of the Brazilian subsalt layer. The research is justified by the expected growth in domestic production of oil and natural gas estimated for the coming years which may cause an imbalance between supply and demand of manpower for their development. The methodological approach developed for conducting the research was an exploratory, descriptive documentary research through qualitative and quantitative longitudinal analysis. As a first result the research has revealed that Petrobras does not use to recruit professionals for positions at managerial positions. The results also demonstrated that 56.8pc of the open recruitment vacancies are for professionals with middle level degree and 76.4pc of the vacancies are related to the manufacturing process showing that Petrobras uses as a gateway to hire professionals with middle level degree with technical training qualification. When performing classification and qualification of job opportunities opened to recruitment the research identified five groups of professionals spread along three carrers aisle and four salarial levels that when classified by career and categorized by levels of competences were responsible for 69% of job opportunities opened to recruitment. The two first relevant groups has career related to industrial operations where the upper level (O6) and the lower level (O1) were responsible for 22pc and 21pc respectively of the total number of job opportunities offered in the period. The third group in importance has career related to engineering, processes and projects which is categorized as medium level (E3) on a scale between two and five and these professionals were responsible for 13pc of total number of job opportunities offered. The fourth and fifth groups has career related to business management and when categorized by levels of competences at third (G3) and fourth levels (G4) on a scale between one and five these professionals are responsible for 7pc and 6pc of job opportunities opened to recruitment. / A pesquisa possui como objetivo geral levantar, analisar, quantificar e classificar por níveis de competências quais foram os profissionais recrutados pela Petrobras no período pós-descoberta da camada do pré-sal brasileiro. A pesquisa se justifica pela previsão de crescimento da produção nacional de petróleo e gás natural estimada para os próximos anos o que poderá causar um descompasso entre a oferta e a demanda de mão de obra para o seu desenvolvimento. A abordagem metodológica desenvolvida para realização da pesquisa foi a da pesquisa exploratória, descritiva e documental, através de análise qualitativa e quantitativa longitudinal. Como resultado, a pesquisa revelou que a Petrobras não recruta profissionais para posições de nível gerencial. Os resultados demonstraram ainda que 56,8% das vagas abertas ao recrutamento são destinadas aos profissionais com formação de nível médio e que 76,4porcento das vagas são relacionadas ao processo fabril evidenciando que a Petrobras utiliza como porta de entrada a contratação de profissionais de nível médio com formação técnica. Ao realizar a classificação e qualificação da oferta de vagas abertas ao recrutamento a pesquisa identificou cinco grupos de profissionais distribuídos por três eixos de carreira e quatro níveis salariais que quando categorizados por níveis de competências que foram responsáveis por 69porcento de todas as vagas abertas ao recrutamento. Os dois primeiros grupos em relevância estão relacionados ao eixo de carreira de operações industriais onde o nível superior (O6) e o nível inferior (O1) foram os responsáveis por 22porcento e 21porcento respectivamente do total da oferta de vagas no período. O terceiro grupo em importância diz respeito ao eixo de carreira engenharia, processos e projetos onde os profissionais categorizados com nível médio (E3) numa escala de dois a cinco foram os responsáveis por 13porcento do total de vagas abertas. O quarto e quinto grupos estão relacionados ao eixo de carreira gestão de negócios e categorizados por níveis de competências nos níveis três (G3) e quatro (G4) em uma escala de um a cinco sendo estes responsáveis 7porcento e 6porcento do total de vagas.

The ever-expanding need for energy, including those related to fossil fuels, is behind the drive to explore more complicated regions, such as salt and subsalt provinces. This exploration quest relies heavily on recorded surface seismic data to provide precise and detailed subsurface properties. However, conventional seismic processing algorithms including the state-of-the-art full-waveform inversion (FWI) fail to recover those features in many areas of salt provinces. Even the industrial solution with substantial involvement of manual human-interpretation has faced challenges in many regions. In this thesis, I attempt to replace those manual, and somewhat erroneous, steps to the velocity building in salt provinces with a mathematically robust algorithm under the FWI machinery. I, specifically, regularize FWI by penalizing the velocity drops with depth with a new more flexible function. Although promising, FWI is computationally very expensive, especially for large 3D seismic data. It updates an initial guess of the model iteratively using the gradient of the misfit function, which requires lengthy computations and large memory space/disc storage. Based on the adjoint state method, gradient computation usually requires us to store the source wavefield, or include an additional extrapolation step to propagate the source wavefield from its temporary storage at the boundary. To mitigate this computational overburden, I propose an amplitude excitation gradient calculation based on representing the source wavefield history by a single, specifically the most energetic arrival. In this thesis, I also propose a novel-multiscale scheme based on ux-corrected transport (FCT) to reduce artifacts in the gradient direction due to the noise present in seismic data. FCT comprises of two finite difference schemes: a transport and a diffusion to compute the flux at a grid point. I observe a couple of benefits in FCT-based FWI. First, it yields a smooth gradient at the earlier iterations of FWI by promoting the lower frequency content of the seismic data. Second, it is easily compatible with the existing FWI code, and with any objective function. The multiscale strategy starts with a large smoothing parameter and relaxes it progressively to zero to achieve the final inverted model from traditional FWI.

Sub-salt oil and gas formations in deep-water northern Gulf of Mexico are high priority targets. Advances in seismic processing allow for high-resolution, below-salt imaging. Understanding the modes of salt emplacement provide insight into sub-salt traps and potential drilling hazards. A sub-salt sedimentary unit lies in the Keathley Canyon protraction. Autosutures created the transport-parallel lineaments of the upper surface of the unit. In addition, highly variable sediment aggradation rates created ramps, flats, and basal cutoffs along the base of the allochthon as salt and sediment competed for space. Seismic models identify modes of salt emplacement, salt/sediment interactions, and mechanisms responsible for the morphology. Petrophysical assessments highlight an abnormally pressured, dirty salt environment transitioning into a gouge zone. Dirty salt adds an element of difficulty to managing borehole pressures requiring a unique mud-weight plan designed to resist formation pressures without fracturing lithology.

In this paper, we present a nonlinear curvelet-based sparsity-promoting formulation for three problems in seismic processing and imaging namely, seismic data regularization from data with large percentages of traces missing; seismic amplitude recovery for subsalt images obtained by reverse-time migration and primary-multiple separation, given an inaccurate multiple prediction. We argue why these nonlinear formulations are beneficial.