Thesis (M.S.)--West Virginia University, 2010. / Title from document title page. Document formatted into pages; contains ix, 38 p. : col. ill., maps (some col.). Includes abstract. Includes bibliographical references (p. 36-37).

The large amount of produced oil and gas come from conventional resources all over the world and these resources are being depleted rapidly. This fact and the increasing oil and gas prices force the producing countries to find and search for new methods to recover more oil and gas. In order to meet the demand, the oil and gas industry has been turning towards to unconventional oil and gas reservoirs which become more popular every passing day. In recent years, they are seriously considered as supplementary to the conventional resources although these reservoirs cannot be produced at an economic rate or cannot produce economic volumes of oil and gas without assistance from massive stimulation treatments, special recovery processes or advanced technologies. The vast increase in demand for petroleum and gas has encouraged the new technological development and implementation. A wide range of technologies have been developed and deployed since 1980. With the wellbore technology, it is possible to make use of highly deviated wellbores, extended reach drilling, horizontal wells, multilateral wells and so on. All of the new technologies and a large number of new innovations have allowed development of increasingly complex economically marginal fields where shale gas and coal bed methane are found. In this study, primary target is to compare different production methods in order to obtain better well performance and improved production from different types of reservoirs. It is also be given some technical information regarding the challenges such as hydraulic fracturing and multilateral well configuration of the unconventional gas reservoir modeling and simulation. With the help of advances in algorithms, computer power, and integrated software, it is possible to apply and analyze the effect of the different well trajectories such as vertical, horizontal, and multilateral well on the future production performance of coal bed methane, shale gas, and tight gas reservoirs. A commercial simulator will be used to run the simulations and achieve the best-case scenarios. The study will lead the determination of optimum production methods for three different reservoirs that are explained above under the various circumstances and the understanding the production characteristic and profile of unconventional gas systems.

[pt] Dentre os custos considerados na explotação de um campo de petróleo, os de perfuração constituem uma parcela significativa do total. Dentro deste cenário, devemos estar atentos à remoção dos cascalhos gerados pela perfuração, também referido como limpeza de poços. Esta operação é, ainda hoje, um tema crítico na perfuração de poços de alta inclinação, pois os cascalhos que se depositam devido à ação da gravidade, formam um leito no interior do espaço anular formado entre a coluna de perfuração e o revestimento. Quando este leito ocupa grande parte do espaço anular, ele é responsável por diversos problemas na perfuração, como por exemplo, desgaste prematuro da broca, baixas taxas de penetração, fraturamento da formação, torques e arrastes excessivos na coluna de perfuração, prisão da coluna de perfuração, interrupção da circulação de fluido, aumento da pressão no anular, etc. Se esta situação não for tratada adequadamente, o problema pode provocar a perda do poço. A tese propõe uma modelagem para o escoamento multifásico na perfuração de poços de petróleo, capaz de avaliar a formação do leito de cascalhos e prever oscilações de pressões no anular decorrentes do escoamento. O modelo adotado é o de duas camadas, onde o espaço anular é dividido em duas regiões: leito e suspensão. O leito (Região 1) é formado pelos cascalhos que se sedimentam devido ao efeito gravitacional enquanto a suspensão (Região 2) é a porção do anular acima do leito depositado, formada pelo fluido de perfuração e os cascalhos transportados. As equações que constituem o modelo implementado são dadas pelas equações de conservação de massa para os sólidos e para o líquido e as equações de conservação de quantidade de movimento para o leito e para a suspensão. O método dos volumes finitos foi utilizado para a discretização das equações diferenciais juntamente com o método de Newton para a solução do sistema não-linear de equações. A solução é dada através das seguintes variáveis: altura do leito, velocidade dos sólidos no leito e na suspensão, velocidade do fluido no leito e na suspensão, pressão no anular e concentração de sólidos no anular. Exemplos de aplicação da metodologia são apresentados e mostram o comportamento das variáveis envolvidas ao longo do tempo. Os exemplos mostram a eficácia da metodologia para simular operações de perfuração, em especial, a limpeza de poço. / [en] Among the costs considered on an oil field exploration, the drilling process related ones constitute a significant share. Consequently, the focus on the removal of cuttings generated by the drilling process, or the hole cleaning operation, is essential. This operation remains a critical issue in the drilling of high inclination-wells, since the cuttings tend to deposit themselves due to gravity´s action, forming a bed in the annular space formed between the drill string and the casing. When this bed takes a sizable fraction of the annular space, it becomes responsible for many problems that appear on the drilling stage, such as premature bit´s exhaustion, low rates of penetration, formation fracture, excessive torque and drag on the drillstring, stuck pipe, fluid flow interruption, etc. If this situation is not treated properly, it may cause the loss of the well. This present thesis proposes a model for multiphase flow in the wellbore drilling, capable of evaluating the formation of the cuttings´ bed and to predict oscillations of pressures in annulus due to the flow. A two-layer model is adopted, where the annular space is divided in two regions: bed and suspension. The bed (Region 1) is formed by the cuttings, which were deposited due to the action of gravitational force, while the suspension (Region 2) is the portion of the annular above the deposited bed, formed by the drilling fluid and cuttings. The constitutive equations of the aforementioned model are given by the equations of mass conservation for solids and liquids and the momentum conservation equations for the bed and the suspension. The finite volumes method was used to turn the differentials equations into discrete ones, while the Newton´s method was applied for the solution of the nonlinear system of equations. The solution is given through the following variables: bed height, solid velocity and fluid velocity both in bed and suspension, annular pressure and solid concentration in the annular. Examples of application of the methodology are presented, showing the behavior of the involved variables through time. The examples show the efficacy of the methodology to simulate drilling operations, in special hole cleaning ones.