Novo m?todo para estimativa do gradiente de fratura para po?os de petr?leo

Made available in DSpace on 2014-12-17T14:09:10Z (GMT). No. of bitstreams: 1 ClovisDF_TESE_partes_autorizadas.pdf: 2764652 bytes, checksum: e400922c312c00169022c2f987a6d8b7 (MD5) Previous issue date: 2010-08-13 === The development of oil wells drilling requires additional cares mainly if the dri...

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Bibliographic Details
Main Author: Ferreira, Cl?vis Dantas
Other Authors: CPF:09453210404
Format: Others
Language:Portuguese
Published: Universidade Federal do Rio Grande do Norte 2014
Subjects:
Online Access:http://repositorio.ufrn.br:8080/jspui/handle/123456789/13006
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Summary:Made available in DSpace on 2014-12-17T14:09:10Z (GMT). No. of bitstreams: 1 ClovisDF_TESE_partes_autorizadas.pdf: 2764652 bytes, checksum: e400922c312c00169022c2f987a6d8b7 (MD5) Previous issue date: 2010-08-13 === The development of oil wells drilling requires additional cares mainly if the drilling is in offshore ultra deep water with low overburden pressure gradients which cause low fracture gradients and, consequently, difficult the well drilling by the reduction of the operational window. To minimize, in the well planning phases, the difficulties faced by the drilling in those sceneries, indirect models are used to estimate fracture gradient that foresees approximate values for leakoff tests. These models generate curves of geopressures that allow detailed analysis of the pressure behavior for the whole well. Most of these models are based on the Terzaghi equation, just differentiating in the determination of the values of rock tension coefficient. This work proposes an alternative method for prediction of fracture pressure gradient based on a geometric correlation that relates the pressure gradients proportionally for a given depth and extrapolates it for the whole well depth, meaning that theses parameters vary in a fixed proportion. The model is based on the application of analytical proportion segments corresponding to the differential pressure related to the rock tension. The study shows that the proposed analytical proportion segments reaches values of fracture gradient with good agreement with those available for leakoff tests in the field area. The obtained results were compared with twelve different indirect models for fracture pressure gradient prediction based on the compacting effect. For this, a software was developed using Matlab language. The comparison was also made varying the water depth from zero (onshore wellbores) to 1500 meters. The leakoff tests are also used to compare the different methods including the one proposed in this work. The presented work gives good results for error analysis compared to other methods and, due to its simplicity, justify its possible application === O desenvolvimento da perfura??o de po?os de petr?leo requer cuidados adicionais principalmente se a perfura??o for mar?tima em l?mina d ?gua ultraprofunda, o que levam a baixos gradientes de sobrecarga, ocasionando baixos gradientes de fratura e, conseq?entemente, dificultando as opera??es de perfura??o pela redu??o da janela operacional. Para minimizar as dificuldades enfrentadas pela perfura??o nesses cen?rios, na fase de planejamento, s?o utilizados modelos indiretos para estimativa do gradiente de fratura, que podem prev? valores aproximados dos testes de absor??o. Esses modelos geram perfis de geopress?o que permitem a an?lise detalhada do comportamento das press?es em todo o intervalo do po?o. A maioria dos modelos tem como base a equa??o de Terzaghi, diferenciando apenas na determina??o dos valores do coeficiente de tens?o da matriz da rocha. Este trabalho prop?e uma forma alternativa diferente, para se estimar o gradiente de fratura, por meio de uma correla??o geom?trica que relaciona proporcionalmente os gradientes de press?o para cada profundidade em todo o intervalo do po?o. As grandezas envolvidas variam em uma mesma propor??o em todo intervalo do po?o. O modelo baseia-se na aplica??o da propor??o ?urea do segmento sobre o diferencial de press?o correspondente ? tens?o da matriz. O estudo mostra que a propor??o ?urea encontra valores de gradiente de fratura com grande aproxima??o dos valores de testes de absor??o dispon?veis da ?rea. Os resultados obtidos foram comparados com doze modelos indiretos distintos que estimam gradiente de fratura baseados no efeito da compacta??o. Para isto, um programa em linguagem Matlab foi desenvolvido. A compara??o tamb?m foi feita com a varia??o de l?minas d ?gua variando de zero (para po?os terrestres, por exemplo) a 1500 m. A medida da precis?o para avalia??o de cada m?todo toma como referencial os valores de testes de absor??o e ? feita atrav?s do erro relativo percentual. A precis?o mostrada nos valores apresentados na an?lise de erro e a forma bastante simples do modelo proposto mostram que ? justific?vel a sua aplica??o