Study And Application On Coupled Fluid-Solid And Heat-Fluid-Solid Theories Of Sand Control Technology In Weakly Consolidated Reservoirs

Sanding issue can be widely found in weakly consolidated sandstone reservoirs around the world, and which is one of the main factors that restricts further development of the oilfields. The sanding mechanism and prediction research is not very deeply and sand control technology is not effectively combined with the features of the reservoirs which leads to aimlessness and randomness to some extent in sand control method selection.Based on the study of sanding theory, it is necessary to consider the coupled stress and seepage fields and develop sand management technique, and, enhance the adaptability research of sand control technology and support the optimization and improvement of sand control methods.Adopted with the theory and methods of rock mechanics, the deformation and failure laws and strength parameters of the typical unconsolidated sandstone cores were tested, and the results indicate that the relationship of stress and strain is nonlinear, and the Druck-Prager damage criteria is recommended. The changes of rock properties, sand volume and sand index in different water saturation are studied, which can be used to guide sand prediction in different water cut periods.Considering the principle of effective stress and continuum mechanics theory, a coupled fluid-solid model corresponding to fluid seepage, deformation or failure of stratum and fluidized sand movement, etc, is developed to dynamically and quantitatively predict sand production. There are two kinds of sanding mechanisms, which are coarse sand model due to structural failure and fine sand model due to erosion, and the sanding process is mainly includes deformation or failure of stratum and movement of fluid or sand. And then, a software system with the sequential iterative Galerkin finite element method is developed to solve and validate the model. The problems such as sanding trend under different reservoir, stratum, production parameters and near-wellbore variation of geomechanics parameters in time and space with different sand control methods, etc. are simulated and investigated. The results show that stress around the wellbore and perforation tunnels will redistribute along with failure of the formation and sand production; the reservoir parameters are influenced by the complex sanding and stress changes; the volume of sand production will fluctuate and this phenomenon is consistent with field and laboratory observation.In order to solve the high viscosity problem of crude oil, the steam stimulation technology is generally adopted in heavy oil reservoir exploitation. An improved heat-fluid-solid coupling model considering the influence of heat convection is established to evaluate the formation pressure, deformation and effective stress under steam injection conditions, and it is simulated with the finite element program FEPG. The results show that the high pressure caused by the higher thermal expansion of fluid may lead to displacement, deformation or even failure of structure, which show the important ole of heat-fluid-solid coupling during heavy oil recovery.On the basis of size classification research of the main sanding blocks of Shengli oilfield, the evaluation study of mechanical sand control technology is proceeded with the full-size sand control method selection and evaluation apparatus. The experiments mainly include screen liner sand control tests, conventional wire wrapped screen gravel pack tests, high-pressure gravel pack tests, clay stabilization and formation gravel pack tests, the influence tests of fluid viscosity, size of wire wrapped screen and gravel, screen gauge, etc. Then, the high-pressure gravel pack sand control technology is studied and optimized and has good effects in field application.