Lu Detang

Numerical Well Test Analysis for Polymer Flooding considering the Non-Newtonian Behavior

Well test analysis for polymer flooding is different from traditional well test analysis because of the non-Newtonian properties of underground flow and other mechanisms involved in polymer flooding. Few of the present works have proposed a numerical approach of pressure transient analysis which fully considers the non-Newtonian effect of real polymer solution and interprets the polymer rheology from details of pressure transient response. In this study, a two-phase four-component fully implicit numerical model incorporating shear thinning effect for polymer flooding based on PEBI (Perpendicular Bisection) grid is developed to study transient pressure responses in polymer flooding reservoirs. Parametric studies are conducted to quantify the effect of shear thinning and polymer concentration on the pressure transient response. Results show that shear thinning effect leads to obvious and characteristic nonsmoothness on pressure derivative curves, and the oscillation amplitude of the shear-thinning-induced nonsmoothness is related to the viscosity change decided by shear thinning effect and polymer concentration. Practical applications are carried out with shut-in data obtained in Daqing oil field, which validates our findings. The proposed method and the findings in this paper show significant importance for well test analysis for polymer flooding and the determination of the polymer in situ rheology.

Shale productivity prediction and fracturingoptimization based on compositional simulation

The reserves of unconventional gas, such as shale and tight gas, is enormous in China. The exploitation of unconventional gas is of significance to secure our nation’s energy future. Precise simulation and prediction of gas flowing behavior in such formations is the key to economic efficiency of exploitation. Different from conventional formations, in shale exist slip flow and gas adsorption. To accurately simulate gas flow in shale, we developed a compositional model based on the hybrid grid which is mainly composed by unstructured PEBI (Perpendicular Bisection) grids. Upon this model, the effects of gas composition, adsorption and slip flow on gas production are analyzed. Horizontal well fracturing in a shale gas reservoir is optimized with the help of this model. The results show that the production of shale gas increases rapidly with the number and effective half-length of fractures, and reaches a plateau when they get large or long enough. Therefore, in order to achieve the maximum economic efficiency, the fracture quantity and effective half-length should be reasonably designed.