Yonggang Duan

ANALYSIS OF FRACTIONAL FLOW FOR TRANSIENT TWO-PHASE FLOW IN FRACTAL POROUS MEDIUM

Prediction of fractional flow in fractal porous medium is important for reservoir engineering and chemical engineering as well as hydrology. A physical conceptual fractional flow model of transient two-phase flow is developed in fractal porous medium based on the fractal characteristics of pore-size distribution and on the approximation that porous medium consist of a bundle of tortuous capillaries. The analytical expression for fractional flow for wetting phase is presented, and the proposed expression is the function of structural parameters (such as tortuosity fractal dimension, pore fractal dimension, maximum and minimum diameters of capillaries) and fluid properties (such as contact angle, viscosity and interfacial tension) in fractal porous medium. The sensitive parameters that influence fractional flow and its derivative are formulated, and their impacts on fractional flow are discussed.

Pressure transient model for supercritical CO2 sequestration in deep saline aquifers and its application in Ordos Basin, China

CO2 geological sequestration in the deep saline aquifer is considered as a promising technology to reduce CO2 emissions and prevent global warming. Continuous injection, however, will cause pressurization which may lead to CO2 leaking from the target zone. For the CO2 sequestration, the accuracy of formation parameters is the basis for predicting formation pressure and storage capacity. Even though the pressure transient analysis (PTA) method is useful to obtain the reservoir and well properties accurately, the corresponding reports on supercritical CO2 are rare. Thus, the aim of this work was to address the parameters required to estimate for the supercritical CO2 sequestration in deep saline aquifers. Based on the well testing theory in petroleum engineering, a two-region composite PTA model is established by introducing a new pseudo-pressure which takes supercritical CO2 physical properties into consideration. Then, combined with the definition of dimensionless parameters and the Laplace transform method, the analytical solution of the two-region composite model is obtained. The standard log–log typical curves of PTA are drawn and analyzed. The model is further validated by matching the field data from the Ordos Basin of China with type curves. The changes in the reservoir parameters (e.g., permeability and mobility ratio) over time are also analyzed. The results suggest that the method and model are reliable and can be applied in a transient pressure analysis of the CO2 sequestration in deep saline aquifers to evaluate the flow parameters, to determine the reservoirs properties and to track the location of the CO2–brine front.

The Foundation and Application of Horizontal Well Deliverability Type Curves

As a development technique to improve oil and gas deliverability, horizontal wells have recently become an important technical support to develop low permeability or extra-low permeability and unconventional oil and gas fields. Therefore, it is quite necessary to carry out the analysis methods of horizontal well deliverability. Based on the point source function, this paper started with unsteady seepage, established the seepage physical models of horizontal well in the homogeneous reservoir with closed circular boundary, and derived the solution by using Lap lace transformation and Stehfest numerical inversion and so on, then drawn the deliverability decline curve. Furthermore, we have developed the type curves of horizontal well deliverability by using Blasingame analysis method, made an analysis of dynamic feature and achieved reservoir relevant parameters by using it to analyze actual horizontal well. Through the research results, it can be concluded: The deliverability decreases with time. When the pressure wave reaches the outer boundaries, the declining rate becomes faster, and achieves pseudo-steady flow. Blasingame curves also have a feature to be steady flow. We can evaluate single well dynamic reserves, outer boundary distance and permeability by matching.