PORE STRUCTURE AND EVALUATION OF UPPER PALEOZOIC RESERVOIRS AT YIMENG UPLIFT, ORDOS BASIN

As the carrier of oil and gas, the porosity and permeability of a reservoir play a critical role in oil and gas exploitation and determine the recoverable amount of oil and gas, particularly in the later stage. Among many of the factors that affect reservoir physical properties, the pore structure is the key. In this paper, we studied the lithology and pore permeability parameters of the Upper Paleozoic reservoir at the Yimeng Uplift of Ordos basin. Results show that the Shihezi Formation is the best followed by the Shanxi Formation, and the Taiyuan Formation is the worst in terms of pore connectivity and flowing property. Pore structures there can be divided into four categories according to mercury injection data and capillary pressure curve. The upper Paleozoic sandstone is then divided into four classes dominated by class Ⅱ and Ⅲ reservoirs based on the statistical data of porosity and permeability. The reservoirs are mainly sand bodies formed in braided channels of alluvial fans, channel-mouth bars of meandering and braided rivers as well as the distributary channels of deltaic plains. The study results may help oil and gas development in the Upper Paleozoic of the Yimeng Uplift.