鄂尔多斯盆地北部上古生界致密气藏储层特征分析

以鄂尔多斯盆地北部上古生界致密气藏储层为研究对象,在对大量岩心观察分析实验的基础上,深入研究了该研究区的储集特征。分析发现该地区储层物性以低渗致密为主,部分地区发育数量较少的优质储层,沉积作用和成岩作用的共同作用是该地区储层致密的主要原因。在不同沉积背景下形成的储层物性差异明显,天然堤与边滩砂体微相背景下形成的砂体是研究区优质储层分布的主要地带;成分成熟度和结构成熟度较低是造成储层物性减少的物质基础;而后期的成岩过程中的压实作用可大幅度降低原始孔隙度,各类次生矿物的胶结作用使储层砂岩致密胶结、物性变差,后期的溶蚀作用和少量成岩微裂缝的产生对储层已达特低渗透级别的致密砂岩物性的改善起到了关键性作用。

Analysis on the Features of Upper Paleozoic Tight-gas Reservoirs in North Ordos Basin

Taking the upper paleozoic tight-gas reservoirs in North Ordos Basin as the research object, and based on large number of rock core＇s observation, analysis and experiment, this paper deeply researches the reservoirs characteristics of the study area; and through the analysis, finds out that the reservoirs of this area was mainly the low- permeability s tight-gas reservoirs with small number of high quality reservoirs, and the combined action of sedimentation and diagenesis was the main reason of the formation of tight reservoirs in this area; the difference of reservoirs＇ physical characteristics, having formed under different sedimentation backgrounds was quite obvious, the sand-bodies having formed under the micro phase background of natural levees and beach sand-bodies were the main area with the distribution of high-quality reservoirs in the study area; the lower composition maturity and structure maturity were the material bases causing the reduction of reservoirs＇ physical property; the consolidation in later diagenetic process could greatly reduce the original porosity, and the cementation of different kinds of secondary minerals made the reservoir sandstone tightly cemented and made the physical property of the reservoir sandstone poorer, and the later dissolution and the generation of a few diagenetic tiny cracks played the key role in the improvement of the physical property of low-permeability tightsandstone in the reservoirs.