鄂尔多斯盆地镇泾地区长8低渗透储层成因

Chang 8 low permeability reservoirs genesis of Zhenting area in Ordos basin

鄂尔多斯盆地镇泾地区长8储层主要为长石岩屑砂岩,孔隙度平均值11.7%,渗透率平均值0.56×10-3μm2,属于典型的低孔低渗储层。通过对长8储层铸体薄片的观察:明确了该区储层的成岩作用特征,通过定量分析各种成岩作用对储层造成的影响,探讨了该区低渗透储层形成的原因:低渗透储层形成的主要原因是压实作用,但晚期胶结作用,尤其是方解石的大量充填是导致储层低孔渗的直接原因。研究结果表明,在大规模生烃之前储层孔隙度应为15%~25%,属于中高孔储层;而随后大规模的胶结作用导致储层孔隙度迅速下降至现今的8%~18%,形成了低孔低渗储层。

Chang 8 reservoirs of Zhenting area in Ordos basin are mainly of feldspar lithic sandstone,with average porosity of 11.7% and permeability of 0.56 ×10-3μm2,and therefore it belongs to a typical low porosity low permeability reservoir.Through the casting thin sections observation of Chang 8 reservoir,the diagenesis characteristics of the reservoir has been made clear and the quantitative analysis of the impact of various diagenesis on reservoirs has been carried out.And then the causes of the permeability reservoir formation have been discussed.The main reason of the low permeability reservoir is the compaction,while the late cementation,especially the calcite filling is the direct cause of the low permeability reservoir.Results show that before the large-scale hydrocarbon generation the reservoir porosity should be a round 15% ~ 25%,belonging to high porosity reservoir While a massive cementation can lead to reservoir porosity quickly dropped to 8% ~ 18%,forming the low porosity low permeability reservoir at present.