鄂尔多斯盆地二叠系天然气储层特征及有利区预测

鄂尔多斯盆地内蕴藏有丰富的天然气资源,是我国重要的能源基地之一.其中,二叠系山西组和下石盒子组为最主要的产气层,储集了该区70%以上的天然气探明储量.二叠系主要的含气层段为山西组的山1段、山2段和下石盒子盒8段,为一套陆相的河流-三角洲沉积,山2段发育曲流河、曲流三角洲沉积,山1段发育辫状河、曲流河、辫状三角洲和曲流三角洲沉积,盒8段发育冲积扇、辫状河、辫状三角洲沉积.储层总体上具有低孔低渗特征,储集空间类型有粒间孔、粒内溶孔、高岭石晶间孔、微裂缝.对山西组和下石盒子组沉积特征、岩石物性资料统计分析并对其主要控制因素进行了研究,认为储层物性主要受控于沉积相、压实作用、胶结作用和溶蚀作用,其中沉积相是最主要的控制因素.根据对该区二叠系岩相古地理的研究和各气田物性统计分析,将该区储层划分为好(Ⅰ)、较好(Ⅱ)、一般(Ⅲ)3类,其中Ⅰ类和Ⅱ类储层区是气藏发育区,也是进一步勘探的首选区域.

Characteristics of Permian natural gas reservoirs in Ordos Basin and prediction of favorable regions

Ordos Basin contains abundant natural gas resource,and it is an important energy base in China.Shan-1 Member and Shan-2 Member of Shanxi Formation and He-8 Member of Lower Shihezi Formation of Permian are the main natural gas producing formations in this area,and the natural gas from them is above 70% of the proved reserves in the area.There are meandering river and meander delta sedimentations in Shan-2 Member,there are braided river,meandering river,braided delta and meander delta sedimentations in Shan-1 Member,and alluvial fan,braided river and braided delta sedimentations in He-8 Member.The reservoirs have lower porosity and permeability,and the types of their reservoir pore are intergranular pore,intragranular dissolved pore,kaolinite intercrystal pore and microfractures.According to the reservoir sedimentary characteristics and the statistical analysis of the data of rock properties,it is held that the physical properties of the reservoirs are controlled mainly by sedimentary facies,compaction,cementation and corrosion,with sedimentary facies being the most important control factor.Based on the statistic data of the property of the reservoirs and the petrography-palaeogeography and petrophysical property of core sandstones,the reservoirs are divided into three types—excellent(Ⅰ),good(Ⅱ)and general(Ⅲ).TypeⅠand type Ⅱ reservoirs produce natural gas pools,and they are the favorable zones for future exploration.