利用视波阻抗法识别致密气层——以子洲气田山_2段为例

Identifying Tight Gas Reservoir using Apparent Wave Impedance Method——A case study of the Shan2 reservoir in Zizhou gas field

鄂尔多斯盆地子洲气田已发现多个致密气藏,其中山2段具有较大的开发潜力,但由于山2段储集层物性差、孔隙结构复杂,储层含气与否,其测井响应的差异性较小,尤其利用单一常规测井方法不能有效识别气水层。以子洲气田山2段致密气藏为研究对象,通过对典型气水层测井响应特征的翔实分析和深入解剖,得知三孔隙度测井对致密气水层均具有一定的敏感性,但对物性较差的气层、气水同层与水层识别精度较低。为了突出致密储层中气体对测井响应的贡献量,利用密度和声波时差测井构建了视波阻抗参数,进而制作了用于识别研究区致密气层的视波阻抗-补偿中子交会图版。利用该图版对研究区致密储层气水层进行了识别,识别结果与气测录井、试气成果对比表明,该方法能够较有效地识别致密储层的流体性质,对相邻区块内的流体性质识别具有参考价值。

Several tight gas reservoirs were found in Zizhou gas field of Ordos Basin, among them Shan2 member has great development potential.But the physical properties of the Shan2 reservoir are poor,and its pore structure is complex and few differences between log response of reservoirs with or without gas-bearing,so it is difficult to effectively identify gas-water layers using single common logging method.Shan2 tight gas reservoirs in Zizhou gas field were studied.After detailed and thorough analysis on the log response character-istics of the typical gas-water layers,it is known that tri-porosity logging has certain sensitivity on the tight gas-water layers,but it has lower recognition accuracy on the gas layer,gas-water in the same interval,water-bearing formation with poor physical properties.In order to highlight the gas contribution of the log re-sponse in the tight reservoirs, a parameter called ' apparent wave impedance ' was constructed using density and acoustic logging,and then cross plot of the apparent wave impedance and compensated neutron was drawn to recognize the tight gas reservoirs in the study area.The gas-water layers of the tight reservoirs in the study area were identified using the chart.Compared with the result of gas logging and gas test,the recognition results show that this method can identify fluid properties in the tight reservoirs more effectively and it has reference value on the fluid property recognition of the adjacent blocks.