致密砂岩气藏地层水对含气性响应机理分析——以鄂尔多斯盆地杭锦旗地区下石盒子组气藏为例  

Mechanism of formation-water property responding to gas saturation in tight sandstone gas reservoirs:Examples from Lower Shihezi gas reservoirs,Hangjinqi area,Ordos Basin

作　　者：徐思阳 刘岩[1] 李可赛 Xu Siyang;Liu Yan;Li Kesai(College of Energy,Chengdu University of Technology,Chengdu,Sichuan 610059,China)

机构地区：[1]成都理工大学能源学院

出　　处：《天然气勘探与开发》2022年第2期81-91,共11页Natural Gas Exploration and Development

摘　　要：鄂尔多斯盆地杭锦旗地区上古生界下二叠统下石盒子组1段致密砂岩储层具有较高的束缚水饱和度,且地层水矿化度差异性大,导致通过测井解释的含气饱和度与最终的测试结论不符,极大地制约了天然气的有效开发。前人对杭锦旗地区上古生界气水关系规律进行了一定的研究,取得了一些的认识,但绝大多数都是从储层物理属性出发,为此,通过对杭锦旗地区石盒子组1段地层水矿化度的差异性分析,结合测试资料和测井资料,采用体积模型对不同含气饱和度条件下的矿化度、地层温度变化和电阻率响应关系的理论影响进行分析,弄清了地层水性质对含气性响应的影响机理。研究结果表明:①以40 g/L为界,高矿化度地层水条件下测井识别气层的电阻率下限值较低矿化度地层水条件下的地层电阻率低;②地层水矿化度对地层水电阻率的影响大于地层温度的影响,含气饱和度越高(S_(g)>60%),地层电阻率受地层水矿化度影响越大,因此利用测井进行含气性解释时应充分考虑地层水矿化度差异性对原状地层电阻率的影响。该结论对低孔低渗的致密气藏含气饱和度的准确计算可提供新的技术支持。In Hangjinqi area,Ordos Basin,most tight sandstone reservoirs of Upper Paleozoic Lower Permian Shihezi 1 Member are featured by higher irreducible-water saturation and very difference in formation-water salinity,which makes the gas saturation obtained from logging interpretation inconsistent with the measured one,thus to further restrict an effective development.However,previous study on the gas-water contact in the Upper Paleozoic mostly focused on the physical properties of reservoirs.So,the differential salinity of formation water in Shihezi 1 Member was analyzed.Then,combining with testing and logging data,the influence on the relationship of salinity-temperature change under various gas saturation responding to resistivity was investigated by using a volume model.Finally,certain mechanism of formation-water property responding to gas saturation was made clear.Results show that(1)using logging identification method and taking 40 g/L as a boundary,the lower limit of resistivity in a gas layer with high water salinity is lower than that at low salinity;(2)the influence of salinity on formation resistivity is greater than that of formation temperature.The higher the gas saturation(S_(g)>60%),the greater the influence.Therefore,when the gas saturation is interpreted by logging,the difference in formation-water salinity affecting the in-situ formation resistivity should be fully considered.These results may provide new technical support for accurate calculating the gas saturation in tight gas reservoirs with low porosity and low permeability.

关 键 词：鄂尔多斯盆地 杭锦旗地区 早二叠世 下石盒子组 水矿化度 含气饱和度 电阻率 低阻气藏 

分 类 号：P618.13[天文地球—矿床学]