柴达木盆地复杂基岩气藏储层参数测井评价

火成岩、变质岩气藏的测井综合评价面临的挑战有岩性的划分、有效储层的确定、裂缝孔隙度及溶蚀孔的计算、流体性质的识别等。为此,综合岩心、元素俘获谱、自然伽马能谱测井等资料,划分了柴达木盆地东坪基岩气藏的岩性:研究区北部区块主要为酸性侵入岩,并夹有薄层的中基性岩脉;南部区块则以花岗片麻岩、斜长片麻岩和钙质片麻岩为主,岩性与物性无明确的关系。在岩性识别的基础上,将核磁测井、高分辨率电成像测井与常规测井相结合,建立了基岩的孔隙度计算公式,分别求取了总孔隙度、裂缝孔隙度及溶蚀孔隙度。最后,采用双孔介质裂缝储层饱和度模型计算了含气饱和度,并在多井分析的基础上,结合试气、试采等资料分析了该基岩气藏的成藏特征。结论认为,研究区为底水块状气藏,北部区块气柱高度相对低,南部区块的气柱高度超过350m。该认识已被后续新钻井的测试所证实,所形成的一整套测井综合评价方法为类似气藏的勘探开发提供了技术支撑。

Logging evaluation of parameters for the complex basement gas reservoir in the Qaidam Basin

The major challenges facing the logging evaluation of igneous and metamorphic gas reservoirs include lithology identification, effective reservoir determination, fracture and corrosion porosity estimation, and fluid type identification. One integrated solution was put forward with a case study in this paper. The lithology of the Dongping basement reservoir in the Qaidam Basin was identified based on core, elemental capture spectroscopy (ECS), and natural gamma ray spectrum logging data. The acid intrusive rocks with some thin basic rock dyke is predominant in the northern part of the study area, while metamorphic rocks such as granite metamorphic, amphibolite metamorphic and calcium metamorphic rocks are dominant in the southern part. There is no obvious relationship between lithology and poroperm characteristics. A formula for matrix porosity was established through the integration of NMR, resistivity image, and triple combo data, and was used to calculate the total porosity, fracture porosity, and dissolution pore porosity respectively. The dual porosity fractured reservoir saturation model was adopted to calculate the gas saturation. The basement reservoir was analyzed based on testing and pilot production well data of multiple wells. It was believed that the gas reservoir in the study area is a massive gas reservoir with bottom water, the gas column height of which was relatively low in the north, and the gas column height is more than 350 m in the south. This was validated by the new data of subsequent new drilling wells. These logging evaluation methods can aid exploration and development of similar gas reservoirs.