应用三重孔隙模型评价火成岩储层

Tri-Porosity Model and Its Application in Igneous Reservoir

火成岩岩性特殊,储层非均质性非常严重,裂缝、孔洞发育,属于典型的多重孔隙介质储层,定量计算火成岩储层基质和裂缝的孔隙度和饱和度是评价火成岩油气层的关键。由基质、天然裂缝和非连通孔洞组成的储层可以模拟成基质和裂缝的并联导电网络,非连通孔洞和基质/裂缝的组合的串联导电网络。采用密度测井资料求取总孔隙度,用深浅双侧向电阻率计算裂缝孔隙度,采用密闭取心分析的孔隙度作为基质孔隙度。通过建立以基质、天然裂缝和非连通孔洞组成的储层的三重孔隙解释模型,找到适合于火成岩缝洞型复杂储层的饱和度方程。将三重孔隙解释模型应用于松辽盆地北部火成岩储层,计算的含水饱和度平均相对误差由16.85%降低至12.42%,精度明显提高,为火成岩储层评价、储量计算与地质建模提供了定量参数。

Igneous reservoir is categorized into multi-porous medium reservoir. A tri-porosity interpretation model considers that： total porosity of fractured igneous reservoir is composed of matrix porosity, fracture porosity and non-connected vug porosity; its resistivity can be modeled as a resistance network in which the matrix and fracture resistivity are firstly connected in parallel, and then the parallel connected resistivity of matrix/fracture and the non-connected vug resistivity are connected in series; a saturation equation of complex fracture-porous-vuggy-type igneous reservoir is deduced. It is the key of applying the tri-porosity model how to determine the values of the 3 kinds of porosities. In condition of no imaging logging data, the total porosity can be gotten by neutron and density logging, the fracture porosity can be calculated by resistivities of dual laterolog and mud, and the matrix porosity can be gotten from pressure coring analysis or acoustic slowness porosity in case of no pressure coring analysis available. Comparison with conventional dual-porosity model, the accuracy of water saturation calculated by the tri-porosity model in igneous reservoir of deep northern Songliao Basin has got obvious improvement, its average relative error of water saturation to the pressure coring analysis result decreased from 16. 8% to 12. 4%.