四川盆地井研地区栖霞组白云岩储层识别及有利区预测

四川盆地井研地区中二叠统栖霞组白云岩储层取得突破, 但其储层类型多样、非均质性强, 不同类型储层地震响应特征及平面分布规律不清, 制约着该区下一步油气勘探方向。在区域地质背景研究基础上, 利用钻井、测井、地震等资料建立不同类型、不同厚度、不同发育位置的白云岩、白云质灰岩储层正演模型并进行正演模拟, 总结影响栖霞组内部地震反射特征变化的主要因素, 建立不同类型储层识别模式; 利用已钻井岩性组合、测井相、地震相分布和古地貌高、低起伏变化确定白云岩储层发育有利相带; 利用波形分解与重构技术和振幅属性定性区分白云岩、白云质灰岩或灰质白云岩储层的平面分布, 利用有色滤波波阻抗反演技术定量预测不同类型储层的空间分布; 综合地质和地震预测等结果圈定栖霞组储层发育有利区, 明确有利勘探目标。研究结果表明, 井研地区位于川中古隆起南缘, 栖霞组不同类型储层受古地貌控制明显, 古地貌越高白云岩化程度越高, 厚大白云岩储层主要分布在工区西北部, 薄层白云岩、白云质灰岩或灰质白云岩等储层主要分布在工区南部和东北部, 储层发育有利区与构造、溶蚀裂缝发育的叠合区是下一步油气勘探的有利目标区。

There has been a breakthrough in the study of the Middle Permian Qixia Formation in the Jingyan area of the Sichuan Basin. However, the highly diverse and heterogeneous reservoirs, and the unclear seismic response characteristics and plane distribution rules of the different dolomite and dolomitic limestone reservoirs, restrict the direction of oil and gas exploration in this area. Based on the regional geological research background, two forward models of dolomite and dolomitic limestone reservoirs of different types, thicknesses, and development positions were established and simulated using drilling, logging, and seismic data. The main factors affecting the variation of seismic reflection characteristics in the Qixia Formation were summarized, and the identification modes for different types of reservoirs were established. The plane change of the sedimentary environment was determined by combining drilling lithology, logging facies, and seismic facies, while the favorable position of dolomite reservoir development was determined by the fluctuation of paleogeomorphology. In the existing seismic data, the seismic response characteristics of the thin-layer dolomite, dolomitic limestone, and calcareous dolomite thin-interbedded reservoirs were not significantly different. Using waveform decomposition and reconstruction technologies, the study statistically classified seismic waveforms with different energies. Based on the reservoir fine calibration, the waveform components representing the response characteristics of the dolomite, dolomitic limestone, and calcareous dolomite reservoirs were optimized. This allowed for qualitative determination of the plane distribution of different types of reservoirs, while the spatial distribution was quantitatively determined using color filter impedance inversion technology. Combined with the sedimentation, structure, reservoir, and hydrocarbon sources, favorable areas for reservoir development in the Qixia Formation were delineated, and favorable exploration targets were defined. The results of this study show that the Jingyan area is located on the southern margin of the central Sichuan Paleo-uplift and the different types of reservoirs in the Qixia Formation are controlled by paleogeomorphology. A higher paleogeomorphology indicates higher degree of dolomitization. Thick and large dolomite reservoirs are mainly distributed in the northwest of the study area, while thin dolomite, dolomitic limestone, and calcareous dolomite reservoirs are mainly distributed in the south and northeast. Favorable reservoir development areas and superimposed areas with structural and dissolution fractures are favorable for further oil and gas exploration.