塔中顺南沙漠区碳酸盐岩天然气藏三维地震勘探技术

塔中顺南沙漠区地表沙丘起伏大,地震信号吸收衰减剧烈,深层奥陶系碳酸盐岩目的层非均质性强,导致碳酸盐岩缝洞体及小断层成像精度不高、储层预测与圈闭落实难度大.为此,在该区统筹开展三维地震采集、目标处理、综合解释等一体化勘探技术攻关.首先,基于碳酸盐岩缝洞体目标优化采集方案设计,优化激发接收参数的采集技术,提高了采集数据质量;其次,在保幅、保真的前提下,形成了叠前时间偏移和逆时叠前深度偏移(RTM)成像技术等对奥陶系缝洞型储层反映敏感的关键参数及流程组合,提高了缝洞体及小断层的成像精度;再次,依据奥陶系碳酸盐岩储层类型及反射结构特征,分组段建立储层地震识别模式,开展储层敏感属性分析,形成了针对内幕缝洞型储层、一间房组储层及裂缝型储层的一系列储层预测及烃类检测技术;最终,建立了"断裂分区带、属性定边界"的圈闭落实与描述技术及"定类型、定控因、定模型、定技术、定目标"的"五定"目标优选与评价技术.多口钻井在该区实现天然气重大突破,证实了顺南沙漠区碳酸盐岩地层天然气藏的三维地震勘探技术的有效性及适用性.

3D seismic exploration technology of carbonate gas reservoir in Shunnan desert area of Central Tarim Basin

In Shunan desert area of central Tarim Basin, large sand-dunes with large relief cause great attenuation and absorption of seismic signals. In addition, the deep Ordovician carbonates have strong heterogeneity. All these unfavorable conditions give rise to poor imaging of the fractured-vuggy reservoirs and small faults, bringing significant difficulties to reservoir prediction and trap identification. Therefore, in this paper, a comprehensive research of 3D seismic acquisition, target-oriented processing and interpretation is carried out to solve the above problems. First, a better acquisition scheme based on fractured-vuggy carbonate reservoir imaging is designed, in which the shooting and receiving parameters are optimized to improve seismic data quality. Then, a series of imaging techniques like pre-stack time migration and RTM migration imagining with suitable key parameters for the Ordovician carbonate reservoirs are established to improve imaging precision of the fractured-vuggy carbonate reservoirs and small faults while preserving true amplitude. In addition, accor-ding to the seismic reflection features and types of carbonate reservoirs in the Ordovician, a set of reservoir prediction and hydrocarbon detection techniques for fractured-vuggy reservoirs and fractured traps is developed including seismic pattern recognition of reservoir in different stratigraphic section and sensitive attributes analysis. Finally, special techniques of traps prediction and characterization are developed and they divide different zones by using faults and define borders of traps by using attributes. Techniques featuring in five factors including type, genesis, model and technique are developed for target optimization and evaluation. Several wells discovered natural gas in this area, providing a solid proof for the effectiveness and applicability of 3D seismic exploration technology of carbonate gas reservoir in Shunnan Desert Area.