深层碳酸盐岩地震储层预测

狄贵东+彭更新+庞雄奇+刘立峰+李国会+李刚+谭杨



摘 要:塔里木盆地碳酸盐岩油气藏具有埋藏深,储集空间和流体性质十分复杂,地震反射信号弱的特点。传统叠后地震资料和技术手段难于准确预测这类油气藏的分布和品质。基于地震资料保幅叠前道集,运用纯纵波储层反演技术分析岩溶储层发育的有利部位;运用频率依赖AVO反演方法预测一间房组含油气性,实际应用效果证实预测结果良好;通过古地貌恢复技术预测碳酸盐岩储层有利分布区,能够为溶蚀孔洞储层的展布提供可靠的地质依据。以此为基础,进一步探讨了该区深层次生碳酸盐岩油气藏的分布主要受古地貌、断裂、不整合、构造背景下的上倾部位等因素的控制。地球物理新方法在碳酸盐岩油气藏预测中的成功应用对塔里木盆地下一步深层油气勘探具有重要意义。
关键词:储层;流体;预测;一间房组;古地貌;碳酸盐岩;控制因素;塔里木盆地
中图分类号:P631.4;TE122 文献标志码:A
文章编号:1672-6561(2016)05-0715-12
Abstract: The hydrocarbon reservoirs of carbonatite in Tarim Basin have the characteristics of deep buried, complicated reservoir space and fluid properties and weak seismic reflection signal. The conventional post-stack seismic data and corresponding techniques are not competent to accurately predict the distribution and quality of this kind of reservoirs. Based on the preserved pre-stack gathers of seismic data, the pure longitudinal wave reservoir inversion technology was used to analyze the favorable position of karstic reservoir; the frequency-dependent AVO inversion method was used to predict the oil-gas-bearing of Yiijanfang Formation; the paleogeomorphy recovery technology was used to predict the favorable distribution of carbonate reservoirs in order to provide a reliable geological basis for the distribution of dissolved pore reservoir; further, the distribution of deep secondary carbonate reservoirs was discussed. The results show that the prediction results by the frequency-dependent AVO inversion method are coincident with the actual drilling and logging data; the distribution of carbonate reservoirs is controlled by paleogeomorphy, fault, unconformity and the updip part of tectonic setting. The above new geophysical method is successfully applied in the prediction of carbonate reservoirs, promoting the further deep hydrocarbon exploration in Tarim Basin.
Key words: reservoir; fluid; prediction; Yijianfang Formation; palaeogeomorphology; carbonatite; controlling factor; Tarim Basin
0 引 言
哈拉哈塘地区位于塔里木盆地北部,东与轮南低凸起相连,西与英买力低凸起相接,南部紧邻满加尔凹陷,北部为塔北隆起轮台凸起。该区碳酸盐岩是塔里木盆地油气勘探的重点领域之一,勘探面积约4 000 km2,拥有巨大的油气资源潜力[1]。哈得逊区块位于哈拉哈塘东南侧哈得逊鼻状隆起构造带主体构造高部位上,其奥陶系一间房组以发育厚层—巨厚层灰色和褐灰色砂屑灰岩、鲕粒灰岩和砂砾砂屑灰岩为主,具有低孔、低渗的特点[2-3]。长期有利于大气淡水淋滤溶蚀的物理条件及地质条件使得哈得逊地区岩溶得到充分发育,位于一间房组不整合面以下发育的次生溶蚀孔洞缝为有效的储集空间。这些储集空间类型多种多样,主要包括洞穴型、孔洞型、裂缝-孔洞型等[1-7]。
溶蚀孔洞缝常在叠后剖面上表现出强的反射振幅特征,按规模大小主要包括“串珠状-片状”大型缝洞体[图1(a)、(b)]及单独“串珠状”[图1(c)]强反射,这也是传统方法依据叠后资料进行这类储层识别的基本依据。图1为哈得逊井区针对强反射的30口已钻井的钻探效果统计和典型叠后反射特征。从图1可以看出:虽然有22口井成功获得工业油流(占全井总数的73.3%),但仍有7口井(占全井总数的23.3%)以钻遇出水为主。显然,传统单一叠加资料可以找到储层的发育区域,但难以判别储集体的流体(水、油气等)充填性质。此外,传统叠加资料受AVO效应(振幅随偏移距变化而变化)的影响并非真正的零检距反射,对储层的具体分布描述精度有限[8]。