塔里木轮古西奥陶系碳酸盐岩岩溶孔洞充填特征识别方法

Method for Identification of LGX Ordovician Carbonate Karst Cave Packing Feature in Tarim

塔里木盆地轮古西地区奥陶系大量溶洞作为存储油气的岩溶孔洞,对该区产能建设具有举足轻重的作用。钻井证实,该区油气主要分布于潜山顶面以下50m范围内,但这个领域也是岩溶孔洞充填较为严重的地方。在常规地震剖面上,充填洞穴及未充填洞穴均表现"串珠状"反射特征,仅靠单一的地球物理手段很难识别出有效储层。通过对工区内多口井的岩心观察,结合地球物理响应特征,通过模型正演,划分出不同盖层条件下的溶洞充填相,并利用频谱分析技术,识别出有效储层的反射特征,在实际生产中得到较好应用。

A large quantity of Ordovician krast caves in Lunguxi （LGX） region of Tarim Basin act as krast vugs to hold oil and gas, exerting a great influence on the productivity in this region. The drilling results showed that oil and gas in this region were distributed mainly less than 50 meters below the top surface of buried hill. However, krast caves are seriously packed in this area. On the conventional seismic profile, the caves both packed and unpacked show ＂beaded＂ reflective characteristics. It is difficult to identify the effective reservoir by means of a single geophysical method. Based on observation of cores from a number of wells in the operational zone and combined with the geophysical response characteristics and forward model, the packed krast caves under different cap-rock conditions were distinguished. The reflective characteristics of effective reservoir can be identified with the help of frequency spectrum analysis technology. This method has achieved good results in actual application,