摘要:
塔里木盆地轮古地区奥陶系碳酸盐岩储层受多期构造运动及古岩溶作用的叠加改造,该地区古岩溶作用形成的溶洞、裂缝等次生孔隙是主要的油气储集空间。因此古岩溶发育研究是碳酸盐储层评价极为重要的研究内容。文章在对轮古地区奥陶系碳酸盐岩储层大量成像测井资料处理基础上,主要通过对溶蚀裂缝、溶洞的成像测井响应特征进行分析,总结古岩溶标志的成像测井响应规律。高导缝在成像测井图像上表现为褐黑色正弦曲线,溶蚀缝表现为裂缝图像边缘不平直,未充填溶洞在图像上表现为暗色的团块分布,对于全充填洞,可在成像测井图中见到层理等沉积现象。溶蚀程度的差异可根据成像测井资料上解释的裂缝及溶洞中角砾的多寡来度量。轮古西井区,其大溶洞中角砾已溶蚀掉,部分溶洞充填泥砂,表明溶蚀程度很高;轮古中部各井溶洞中的角砾还比较大,单产状裂缝溶洞的规模比轮古西井区小,溶洞溶蚀程度较弱;轮古东井区未见单产状小溶洞,仅见大溶洞的雏形或只有交叉缝和溶蚀裂缝。对区域大量成像测井识别的洞穴数据统计结果表明轮古地区奥陶系洞穴型岩溶储层的分布主要受表层岩溶作用控制。
Abstract:
The Ordovician carbonate reservoir in the Lungu area of Tarim basin has been reformed by the su-perimposition of multi-stage tectonic movement and karstification.Primary oil and gas storage space can be found in the secondary pore structures,such as caves and fractures,formed by paleokarstification.Evalua-tion of karstification is an important area of research for evaluation of carbonate reservoirs.Based on process-ing of a large set of imaging logging data from the Lungu area,and mainly through analysis of the imaging logging response of caves and fractures,karstification rules are determined for the area.In imaging logging, a high conductivity fracture often manifests as a brown-black sine curve,generally with higher continuity;a corrosion fracture generally corresponds to a sine curve with irregular edges;a unfilled cave appears as dark clumps with local light-colored clumps;additionally,fully-filled caves,bedding and other sedimentary phe-nomenon can be observed in the resulting imaging logging map.The different levels of karstification can be i-dentified by fractures and breccias in caves,which are interpreted by imaging logging.In western Lungu,the breccias in some large caves have been completely corroded and were filled with mud and sand,indicating a high level of karstification in this area.In central Lungu region,where some caves have greater amounts of breccia,the size of the cave produced by the corrosion of a single strike fracture is clearly smaller than that in western Lungu.This indicates weaker karstification in central Lungu compared with the western region.In eastern Lungu,small caves have not been produced by the corrosion of single strike fractures,only proto-ca-ves or cross cracks and karst fissures can be observed by imaging logging.Statistical analysis of the number of caves in Lungu area indicates that the distribution of cave reservoirs is mainly affected by epigenetic karst zones.
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