岩性指示曲线重构及其在储层预测中的应用

Reconfiguration of lithologic index curve and its application in reservoir prediction

中国石油化工股份有限公司石油勘探开发研究院, 北京 100083

Exploration and Production Research Institute SIN- OPEC, Beijing 100083, China

大牛地上古生界岩性气藏主要发育在三角洲分流河道沉积的下石盒子组、海陆交互沉积的山西组及以潮坪相沉积为主的太原组,储层是储集性能较差的致密砂岩,平均孔隙度小于10％,渗透率小于1×10^-2μm²,储层单层厚度一般小于10 m,砂体横向连通性较差。由于低孔、低渗特征导致储层与围岩的波阻抗差异微弱,用地震资料进行储层预测困难。为此,针对大牛地石板太工区优质储层的岩性特征和测井响应特征进行了测井综合分析,利用对岩性粒度敏感的自然伽马曲线,以及对岩性粒度响应频率较低,且与波阻抗有较好对应关系的中子曲线重构了岩性指示曲线。岩性指示曲线不仅可以有效地识别优质砂体,划分不同岩性,为地震、测井信息结合的岩性反演建立桥梁,同时也为反演结果识别气层打下了基础。利用岩性指示曲线、波阻抗和电阻率曲线进行的地震、测井联合反演技术在石板太工区取得了较好的效果,同时,对石板太工区下石盒子组盒2段、山2段进行了储层和含气性预测,划分了有利含气区带,部署的2口开发井和1口探井有2口井见气,其中1口井获高产气流。

The Neopaleozoic lithologic gas reservoir in Daniudi area is mainly developed in the delta distributary channel deposit of lower Shihezi formation, alternating deposits of Shanxi formation, and tidal flat facies of Taiyuan formation. The reservoir is compact sand, which is poorly connected horizontally, poor in accumulating ability, with an average porosity of less than 10%, a permeability of lower than 1×10^-2μm², and an individual bed thickness of less than 10 m. The low permeability and low porosity lead to a feeble difference in acoustic impendence between the reservoir and the surrounding rock, making it difficult to predict reservoir according to the seismic data. For this reason, the lithologic characteristic and log response feature of Shibantai area in Daniudi are analyzed and the lithologic index curve is reconstituted by using the gamma curve which is sensitive to sand particles and the neutron curve which has a low response frequency to sand particle size and has a good corresponding relationship to acoustic impendence. The lithologic index curve can distinguish the fine sandstone from mud- stone more effectively, providing a foundation for gas recognition by using the inversion result. The combined inversion of seismic and logging using lithologic index curve, acoustic impendence, and resistivity curve is carried out in Shibantai work area, obtaining a good results in this area. At the same time, the method is also used to predict reservoir and gas in He 2 member of Shihezi formation and Shan 2 member of Shanxi formation, classify favorable gaseous section, two exploitation wells and one prospecting well are deployed, of which two wells has produced gas, with one of the two achieving a high output.