川中地区震旦系灯影组丘滩相储层差异性对勘探模式的影响

Influence of difference among bioherm beach facies reservoirs on exploration model: An example from Sinian Dengying Formation, central Sichuan Basin

四川盆地震旦系灯影组四段是重要勘探层系之一,发育受岩溶作用改造的丘滩相储层,截至2018年高石梯—磨溪地区灯影组四段台缘区整体探明储量规模达4.085×10^11m^3。目前,灯四段勘探从台缘区走向台内地区,台缘和台内储层品质差异较大,台内储层发育分布的研究对后期勘探开发尤为重要。为此,基于实钻井岩心观察、地震以及测录井等资料,从沉积环境及储层成岩作用等方面入手,分析川中地区震旦系灯影组四段台缘区及台内区储层共性与差异性特征,并探讨其控制因素。研究表明:①台缘区与台内区均发育丘滩相+岩溶作用控制的裂缝-孔洞型储层,储层大面积叠置连片发育;②造成两者储层品质差异如此大的主要影响因素包括有利丘滩相发育程度、桐湾末期表生岩溶强度、储层纵向发育程度及储层发育位置等方面;③根据储层发育特征研究,建立台缘区与台内区储层地震反射模式,优选及设计井型,提出针对台内区薄储层应采用水平井及大斜度井为主的勘探模式,以利于提高台内区储层钻遇率,提高单井产量。以此勘探模式指导台内区薄储层的井位部署并取得良好应用效果。

As developed karstification-reformed bioherm beach facies reservoirs, the Sinian Dengying 4 Member is one of the main exploration layers in Sichuan Basin. As of 2018, its overall proved reserves in marginal platform, Gaoshiti-Moxi area, reached 4 085 ×10^8 m^3. Currently, its exploration is moving to intra-platform from marginal platform. And there is greater difference between reservoir quality in these two platforms. It's essential to carry out a study on reservoir development and distribution in intra-platform for further exploration and development. So, based on core analysis, and seismic and well-logging data, the reservoir characteristics in common and those in difference between marginal platform and intra-platform of Dengying 4 Member in central basin were analyzed with sedimentary environment and diagenesis as the beginning point. In addition, many influencing factors were discussed. Results show that (1) fractured-vuggy reservoirs influenced by bioherm beach facies and karstification are developed in both marginal platform and intra-platform. Superimposed and massive reservoirs are also developed extensively;(2) the main influential factors leading to such large difference in reservoir quality between these two platforms include the development degree of favorable bioherm beach facies, the epigenetic karstification strength at the end of Tongwanian period, the vertical development degree, and the development position;and (3) a seismic reflection pattern is established for the reservoirs in marginal platform and intra-platform, well types are optimized and designed. And it is recommended to apply an exploration model with horizontal and highly deviated wells as the dominant to those thin reservoirs in intra-platform so as to improve drilling rate and single-well production. This model has been well used to guide gas exploration and well deployment in these thin reservoirs in intra-platform.