重庆涪陵地区台内高能滩特征与天然气富集高产主控因素

High-energy shoals and the controls of the gas enrichment in northern Fuling,Chongqing

四川盆地二叠-三叠系碳酸盐岩层系除发育台缘高能礁滩优质储层外,还广泛发育以二、三类储层为主的台内高能滩相储层。本文在对重庆涪陵地区长兴组、飞仙关组沉积背景认识的基础上,结合钻井、测录井、成像测井和地震资料的综合分析,通过与台内低能滩在微观镜下特征、电性特征和地震响应特征的精细对比研究,分析了涪陵地区海相地层台内高能滩的沉积特征和识别标志。长兴组台内高能滩的岩性识别标志以亮晶生屑灰岩为主,具有局部白云石化,发育溶蚀孔洞裂缝。电性标志为以低速低伽马为特征,其中V<6100m/s,GR<36API。地震响应标志为储层顶部表现为低频、中弱振幅、微幅丘状反射特征,储层内部表现为杂乱反射。飞仙关组台内高能与低能滩鲕粒颗粒微观结构差别明显,鲕粒同心圈层多(>7层),同心圈层形态规则(圆形),核心具有白云石化和暴露溶蚀的高能鲕粒滩标志。涪陵地区台内高能滩天然气富集高产主要受多期高能滩的叠置发育、成岩作用改造、裂缝的沟通及构造等因素的控制。

The intraplatform high-energy shoal reservoirs occur on a wide range of scales in the Permian to Triassic carbonate rocks in the Sichuan Basin. The present paper deals, in terms of well logs and seismic data for the Changxing and Feixianguan Formations, with the characteristics and criteria for the recognition of the intraplatform high-energy shoal reservoirs in the marine strata in the Fuling region, Chongqing. Lithologically, the intraplatform high-energy shoal reservoirs in the Changxing Formation are dominated by sparry bioclastic limestones with partial dolomitization and dissolution pores and fissures. The electrical measurements include V 〈 6100m/s and GR 〈 36API. The seismic reponses are indicated by low-frequency, moderate to weak amplitudes and slightly hummocky seismic reflection configurations in the topmost part and chaotic seismic reflection configurations in the inner part of the reservoirs. In the Feixianguan Formation, Fuling region, multiple phases of oolitic shoals have greater thickness and widespread occurrence, and thus have excellent potential of oil and gas exploration. The main controlling factors include multiple stacking of high-energy shoal reservoirs, favourable diagenetic reworking such as dolomitization and dissolution, development of structural fissures/cracks.