川东北元坝区块中下侏罗统页岩油气地质分析

Geologic analysis of Middle-Lower Jurassic shale reservoirs in Yuanba area,northeastern Sichuan Basin

结合钻井、岩心、野外露头、测井等成果，从富含有机质页岩空间展布、地化特征、岩石矿物学、储集空间特征、孔渗性特征和地质力学性质等方面，对川东北元坝区块中下侏罗统页岩油气地质特征进行了综合研究。显著地质特征是：富有机质泥页岩主要发育于自流井组大安寨段和千佛崖组千一一二段，为浅湖一半深湖沉积，黑色泥页岩夹灰岩或砂岩。有机质较为发育，有机碳含量平均为1．14％，有机质类型以Ⅱ，型为主，镜质体反射率（R0）介于1．4％～1．6％之间，均处于凝析油-湿气的成熟-高成熟阶段。总体上，中下侏罗统页岩气构造简单、稳定，断裂不发育，保存条件良好，有利于烃类形成。大安寨段湖相页岩油气总体与北美E列eFord页岩气特征相似。大安寨段暗色泥页岩厚40～115m，孔隙类型丰富，发育水平缝和微裂缝，脆性矿物含量平均为52．7％．杨氏模量平均为37GPa．泊松比平均为0．30．有利于压裂形成网络裂缝。

Integrating with drillings, cores, outcrops and logging data, we made a comprehensive geologic analy- sis of the Middle-Lower Jurassic shale reservoirs in the Yuanba area of the northeastern Sichuan Basin, from the aspects such as organic-rich shale distribution, geochemical characterization, mineral composition, hydrocarbon store space property, shale porosity and permeability condition, and geomechanical nature. The organic-rich shales mainly generated from the Daanzhai member of the Ziliujing Formation to the 1st and 2nd members of the Qianfoya Formation. They are shallow to semi-deep lacustrine facies, and mainly consist of dark shales with limes and sand stones. Organic matters are rich, and of type I12- The average TOC content is 1.14%. The vitrinite reflectance （Ro ） ranges from 1.4% to 1.6%, indicating for the mature and high-mature stages of condensate oil and wet gas. Generally, the Middle-Lower Jurassic shales have simple and stable structure with few fractures developed, hence are favorable for hydrocarbon generation and preservation. The lacustrine facies shales in the Daanzhai member are similar to the Eagle Ford shales in the North America in general. The dark shales in the Daanzhai member are 40-115 m thick with various pore types. Horizontal and micro fractures are well-developed. The average brittle mineral content, Young＇ s modulus and Poisson ratio are 52.7%, 37 GPa and 0.30, respec- tively, all contributing to the formation of fracture network.