赣东北荷塘组页岩气成藏条件及有利区评价

Reservoir-forming conditions and favorable areas evaluation of shale gas reservoir in Hetang formation,northeastern Jiangxi area

为了探讨赣东北地区下寒武统荷塘组页岩气成藏地质条件,以野外荷塘组页岩实测剖面、露头地质调查资料及样品的分析测试结果为基础,对研究区页岩的分布与沉积特征、地球化学特征、储层特征及页岩气保存条件等方面的综合分析,认为赣东北地区荷塘组页岩的储层物性条件较好.结果表明：赣东北地区下寒武统荷塘组页岩沉积厚度一般在25～200m,分布较广泛,主要为深水陆棚相沉积环境.页岩的有机质类型主要为I型,有机碳含量高,达0.54%～11.40%,平均为5.75%,热演化程度高（Ro为2.35%～4.90%,平均为3.22%）,达到过成熟阶段.页岩脆性矿物含量高,主要为石英及少量的长石、碳酸盐矿物.黏土矿物含量中等,以伊利石为主,其次伊/蒙混层,不含蒙脱石.页岩微孔隙类型主要为矿物晶间孔、有机质孔、粒间溶蚀孔及微裂缝.页岩的孔隙度平均为2.2%,渗透率平均为0.006mD.根据中国海相页岩气有利区的评价标准,优选出赣东北地区页岩气勘探开发的有利区——磨盘山、上饶2个区块。

Based on measured sections,geological survey on outcrops and test results analysis of samples,the reservoir-forming geological conditions of the Hetang Formation shale gas reservoir in northeastern Jiangxi area was discussed in the following aspects：shale distribution and sedimentary characteristics,geochemical characteristics,reservoir characteristics and preservation conditions of shale gas;and this shale reservoir was considered to have a good physical properties.The results show that the reservoir thickness of Hetang Formation shale ranges from 25 mto 200m;the shale is widely distributed and developed in deep-water shelf sedimentary environment.The organic matter type of shale is type I;the total organic carbon content is high and in the range of 0.54%—11.40% with the average of 5.75%;the thermal evolution degree is also high with Ro ranging from 2.35%to 4.90% with the average of 3.22%,being in the postmaturity stage.The shale has abundant brittle minerals consisting of the primary quartz and a small quantity of feldspar and carbonate minerals.The clay minerals content is moderate with the primary illite and secondary illite-montmorillonite mixed-layer mineral.Thetypes of micropore of shale include inter-crystalline pores,organic pores,secondary dissolution pores and microcracks.The shale reservoirs have an average porosity of 2.2%and average permeability of 0.006 mD.Moreover,based on the favorable area optimization standard of China＇s marine shale gas,the Lower Cambrian Hetang Formation shale in northeastern Jiangxi Province has ideal shale gas exploration and development conditions and the favorable areas are located in the Mopanshan and Shangrao areas.