渤海海域西南部太古宙变质岩岩性对裂缝的控制作用

Controlling Effect of Archaean Metamorphic Rocks on Fractures in Southwest Bohai Sea

近年来渤海海域太古宇变质岩油气藏为潜山新增探明储量做出了巨大贡献,并形成了亿吨级储量规模。通过详细分析大量钻井取心、测井、录井以及分析化验等资料信息,对渤海西南部太古宇变质岩的岩性特征、岩性与裂缝关系及其控缝机制开展了系统研究。研究表明:以自然伽马为主、岩石密度和补偿中子曲线为辅助的岩矿和测井联合识别方法能够经济有效地划分出变质岩的岩石类型。引入加权裂缝面密度和岩石脆度等量化参数,可以准确反映构造裂缝的整体发育情况,并进一步总结出了成缝优势岩性序列(由好到差):浅粒质混合岩>混合岩化浅粒岩>浅粒岩>混合花岗岩>混合片麻岩>斜长片麻岩。综合分析表明,构造裂缝的形成和发育主要受矿物成分、晶粒大小、(成分/结构)非均质程度以及混合岩化作用4个方面的共同影响,其中岩石类型从根本上决定了裂缝的密度和规模。

Neo-Archean metamorphic buried hill oil pool is a potential reservoir type with hundred million tons of reserves , and contributes immensely to newly found proven reserves. Based on the analysis of cores, well logging, logging and test data, this paper studies the lithologic character, relation between li- thology and the fracture and mechanism for its controling the fractures of metamorphic rocks in southwest Bohai Sea. According to the studies, the federated approach of rock ore appraisal and logging responses are developed. Rock types of metamorphic rocks are effectively identified that is mainly based on the gamma rays, and partially based on the density logging and compensated neutron logging. The method of weigh- ting areal density of fractures and degree of brittleness of rock can be used to reveal the development char- acteristics of structural fractures in the whole target strata. Further, the lithologic sequence of fracture de- velopment is put forward（ from good to bad） ： leptite migmatite, migmatization leptite, leptite, migmatitic granite, migmatitic gneiss and plagioclase gneiss. The comprehensive analysis illustrates the rock types fundamentally determine the developing degree of structural fractures. The results show that the develop- ment characteristics of fractures are effected by the mineral composition, grain size, component or struc- ture heterogeneity and migmatization.