鄂尔多斯盆地庆阳气田二叠系山西组山13沉积相类型论证

鄂尔多斯盆地庆阳气田山1段是其主力产层,其沉积环境及其相类型一直争议较多,不同认识导致各个沉积相域内砂体对比模式和砂体分布形态存在着一定差异,从而给勘探井位部署增加了难度。笔者在前人研究成果基础上,综合地震、测井、岩心、露头及室内分析化验等资料,结合地震反射结构揭示的溯源退覆特征、岩心显示的岩性粒度与层理构造、测井沉积旋回特征、现代沉积学的比较等等多视角证据链,对该区山₁₃^小层的沉积相进行了详细论证、分析和描述。研究结果表明,研究区岩性以中粗砂岩为主,多发育块状、板状及小型槽状交错层理,测井相既有河流“二元结构”发育完整的井段,也有只发育下部粗粒端元河流“二元结构”发育不完整的井段,前者揭示发育曲流河,后者则与辫状河发育有关;粒度分析结果显示主要以跳跃粒度成分为主,说明古水动力强;研究区周边露头资料显示既有曲流河发育也有辫状河发育,说明山1段沉积期曲流河和辫状河是同期存在的;现代卫星照片揭示,曲流河和辫状河共生共存发育是普遍存在的,综合上述证据,最终确定研究区山13^发育相类型为河流相,且表现为曲辫共存特征,曲流河的频繁侧积以及平面多种河型共存以及垂向河道的多期叠置是导致砂体分布复杂化和横向相变化快速的主控因素。

Demonstration of sedimentary facies types of Shan13 in Qingyang Gas field, Ordos BasinDemonstration and Analysis Braided River in the Lower He8 Member in Western Sulige Gas Field

Shan1 member of Qingyang Gas Field in Ordos Basin is the main production layer, and its sedimentary environment and facies types have been controversial. Different understanding leads to certain differences in sand body correlation patterns and sand body distribution patterns in each sedimentary facies domain, which increases the difficulty of exploration well location deployment. On the basis of previous research results, the author made comprehensive use of seismic, logging, core, seismic, analytical and laboratory data and field outcrop data, and made use of various research methods and methods such as the traceability and overlying characteristics revealed by seismic reflection structure, the lithological grain size and bedding structure revealed by core, the characteristics of logging sedimentary cycles, and the comparison of modern sedimentology. The sedimentary facies of Shan13 strata in this area are discussed, analyzed and described in detail. The results show that the lithology of the study area is mainly medium and coarse sandstone with block, slab and small trough cross-bedding. The logging facies includes both well sections with complete river "binary structure" and incomplete coarse-grained end-member river "binary structure". The former shows meandering river development, while the latter is related to braided river development. The results of particle size analysis show that the main composition of jump particle size indicates that the paleohydrodynamic force is strong. The outcrop data around the study area show that both meander and braided rivers developed, indicating that meander and braided rivers existed at the same time during the deposition period of Shan1 member. Modern satellite photos reveal that the symbiosis and development of meandering rivers and braided rivers are common. Based on the above evidence, it is finally determined that the development facies of Shan13 in the study area are fluvial facies, which are characterized by the coexistence of curved braided rivers. The frequent lateral deposition of meandering rivers, the coexistence of multiple river types in planes, and the multi-stage superposition of vertical channels are the main factors leading to the complexity of sand body distribution and the rapid change of transverse phases.