浅水三角洲分流河道砂体构型-古气候响应模式

Shallow water deltaic distributary channels are important hydrocarbon reservoirs in continental lacustrine basins. Investigations of shallow water deltas have revealed that seasonal variation of climate has significant controlling effects to architecture of sand bodies in distributary channels. However, architectural response to seasonal variation of paleoclimate in shallow water deltaic distributary channels is still a difficult scientific problem which needs to be further explored. This project intends to select shallow-water delta deposits of the Cretaceous Yaojia Formation the southern Songliao Basin as research object. Using data from geochemical tests, interpretation of modern delta research, outcrop and subsurface, this project will investigate the controlling mechanism of seasonal variation of paleoclimate conditions on the architecture of sand bodies in shallow water deltaic distributary channels. Paleoclimate conditions during sedimentary period of the shallow water delta will be constructed through qualitative and quantitative analysis of seasonal variation of paleoclimate. This process is carried out based on interpretation of paleoclimate related deposits in high-frequency cycles of the Yaojia Formation. Using remote sensing image interpretation and subsurface geological analysis, this project will investigate different levels of sedimentary architectural elements of the distributary channels. Then this project will reveal controlling mechanism of seasonal paleoclimate variation on sedimentary process of various genetic types of the architectural elements. Architectural response model of sand bodies controlled by paleoclimate will be established in seasonal shallow water deltaic distributary channels. This project will focus on the international sedimentological hot topic about controlling effect of seasonal variable climate condition on fluvial-deltaic deposits. This project not only has important academic value for the further study of shallow water deltaic sedimentology, but also provides theoretical basis for efficient exploration and development of shallow-water deltaic hydrocarbon reservoirs.

浅水三角洲分流河道砂体是陆相湖盆中重要的油气储集体，研究表明气候的季节性变化对分流河道砂体沉积具有重要控制作用。分流河道砂体构型对古气候季节性变化的响应是目前沉积学研究亟待深入探索的难点问题。本项目拟选取松辽盆地南部白垩系姚家组浅水三角洲沉积为研究对象，应用地球化学测试、现代沉积解译、野外露头和地下地质资料探索古气候季节性变化对分流河道砂体构型的控制作用。本研究通过高频旋回内部沉积信息的定性-定量分析，重建浅水三角洲沉积时期的古气候条件；在此基础上，采用现代沉积遥感影像解译与地下地质分析相结合的方法，分级次解剖分流河道砂体构型，揭示古气候季节性变化对不同级次构型单元形成的控制机理；最终建立季节性浅水三角洲分流河道砂体构型-古气候响应模式。本研究聚焦分流河道砂体构型对古气候季节性变化的响应，不仅对浅水三角洲沉积学研究具有重要的学术价值，而且可以为浅水三角洲油气储层高效勘探开发提供理论依据。

本项目聚焦分流河道砂体构型对古气候季节性变化的响应问题，以松辽盆地南部白垩系姚家组发育的季节性浅水三角洲沉积为研究对象，利用野外剖面、岩心、测井、三维地震数据和现代沉积考察，解释了古气候季节性变化对浅水三角洲分流河道砂体构型的控制作用。首先利用古土壤沉积学研究，厘清了晚白垩世姚家组浅水三角洲沉积时期深时古气候季节性变化。姚家组古土壤中发育旱成土、淋溶土、变性土等古土壤类型。通过相关地球化学指标的求取以及古气候参数的计算，证明古土壤形成于半干旱的古气候条件下，具备季节性干湿交替的古气候条件。然后，完成了古气候条件控制的季节性浅水三角洲分流河道砂体构型表征。利用地下岩心、三维地震及测井资料在精细地层格架内利用地震沉积学方法开展分流河道不同级次构型单元特征解剖。在古气候季节性变化的影响下，浅水三角洲分流河道发育主干分流河道和决口分流河道沉积单元并存的河道网络结构。主干分流河道是砂体沉积的主要部位，内部发育边滩、活动河道沉积构型单元。分流河道内部发育高流态沉积构造，例如流槽冲坑、泥岩撕裂屑、块状层理、低角度交错层理、平行层理等，普遍缺乏低流态沙丘底形相关的大型的交错层理沉积构造。在枯水期，决口分流河道暴露，发育特殊的红层沉积砂体，导致内部高流态的沉积构造和暴露相关沉积构造并存发育，形成了特殊的沉积充填机制。在此基础上，建立了季节性浅水三角洲分流河道砂体构型-古气候响应模式。本研究在该构型模式的实际应用方面做了进一步延伸讨论，探讨了季节性浅水三角洲分流河道砂体构型对储层质量的影响机制，并建立了沉积构型-成岩演化地质模式。