坡折带约束下的湖相重力流流态转化与储层构型差异OA

The second Member of the lower Jurassic Sangonghe Formation in the deep Moxizhuang-Yongjin area,the center of the Junggar Basin,has long been interpreted as a braided river delta depositional system.However,recent core data from multiple wells have ubiquitously revealed typical gravity flow sedimentary features,including slump deformation,massive bedding,and floating clasts,indicating a significant departure from the traditional understanding and necessitating a reevaluation of its genetic mechanisms,flow regime evolution,and sandbody distribution patterns.By taking the Moxizhuang area as a case study,this research integrated core,well logging,and 3D seismic data from 17 cored wells to systematically investigate lacustrine gravity flow lithofacies identification,flow regime evolution,and reservoir architecture within a sequence-stratigraphic framework,with particular emphasis on the control of slope break zone paleogeomorphology on flow regime transformation of gravity flow and sandbody accumulation.Four major lithofacies categories were identified:plastic-viscous flow-dominated,high-density sandy laminar flow-dominated,sandy debris-flow turbulent flow-dominated,and flow regime transformation and hybrid flow types,from which six typical lithofacies associations(T1-T6)were summarized.The results demonstrate that the slope break zone serves as a critical geomorphic unit governing flow regime transformation of lacustrine gravity flow.It triggers destabilization of fan-delta front deposits and induces intense shear-driven hydraulic fractionation during slope traversal,promoting the continuous evolution of high-concentration viscous fluids into quasi-steady turbidity currents and mud-rich hybrid flows.Under this constraint,the gravity flow system develops differentiated"source-to-sink"depositional and reservoir architectures along the slope break zone:Above the slope break zone,confined slumps and chaotic infill sandbodies predominate;within the slope break,strongly erosive and multi-phase confined bypass channels develop;below the slope break zone,unconfined channel-lobe complexes form.Provenance supply intensity controls variations in sandbody architecture and hydrocarbon accumulation styles:High sediment-supply periods generate well-connected deepwater fan systems favorable for structural-lithologic composite reservoirs,whereas low sediment-supply periods produce smaller-scale sandbodies with enhanced lateral sealing,more conducive to the formation of subtle lithologic traps.Clean sandy lithofacies assemblages(dominantly T5a and T3b)located in the middle-lower slope break zone and its flanks exhibit better sorting and lower matrix content,representing favorable zones for high-quality deep reservoir development.