Drought Alluvial Fan Reservoir Architecture Model Based on Architecture Analysis of Modern Deposition, Outcrop and Underground Reservoir

Abstract

Taking the alluvial fan reservoir of Lower Karamay Formation, Triassic in the northwestern margin of Junggar Basin as example, differences in the deposition mechanism of alluvial fan deposition process were analyzed by using well logging, core and outcrop. Facies belts of alluvial fan were divided and configuration patterns and scales of architecture elements were clarified, constructing the architecture model of alluvial fan. Along the source direction, the alluvial fan was divided into four facies belts: trench flow belt, sheet flooding belt, braided stream-overbank flow belt and runoff flow belt. The trench flow belt, sheet flooding belt and the proximal part of braided stream-overbank flow belt were controlled by debris flow. On the contrary, the distal part of braided stream-overbank flow belt and the runoff flow belt were controlled by the traction current. Configuration characteristics in different facies belts had large diversity. Trench flow belt was a wide strip on the plane. On the section, it was overall lenticular. Its subject was multiple superimposed trench flow sand-gravel body and sheetflood sand body developed along lateral margin of main channel. Sheet flooding belt was fan-shaped and it can be divided into many sheet flooding lobes along fan radiation direction. Sheet flooding lobe was often ligulate shaped, along whose boundary muddy coating intercalation or calcareous intercalation grew. Braided channel complex, which can be divided into flooding channels and non-flooding channels according to the causes of formation, were the subject of braided stream-overbank flow belt. Flooding channel belt was a large-scale channel complex formed under strong hydrodynamic flood period. It can be divided into many single channels. Single flooding channel, which mainly distributed at the proximal part of braided stream-overbank flow belt, had large scale, good property and formed channeling-path easily. Non-flooding channel belt, which developed in non-flood period, formed sand filling channels by scouring former deposition. Non-flooding channel complex developed along palaeocurrent direction, which can be divided into many single non-flooding channels. Single non-flooding channel, which was narrow-strip, small scale and poor property, can usually be found calcareous cementation and mainly locate at the distal part of braided stream-overbank flow belt. Runoff flow-overbank flow belt mainly developed small, isolated runoff channel on the background of overbank fine grain.

AAPG Datapages/Search and Discovery Article #90217 © 2015 International Conference & Exhibition, Melbourne, Australia, September 13-16, 2015