Research Of Alluvial Fan Reservoir Architecture In Qizhong Zone Of Karamay Oilfield

The depositional process of alluvial fan reservoir is complex and heterogeneous.In the development process,the difference of sand connectivity leads to the difference of oil field development effect.Therefore,the architecture anatomy of alluvial fan reservoir will provide geological basis for the efficient development of oil field.This paper aims at alluvial fan deposits of Lower Karamay Formation in Qizhong Zone of Karamay Oilfield.The core and logging data are synthetically applied,and highprecision isochronal stratigraphic framework is established.Meanwhile,the stratigraphic development pattern and control mechanism are analyzed,the lithofacies and its combination characteristics are clarified,and the alluvial fan sedimentary architecture research is carries out to clarifies the distribution characteristics of various architecture elements,so as to provide reliable geological evidence for the development scheme of binary chemical flooding.The results show that:(1)The thickness of strata in the study area decreases gradually from north to south,from both sides of east and west to middle,and along Kewu fault,the thickness of strata fluctuates greatly,and the thickness distribution of each sublayer is consistent with the total thickness of Lower Karamay Formation.(2)Carboniferous palaeogeomorphology has resulted in the strata development pattern,whose bottom is filled and completed,and the associated structures of syngenetic reverse faults,positive traction and fault slope,have resulted in the thinning and thickening of strata correspondingly,forming the difference in subsidence amplitude,and the more active the syngenetic reverse faults are,the more significant the difference in subsidence amplitude is.(3)The trough flow gravel body is top-flat-bottom-convex broad-band shaped,and the sheet flow gravel body is top-convex-bottom-flat sheet or lobar shaped.The combination relationship between braided channel and overflow sedimentation can be divided into four types: the main channel cut and overlapped into sheet sand body,the channel edge cut and overlapped into broad-band sand body,the channel and overflow sand body spliced into narrow-band sand body,and the water channel separated into isolated sand body by overflow fine grains.The runoff channel distributes in the overflow fine grains in top-flat-bottom-convex shape.(4)Syngenetic reverse faults have a certain effect on the size and distribution of alluvial fan architecture.The palaeogeomorphological elevation difference caused by faults makes the alluvial fan glutenite,which gradually disperses out of the mountain pass,to re-accumulate in the lower wall,forming a larger glutenite architecture unit than the upper wall,and the stronger the activity of syngenetic reverse faults is,the stronger the influence is.