The Shaanbei Chang 7 shale oil members in the Ordos Basin develops vertically with multiple lithologic superimpositions. The interlayer stress of the sand-mud-shale thin interlayer is different, and the stress in the small layer is variable, resulting in high hydraulic pressure fractures and short extension distances. The effective retrofit volume did not meet expectations. According to the characteristics of 3 small reservoirs in Chang 7 Member in Xin’anbian area of Shaanbei, combined with the geological, structural, and sedimentary characteristics of the block, the in-situ stress distribution law of vertical multi-interbedded layers with different lithologies was obtained by finely interpreting the in-situ stress logging results of the single well, and the sand was simulated. A three-dimensional regional model of in-situ stress of mud-sheet multi-thin interbedded lithologic reservoirs. The calculation results show that the overall three-dimensional stress of the block is σ
V > σ
H > σ
h (the σ
V is vertical stress, the σ
H is horizontal maximum stress, and the σ
h is horizontal minimum ground stress), the stress value of sandstone in the lateral upper layer is greater than that of shale and that of mudstone, and the difference of horizontal stress in the vertical direction increases with the increase of depth. Combined with the hydraulic fracturing physical model experiment, the fracture initiation and vertical extension patterns of hydraulic fractures in shale oil reservoirs under different stress differences were analyzed. The experiment found that the perforation of the horizon with a large difference between the vertical stress and the minimum horizontal principal stress is preferred, which is beneficial to hydraulic pressure. The expansion of fractures through layers increases the volume of complex fractures and improves the effect of volume stimulation of shale oil reservoirs.
抄録全体を表示