The Study Of Structure Modeling And Structure Interpretation Of DaYi Structure In Sichuan Basin

DaYi Structure is located at the northwest DaYi town, is the transition unit between the foreland and orogene, endured intensive tectonic activities during YinZhi and XiShan period, generated multiple stacking tectonic distortion. It's located in the same tectonic belt with QiongXi Structure where industrial gas has been discovered, so, it has very important meaning to make clear the structure mode and the evolve history of DaYi Structure for oil and gas resource evaluation.This paper utilized the modern tectonics theory, using fault related folding theory and geometric analysis methods, mixing with balanced geologic section technique and forward modeling, combined the outcrop and measurement we've done, we finely analyzed the seismic section of DaYi Structure, and we got to the following conclusion:1. DaYi Structure was stacked by the fault bend fold of YinZhi period in deep and the fault propagation fold of XiShan period in top. The fault-bend fold in deep is the main exploration target.2. The T₃x4～T₃x5 unconformity interface that broadly distributed in the studding area is the demarcation line of tectonic activity, and also the immediacy evidence of timing the period that the structure formed.3. There's a Pop up at the footwall ramp of YinZhi period fault, and the sub faults on its upper flat, and caused the sub folding in the forelimb of the fault bend folding in deep.4. All the sub faults on the YinZhi period fault has a small extensional scale in lengthways, did not piercing the T3x5, the anticline under the unconformity interface is unabridged.5. The upheaval scope of deeper structure weakened from the west to east, the upper structure was fiercely draped at west and east section, the middle section mild, which suggests the intension of the tectonic activity.