Structural interpretation and petroleum exploration targets in northern slope of middle Tarim Basin

Based on the 3D seismic interpretation of the northern slope of the middle Tarim Basin, the evolution features, activity phases and their controlling on reservoirs of main faults were studied. There were 8 rows of NNE- or NEE-trending sinistral strike-slip faults in the study area, and the faults were active mainly during the middle Caledonian (the end of the Middle Ordovician) and the early Hercynian (the end of the Middle Devonian). The early Hercynian tense-shearing strike-slip faults developed based on the middle Caledonian compressive-torsional faults, and were controlled by previous basement weak zone and disproportion tectonic stress, hence belonged to typical passive strike-slip faults. Fractures and hydrothermal activities played important roles in the generation of fractured and vuggy reservoirs in Ordovician carbonate rocks. 3 main reservoir charging episodes were concluded including the late Caledonian, the late Hercynian and the Himalayan. Paleozoic tectonic frameworks and strike-slip fault activities controlled the longitudinal distribution and enrichment of hydrocarbon, featured by dry gas in the Middle and Lower Ordovician and oil in the Lower Silurian. The Ordovician carbonate rocks in northern slope of the middle Tarim Basin are actual domains for the industrial production of natural gas. The beaded seismic reflection anomalies near to strike-slip faults are most favorable exploration targets. The "desserts" in sands under mudstones in the middle Kepingtage Formation are also favorable targets.